Bump version to 0.0.50

.editorconfig

@@ -0,0 +1,14 @@
+# Check http://editorconfig.org for more information
+# This is the main config file for this project:
+root = true
+
+[*]
+charset = utf-8
+trim_trailing_whitespace = true
+end_of_line = lf
+indent_style = space
+insert_final_newline = true
+indent_size = 2
+
+[*.{rs,py}]
+indent_size = 4

.github/workflows/ci.yaml

@@ -2,16 +2,16 @@ name: CI
 
 on:
   push:
-    branches: [ main ]
+    branches: [main]
   pull_request:
-    branches: [ main ]
+    branches: [main]
 
 jobs:
   cargo_build:
     name: "cargo build"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: actions-rs/toolchain@v1
         with:
           toolchain: stable
@@ -33,7 +33,7 @@ jobs:
     name: "cargo fmt"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: actions-rs/toolchain@v1
         with:
           toolchain: stable
@@ -55,7 +55,7 @@ jobs:
     name: "cargo clippy"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: actions-rs/toolchain@v1
         with:
           toolchain: stable
@@ -77,7 +77,7 @@ jobs:
     name: "cargo test"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: actions-rs/toolchain@v1
         with:
           toolchain: stable
@@ -99,13 +99,13 @@ jobs:
     name: "maturin build"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: actions-rs/toolchain@v1
         with:
           toolchain: stable
       - uses: actions/setup-python@v4
         with:
-          python-version: '3.10'
+          python-version: "3.10"
       - run: pip install maturin
       - uses: actions/cache@v3
         env:

.github/workflows/release.yaml

@@ -1,49 +1,71 @@
 name: Release
 
 on:
+  pull_request:
+    branches: [main]
   create:
     tags:
       - v*
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+env:
+  PACKAGE_NAME: ruff
+  PYTHON_VERSION: "3.7" # to build abi3 wheels
+
 jobs:
-  macos:
+  macos-x86_64:
     runs-on: macos-latest
-    strategy:
-      matrix:
-        python-version: ['3.7', '3.8', '3.9', '3.10']
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/setup-python@v2
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
         with:
-          python-version: ${{ matrix.python-version }}
+          python-version: ${{ env.PYTHON_VERSION }}
+          architecture: x64
       - name: Install Rust toolchain
         uses: actions-rs/toolchain@v1
         with:
           toolchain: stable
-          target: aarch64-apple-darwin
           profile: minimal
           default: true
-      - name: Build
-        run: cargo build --release
-      - name: Tests
-        run: cargo test --no-default-features --release
       - name: Build wheels - x86_64
         uses: messense/maturin-action@v1
         with:
           target: x86_64
-          args: -i python --release --out dist --sdist
+          args: --release --out dist --sdist
+          maturin-version: "v0.13.0"
       - name: Install built wheel - x86_64
         run: |
-          pip install ruff --no-index --find-links dist --force-reinstall
+          pip install dist/${{ env.PACKAGE_NAME }}-*.whl --force-reinstall
+      - name: Upload wheels
+        uses: actions/upload-artifact@v2
+        with:
+          name: wheels
+          path: dist
+  macos-universal:
+    runs-on: macos-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: ${{ env.PYTHON_VERSION }}
+          architecture: x64
+      - name: Install Rust toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+          profile: minimal
+          default: true
       - name: Build wheels - universal2
-        if: ${{ matrix.python-version >= '3.8' || matrix.python-version == '3.10' }}
         uses: messense/maturin-action@v1
         with:
-          args: -i python --release --universal2 --out dist
+          args: --release --universal2 --out dist
+          maturin-version: "v0.13.0"
       - name: Install built wheel - universal2
-        if: ${{ matrix.python-version >= '3.8' }}
         run: |
-          pip install ruff --no-index --find-links dist --force-reinstall
+          pip install dist/${{ env.PACKAGE_NAME }}-*universal2.whl --force-reinstall
       - name: Upload wheels
         uses: actions/upload-artifact@v2
         with:
@@ -54,36 +76,29 @@ jobs:
     runs-on: windows-latest
     strategy:
       matrix:
-        python-version: ['3.7', '3.8', '3.9', '3.10']
         target: [x64, x86]
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/setup-python@v2
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
         with:
-          python-version: ${{ matrix.python-version }}
+          python-version: ${{ env.PYTHON_VERSION }}
           architecture: ${{ matrix.target }}
-      - name: Update rustup
-        run: rustup self update
       - name: Install Rust toolchain
         uses: actions-rs/toolchain@v1
         with:
           toolchain: stable
           profile: minimal
           default: true
-      - name: Build
-        if: matrix.target == 'x64'
-        run: cargo build --release
-      - name: Tests
-        if: matrix.target == 'x64'
-        run: cargo test --no-default-features --release
       - name: Build wheels
         uses: messense/maturin-action@v1
         with:
           target: ${{ matrix.target }}
-          args: -i python --release --out dist
+          args: --release --out dist
+          maturin-version: "v0.13.0"
       - name: Install built wheel
+        shell: bash
         run: |
-          pip install ruff --no-index --find-links dist --force-reinstall
+          python -m pip install dist/${{ env.PACKAGE_NAME }}-*.whl --force-reinstall
       - name: Upload wheels
         uses: actions/upload-artifact@v2
         with:
@@ -94,96 +109,195 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ['3.7', '3.8', '3.9', '3.10']
         target: [x86_64, i686]
     steps:
-    - uses: actions/checkout@v2
-    - name: Install Rust toolchain
-      uses: actions-rs/toolchain@v1
-      with:
-        toolchain: stable
-        profile: minimal
-        default: true
-    - name: Build
-      run: cargo build --release
-    - name: Tests
-      run: cargo test --no-default-features --release
-    - uses: actions/setup-python@v2
-      with:
-        python-version: ${{ matrix.python-version }}
-    - name: Build Wheels
-      uses: messense/maturin-action@v1
-      with:
-        target: ${{ matrix.target }}
-        manylinux: auto
-        args: -i ${{ matrix.python-version }} --release --out dist
-    - name: Install built wheel
-      if: matrix.target == 'x86_64'
-      run: |
-        pip install ruff --no-index --find-links dist --force-reinstall
-    - name: Upload wheels
-      uses: actions/upload-artifact@v2
-      with:
-        name: wheels
-        path: dist
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: ${{ env.PYTHON_VERSION }}
+          architecture: x64
+      - name: Build wheels
+        uses: messense/maturin-action@v1
+        with:
+          target: ${{ matrix.target }}
+          manylinux: auto
+          args: --release --out dist
+          maturin-version: "v0.13.0"
+      - name: Install built wheel
+        if: matrix.target == 'x86_64'
+        run: |
+          pip install dist/${{ env.PACKAGE_NAME }}-*.whl --force-reinstall
+      - name: Upload wheels
+        uses: actions/upload-artifact@v2
+        with:
+          name: wheels
+          path: dist
 
   linux-cross:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ['3.7', '3.8', '3.9', '3.10']
-        target: [aarch64, armv7, s390x, ppc64le]
+        target: [aarch64, armv7, s390x, ppc64le, ppc64]
     steps:
-    - uses: actions/checkout@v2
-    - name: Build Wheels
-      uses: messense/maturin-action@v1
-      with:
-        target: ${{ matrix.target }}
-        manylinux: auto
-        args: -i ${{ matrix.python-version }} --release --out dist
-    - uses: uraimo/run-on-arch-action@v2.2.0
-      name: Install built wheel
-      with:
-        arch: ${{ matrix.target }}
-        distro: ubuntu20.04
-        githubToken: ${{ github.token }}
-        # Mount the dist directory as /artifacts in the container
-        dockerRunArgs: |
-          --volume "${PWD}/dist:/artifacts"
-        install: |
-          apt-get update
-          apt-get install -y --no-install-recommends python3 python3-venv software-properties-common
-          add-apt-repository ppa:deadsnakes/ppa
-          apt-get update
-          apt-get install -y curl python3.7-venv python3.9-venv python3.10-venv
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: ${{ env.PYTHON_VERSION }}
+      - name: Build wheels
+        uses: messense/maturin-action@v1
+        with:
+          target: ${{ matrix.target }}
+          manylinux: auto
+          args: --no-default-features --release --out dist
+          maturin-version: "v0.13.0"
+      - uses: uraimo/run-on-arch-action@v2.0.5
+        if: matrix.target != 'ppc64'
+        name: Install built wheel
+        with:
+          arch: ${{ matrix.target }}
+          distro: ubuntu20.04
+          githubToken: ${{ github.token }}
+          install: |
+            apt-get update
+            apt-get install -y --no-install-recommends python3 python3-pip
+            pip3 install -U pip
+          run: |
+            pip3 install ${{ env.PACKAGE_NAME }} --no-index --find-links dist/ --force-reinstall
+      - name: Upload wheels
+        uses: actions/upload-artifact@v2
+        with:
+          name: wheels
+          path: dist
+
+  musllinux:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        target:
+          - x86_64-unknown-linux-musl
+          - i686-unknown-linux-musl
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: ${{ env.PYTHON_VERSION }}
+          architecture: x64
+      - name: Build wheels
+        uses: messense/maturin-action@v1
+        with:
+          target: ${{ matrix.target }}
+          manylinux: musllinux_1_2
+          args: --release --out dist
+          maturin-version: "v0.13.0"
+      - name: Install built wheel
+        if: matrix.target == 'x86_64-unknown-linux-musl'
+        uses: addnab/docker-run-action@v3
+        with:
+          image: alpine:latest
+          options: -v ${{ github.workspace }}:/io -w /io
+          run: |
+            apk add py3-pip
+            pip3 install ${{ env.PACKAGE_NAME }} --no-index --find-links /io/dist/ --force-reinstall
+      - name: Upload wheels
+        uses: actions/upload-artifact@v2
+        with:
+          name: wheels
+          path: dist
+
+  musllinux-cross:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        platform:
+          - target: aarch64-unknown-linux-musl
+            arch: aarch64
+          - target: armv7-unknown-linux-musleabihf
+            arch: armv7
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: ${{ env.PYTHON_VERSION }}
+      - name: Build wheels
+        uses: messense/maturin-action@v1
+        with:
+          target: ${{ matrix.platform.target }}
+          manylinux: musllinux_1_2
+          args: --release --out dist
+          maturin-version: "v0.13.0"
+      - uses: uraimo/run-on-arch-action@master
+        name: Install built wheel
+        with:
+          arch: ${{ matrix.platform.arch }}
+          distro: alpine_latest
+          githubToken: ${{ github.token }}
+          install: |
+            apk add py3-pip
+          run: |
+            pip3 install ${{ env.PACKAGE_NAME }} --no-index --find-links dist/ --force-reinstall
+      - name: Upload wheels
+        uses: actions/upload-artifact@v2
+        with:
+          name: wheels
+          path: dist
+
+  pypy:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+        target: [x86_64, aarch64]
+        python-version:
+          - "3.7"
+          - "3.8"
+          - "3.9"
+        exclude:
+          - os: macos-latest
+            target: aarch64
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: pypy${{ matrix.python-version }}
+      - name: Build wheels
+        uses: messense/maturin-action@v1
+        with:
+          maturin-version: "v0.13.0"
+          target: ${{ matrix.target }}
+          manylinux: auto
+          args: --release --out dist -i pypy${{ matrix.python-version }}
+      - name: Install built wheel
+        if: matrix.target == 'x86_64'
         run: |
-          ls -lrth /artifacts
-          PYTHON=python${{ matrix.python-version }}
-          $PYTHON -m venv venv
-          venv/bin/pip install -U pip
-          venv/bin/pip install ruff --no-index --find-links /artifacts --force-reinstall
-    - name: Upload wheels
-      uses: actions/upload-artifact@v2
-      with:
-        name: wheels
-        path: dist
+          pip install dist/${{ env.PACKAGE_NAME }}-*.whl --force-reinstall
+      - name: Upload wheels
+        uses: actions/upload-artifact@v2
+        with:
+          name: wheels
+          path: dist
 
   release:
     name: Release
     runs-on: ubuntu-latest
+    needs:
+      - macos-universal
+      - macos-x86_64
+      - windows
+      - linux
+      - linux-cross
+      - musllinux
+      - musllinux-cross
+      - pypy
     if: "startsWith(github.ref, 'refs/tags/')"
-    needs: [ macos, windows, linux, linux-cross ]
     steps:
       - uses: actions/download-artifact@v2
         with:
           name: wheels
-      - uses: actions/setup-python@v2
-        with:
-          python-version: '3.10'
+      - uses: actions/setup-python@v4
       - name: Publish to PyPi
         env:
           TWINE_USERNAME: __token__
           TWINE_PASSWORD: ${{ secrets.PYPI_TOKEN }}
         run: |
-          pip install --upgrade wheel pip setuptools twine
-          twine upload --skip-existing *
+          pip install --upgrade twine
+          twine upload --skip-existing *

.gitignore

@@ -1,5 +1,5 @@
 # Local cache
-.cache
+.ruff_cache
 resources/test/cpython
 
 ###

.pre-commit-config.yaml

@@ -0,0 +1,10 @@
+repos:
+  - repo: https://github.com/charliermarsh/ruff-pre-commit
+    rev: v0.0.40
+    hooks:
+      - id: lint
+
+  - repo: https://github.com/abravalheri/validate-pyproject
+    rev: v0.10.1
+    hooks:
+      - id: validate-pyproject

CODE_OF_CONDUCT.md

@@ -0,0 +1,128 @@
+# Contributor Covenant Code of Conduct
+
+## Our Pledge
+
+We as members, contributors, and leaders pledge to make participation in our
+community a harassment-free experience for everyone, regardless of age, body
+size, visible or invisible disability, ethnicity, sex characteristics, gender
+identity and expression, level of experience, education, socio-economic status,
+nationality, personal appearance, race, religion, or sexual identity
+and orientation.
+
+We pledge to act and interact in ways that contribute to an open, welcoming,
+diverse, inclusive, and healthy community.
+
+## Our Standards
+
+Examples of behavior that contributes to a positive environment for our
+community include:
+
+* Demonstrating empathy and kindness toward other people
+* Being respectful of differing opinions, viewpoints, and experiences
+* Giving and gracefully accepting constructive feedback
+* Accepting responsibility and apologizing to those affected by our mistakes,
+  and learning from the experience
+* Focusing on what is best not just for us as individuals, but for the
+  overall community
+
+Examples of unacceptable behavior include:
+
+* The use of sexualized language or imagery, and sexual attention or
+  advances of any kind
+* Trolling, insulting or derogatory comments, and personal or political attacks
+* Public or private harassment
+* Publishing others' private information, such as a physical or email
+  address, without their explicit permission
+* Other conduct which could reasonably be considered inappropriate in a
+  professional setting
+
+## Enforcement Responsibilities
+
+Community leaders are responsible for clarifying and enforcing our standards of
+acceptable behavior and will take appropriate and fair corrective action in
+response to any behavior that they deem inappropriate, threatening, offensive,
+or harmful.
+
+Community leaders have the right and responsibility to remove, edit, or reject
+comments, commits, code, wiki edits, issues, and other contributions that are
+not aligned to this Code of Conduct, and will communicate reasons for moderation
+decisions when appropriate.
+
+## Scope
+
+This Code of Conduct applies within all community spaces, and also applies when
+an individual is officially representing the community in public spaces.
+Examples of representing our community include using an official e-mail address,
+posting via an official social media account, or acting as an appointed
+representative at an online or offline event.
+
+## Enforcement
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be
+reported to the community leaders responsible for enforcement at
+charlie.r.marsh@gmail.com.
+All complaints will be reviewed and investigated promptly and fairly.
+
+All community leaders are obligated to respect the privacy and security of the
+reporter of any incident.
+
+## Enforcement Guidelines
+
+Community leaders will follow these Community Impact Guidelines in determining
+the consequences for any action they deem in violation of this Code of Conduct:
+
+### 1. Correction
+
+**Community Impact**: Use of inappropriate language or other behavior deemed
+unprofessional or unwelcome in the community.
+
+**Consequence**: A private, written warning from community leaders, providing
+clarity around the nature of the violation and an explanation of why the
+behavior was inappropriate. A public apology may be requested.
+
+### 2. Warning
+
+**Community Impact**: A violation through a single incident or series
+of actions.
+
+**Consequence**: A warning with consequences for continued behavior. No
+interaction with the people involved, including unsolicited interaction with
+those enforcing the Code of Conduct, for a specified period of time. This
+includes avoiding interactions in community spaces as well as external channels
+like social media. Violating these terms may lead to a temporary or
+permanent ban.
+
+### 3. Temporary Ban
+
+**Community Impact**: A serious violation of community standards, including
+sustained inappropriate behavior.
+
+**Consequence**: A temporary ban from any sort of interaction or public
+communication with the community for a specified period of time. No public or
+private interaction with the people involved, including unsolicited interaction
+with those enforcing the Code of Conduct, is allowed during this period.
+Violating these terms may lead to a permanent ban.
+
+### 4. Permanent Ban
+
+**Community Impact**: Demonstrating a pattern of violation of community
+standards, including sustained inappropriate behavior,  harassment of an
+individual, or aggression toward or disparagement of classes of individuals.
+
+**Consequence**: A permanent ban from any sort of public interaction within
+the community.
+
+## Attribution
+
+This Code of Conduct is adapted from the [Contributor Covenant][homepage],
+version 2.0, available at
+https://www.contributor-covenant.org/version/2/0/code_of_conduct.html.
+
+Community Impact Guidelines were inspired by [Mozilla's code of conduct
+enforcement ladder](https://github.com/mozilla/diversity).
+
+[homepage]: https://www.contributor-covenant.org
+
+For answers to common questions about this code of conduct, see the FAQ at
+https://www.contributor-covenant.org/faq. Translations are available at
+https://www.contributor-covenant.org/translations.

CONTRIBUTING.md

@@ -0,0 +1,105 @@
+# Contributing to ruff
+
+Welcome! We're happy to have you here. Thank you in advance for your contribution to ruff.
+
+## The basics
+
+ruff welcomes contributions in the form of Pull Requests. For small changes (e.g., bug fixes), feel
+free to submit a PR. For larger changes (e.g., new lint rules, new functionality, new configuration
+options), consider submitting an [Issue](https://github.com/charliermarsh/ruff/issues) outlining
+your proposed change.
+
+### Prerequisites
+
+ruff is written in Rust (1.63.0). You'll need to install the
+[Rust toolchain](https://www.rust-lang.org/tools/install) for development.
+
+### Development
+
+After cloning the repository, run ruff locally with:
+
+```shell
+cargo run resources/test/fixtures --no-cache
+```
+
+Prior to opening a pull request, ensure that your code has been auto-formatted, and that it passes
+both the lint and test validation checks:
+
+```shell
+cargo fmt     # Auto-formatting...
+cargo clippy  # Linting...
+cargo test    # Testing...
+```
+
+These checks will run on GitHub Actions when you open your Pull Request, but running them locally
+will save you time and expedite the merge process.
+
+Your Pull Request will be reviewed by a maintainer, which may involve a few rounds of iteration
+prior to merging.
+
+### Example: Adding a new lint rule
+
+There are three phases to adding a new lint rule:
+
+1. Define the rule in `src/checks.rs`.
+2. Define the _logic_ for triggering the rule in `src/check_ast.rs` (for AST-based checks)
+   or `src/check_lines.rs` (for text-based checks).
+3. Add a test fixture.
+
+To define the rule, open up `src/checks.rs`. You'll need to define both a `CheckCode` and
+`CheckKind`. As an example, you can grep for `E402` and `ModuleImportNotAtTopOfFile`, and follow the
+pattern implemented therein.
+
+To trigger the rule, you'll likely want to augment the logic in `src/check_ast.rs`, which defines
+the Python AST visitor, responsible for iterating over the abstract syntax tree and collecting
+lint-rule violations as it goes. Grep for the `Check::new` invocations to understand how other,
+similar rules are implemented.
+
+To add a test fixture, create a file under `resources/test/fixtures`, named to match the `CheckCode`
+you defined earlier (e.g., `E402.py`). This file should contain a variety of violations and
+non-violations designed to evaluate and demonstrate the behavior of your lint rule. Run ruff locally
+with (e.g.) `cargo run resources/test/fixtures/E402.py`. Once you're satisified with the output,
+codify the behavior as a snapshot test by adding a new function to the `mod tests` section of
+`src/linter.rs`, like so:
+
+```rust
+#[test]
+fn e402() -> Result<()> {
+    let mut checks = check_path(
+        Path::new("./resources/test/fixtures/E402.py"),
+        &settings::Settings::for_rule(CheckCode::E402),
+        &fixer::Mode::Generate,
+    )?;
+    checks.sort_by_key(|check| check.location);
+    insta::assert_yaml_snapshot!(checks);
+    Ok(())
+}
+```
+
+Then, run `cargo test`. Your test will fail, but you'll be prompted to follow-up with
+`cargo insta review`. Accept the generated snapshot, then commit the snapshot file alongside the
+rest of your changes.
+
+### Example: Adding a new configuration option
+
+ruff's user-facing settings live in two places: first, the command-line options defined with
+[clap](https://docs.rs/clap/latest/clap/) via the `Cli` struct in `src/main.rs`; and second, the
+`Config` struct defined `src/pyproject.rs`, which is responsible for extracting user-defined
+settings from a `pyproject.toml` file.
+
+Ultimately, these two sources of configuration are merged into the `Settings` struct defined
+in `src/settings.rs`, which is then threaded through the codebase.
+
+To add a new configuration option, you'll likely want to _both_ add a CLI option to `src/main.rs`
+_and_ a `pyproject.toml` parameter to `src/pyproject.rs`. If you want to pattern-match against an
+existing example, grep for `dummy_variable_rgx`, which defines a regular expression to match against
+acceptable unused variables (e.g., `_`).
+
+## Release process
+
+As of now, ruff has an ad hoc release process: releases are cut with high frequency via GitHub
+Actions, which automatically generates the appropriate wheels across architectures and publishes
+them to [PyPI](https://pypi.org/project/ruff/).
+
+ruff follows the [semver](https://semver.org/) versioning standard. However, as pre-1.0 software,
+even patch releases may contain [non-backwards-compatible changes](https://semver.org/#spec-item-4).

Cargo.lock

@@ -2,6 +2,12 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "adler"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f26201604c87b1e01bd3d98f8d5d9a8fcbb815e8cedb41ffccbeb4bf593a35fe"
+
 [[package]]
 name = "ahash"
 version = "0.7.6"
@@ -31,6 +37,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "annotate-snippets"
+version = "0.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c7021ce4924a3f25f802b2cccd1af585e39ea1a363a1aa2e72afe54b67a3a7a7"
+
 [[package]]
 name = "anyhow"
 version = "1.0.60"
@@ -197,6 +209,12 @@ dependencies = [
  "byteorder",
 ]
 
+[[package]]
+name = "base64"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "904dfeac50f3cdaba28fc6f57fdcddb75f49ed61346676a78c4ffe55877802fd"
+
 [[package]]
 name = "bincode"
 version = "1.3.3"
@@ -347,6 +365,15 @@ version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
+[[package]]
+name = "chic"
+version = "1.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a5b5db619f3556839cb2223ae86ff3f9a09da2c5013be42bc9af08c9589bf70c"
+dependencies = [
+ "annotate-snippets",
+]
+
 [[package]]
 name = "chrono"
 version = "0.4.21"
@@ -363,27 +390,31 @@ dependencies = [
 ]
 
 [[package]]
-name = "clap"
-version = "3.2.16"
+name = "chunked_transfer"
+version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a3dbbb6653e7c55cc8595ad3e1f7be8f32aba4eb7ff7f0fd1163d4f3d137c0a9"
+checksum = "fff857943da45f546682664a79488be82e69e43c1a7a2307679ab9afb3a66d2e"
+
+[[package]]
+name = "clap"
+version = "4.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dd03107d0f87139c1774a15f3db2165b0652b5460c58c27e561f89c20c599eaf"
 dependencies = [
  "atty",
  "bitflags",
  "clap_derive",
  "clap_lex",
- "indexmap",
  "once_cell",
  "strsim",
  "termcolor",
- "textwrap",
 ]
 
 [[package]]
 name = "clap_derive"
-version = "3.2.15"
+version = "4.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9ba52acd3b0a5c33aeada5cdaa3267cdc7c594a98731d4268cdc1532f4264cb4"
+checksum = "ca689d7434ce44517a12a89456b2be4d1ea1cafcd8f581978c03d45f5a5c12a7"
 dependencies = [
  "heck",
  "proc-macro-error",
@@ -394,9 +425,9 @@ dependencies = [
 
 [[package]]
 name = "clap_lex"
-version = "0.2.4"
+version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2850f2f5a82cbf437dd5af4d49848fbdfc27c157c3d010345776f952765261c5"
+checksum = "0d4198f73e42b4936b35b5bb248d81d2b595ecb170da0bac7655c54eedfa8da8"
 dependencies = [
  "os_str_bytes",
 ]
@@ -440,6 +471,19 @@ dependencies = [
  "cache-padded",
 ]
 
+[[package]]
+name = "console"
+version = "0.15.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "89eab4d20ce20cea182308bca13088fecea9c05f6776cf287205d41a0ed3c847"
+dependencies = [
+ "encode_unicode",
+ "libc",
+ "once_cell",
+ "terminal_size",
+ "winapi 0.3.9",
+]
+
 [[package]]
 name = "core-foundation"
 version = "0.9.3"
@@ -465,6 +509,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "crc32fast"
+version = "1.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b540bd8bc810d3885c6ea91e2018302f68baba2129ab3e88f32389ee9370880d"
+dependencies = [
+ "cfg-if 1.0.0",
+]
+
 [[package]]
 name = "crossbeam-channel"
 version = "0.5.6"
@@ -550,6 +603,15 @@ dependencies = [
  "generic-array 0.14.6",
 ]
 
+[[package]]
+name = "directories"
+version = "4.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f51c5d4ddabd36886dd3e1438cb358cdcb0d7c499cb99cb4ac2e38e18b5cb210"
+dependencies = [
+ "dirs-sys",
+]
+
 [[package]]
 name = "dirs"
 version = "2.0.2"
@@ -616,6 +678,12 @@ dependencies = [
  "log",
 ]
 
+[[package]]
+name = "encode_unicode"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a357d28ed41a50f9c765dbfe56cbc04a64e53e5fc58ba79fbc34c10ef3df831f"
+
 [[package]]
 name = "event-listener"
 version = "2.5.3"
@@ -664,12 +732,32 @@ version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0ce7134b9999ecaf8bcd65542e436736ef32ddca1b3e06094cb6ec5755203b80"
 
+[[package]]
+name = "flate2"
+version = "1.0.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f82b0f4c27ad9f8bfd1f3208d882da2b09c301bc1c828fd3a00d0216d2fbbff6"
+dependencies = [
+ "crc32fast",
+ "miniz_oxide",
+]
+
 [[package]]
 name = "fnv"
 version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3f9eec918d3f24069decb9af1554cad7c880e2da24a9afd88aca000531ab82c1"
 
+[[package]]
+name = "form_urlencoded"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5fc25a87fa4fd2094bffb06925852034d90a17f0d1e05197d4956d3555752191"
+dependencies = [
+ "matches",
+ "percent-encoding",
+]
+
 [[package]]
 name = "fsevent"
 version = "0.4.0"
@@ -850,6 +938,12 @@ dependencies = [
  "wasi 0.11.0+wasi-snapshot-preview1",
 ]
 
+[[package]]
+name = "glob"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9b919933a397b79c37e33b77bb2aa3dc8eb6e165ad809e58ff75bc7db2e34574"
+
 [[package]]
 name = "gloo-timers"
 version = "0.2.4"
@@ -908,6 +1002,17 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
+[[package]]
+name = "idna"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "418a0a6fab821475f634efe3ccc45c013f742efe03d853e8d3355d5cb850ecf8"
+dependencies = [
+ "matches",
+ "unicode-bidi",
+ "unicode-normalization",
+]
+
 [[package]]
 name = "indexmap"
 version = "1.9.1"
@@ -918,12 +1023,6 @@ dependencies = [
  "hashbrown",
 ]
 
-[[package]]
-name = "indoc"
-version = "1.0.7"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "adab1eaa3408fb7f0c777a73e7465fd5656136fc93b670eb6df3c88c2c1344e3"
-
 [[package]]
 name = "inotify"
 version = "0.7.1"
@@ -944,6 +1043,20 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "insta"
+version = "1.19.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fc61e98be01e89296f3343a878e9f8ca75a494cb5aaf29df65ef55734aeb85f5"
+dependencies = [
+ "console",
+ "linked-hash-map",
+ "once_cell",
+ "serde",
+ "similar",
+ "yaml-rust",
+]
+
 [[package]]
 name = "instant"
 version = "0.1.12"
@@ -964,9 +1077,9 @@ dependencies = [
 
 [[package]]
 name = "itertools"
-version = "0.10.3"
+version = "0.10.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a9a9d19fa1e79b6215ff29b9d6880b706147f16e9b1dbb1e4e5947b5b02bc5e3"
+checksum = "b0fd2260e829bddf4cb6ea802289de2f86d6a7a690192fbe91b3f46e0f2c8473"
 dependencies = [
  "either",
 ]
@@ -1055,6 +1168,36 @@ version = "0.2.127"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "505e71a4706fa491e9b1b55f51b95d4037d0821ee40131190475f692b35b009b"
 
+[[package]]
+name = "libcst"
+version = "0.1.0"
+source = "git+https://github.com/charliermarsh/LibCST?rev=32a044c127668df44582f85699358e67803b0d73#32a044c127668df44582f85699358e67803b0d73"
+dependencies = [
+ "chic",
+ "itertools",
+ "libcst_derive",
+ "once_cell",
+ "paste",
+ "peg",
+ "regex",
+ "thiserror",
+]
+
+[[package]]
+name = "libcst_derive"
+version = "0.1.0"
+source = "git+https://github.com/charliermarsh/LibCST?rev=32a044c127668df44582f85699358e67803b0d73#32a044c127668df44582f85699358e67803b0d73"
+dependencies = [
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "linked-hash-map"
+version = "0.5.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0717cef1bc8b636c6e1c1bbdefc09e6322da8a9321966e8928ef80d20f7f770f"
+
 [[package]]
 name = "lock_api"
 version = "0.4.7"
@@ -1084,6 +1227,12 @@ dependencies = [
  "twox-hash",
 ]
 
+[[package]]
+name = "matches"
+version = "0.1.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a3e378b66a060d48947b590737b30a1be76706c8dd7b8ba0f2fe3989c68a853f"
+
 [[package]]
 name = "memchr"
 version = "2.5.0"
@@ -1108,6 +1257,15 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "miniz_oxide"
+version = "0.5.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6f5c75688da582b8ffc1f1799e9db273f32133c49e048f614d22ec3256773ccc"
+dependencies = [
+ "adler",
+]
+
 [[package]]
 name = "mio"
 version = "0.6.23"
@@ -1260,9 +1418,9 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.13.0"
+version = "1.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "18a6dbe30758c9f83eb00cbea4ac95966305f5a7772f3f42ebfc7fc7eddbd8e1"
+checksum = "e82dad04139b71a90c080c8463fe0dc7902db5192d939bd0950f074d014339e1"
 
 [[package]]
 name = "opaque-debug"
@@ -1311,6 +1469,63 @@ dependencies = [
  "windows-sys",
 ]
 
+[[package]]
+name = "paste"
+version = "1.0.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b1de2e551fb905ac83f73f7aedf2f0cb4a0da7e35efa24a202a936269f1f18e1"
+
+[[package]]
+name = "path-absolutize"
+version = "3.0.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d3de4b40bd9736640f14c438304c09538159802388febb02c8abaae0846c1f13"
+dependencies = [
+ "path-dedot",
+]
+
+[[package]]
+name = "path-dedot"
+version = "3.0.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d611d5291372b3738a34ebf0d1f849e58b1dcc1101032f76a346eaa1f8ddbb5b"
+dependencies = [
+ "once_cell",
+]
+
+[[package]]
+name = "peg"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a07f2cafdc3babeebc087e499118343442b742cc7c31b4d054682cc598508554"
+dependencies = [
+ "peg-macros",
+ "peg-runtime",
+]
+
+[[package]]
+name = "peg-macros"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4a90084dc05cf0428428e3d12399f39faad19b0909f64fb9170c9fdd6d9cd49b"
+dependencies = [
+ "peg-runtime",
+ "proc-macro2",
+ "quote",
+]
+
+[[package]]
+name = "peg-runtime"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9fa00462b37ead6d11a82c9d568b26682d78e0477dc02d1966c013af80969739"
+
+[[package]]
+name = "percent-encoding"
+version = "2.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d4fd5641d01c8f18a23da7b6fe29298ff4b55afcccdf78973b24cf3175fee32e"
+
 [[package]]
 name = "petgraph"
 version = "0.6.2"
@@ -1473,66 +1688,6 @@ dependencies = [
  "unicode-ident",
 ]
 
-[[package]]
-name = "pyo3"
-version = "0.17.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "12f72538a0230791398a0986a6518ebd88abc3fded89007b506ed072acc831e1"
-dependencies = [
- "cfg-if 1.0.0",
- "indoc",
- "libc",
- "memoffset",
- "parking_lot",
- "pyo3-build-config",
- "pyo3-ffi",
- "pyo3-macros",
- "unindent",
-]
-
-[[package]]
-name = "pyo3-build-config"
-version = "0.17.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fc4cf18c20f4f09995f3554e6bcf9b09bd5e4d6b67c562fdfaafa644526ba479"
-dependencies = [
- "once_cell",
- "target-lexicon",
-]
-
-[[package]]
-name = "pyo3-ffi"
-version = "0.17.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a41877f28d8ebd600b6aa21a17b40c3b0fc4dfe73a27b6e81ab3d895e401b0e9"
-dependencies = [
- "libc",
- "pyo3-build-config",
-]
-
-[[package]]
-name = "pyo3-macros"
-version = "0.17.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2e81c8d4bcc2f216dc1b665412df35e46d12ee8d3d046b381aad05f1fcf30547"
-dependencies = [
- "proc-macro2",
- "pyo3-macros-backend",
- "quote",
- "syn",
-]
-
-[[package]]
-name = "pyo3-macros-backend"
-version = "0.17.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "85752a767ee19399a78272cc2ab625cd7d373b2e112b4b13db28de71fa892784"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn",
-]
-
 [[package]]
 name = "quote"
 version = "1.0.21"
@@ -1699,9 +1854,24 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
+[[package]]
+name = "ring"
+version = "0.16.20"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3053cf52e236a3ed746dfc745aa9cacf1b791d846bdaf412f60a8d7d6e17c8fc"
+dependencies = [
+ "cc",
+ "libc",
+ "once_cell",
+ "spin",
+ "untrusted",
+ "web-sys",
+ "winapi 0.3.9",
+]
+
 [[package]]
 name = "ruff"
-version = "0.0.18"
+version = "0.0.50"
 dependencies = [
  "anyhow",
  "bincode",
@@ -1714,22 +1884,40 @@ dependencies = [
  "dirs 4.0.0",
  "fern",
  "filetime",
+ "glob",
+ "insta",
+ "itertools",
+ "libcst",
  "log",
  "notify",
- "pyo3",
+ "once_cell",
+ "path-absolutize",
  "rayon",
  "regex",
  "rustpython-parser",
  "serde",
  "serde_json",
  "toml",
+ "update-informer",
  "walkdir",
 ]
 
+[[package]]
+name = "rustls"
+version = "0.20.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5aab8ee6c7097ed6057f43c187a62418d0c05a4bd5f18b3571db50ee0f9ce033"
+dependencies = [
+ "log",
+ "ring",
+ "sct",
+ "webpki",
+]
+
 [[package]]
 name = "rustpython-ast"
 version = "0.1.0"
-source = "git+https://github.com/RustPython/RustPython.git?rev=7a688e0b6c2904f286acac1e4af3f1628dd38589#7a688e0b6c2904f286acac1e4af3f1628dd38589"
+source = "git+https://github.com/charliermarsh/RustPython.git?rev=4f457893efc381ad5c432576b24bcc7e4a08c641#4f457893efc381ad5c432576b24bcc7e4a08c641"
 dependencies = [
  "num-bigint",
  "rustpython-compiler-core",
@@ -1738,7 +1926,7 @@ dependencies = [
 [[package]]
 name = "rustpython-compiler-core"
 version = "0.1.2"
-source = "git+https://github.com/RustPython/RustPython.git?rev=7a688e0b6c2904f286acac1e4af3f1628dd38589#7a688e0b6c2904f286acac1e4af3f1628dd38589"
+source = "git+https://github.com/charliermarsh/RustPython.git?rev=4f457893efc381ad5c432576b24bcc7e4a08c641#4f457893efc381ad5c432576b24bcc7e4a08c641"
 dependencies = [
  "bincode",
  "bitflags",
@@ -1755,7 +1943,7 @@ dependencies = [
 [[package]]
 name = "rustpython-parser"
 version = "0.1.2"
-source = "git+https://github.com/RustPython/RustPython.git?rev=7a688e0b6c2904f286acac1e4af3f1628dd38589#7a688e0b6c2904f286acac1e4af3f1628dd38589"
+source = "git+https://github.com/charliermarsh/RustPython.git?rev=4f457893efc381ad5c432576b24bcc7e4a08c641#4f457893efc381ad5c432576b24bcc7e4a08c641"
 dependencies = [
  "ahash",
  "anyhow",
@@ -1803,6 +1991,22 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
 
+[[package]]
+name = "sct"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d53dcdb7c9f8158937a7981b48accfd39a43af418591a5d008c7b22b5e1b7ca4"
+dependencies = [
+ "ring",
+ "untrusted",
+]
+
+[[package]]
+name = "semver"
+version = "1.0.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93f6841e709003d68bb2deee8c343572bf446003ec20a583e76f7b15cebf3711"
+
 [[package]]
 name = "serde"
 version = "1.0.143"
@@ -1903,6 +2107,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "similar"
+version = "2.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "62ac7f900db32bf3fd12e0117dd3dc4da74bc52ebaac97f39668446d89694803"
+
 [[package]]
 name = "siphasher"
 version = "0.3.10"
@@ -1934,13 +2144,19 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
+[[package]]
+name = "spin"
+version = "0.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"
+
 [[package]]
 name = "ssri"
 version = "7.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a9cec0d388f39fbe79d7aa600e8d38053bf97b1bc8d350da7c0ba800d0f423f2"
 dependencies = [
- "base64",
+ "base64 0.10.1",
  "digest 0.8.1",
  "hex 0.3.2",
  "serde",
@@ -1985,12 +2201,6 @@ dependencies = [
  "unicode-ident",
 ]
 
-[[package]]
-name = "target-lexicon"
-version = "0.12.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c02424087780c9b71cc96799eaeddff35af2bc513278cda5c99fc1f5d026d3c1"
-
 [[package]]
 name = "tempfile"
 version = "3.3.0"
@@ -2025,6 +2235,16 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "terminal_size"
+version = "0.1.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "633c1a546cee861a1a6d0dc69ebeca693bf4296661ba7852b9d21d159e0506df"
+dependencies = [
+ "libc",
+ "winapi 0.3.9",
+]
+
 [[package]]
 name = "terminfo"
 version = "0.7.3"
@@ -2038,26 +2258,20 @@ dependencies = [
  "phf_codegen 0.8.0",
 ]
 
-[[package]]
-name = "textwrap"
-version = "0.15.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b1141d4d61095b28419e22cb0bbf02755f5e54e0526f97f1e3d1d160e60885fb"
-
 [[package]]
 name = "thiserror"
-version = "1.0.32"
+version = "1.0.37"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f5f6586b7f764adc0231f4c79be7b920e766bb2f3e51b3661cdb263828f19994"
+checksum = "10deb33631e3c9018b9baf9dcbbc4f737320d2b576bac10f6aefa048fa407e3e"
 dependencies = [
  "thiserror-impl",
 ]
 
 [[package]]
 name = "thiserror-impl"
-version = "1.0.32"
+version = "1.0.37"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "12bafc5b54507e0149cdf1b145a5d80ab80a90bcd9275df43d4fff68460f6c21"
+checksum = "982d17546b47146b28f7c22e3d08465f6b8903d0ea13c1660d9d84a6e7adcdbb"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -2084,6 +2298,21 @@ dependencies = [
  "crunchy",
 ]
 
+[[package]]
+name = "tinyvec"
+version = "1.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "87cc5ceb3875bb20c2890005a4e226a4651264a5c75edb2421b52861a0a0cb50"
+dependencies = [
+ "tinyvec_macros",
+]
+
+[[package]]
+name = "tinyvec_macros"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cda74da7e1a664f795bb1f8a87ec406fb89a02522cf6e50620d016add6dbbf5c"
+
 [[package]]
 name = "toml"
 version = "0.5.9"
@@ -2161,12 +2390,27 @@ dependencies = [
  "unic-common",
 ]
 
+[[package]]
+name = "unicode-bidi"
+version = "0.3.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "099b7128301d285f79ddd55b9a83d5e6b9e97c92e0ea0daebee7263e932de992"
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c4f5b37a154999a8f3f98cc23a628d850e154479cd94decf3414696e12e31aaf"
 
+[[package]]
+name = "unicode-normalization"
+version = "0.1.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "854cbdc4f7bc6ae19c820d44abdc3277ac3e1b2b93db20a636825d9322fb60e6"
+dependencies = [
+ "tinyvec",
+]
+
 [[package]]
 name = "unicode-xid"
 version = "0.2.3"
@@ -2180,10 +2424,54 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "eec8e807a365e5c972debc47b8f06d361b37b94cfd18d48f7adc715fb86404dd"
 
 [[package]]
-name = "unindent"
-version = "0.1.10"
+name = "untrusted"
+version = "0.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "58ee9362deb4a96cef4d437d1ad49cffc9b9e92d202b6995674e928ce684f112"
+checksum = "a156c684c91ea7d62626509bce3cb4e1d9ed5c4d978f7b4352658f96a4c26b4a"
+
+[[package]]
+name = "update-informer"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f154aee470c0882ea0f3b1cc2a46c5f4d24f282655f7b0cec065614fe24c447f"
+dependencies = [
+ "directories",
+ "semver",
+ "serde",
+ "serde_json",
+ "ureq",
+]
+
+[[package]]
+name = "ureq"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b97acb4c28a254fd7a4aeec976c46a7fa404eac4d7c134b30c75144846d7cb8f"
+dependencies = [
+ "base64 0.13.0",
+ "chunked_transfer",
+ "flate2",
+ "log",
+ "once_cell",
+ "rustls",
+ "serde",
+ "serde_json",
+ "url",
+ "webpki",
+ "webpki-roots",
+]
+
+[[package]]
+name = "url"
+version = "2.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a507c383b2d33b5fc35d1861e77e6b383d158b2da5e14fe51b83dfedf6fd578c"
+dependencies = [
+ "form_urlencoded",
+ "idna",
+ "matches",
+ "percent-encoding",
+]
 
 [[package]]
 name = "value-bag"
@@ -2312,6 +2600,25 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "webpki"
+version = "0.22.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f095d78192e208183081cc07bc5515ef55216397af48b873e5edcd72637fa1bd"
+dependencies = [
+ "ring",
+ "untrusted",
+]
+
+[[package]]
+name = "webpki-roots"
+version = "0.22.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f1c760f0d366a6c24a02ed7816e23e691f5d92291f94d15e836006fd11b04daf"
+dependencies = [
+ "webpki",
+]
+
 [[package]]
 name = "wepoll-ffi"
 version = "0.1.2"
@@ -2427,3 +2734,12 @@ dependencies = [
  "winapi 0.2.8",
  "winapi-build",
 ]
+
+[[package]]
+name = "yaml-rust"
+version = "0.4.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "56c1936c4cc7a1c9ab21a1ebb602eb942ba868cbd44a99cb7cdc5892335e1c85"
+dependencies = [
+ "linked-hash-map",
+]

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ruff"
-version = "0.0.18"
+version = "0.0.50"
 edition = "2021"
 
 [lib]
@@ -11,25 +11,44 @@ anyhow = { version = "1.0.60" }
 bincode = { version = "1.3.3" }
 cacache = { version = "10.0.1" }
 chrono = { version = "0.4.21" }
-clap = { version = "3.2.16", features = ["derive"] }
+clap = { version = "4.0.1", features = ["derive"] }
 clearscreen = { version = "1.0.10" }
 colored = { version = "2.0.0" }
 common-path = { version = "1.0.0" }
 dirs = { version = "4.0.0" }
 fern = { version = "0.6.1" }
 filetime = { version = "0.2.17" }
+glob = { version = "0.3.0" }
+itertools = { version = "0.10.5" }
+libcst = { git = "https://github.com/charliermarsh/LibCST", rev = "32a044c127668df44582f85699358e67803b0d73" }
 log = { version = "0.4.17" }
 notify = { version = "4.0.17" }
-pyo3 = { version = "0.17.1", features = ["auto-initialize"] }
+once_cell = { version = "1.13.1" }
+path-absolutize = { version = "3.0.13", features = ["once_cell_cache"] }
 rayon = { version = "1.5.3" }
 regex = { version = "1.6.0" }
-rustpython-parser = { features = ["lalrpop"], git = "https://github.com/RustPython/RustPython.git", rev = "7a688e0b6c2904f286acac1e4af3f1628dd38589" }
+rustpython-parser = { features = ["lalrpop"], git = "https://github.com/charliermarsh/RustPython.git", rev = "4f457893efc381ad5c432576b24bcc7e4a08c641" }
 serde = { version = "1.0.143", features = ["derive"] }
 serde_json = { version = "1.0.83" }
 toml = { version = "0.5.9" }
+update-informer = { version = "0.5.0", default_features = false, features = ["pypi"], optional = true }
 walkdir = { version = "2.3.2" }
 
-[profile.release]
-lto = true
-panic = "abort"
+[dev-dependencies]
+insta = { version = "1.19.1", features = ["yaml"] }
 
+[features]
+default = ["update-informer"]
+update-informer = ["dep:update-informer"]
+
+[profile.release]
+panic = "abort"
+lto = "thin"
+codegen-units = 1
+opt-level = 3
+
+[profile.dev.package.insta]
+opt-level = 3
+
+[profile.dev.package.similar]
+opt-level = 3

README.md

@@ -1,29 +1,30 @@
 # ruff
 
+[![image](https://img.shields.io/pypi/v/ruff.svg)](https://pypi.python.org/pypi/ruff)
+[![image](https://img.shields.io/pypi/l/ruff.svg)](https://pypi.python.org/pypi/ruff)
+[![image](https://img.shields.io/pypi/pyversions/ruff.svg)](https://pypi.python.org/pypi/ruff)
 [![Actions status](https://github.com/charliermarsh/ruff/workflows/CI/badge.svg)](https://github.com/charliermarsh/ruff/actions)
-[![PyPI version](https://badge.fury.io/py/ruff.svg)](https://badge.fury.io/py/ruff)
 
 An extremely fast Python linter, written in Rust.
 
 <p align="center">
-  <img alt="Bar chart with benchmark results" src="https://user-images.githubusercontent.com/1309177/187221271-9db38ced-c622-406a-abf3-dec27ebc1b08.svg">
+  <img alt="Bar chart with benchmark results" src="https://user-images.githubusercontent.com/1309177/187504482-6d9df992-a81d-4e86-9f6a-d958741c8182.svg">
 </p>
 
 <p align="center">
   <i>Linting the CPython codebase from scratch.</i>
 </p>
 
-Major features:
+- ⚡️ 10-100x faster than existing linters
+- 🐍 Installable via `pip`
+- 🤝 Python 3.10 compatibility
+- 🛠️ `pyproject.toml` support
+- 📦 [ESLint](https://eslint.org/docs/latest/user-guide/command-line-interface#caching)-inspired cache support
+- 🔧 [ESLint](https://eslint.org/docs/latest/user-guide/command-line-interface#--fix)-inspired `--fix` support
+- 👀 [TypeScript](https://www.typescriptlang.org/docs/handbook/configuring-watch.html)-inspired `--watch` support
+- ⚖️ [Near-complete parity](#Parity-with-Flake8) with the built-in Flake8 rule set
 
-- 10-100x faster than your current linter.
-- Installable via `pip`.
-- Python 3.10 compatibility.
-- [ESLint](https://eslint.org/docs/latest/user-guide/command-line-interface#caching)-inspired cache semantics.
-- [TypeScript](https://www.typescriptlang.org/docs/handbook/configuring-watch.html)-inspired `--watch` semantics.
-- `pyproject.toml` support.
-
-_ruff is a proof-of-concept and not yet intended for production use. It supports only a small subset
-of the Flake8 rules, and may crash on your codebase._
+Read the [launch blog post](https://notes.crmarsh.com/python-tooling-could-be-much-much-faster).
 
 ## Installation and usage
 
@@ -35,11 +36,6 @@ Available as [ruff](https://pypi.org/project/ruff/) on PyPI:
 pip install ruff
 ```
 
-For now, wheels are only available for macOS (on Python 3.7, 3.8, 3.9, and 3.10). If you're using a
-different operating system or Python version, you'll need to install the [Rust toolchain](https://www.rust-lang.org/tools/install)
-prior to running `pip install ruff`. (This is an effort limitation on my part, not a technical
-limitation.)
-
 ### Usage
 
 To run ruff, try any of the following:
@@ -56,6 +52,16 @@ You can run ruff in `--watch` mode to automatically re-run on-change:
 ruff path/to/code/ --watch
 ```
 
+ruff also works with [pre-commit](https://pre-commit.com):
+
+```yaml
+repos:
+  - repo: https://github.com/charliermarsh/ruff-pre-commit
+    rev: v0.0.48
+    hooks:
+      - id: lint
+```
+
 ## Configuration
 
 ruff is configurable both via `pyproject.toml` and the command line.
@@ -74,31 +80,230 @@ select = [
 Alternatively, on the command-line:
 
 ```shell
-ruff path/to/code/ --select F401 F403
+ruff path/to/code/ --select F401 --select F403
 ```
 
 See `ruff --help` for more:
 
 ```shell
-ruff
-A Python linter written in Rust
+ruff: An extremely fast Python linter.
 
-USAGE:
-    ruff [OPTIONS] <FILES>...
+Usage: ruff [OPTIONS] <FILES>...
 
-ARGS:
-    <FILES>...
+Arguments:
+  <FILES>...
 
-OPTIONS:
-    -e, --exit-zero             Exit with status code "0", even upon detecting errors
-    -h, --help                  Print help information
-        --ignore <IGNORE>...    Comma-separated list of error codes to ignore
-    -n, --no-cache              Disable cache reads
-    -q, --quiet                 Disable all logging (but still exit with status code "1" upon
-                                detecting errors)
-        --select <SELECT>...    Comma-separated list of error codes to enable
-    -v, --verbose               Enable verbose logging
-    -w, --watch                 Run in watch mode by re-running whenever files change
+Options:
+  -v, --verbose
+          Enable verbose logging
+  -q, --quiet
+          Disable all logging (but still exit with status code "1" upon detecting errors)
+  -e, --exit-zero
+          Exit with status code "0", even upon detecting errors
+  -w, --watch
+          Run in watch mode by re-running whenever files change
+  -f, --fix
+          Attempt to automatically fix lint errors
+  -n, --no-cache
+          Disable cache reads
+      --select <SELECT>
+          List of error codes to enable
+      --extend-select <EXTEND_SELECT>
+          Like --select, but adds additional error codes on top of the selected ones
+      --ignore <IGNORE>
+          List of error codes to ignore
+      --extend-ignore <EXTEND_IGNORE>
+          Like --ignore, but adds additional error codes on top of the ignored ones
+      --exclude <EXCLUDE>
+          List of paths, used to exclude files and/or directories from checks
+      --extend-exclude <EXTEND_EXCLUDE>
+          Like --exclude, but adds additional files and directories on top of the excluded ones
+      --per-file-ignores <PER_FILE_IGNORES>
+          List of mappings from file pattern to code to exclude
+      --format <FORMAT>
+          Output serialization format for error messages [default: text] [possible values: text, json]
+      --show-files
+          See the files ruff will be run against with the current settings
+      --show-settings
+          See ruff's settings
+      --add-noqa
+          Enable automatic additions of noqa directives to failing lines
+      --dummy-variable-rgx <DUMMY_VARIABLE_RGX>
+          Regular expression matching the name of dummy variables
+  -h, --help
+          Print help information
+  -V, --version
+          Print version information
+```
+
+### Excluding files
+
+Exclusions are based on globs, and can be either:
+
+- Single-path patterns, like `.mypy_cache` (to exclude any directory named `.mypy_cache` in the
+  tree), `foo.py` (to exclude any file named `foo.py`), or `foo_*.py` (to exclude any file matching
+  `foo_*.py` ).
+- Relative patterns, like `directory/foo.py` (to exclude that specific file) or `directory/*.py`
+  (to exclude any Python files in `directory`). Note that these paths are relative to the
+  project root (e.g., the directory containing your `pyproject.toml`).
+
+### Ignoring errors
+
+To omit a lint check entirely, add it to the "ignore" list via `--ignore` or `--extend-ignore`,
+either  on the command-line or in your `project.toml` file.
+
+To ignore an error in-line, ruff uses a `noqa` system similar to [Flake8](https://flake8.pycqa.org/en/3.1.1/user/ignoring-errors.html).
+To ignore an individual error, add `# noqa: {code}` to the end of the line, like so:
+
+```python
+# Ignore F841.
+x = 1  # noqa: F841
+
+# Ignore E741 and F841.
+i = 1  # noqa: E741, F841
+
+# Ignore _all_ errors.
+x = 1  # noqa
+```
+
+Note that, for multi-line strings, the `noqa` directive should come at the end of the string, and
+will apply to the entire body, like so:
+
+```python
+"""Lorem ipsum dolor sit amet.
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
+"""  # noqa: E501
+```
+
+ruff supports several (experimental) workflows to aid in `noqa` management.
+
+First, ruff provides a special error code, `M001`, to enforce that your `noqa` directives are
+"valid", in that the errors they _say_ they ignore are actually being triggered on that line (and
+thus suppressed). **You can run `ruff /path/to/file.py --extend-select M001` to flag unused `noqa`
+directives.**
+
+Second, ruff can _automatically remove_ unused `noqa` directives via its autofix functionality.
+**You can run `ruff /path/to/file.py --extend-select M001 --fix` to automatically remove unused
+`noqa` directives.**
+
+Third, ruff can _automatically add_ `noqa` directives to all failing lines. This is useful when
+migrating a new codebase to ruff. **You can run `ruff /path/to/file.py --add-noqa` to automatically
+add `noqa` directives to all failing lines, with the appropriate error codes.**
+
+### Compatibility with Black
+
+ruff is compatible with [Black](https://github.com/psf/black) out-of-the-box, as long as
+the `line-length` setting is consistent between the two.
+
+As a project, ruff is designed to be used alongside Black and, as such, will defer implementing
+stylistic lint rules that are obviated by autoformatting.
+
+### Parity with Flake8
+
+ruff's goal is to achieve feature-parity with Flake8 when used (1) without plugins, (2) alongside
+Black, and (3) on Python 3 code.
+
+**Under those conditions, ruff implements 44 out of 60 rules.** (ruff is missing: 14 rules related
+to string `.format` calls, 1 rule related to docstring parsing, and 1 rule related to redefined
+variables.)
+
+Beyond rule-set parity, ruff suffers from the following limitations vis-à-vis Flake8:
+
+1. Flake8 has a plugin architecture and supports writing custom lint rules.
+2. ruff does not yet support a few Python 3.9 and 3.10 language features, including structural
+   pattern matching and parenthesized context managers.
+
+## Rules
+
+| Code | Name | Message |
+| ---- | ----- | ------- |
+| E402 | ModuleImportNotAtTopOfFile | Module level import not at top of file |
+| E501 | LineTooLong | Line too long (89 > 88 characters) |
+| E711 | NoneComparison | Comparison to `None` should be `cond is None` |
+| E712 | TrueFalseComparison | Comparison to `True` should be `cond is True` |
+| E713 | NotInTest | Test for membership should be `not in` |
+| E714 | NotIsTest | Test for object identity should be `is not` |
+| E721 | TypeComparison | do not compare types, use `isinstance()` |
+| E722 | DoNotUseBareExcept | Do not use bare `except` |
+| E731 | DoNotAssignLambda | Do not assign a lambda expression, use a def |
+| E741 | AmbiguousVariableName | ambiguous variable name '...' |
+| E742 | AmbiguousClassName | ambiguous class name '...' |
+| E743 | AmbiguousFunctionName | ambiguous function name '...' |
+| E902 | IOError | ... |
+| E999 | SyntaxError | SyntaxError: ... |
+| F401 | UnusedImport | `...` imported but unused |
+| F402 | ImportShadowedByLoopVar | import '...' from line 1 shadowed by loop variable |
+| F403 | ImportStarUsed | `from ... import *` used; unable to detect undefined names |
+| F404 | LateFutureImport | from __future__ imports must occur at the beginning of the file |
+| F405 | ImportStarUsage | '...' may be undefined, or defined from star imports: ... |
+| F406 | ImportStarNotPermitted | `from ... import *` only allowed at module level |
+| F407 | FutureFeatureNotDefined | future feature '...' is not defined |
+| F541 | FStringMissingPlaceholders | f-string without any placeholders |
+| F601 | MultiValueRepeatedKeyLiteral | Dictionary key literal repeated |
+| F602 | MultiValueRepeatedKeyVariable | Dictionary key `...` repeated |
+| F621 | TooManyExpressionsInStarredAssignment | too many expressions in star-unpacking assignment |
+| F622 | TwoStarredExpressions | two starred expressions in assignment |
+| F631 | AssertTuple | Assert test is a non-empty tuple, which is always `True` |
+| F632 | IsLiteral | use ==/!= to compare constant literals |
+| F633 | InvalidPrintSyntax | use of >> is invalid with print function |
+| F634 | IfTuple | If test is a tuple, which is always `True` |
+| F701 | BreakOutsideLoop | `break` outside loop |
+| F702 | ContinueOutsideLoop | `continue` not properly in loop |
+| F704 | YieldOutsideFunction | a `yield` or `yield from` statement outside of a function/method |
+| F706 | ReturnOutsideFunction | a `return` statement outside of a function/method |
+| F707 | DefaultExceptNotLast | an `except:` block as not the last exception handler |
+| F722 | ForwardAnnotationSyntaxError | syntax error in forward annotation '...' |
+| F821 | UndefinedName | Undefined name `...` |
+| F822 | UndefinedExport | Undefined name `...` in `__all__` |
+| F823 | UndefinedLocal | Local variable `...` referenced before assignment |
+| F831 | DuplicateArgumentName | Duplicate argument name in function definition |
+| F841 | UnusedVariable | Local variable `...` is assigned to but never used |
+| F901 | RaiseNotImplemented | `raise NotImplemented` should be `raise NotImplementedError` |
+| A001 | BuiltinVariableShadowing | Variable `...` is shadowing a python builtin |
+| A002 | BuiltinArgumentShadowing | Argument `...` is shadowing a python builtin |
+| A003 | BuiltinAttributeShadowing | class attribute `...` is shadowing a python builtin |
+| SPR001 | SuperCallWithParameters | Use `super()` instead of `super(__class__, self)` |
+| R001 | UselessObjectInheritance | Class `...` inherits from object |
+| R002 | NoAssertEquals | `assertEquals` is deprecated, use `assertEqual` instead |
+| M001 | UnusedNOQA | Unused `noqa` directive |
+
+## Integrations
+
+### PyCharm
+
+ruff can be installed as an [External Tool](https://www.jetbrains.com/help/pycharm/configuring-third-party-tools.html)
+in PyCharm. Open the Preferences pane, then navigate to "Tools", then "External Tools". From there,
+add a new tool with the following configuration:
+
+![Install ruff as an External Tool](https://user-images.githubusercontent.com/1309177/193155720-336e43f0-1a8d-46b4-bc12-e60f9ae01f7e.png)
+
+ruff should then appear as a runnable action:
+
+![ruff as a runnable action](https://user-images.githubusercontent.com/1309177/193156026-732b0aaf-3dd9-4549-9b4d-2de6d2168a33.png)
+
+### GitHub Actions
+
+GitHub Actions has everything you need to run ruff out-of-the-box:
+
+```yaml
+name: CI
+on: push
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Python
+        uses: actions/setup-python@v2
+        with:
+          python-version: "3.10"
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install ruff
+      - name: Run ruff
+        run: ruff .
 ```
 
 ## Development
@@ -109,7 +314,7 @@ for development.
 Assuming you have `cargo` installed, you can run:
 
 ```shell
-cargo run resources/test/src
+cargo run resources/test/fixtures
 cargo fmt
 cargo clippy
 cargo test
@@ -119,18 +324,7 @@ cargo test
 
 ruff is distributed on [PyPI](https://pypi.org/project/ruff/), and published via [`maturin`](https://github.com/PyO3/maturin).
 
-For now, releases are cut and published manually:
-
-```shell
-for TARGET in x86_64-apple-darwin aarch64-apple-darwin
-do
-  maturin publish --username crmarsh --skip-existing --target ${TARGET} -i \
-    /usr/local/opt/python@3.7/libexec/bin/python \
-    /usr/local/opt/python@3.8/libexec/bin/python \
-    /usr/local/opt/python@3.9/libexec/bin/python \
-    /usr/local/opt/python@3.10/libexec/bin/python
-done
-```
+See: `.github/workflows/release.yaml`.
 
 ## Benchmarking
 
@@ -144,49 +338,25 @@ git clone --branch 3.10 https://github.com/python/cpython.git resources/test/cpy
 Add this `pyproject.toml` to the CPython directory:
 
 ```toml
-[tool.linter]
+[tool.ruff]
 line-length = 88
-exclude = [
-    "Lib/ctypes/test/test_numbers.py",
-    "Lib/dataclasses.py",
+extend-exclude = [
     "Lib/lib2to3/tests/data/bom.py",
     "Lib/lib2to3/tests/data/crlf.py",
     "Lib/lib2to3/tests/data/different_encoding.py",
     "Lib/lib2to3/tests/data/false_encoding.py",
     "Lib/lib2to3/tests/data/py2_test_grammar.py",
-    "Lib/sqlite3/test/factory.py",
-    "Lib/sqlite3/test/hooks.py",
-    "Lib/sqlite3/test/regression.py",
-    "Lib/sqlite3/test/transactions.py",
-    "Lib/sqlite3/test/types.py",
     "Lib/test/bad_coding2.py",
     "Lib/test/badsyntax_3131.py",
     "Lib/test/badsyntax_pep3120.py",
     "Lib/test/encoded_modules/module_iso_8859_1.py",
     "Lib/test/encoded_modules/module_koi8_r.py",
-    "Lib/test/sortperf.py",
-    "Lib/test/test_email/torture_test.py",
     "Lib/test/test_fstring.py",
-    "Lib/test/test_genericpath.py",
-    "Lib/test/test_getopt.py",
     "Lib/test/test_grammar.py",
-    "Lib/test/test_htmlparser.py",
-    "Lib/test/test_importlib/stubs.py",
-    "Lib/test/test_importlib/test_files.py",
-    "Lib/test/test_importlib/test_metadata_api.py",
-    "Lib/test/test_importlib/test_open.py",
     "Lib/test/test_importlib/test_util.py",
     "Lib/test/test_named_expressions.py",
     "Lib/test/test_patma.py",
-    "Lib/test/test_peg_generator/__main__.py",
-    "Lib/test/test_pipes.py",
     "Lib/test/test_source_encoding.py",
-    "Lib/test/test_weakref.py",
-    "Lib/test/test_webbrowser.py",
-    "Lib/tkinter/__main__.py",
-    "Lib/tkinter/test/test_tkinter/test_variables.py",
-    "Modules/_decimal/libmpdec/literature/fnt.py",
-    "Modules/_decimal/tests/deccheck.py",
     "Tools/c-analyzer/c_parser/parser/_delim.py",
     "Tools/i18n/pygettext.py",
     "Tools/test2to3/maintest.py",
@@ -201,124 +371,102 @@ Next, to benchmark the release build:
 ```shell
 cargo build --release
 
-hyperfine --ignore-failure --warmup 1 \
+hyperfine --ignore-failure --warmup 10 --runs 100 \
   "./target/release/ruff ./resources/test/cpython/ --no-cache" \
   "./target/release/ruff ./resources/test/cpython/"
 
 Benchmark 1: ./target/release/ruff ./resources/test/cpython/ --no-cache
-  Time (mean ± σ):     353.6 ms ±   7.6 ms    [User: 2868.8 ms, System: 171.5 ms]
-  Range (min … max):   344.4 ms … 367.3 ms    10 runs
+  Time (mean ± σ):     297.4 ms ±   4.9 ms    [User: 2460.0 ms, System: 67.2 ms]
+  Range (min … max):   287.7 ms … 312.1 ms    100 runs
+
+  Warning: Ignoring non-zero exit code.
 
 Benchmark 2: ./target/release/ruff ./resources/test/cpython/
-  Time (mean ± σ):      59.6 ms ±   2.5 ms    [User: 36.4 ms, System: 345.6 ms]
-  Range (min … max):    55.9 ms …  67.0 ms    48 runs
+  Time (mean ± σ):      79.6 ms ±   7.3 ms    [User: 59.7 ms, System: 356.1 ms]
+  Range (min … max):    62.4 ms … 111.2 ms    100 runs
+
+  Warning: Ignoring non-zero exit code.
 ```
 
-To benchmark the ecosystem's existing tools:
+To benchmark against the ecosystem's existing tools:
 
 ```shell
-hyperfine --ignore-failure --warmup 1 \
+hyperfine --ignore-failure --warmup 5 \
+  "./target/release/ruff ./resources/test/cpython/ --no-cache" \
   "pylint --recursive=y resources/test/cpython/" \
   "pyflakes resources/test/cpython" \
   "autoflake --recursive --expand-star-imports --remove-all-unused-imports --remove-unused-variables --remove-duplicate-keys resources/test/cpython" \
   "pycodestyle resources/test/cpython" \
-  "pycodestyle --select E501 resources/test/cpython" \
   "flake8 resources/test/cpython" \
-  "flake8 --select=F831,F541,F634,F403,F706,F901,E501 resources/test/cpython" \
-  "python -m scripts.run_flake8 resources/test/cpython" \
-  "python -m scripts.run_flake8 resources/test/cpython --select=F831,F541,F634,F403,F706,F901,E501"
+  "python -m scripts.run_flake8 resources/test/cpython"
 ```
 
 In order, these evaluate:
+
+- ruff
 - Pylint
 - PyFlakes
 - autoflake
 - pycodestyle
-- pycodestyle, limited to the checks supported by ruff
 - Flake8
-- Flake8, limited to the checks supported by ruff
 - Flake8, with a hack to enable multiprocessing on macOS
-- Flake8, with a hack to enable multiprocessing on macOS, limited to the checks supported by ruff
 
 (You can `poetry install` from `./scripts` to create a working environment for the above.)
 
 ```shell
 Benchmark 1: ./target/release/ruff ./resources/test/cpython/ --no-cache
-  Time (mean ± σ):     566.9 ms ±  36.6 ms    [User: 2618.0 ms, System: 992.0 ms]
-  Range (min … max):   504.8 ms … 634.0 ms    10 runs
+  Time (mean ± σ):     297.9 ms ±   7.0 ms    [User: 2436.6 ms, System: 65.9 ms]
+  Range (min … max):   289.9 ms … 314.6 ms    10 runs
 
   Warning: Ignoring non-zero exit code.
 
-Benchmark 2: ./target/release/ruff ./resources/test/cpython/
-  Time (mean ± σ):      79.5 ms ±   2.3 ms    [User: 330.1 ms, System: 254.3 ms]
-  Range (min … max):    75.6 ms …  85.2 ms    35 runs
+Benchmark 2: pylint --recursive=y resources/test/cpython/
+  Time (mean ± σ):     37.634 s ±  0.225 s    [User: 36.728 s, System: 0.853 s]
+  Range (min … max):   37.201 s … 38.106 s    10 runs
 
   Warning: Ignoring non-zero exit code.
 
-Benchmark 3: pylint --recursive=y resources/test/cpython/
-  Time (mean ± σ):     27.532 s ±  0.207 s    [User: 26.606 s, System: 0.899 s]
-  Range (min … max):   27.344 s … 28.064 s    10 runs
+Benchmark 3: pyflakes resources/test/cpython
+  Time (mean ± σ):     40.950 s ±  0.449 s    [User: 40.688 s, System: 0.229 s]
+  Range (min … max):   40.348 s … 41.671 s    10 runs
 
   Warning: Ignoring non-zero exit code.
 
-Benchmark 4: pyflakes resources/test/cpython
-  Time (mean ± σ):     28.074 s ±  0.551 s    [User: 27.845 s, System: 0.212 s]
-  Range (min … max):   27.479 s … 29.467 s    10 runs
+Benchmark 4: autoflake --recursive --expand-star-imports --remove-all-unused-imports --remove-unused-variables --remove-duplicate-keys resources/test/cpython
+  Time (mean ± σ):     11.562 s ±  0.160 s    [User: 107.022 s, System: 1.143 s]
+  Range (min … max):   11.417 s … 11.917 s    10 runs
+
+Benchmark 5: pycodestyle resources/test/cpython
+  Time (mean ± σ):     67.428 s ±  0.985 s    [User: 67.199 s, System: 0.203 s]
+  Range (min … max):   65.313 s … 68.496 s    10 runs
 
   Warning: Ignoring non-zero exit code.
 
-Benchmark 5: autoflake --recursive --expand-star-imports --remove-all-unused-imports --remove-unused-variables --remove-duplicate-keys resources/test/cpython
-  Time (mean ± σ):      4.986 s ±  0.190 s    [User: 43.257 s, System: 0.801 s]
-  Range (min … max):    4.837 s …  5.462 s    10 runs
+Benchmark 6: flake8 resources/test/cpython
+  Time (mean ± σ):     116.099 s ±  1.178 s    [User: 115.217 s, System: 0.845 s]
+  Range (min … max):   114.180 s … 117.724 s    10 runs
 
   Warning: Ignoring non-zero exit code.
 
-Benchmark 6: pycodestyle resources/test/cpython
-  Time (mean ± σ):     42.400 s ±  0.211 s    [User: 42.177 s, System: 0.213 s]
-  Range (min … max):   42.106 s … 42.677 s    10 runs
-
-  Warning: Ignoring non-zero exit code.
-
-Benchmark 7: pycodestyle --select E501 resources/test/cpython
-  Time (mean ± σ):     14.578 s ±  0.068 s    [User: 14.466 s, System: 0.108 s]
-  Range (min … max):   14.475 s … 14.726 s    10 runs
-
-  Warning: Ignoring non-zero exit code.
-
-Benchmark 8: flake8 resources/test/cpython
-  Time (mean ± σ):     76.414 s ±  0.461 s    [User: 75.611 s, System: 0.652 s]
-  Range (min … max):   75.691 s … 77.180 s    10 runs
-
-  Warning: Ignoring non-zero exit code.
-
-Benchmark 9: flake8 --select=F831,F541,F634,F403,F706,F901,E501 resources/test/cpython
-  Time (mean ± σ):     75.960 s ±  0.610 s    [User: 75.255 s, System: 0.634 s]
-  Range (min … max):   75.159 s … 77.066 s    10 runs
-
-  Warning: Ignoring non-zero exit code.
-
-Benchmark 10: python -m scripts.run_flake8 resources/test/cpython
-  Time (mean ± σ):     13.536 s ±  0.584 s    [User: 90.911 s, System: 0.934 s]
-  Range (min … max):   12.831 s … 14.699 s    10 runs
-
-Benchmark 11: python -m scripts.run_flake8 resources/test/cpython --select=F831,F541,F634,F403,F706,F901,E501
-  Time (mean ± σ):     12.781 s ±  0.192 s    [User: 89.525 s, System: 0.882 s]
-  Range (min … max):   12.568 s … 13.119 s    10 runs
+Benchmark 7: python -m scripts.run_flake8 resources/test/cpython
+  Time (mean ± σ):     20.477 s ±  0.349 s    [User: 142.372 s, System: 1.504 s]
+  Range (min … max):   20.107 s … 21.183 s    10 runs
 
 Summary
-  './target/release/ruff ./resources/test/cpython/' ran
-    7.13 ± 0.50 times faster than './target/release/ruff ./resources/test/cpython/ --no-cache'
-   62.69 ± 3.01 times faster than 'autoflake --recursive --expand-star-imports --remove-all-unused-imports --remove-unused-variables --remove-duplicate-keys resources/test/cpython'
-  160.71 ± 5.26 times faster than 'python -m scripts.run_flake8 resources/test/cpython --select=F831,F541,F634,F403,F706,F901,E501'
-  170.21 ± 8.86 times faster than 'python -m scripts.run_flake8 resources/test/cpython'
-  183.30 ± 5.40 times faster than 'pycodestyle --select E501 resources/test/cpython'
-  346.19 ± 10.40 times faster than 'pylint --recursive=y resources/test/cpython/'
-  353.00 ± 12.39 times faster than 'pyflakes resources/test/cpython'
-  533.14 ± 15.74 times faster than 'pycodestyle resources/test/cpython'
-  955.13 ± 28.83 times faster than 'flake8 --select=F831,F541,F634,F403,F706,F901,E501 resources/test/cpython'
-  960.82 ± 28.55 times faster than 'flake8 resources/test/cpython'
+  './target/release/ruff ./resources/test/cpython/ --no-cache' ran
+   38.81 ± 1.05 times faster than 'autoflake --recursive --expand-star-imports --remove-all-unused-imports --remove-unused-variables --remove-duplicate-keys resources/test/cpython'
+   68.74 ± 1.99 times faster than 'python -m scripts.run_flake8 resources/test/cpython'
+  126.33 ± 3.05 times faster than 'pylint --recursive=y resources/test/cpython/'
+  137.46 ± 3.55 times faster than 'pyflakes resources/test/cpython'
+  226.35 ± 6.23 times faster than 'pycodestyle resources/test/cpython'
+  389.73 ± 9.92 times faster than 'flake8 resources/test/cpython'
 ```
 
 ## License
 
 MIT
+
+## Contributing
+
+Contributions are welcome and hugely appreciated. To get started, check out the
+[contributing guidelines](https://github.com/charliermarsh/ruff/blob/main/CONTRIBUTORS.md).

examples/generate_rules_table.rs

@@ -0,0 +1,19 @@
+/// Generate a Markdown-compatible table of supported lint rules.
+use ruff::checks::{CheckCode, ALL_CHECK_CODES};
+
+fn main() {
+    let mut check_codes: Vec<CheckCode> = ALL_CHECK_CODES.to_vec();
+    check_codes.sort();
+
+    println!("| Code | Name | Message |");
+    println!("| ---- | ----- | ------- |");
+    for check_code in check_codes {
+        let check_kind = check_code.kind();
+        println!(
+            "| {} | {} | {} |",
+            check_kind.code().as_str(),
+            check_kind.name(),
+            check_kind.body()
+        );
+    }
+}

examples/print_ast.rs

@@ -0,0 +1,25 @@
+/// Print the AST for a given Python file.
+use std::path::PathBuf;
+
+use anyhow::Result;
+use clap::Parser;
+use rustpython_parser::parser;
+
+use ruff::fs;
+
+#[derive(Debug, Parser)]
+struct Cli {
+    #[arg(required = true)]
+    file: PathBuf,
+}
+
+fn main() -> Result<()> {
+    let cli = Cli::parse();
+
+    let contents = fs::read_file(&cli.file)?;
+    let python_ast = parser::parse_program(&contents, &cli.file.to_string_lossy())?;
+
+    println!("{:#?}", python_ast);
+
+    Ok(())
+}

examples/print_tokens.rs

@@ -0,0 +1,25 @@
+/// Print the token stream for a given Python file.
+use std::path::PathBuf;
+
+use anyhow::Result;
+use clap::Parser;
+use rustpython_parser::lexer;
+
+use ruff::fs;
+
+#[derive(Debug, Parser)]
+struct Cli {
+    #[arg(required = true)]
+    file: PathBuf,
+}
+
+fn main() -> Result<()> {
+    let cli = Cli::parse();
+
+    let contents = fs::read_file(&cli.file)?;
+    for (_, tok, _) in lexer::make_tokenizer(&contents).flatten() {
+        println!("{:#?}", tok);
+    }
+
+    Ok(())
+}

publish/Dockerfile

@@ -1,5 +0,0 @@
-FROM python:3.10.6-buster
-
-RUN pip install ruff
-RUN touch foo.py
-RUN ruff foo.py

pyproject.toml

@@ -8,7 +8,6 @@ classifiers = [
     "License :: OSI Approved :: MIT License",
     "Operating System :: OS Independent",
     "Programming Language :: Python",
-    "Programming Language :: Python :: 3.6",
     "Programming Language :: Python :: 3.7",
     "Programming Language :: Python :: 3.8",
     "Programming Language :: Python :: 3.9",
@@ -19,10 +18,12 @@ classifiers = [
 ]
 author = "Charlie Marsh"
 author_email = "charlie.r.marsh@gmail.com"
-url = "https://github.com/charliermarsh/ruff"
 description = "An extremely fast Python linter, written in Rust."
 requires-python = ">=3.7"
 
+[project.urls]
+repository = "https://github.com/charliermarsh/ruff"
+
 [build-system]
 requires = ["maturin>=0.13,<0.14"]
 build-backend = "maturin"

resources/test/fixtures/A001.py

@@ -0,0 +1,27 @@
+import some as sum
+from some import other as int
+
+print = 1
+copyright: 'annotation' = 2
+(complex := 3)
+float = object = 4
+min, max = 5, 6
+
+def bytes():
+    pass
+
+class slice:
+    pass
+
+try:
+    ...
+except ImportError as ValueError:
+    ...
+
+for memoryview, *bytearray in []:
+    pass
+
+with open('file') as str, open('file2') as (all, any):
+    pass
+
+[0 for sum in ()]

resources/test/fixtures/A002.py

@@ -0,0 +1,9 @@
+def func1(str, /, type, *complex, Exception, **getattr):
+    pass
+
+
+async def func2(bytes):
+    pass
+
+
+map([], lambda float: ...)

resources/test/fixtures/A003.py

@@ -0,0 +1,8 @@
+class MyClass:
+    ImportError = 4
+
+    def __init__(self):
+        self.float = 5  # is fine
+
+    def str(self):
+        pass

resources/test/fixtures/E402.py

@@ -0,0 +1,32 @@
+"""Top-level docstring."""
+
+__all__ = ["y"]
+__version__: str = "0.1.0"
+
+import a
+
+try:
+    import b
+except ImportError:
+    pass
+else:
+    pass
+
+import c
+
+if x > 0:
+    import d
+else:
+    import e
+
+y = x + 1
+
+import f
+
+
+def foo() -> None:
+    import e
+
+
+if __name__ == "__main__":
+    import g

resources/test/fixtures/E501.py

@@ -0,0 +1,16 @@
+"""Lorem ipsum dolor sit amet.
+
+    https://github.com/PyCQA/pycodestyle/pull/258/files#diff-841c622497a8033d10152bfdfb15b20b92437ecdea21a260944ea86b77b51533
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
+"""
+
+_ = """Lorem ipsum dolor sit amet.
+
+    https://github.com/PyCQA/pycodestyle/pull/258/files#diff-841c622497a8033d10152bfdfb15b20b92437ecdea21a260944ea86b77b51533
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
+"""  # noqa: E501
+
+_ = "---------------------------------------------------------------------------AAAAAAA"
+_ = "---------------------------------------------------------------------------亜亜亜亜亜亜亜"

resources/test/fixtures/E711.py

@@ -0,0 +1,50 @@
+#: E711
+if res == None:
+    pass
+#: E711
+if res != None:
+    pass
+#: E711
+if None == res:
+    pass
+#: E711
+if None != res:
+    pass
+#: E711
+if res[1] == None:
+    pass
+#: E711
+if res[1] != None:
+    pass
+#: E711
+if None != res[1]:
+    pass
+#: E711
+if None == res[1]:
+    pass
+
+#: Okay
+if x not in y:
+    pass
+
+if not (X in Y or X is Z):
+    pass
+
+if not (X in Y):
+    pass
+
+if x is not y:
+    pass
+
+if X is not Y is not Z:
+    pass
+
+if TrueElement.get_element(True) == TrueElement.get_element(False):
+    pass
+
+if (True) == TrueElement or x == TrueElement:
+    pass
+
+assert (not foo) in bar
+assert {"x": not foo} in bar
+assert [42, not foo] in bar

resources/test/fixtures/E712.py

@@ -0,0 +1,46 @@
+#: E712
+if res == True:
+    pass
+#: E712
+if res != False:
+    pass
+#: E712
+if True != res:
+    pass
+#: E712
+if False == res:
+    pass
+#: E712
+if res[1] == True:
+    pass
+#: E712
+if res[1] != False:
+    pass
+#: E712
+var = 1 if cond == True else -1 if cond == False else cond
+#: E712
+if (True) == TrueElement or x == TrueElement:
+    pass
+
+#: Okay
+if x not in y:
+    pass
+
+if not (X in Y or X is Z):
+    pass
+
+if not (X in Y):
+    pass
+
+if x is not y:
+    pass
+
+if X is not Y is not Z:
+    pass
+
+if TrueElement.get_element(True) == TrueElement.get_element(False):
+    pass
+
+assert (not foo) in bar
+assert {"x": not foo} in bar
+assert [42, not foo] in bar

resources/test/fixtures/E713.py

@@ -0,0 +1,38 @@
+#: E713
+if not X in Y:
+    pass
+#: E713
+if not X.B in Y:
+    pass
+#: E713
+if not X in Y and Z == "zero":
+    pass
+#: E713
+if X == "zero" or not Y in Z:
+    pass
+#: E713
+if not (X in Y):
+    pass
+
+#: Okay
+if x not in y:
+    pass
+
+if not (X in Y or X is Z):
+    pass
+
+if x is not y:
+    pass
+
+if X is not Y is not Z:
+    pass
+
+if TrueElement.get_element(True) == TrueElement.get_element(False):
+    pass
+
+if (True) == TrueElement or x == TrueElement:
+    pass
+
+assert (not foo) in bar
+assert {"x": not foo} in bar
+assert [42, not foo] in bar

resources/test/fixtures/E714.py

@@ -0,0 +1,38 @@
+#: E714
+if not X is Y:
+    pass
+#: E714
+if not X.B is Y:
+    pass
+#: E714
+if not X is Y is not Z:
+    pass
+
+#: Okay
+if not X is not Y:
+    pass
+
+if x not in y:
+    pass
+
+if not (X in Y or X is Z):
+    pass
+
+if not (X in Y):
+    pass
+
+if x is not y:
+    pass
+
+if X is not Y is not Z:
+    pass
+
+if TrueElement.get_element(True) == TrueElement.get_element(False):
+    pass
+
+if (True) == TrueElement or x == TrueElement:
+    pass
+
+assert (not foo) in bar
+assert {"x": not foo} in bar
+assert [42, not foo] in bar

resources/test/fixtures/E721.py

@@ -0,0 +1,54 @@
+#: E721
+if type(res) == type(42):
+    pass
+#: E721
+if type(res) != type(""):
+    pass
+#: E721
+import types
+
+if res == types.IntType:
+    pass
+#: E721
+import types
+
+if type(res) is not types.ListType:
+    pass
+#: E721
+assert type(res) == type(False) or type(res) == type(None)
+#: E721
+assert type(res) == type([])
+#: E721
+assert type(res) == type(())
+#: E721
+assert type(res) == type((0,))
+#: E721
+assert type(res) == type((0))
+#: E721
+assert type(res) != type((1,))
+#: E721
+assert type(res) is type((1,))
+#: E721
+assert type(res) is not type((1,))
+#: E211 E721
+assert type(res) == type(
+    [
+        2,
+    ]
+)
+#: E201 E201 E202 E721
+assert type(res) == type(())
+#: E201 E202 E721
+assert type(res) == type((0,))
+
+#: Okay
+import types
+
+if isinstance(res, int):
+    pass
+if isinstance(res, str):
+    pass
+if isinstance(res, types.MethodType):
+    pass
+if type(a) != type(b) or type(a) == type(ccc):
+    pass

resources/test/fixtures/E722.py

@@ -0,0 +1,33 @@
+#: E722
+try:
+    pass
+except:
+    pass
+#: E722
+try:
+    pass
+except Exception:
+    pass
+except:
+    pass
+#: E722
+try:
+    pass
+except:
+    pass
+#: Okay
+fake_code = """"
+try:
+    do_something()
+except:
+    pass
+"""
+try:
+    pass
+except Exception:
+    pass
+#: Okay
+from . import compute_type
+
+if compute_type(foo) == 5:
+    pass

resources/test/fixtures/E731.py

@@ -0,0 +1,21 @@
+#: E731
+f = lambda x: 2 * x
+#: E731
+f = lambda x: 2 * x
+#: E731
+while False:
+    this = lambda y, z: 2 * x
+
+
+f = object()
+#: E731
+f.method = lambda: "Method"
+
+f = {}
+#: E731
+f["a"] = lambda x: x ** 2
+
+f = []
+f.append(lambda x: x ** 2)
+
+lambda: "no-op"

resources/test/fixtures/E741.py

@@ -0,0 +1,75 @@
+from contextlib import contextmanager
+
+l = 0
+I = 0
+O = 0
+l: int = 0
+
+a, l = 0, 1
+[a, l] = 0, 1
+a, *l = 0, 1, 2
+a = l = 0
+
+o = 0
+i = 0
+
+for l in range(3):
+    pass
+
+
+for a, l in zip(range(3), range(3)):
+    pass
+
+
+def f1():
+    global l
+    l = 0
+
+
+def f2():
+    l = 0
+
+    def f3():
+        nonlocal l
+        l = 1
+
+    f3()
+    return l
+
+
+def f4(l, /, I):
+    return l, I, O
+
+
+def f5(l=0, *, I=1):
+    return l, I
+
+
+def f6(*l, **I):
+    return l, I
+
+
+@contextmanager
+def ctx1():
+    yield 0
+
+
+with ctx1() as l:
+    pass
+
+
+@contextmanager
+def ctx2():
+    yield 0, 1
+
+
+with ctx2() as (a, l):
+    pass
+
+try:
+    pass
+except ValueError as l:
+    pass
+
+if (l := 5) > 0:
+    pass

resources/test/fixtures/E742.py

@@ -0,0 +1,14 @@
+class l:
+    pass
+
+
+class I:
+    pass
+
+
+class O:
+    pass
+
+
+class X:
+    pass

resources/test/fixtures/E743.py

@@ -0,0 +1,15 @@
+def l():
+    pass
+
+
+def I():
+    pass
+
+
+class X:
+    def O(self):
+        pass
+
+
+def x():
+    pass

resources/test/fixtures/E999.py

@@ -0,0 +1,2 @@
+def x():
+

resources/test/fixtures/F401.py

@@ -0,0 +1,41 @@
+from __future__ import all_feature_names
+import os
+import functools
+from datetime import datetime
+from collections import (
+    Counter,
+    OrderedDict,
+    namedtuple,
+)
+import multiprocessing.pool
+import multiprocessing.process
+import logging.config
+import logging.handlers
+from typing import TYPING_CHECK, NamedTuple, Dict, Type, TypeVar, List, Set, Union, cast
+
+from blah import ClassA, ClassB, ClassC
+
+if TYPING_CHECK:
+    from models import Fruit, Nut, Vegetable
+
+
+class X:
+    datetime: datetime
+    foo: Type["NamedTuple"]
+
+    def a(self) -> "namedtuple":
+        x = os.environ["1"]
+        y = Counter()
+        z = multiprocessing.pool.ThreadPool()
+
+
+__all__ = ["ClassA"] + ["ClassB"]
+__all__ += ["ClassC"]
+
+X = TypeVar("X")
+Y = TypeVar("Y", bound="Dict")
+Z = TypeVar("Z", "List", "Set")
+
+a = list["Fruit"]
+b = Union["Nut", None]
+c = cast("Vegetable", b)

resources/test/fixtures/F402.py

@@ -0,0 +1,9 @@
+import os
+import os.path as path
+
+
+for os in range(3):
+    pass
+
+for path in range(3):
+    pass

resources/test/fixtures/F404.py

@@ -0,0 +1,7 @@
+from __future__ import print_function
+"""Docstring"""
+from __future__ import absolute_import
+
+from collections import namedtuple
+
+from __future__ import print_function

resources/test/fixtures/F405.py

@@ -0,0 +1,11 @@
+from mymodule import *
+
+
+def print_name():
+    print(name)
+
+
+def print_name(name):
+    print(name)
+
+__all__ = ['a']

resources/test/fixtures/F406.py

@@ -0,0 +1,9 @@
+from F634 import *
+
+
+def f():
+    from F634 import *
+
+
+class F:
+    from F634 import *

resources/test/fixtures/F407.py

@@ -0,0 +1,2 @@
+from __future__ import print_function
+from __future__ import non_existent_feature

resources/test/fixtures/F601.py

@@ -0,0 +1,12 @@
+x = {
+    "a": 1,
+    "a": 2,
+    "b": 3,
+    ("a", "b"): 3,
+    ("a", "b"): 4,
+    1.0: 2,
+    1: 0,
+    1: 3,
+    b"123": 1,
+    b"123": 4,
+}

resources/test/fixtures/F602.py

@@ -0,0 +1,7 @@
+a = 1
+b = 2
+x = {
+    a: 1,
+    a: 2,
+    b: 3,
+}

resources/test/fixtures/F622.py

@@ -0,0 +1,3 @@
+*a, *b, c = (1, 2, 3)
+*a, b, c = (1, 2, 3)
+a, b, *c = (1, 2, 3)

resources/test/fixtures/F631.py

@@ -0,0 +1,4 @@
+assert (False, "x")
+assert (False,)
+assert ()
+assert True

resources/test/fixtures/F632.py

@@ -0,0 +1,5 @@
+if x is "abc":
+    pass
+
+if 123 is not y:
+    pass

resources/test/fixtures/F633.py

@@ -0,0 +1,4 @@
+from __future__ import print_function
+import sys
+
+print >> sys.stderr, "Hello"

resources/test/fixtures/F634.py

@@ -6,3 +6,5 @@ for _ in range(5):
         pass
     elif (3, 4):
         pass
+    elif ():
+        pass

resources/test/fixtures/F701.py

@@ -0,0 +1,23 @@
+for i in range(10):
+    break
+else:
+    break
+
+i = 0
+while i < 10:
+    i += 1
+    break
+
+
+def f():
+    for i in range(10):
+        break
+
+    break
+
+
+class Foo:
+    break
+
+
+break

resources/test/fixtures/F702.py

@@ -0,0 +1,23 @@
+for i in range(10):
+    continue
+else:
+    continue
+
+i = 0
+while i < 10:
+    i += 1
+    continue
+
+
+def f():
+    for i in range(10):
+        continue
+
+    continue
+
+
+class Foo:
+    continue
+
+
+continue

resources/test/fixtures/F704.py

@@ -0,0 +1,10 @@
+def f() -> int:
+    yield 1
+
+
+class Foo:
+    yield 2
+
+
+yield 3
+yield from 3

resources/test/fixtures/F707.py

@@ -0,0 +1,46 @@
+try:
+    pass
+except:
+    pass
+except ValueError:
+    pass
+
+try:
+    pass
+except:
+    pass
+except ValueError:
+    pass
+finally:
+    pass
+
+try:
+    pass
+except:
+    pass
+except ValueError:
+    pass
+else:
+    pass
+
+try:
+    pass
+except:
+    pass
+
+try:
+    pass
+except ValueError:
+    pass
+except:
+    pass
+
+try:
+    pass
+except ValueError:
+    pass
+
+try:
+    pass
+finally:
+    pass

resources/test/fixtures/F722.py

@@ -0,0 +1,10 @@
+class A:
+    pass
+
+
+def f() -> "A":
+    pass
+
+
+def g() -> "///":
+    pass

resources/test/fixtures/F821.py

@@ -0,0 +1,91 @@
+def get_name():
+    return self.name
+
+
+def get_name():
+    return (self.name,)
+
+
+def get_name():
+    del self.name
+
+
+def get_name(self):
+    return self.name
+
+
+x = list()
+
+
+def randdec(maxprec, maxexp):
+    return numeric_string(maxprec, maxexp)
+
+
+def ternary_optarg(prec, exp_range, itr):
+    for _ in range(100):
+        a = randdec(prec, 2 * exp_range)
+        b = randdec(prec, 2 * exp_range)
+        c = randdec(prec, 2 * exp_range)
+        yield a, b, c, None
+        yield a, b, c, None, None
+
+
+class Foo:
+    CLASS_VAR = 1
+    REFERENCES_CLASS_VAR = {"CLASS_VAR": CLASS_VAR}
+    ANNOTATED_CLASS_VAR: int = 2
+
+
+from typing import Literal
+
+
+class Class:
+    copy_on_model_validation: Literal["none", "deep", "shallow"]
+    post_init_call: Literal["before_validation", "after_validation"]
+
+    def __init__(self):
+        Class
+
+
+try:
+    x = 1 / 0
+except Exception as e:
+    print(e)
+
+
+y: int = 1
+
+x: "Bar" = 1
+
+[first] = ["yup"]
+
+
+from typing import List, TypedDict
+
+
+class Item(TypedDict):
+    nodes: List[TypedDict("Node", {"name": str})]
+
+
+from enum import Enum
+
+
+class Ticket:
+    class Status(Enum):
+        OPEN = "OPEN"
+        CLOSED = "CLOSED"
+
+    def set_status(self, status: Status):
+        self.status = status
+
+
+def update_tomato():
+    print(TOMATO)
+    TOMATO = "cherry tomato"
+
+
+A = f'{B}'
+A = (
+    f'B'
+    f'{B}'
+)

resources/test/fixtures/F822.py

@@ -0,0 +1,3 @@
+a = 1
+
+__all__ = ["a", "b"]

resources/test/fixtures/F823.py

@@ -0,0 +1,27 @@
+my_dict = {}
+my_var = 0
+
+
+def foo():
+    my_var += 1
+
+
+def bar():
+    global my_var
+    my_var += 1
+
+
+def baz():
+    global my_var
+    global my_dict
+    my_dict[my_var] += 1
+
+
+def dec(x):
+    return x
+
+
+@dec
+def f():
+    dec = 1
+    return dec

resources/test/fixtures/F841.py

@@ -0,0 +1,37 @@
+try:
+    1 / 0
+except ValueError as e:
+    pass
+
+
+try:
+    1 / 0
+except ValueError as e:
+    print(e)
+
+
+def f1():
+    x = 1
+    y = 2
+    z = x + y
+
+
+def f2():
+    foo = (1, 2)
+    (a, b) = (1, 2)
+
+    bar = (1, 2)
+    (c, d) = bar
+
+    (x, y) = baz = bar
+
+
+def f3():
+    locals()
+    x = 1
+
+
+def f4():
+    _ = 1
+    __ = 1
+    _discarded = 1

resources/test/fixtures/M001.py

@@ -0,0 +1,57 @@
+def f() -> None:
+    # Valid
+    a = 1  # noqa
+
+    # Valid
+    b = 2  # noqa: F841
+
+    # Invalid
+    c = 1  # noqa
+    print(c)
+
+    # Invalid
+    d = 1  # noqa: E501
+
+    # Invalid
+    d = 1  # noqa: F841, E501
+
+
+# Valid
+_ = """Lorem ipsum dolor sit amet.
+
+    https://github.com/PyCQA/pycodestyle/pull/258/files#diff-841c622497a8033d10152bfdfb15b20b92437ecdea21a260944ea86b77b51533
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
+"""  # noqa: E501
+
+# Valid
+_ = """Lorem ipsum dolor sit amet.
+
+    https://github.com/PyCQA/pycodestyle/pull/258/files#diff-841c622497a8033d10152bfdfb15b20b92437ecdea21a260944ea86b77b51533
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
+"""  # noqa
+
+# Invalid
+_ = """Lorem ipsum dolor sit amet.
+
+    https://github.com/PyCQA/pycodestyle/pull/258/files#diff-841c622497a8033d10152bfdfb15b20b92437ecdea21a260944ea86b77b51533
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
+"""  # noqa: E501, F841
+
+# Invalid
+_ = """Lorem ipsum dolor sit amet.
+
+    https://github.com/PyCQA/pycodestyle/pull/258/files#diff-841c622497a8033d10152bfdfb15b20b92437ecdea21a260944ea86b77b51533
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor.
+"""  # noqa: E501
+
+# Invalid
+_ = """Lorem ipsum dolor sit amet.
+
+    https://github.com/PyCQA/pycodestyle/pull/258/files#diff-841c622497a8033d10152bfdfb15b20b92437ecdea21a260944ea86b77b51533
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor.
+"""  # noqa

resources/test/fixtures/R001.py

@@ -0,0 +1,141 @@
+class A:
+    ...
+
+
+class A(object):
+    ...
+
+
+class A(
+    object,
+):
+    ...
+
+
+class A(
+    object,
+    #
+):
+    ...
+
+
+class A(
+    #
+    object,
+):
+    ...
+
+
+class A(
+    #
+    object
+):
+    ...
+
+
+class A(
+    object
+    #
+):
+    ...
+
+
+class A(
+    #
+    object,
+    #
+):
+    ...
+
+
+class A(
+    #
+    object,
+    #
+):
+    ...
+
+
+class A(
+    #
+    object
+    #
+):
+    ...
+
+
+class A(
+    #
+    object
+    #
+):
+    ...
+
+
+class B(A, object):
+    ...
+
+
+class B(object, A):
+    ...
+
+
+class B(
+    object,
+    A,
+):
+    ...
+
+
+class B(
+    A,
+    object,
+):
+    ...
+
+
+class B(
+    object,
+    # Comment on A.
+    A,
+):
+    ...
+
+
+class B(
+    # Comment on A.
+    A,
+    object,
+):
+    ...
+
+
+def f():
+    class A(object):
+        ...
+
+
+class A(
+    object,
+):
+    ...
+
+
+class A(
+    object,  # )
+):
+    ...
+
+
+class A(
+    object  # )
+    ,
+):
+    ...
+
+
+object = A
+
+
+class B(object):
+    ...

resources/test/fixtures/R002.py

@@ -0,0 +1,3 @@
+self.assertEquals (1, 2)
+self.assertEquals(1, 2)
+self.assertEqual(3, 4)

resources/test/fixtures/SPR001.py

@@ -0,0 +1,22 @@
+class Parent:
+    def method(self):
+        pass
+
+    def wrong(self):
+        pass
+
+
+class Child(Parent):
+    def method(self):
+        parent = super()  # ok
+        super().method()  # ok
+        Parent.method(self)  # ok
+        Parent.super(1, 2)  # ok
+
+    def wrong(self):
+        parent = super(Child, self)  # wrong
+        super(Child, self).method  # wrong
+        super(
+            Child,
+            self,
+        ).method()  # wrong

resources/test/fixtures/__init__.py

@@ -0,0 +1,3 @@
+print(__path__)
+
+__all__ = ["a", "b", "c"]

resources/test/fixtures/directory/also_excluded.py

@@ -0,0 +1,9 @@
+a = "abc"
+b = f"ghi{'jkl'}"
+
+c = f"def"
+d = f"def" + "ghi"
+e = (
+    f"def" +
+    "ghi"
+)

resources/test/fixtures/excluded.py

@@ -0,0 +1,9 @@
+a = "abc"
+b = f"ghi{'jkl'}"
+
+c = f"def"
+d = f"def" + "ghi"
+e = (
+    f"def" +
+    "ghi"
+)

resources/test/fixtures/foo/migrations/migration.py

@@ -0,0 +1,9 @@
+a = "abc"
+b = f"ghi{'jkl'}"
+
+c = f"def"
+d = f"def" + "ghi"
+e = (
+    f"def" +
+    "ghi"
+)

resources/test/fixtures/future_annotations.py

@@ -0,0 +1,27 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+from models import Fruit, Nut
+
+
+@dataclass
+class Foo:
+    x: int
+    y: int
+
+    @classmethod
+    def a(cls) -> Foo:
+        return cls(x=0, y=0)
+
+    @classmethod
+    def b(cls) -> "Foo":
+        return cls(x=0, y=0)
+
+    @classmethod
+    def c(cls) -> Bar:
+        return cls(x=0, y=0)
+
+    @classmethod
+    def d(cls) -> Fruit:
+        return cls(x=0, y=0)

resources/test/fixtures/pyproject.toml

@@ -0,0 +1,7 @@
+[tool.ruff]
+line-length = 88
+extend-exclude = [
+    "excluded.py",
+    "migrations",
+    "directory/also_excluded.py",
+]

resources/test/src/E501.py

@@ -1,6 +0,0 @@
-"""Lorem ipsum dolor sit amet.
-
-    https://github.com/PyCQA/pycodestyle/pull/258/files#diff-841c622497a8033d10152bfdfb15b20b92437ecdea21a260944ea86b77b51533
-
-Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
-"""

resources/test/src/F401.py

@@ -1,14 +0,0 @@
-import os
-import functools
-from collections import (
-    Counter,
-    OrderedDict,
-    namedtuple,
-)
-
-
-class X:
-    def a(self) -> "namedtuple":
-        x = os.environ["1"]
-        y = Counter()
-        return X

resources/test/src/pyproject.toml

@@ -1,13 +0,0 @@
-[tool.ruff]
-line-length = 88
-exclude = ["excluded.py"]
-select = [
-    "E501",
-    "F401",
-    "F403",
-    "F541",
-    "F634",
-    "F706",
-    "F831",
-    "F901",
-]

src/ast.rs

@@ -0,0 +1,5 @@
+pub mod checks;
+pub mod operations;
+pub mod relocate;
+pub mod types;
+pub mod visitor;

src/ast/checks.rs

@@ -0,0 +1,723 @@
+use std::collections::BTreeSet;
+
+use itertools::izip;
+use regex::Regex;
+use rustpython_parser::ast::{
+    Arg, Arguments, Cmpop, Constant, Excepthandler, ExcepthandlerKind, Expr, ExprKind, Keyword,
+    Location, Stmt, StmtKind, Unaryop,
+};
+
+use crate::ast::operations::SourceCodeLocator;
+use crate::ast::types::{
+    Binding, BindingKind, CheckLocator, FunctionScope, Range, Scope, ScopeKind,
+};
+use crate::autofix::{fixer, fixes};
+use crate::checks::{Check, CheckKind, Fix, RejectedCmpop};
+use crate::python::builtins::BUILTINS;
+
+/// Check IfTuple compliance.
+pub fn check_if_tuple(test: &Expr, location: Range) -> Option<Check> {
+    if let ExprKind::Tuple { elts, .. } = &test.node {
+        if !elts.is_empty() {
+            return Some(Check::new(CheckKind::IfTuple, location));
+        }
+    }
+    None
+}
+
+/// Check AssertTuple compliance.
+pub fn check_assert_tuple(test: &Expr, location: Range) -> Option<Check> {
+    if let ExprKind::Tuple { elts, .. } = &test.node {
+        if !elts.is_empty() {
+            return Some(Check::new(CheckKind::AssertTuple, location));
+        }
+    }
+    None
+}
+
+/// Check NotInTest and NotIsTest compliance.
+pub fn check_not_tests(
+    op: &Unaryop,
+    operand: &Expr,
+    check_not_in: bool,
+    check_not_is: bool,
+    locator: &dyn CheckLocator,
+) -> Vec<Check> {
+    let mut checks: Vec<Check> = vec![];
+
+    if matches!(op, Unaryop::Not) {
+        if let ExprKind::Compare { ops, .. } = &operand.node {
+            for op in ops {
+                match op {
+                    Cmpop::In => {
+                        if check_not_in {
+                            checks.push(Check::new(
+                                CheckKind::NotInTest,
+                                locator.locate_check(Range::from_located(operand)),
+                            ));
+                        }
+                    }
+                    Cmpop::Is => {
+                        if check_not_is {
+                            checks.push(Check::new(
+                                CheckKind::NotIsTest,
+                                locator.locate_check(Range::from_located(operand)),
+                            ));
+                        }
+                    }
+                    _ => {}
+                }
+            }
+        }
+    }
+
+    checks
+}
+
+/// Check UnusedVariable compliance.
+pub fn check_unused_variables(
+    scope: &Scope,
+    locator: &dyn CheckLocator,
+    dummy_variable_rgx: &Regex,
+) -> Vec<Check> {
+    let mut checks: Vec<Check> = vec![];
+
+    if matches!(
+        scope.kind,
+        ScopeKind::Function(FunctionScope { uses_locals: true })
+    ) {
+        return checks;
+    }
+
+    for (name, binding) in scope.values.iter() {
+        if binding.used.is_none()
+            && matches!(binding.kind, BindingKind::Assignment)
+            && !dummy_variable_rgx.is_match(name)
+            && name != "__tracebackhide__"
+            && name != "__traceback_info__"
+            && name != "__traceback_supplement__"
+        {
+            checks.push(Check::new(
+                CheckKind::UnusedVariable(name.to_string()),
+                locator.locate_check(binding.location),
+            ));
+        }
+    }
+
+    checks
+}
+
+/// Check DoNotAssignLambda compliance.
+pub fn check_do_not_assign_lambda(value: &Expr, location: Range) -> Option<Check> {
+    if let ExprKind::Lambda { .. } = &value.node {
+        Some(Check::new(CheckKind::DoNotAssignLambda, location))
+    } else {
+        None
+    }
+}
+
+fn is_ambiguous_name(name: &str) -> bool {
+    name == "l" || name == "I" || name == "O"
+}
+
+/// Check AmbiguousVariableName compliance.
+pub fn check_ambiguous_variable_name(name: &str, location: Range) -> Option<Check> {
+    if is_ambiguous_name(name) {
+        Some(Check::new(
+            CheckKind::AmbiguousVariableName(name.to_string()),
+            location,
+        ))
+    } else {
+        None
+    }
+}
+
+/// Check AmbiguousClassName compliance.
+pub fn check_ambiguous_class_name(name: &str, location: Range) -> Option<Check> {
+    if is_ambiguous_name(name) {
+        Some(Check::new(
+            CheckKind::AmbiguousClassName(name.to_string()),
+            location,
+        ))
+    } else {
+        None
+    }
+}
+
+/// Check AmbiguousFunctionName compliance.
+pub fn check_ambiguous_function_name(name: &str, location: Range) -> Option<Check> {
+    if is_ambiguous_name(name) {
+        Some(Check::new(
+            CheckKind::AmbiguousFunctionName(name.to_string()),
+            location,
+        ))
+    } else {
+        None
+    }
+}
+
+/// Check UselessObjectInheritance compliance.
+pub fn check_useless_object_inheritance(
+    stmt: &Stmt,
+    name: &str,
+    bases: &[Expr],
+    keywords: &[Keyword],
+    scope: &Scope,
+    locator: &mut SourceCodeLocator,
+    autofix: &fixer::Mode,
+) -> Option<Check> {
+    for expr in bases {
+        if let ExprKind::Name { id, .. } = &expr.node {
+            if id == "object" {
+                match scope.values.get(id) {
+                    None
+                    | Some(Binding {
+                        kind: BindingKind::Builtin,
+                        ..
+                    }) => {
+                        let mut check = Check::new(
+                            CheckKind::UselessObjectInheritance(name.to_string()),
+                            Range::from_located(expr),
+                        );
+                        if matches!(autofix, fixer::Mode::Generate | fixer::Mode::Apply) {
+                            if let Some(fix) = fixes::remove_class_def_base(
+                                locator,
+                                &stmt.location,
+                                expr.location,
+                                bases,
+                                keywords,
+                            ) {
+                                check.amend(fix);
+                            }
+                        }
+                        return Some(check);
+                    }
+                    _ => {}
+                }
+            }
+        }
+    }
+
+    None
+}
+
+/// Check DefaultExceptNotLast compliance.
+pub fn check_default_except_not_last(handlers: &Vec<Excepthandler>) -> Option<Check> {
+    for (idx, handler) in handlers.iter().enumerate() {
+        let ExcepthandlerKind::ExceptHandler { type_, .. } = &handler.node;
+        if type_.is_none() && idx < handlers.len() - 1 {
+            return Some(Check::new(
+                CheckKind::DefaultExceptNotLast,
+                Range::from_located(handler),
+            ));
+        }
+    }
+
+    None
+}
+
+/// Check RaiseNotImplemented compliance.
+pub fn check_raise_not_implemented(expr: &Expr) -> Option<Check> {
+    match &expr.node {
+        ExprKind::Call { func, .. } => {
+            if let ExprKind::Name { id, .. } = &func.node {
+                if id == "NotImplemented" {
+                    return Some(Check::new(
+                        CheckKind::RaiseNotImplemented,
+                        Range::from_located(expr),
+                    ));
+                }
+            }
+        }
+        ExprKind::Name { id, .. } => {
+            if id == "NotImplemented" {
+                return Some(Check::new(
+                    CheckKind::RaiseNotImplemented,
+                    Range::from_located(expr),
+                ));
+            }
+        }
+        _ => {}
+    }
+
+    None
+}
+
+/// Check DuplicateArgumentName compliance.
+pub fn check_duplicate_arguments(arguments: &Arguments) -> Vec<Check> {
+    let mut checks: Vec<Check> = vec![];
+
+    // Collect all the arguments into a single vector.
+    let mut all_arguments: Vec<&Arg> = arguments
+        .args
+        .iter()
+        .chain(arguments.posonlyargs.iter())
+        .chain(arguments.kwonlyargs.iter())
+        .collect();
+    if let Some(arg) = &arguments.vararg {
+        all_arguments.push(arg);
+    }
+    if let Some(arg) = &arguments.kwarg {
+        all_arguments.push(arg);
+    }
+
+    // Search for duplicates.
+    let mut idents: BTreeSet<&str> = BTreeSet::new();
+    for arg in all_arguments {
+        let ident = &arg.node.arg;
+        if idents.contains(ident.as_str()) {
+            checks.push(Check::new(
+                CheckKind::DuplicateArgumentName,
+                Range::from_located(arg),
+            ));
+        }
+        idents.insert(ident);
+    }
+
+    checks
+}
+
+/// Check AssertEquals compliance.
+pub fn check_assert_equals(expr: &Expr, autofix: &fixer::Mode) -> Option<Check> {
+    if let ExprKind::Attribute { value, attr, .. } = &expr.node {
+        if attr == "assertEquals" {
+            if let ExprKind::Name { id, .. } = &value.node {
+                if id == "self" {
+                    let mut check =
+                        Check::new(CheckKind::NoAssertEquals, Range::from_located(expr));
+                    if matches!(autofix, fixer::Mode::Generate | fixer::Mode::Apply) {
+                        check.amend(Fix {
+                            content: "assertEqual".to_string(),
+                            location: Location::new(
+                                expr.location.row(),
+                                expr.location.column() + 1,
+                            ),
+                            end_location: Location::new(
+                                expr.location.row(),
+                                expr.location.column() + 1 + "assertEquals".len(),
+                            ),
+                            applied: false,
+                        });
+                    }
+                    return Some(check);
+                }
+            }
+        }
+    }
+    None
+}
+
+#[derive(Debug, PartialEq)]
+enum DictionaryKey<'a> {
+    Constant(&'a Constant),
+    Variable(&'a String),
+}
+
+fn convert_to_value(expr: &Expr) -> Option<DictionaryKey> {
+    match &expr.node {
+        ExprKind::Constant { value, .. } => Some(DictionaryKey::Constant(value)),
+        ExprKind::Name { id, .. } => Some(DictionaryKey::Variable(id)),
+        _ => None,
+    }
+}
+
+/// Check MultiValueRepeatedKeyLiteral and MultiValueRepeatedKeyVariable compliance.
+pub fn check_repeated_keys(
+    keys: &Vec<Expr>,
+    check_repeated_literals: bool,
+    check_repeated_variables: bool,
+    locator: &dyn CheckLocator,
+) -> Vec<Check> {
+    let mut checks: Vec<Check> = vec![];
+
+    let num_keys = keys.len();
+    for i in 0..num_keys {
+        let k1 = &keys[i];
+        let v1 = convert_to_value(k1);
+        for k2 in keys.iter().take(num_keys).skip(i + 1) {
+            let v2 = convert_to_value(k2);
+            match (&v1, &v2) {
+                (Some(DictionaryKey::Constant(v1)), Some(DictionaryKey::Constant(v2))) => {
+                    if check_repeated_literals && v1 == v2 {
+                        checks.push(Check::new(
+                            CheckKind::MultiValueRepeatedKeyLiteral,
+                            locator.locate_check(Range::from_located(k2)),
+                        ))
+                    }
+                }
+                (Some(DictionaryKey::Variable(v1)), Some(DictionaryKey::Variable(v2))) => {
+                    if check_repeated_variables && v1 == v2 {
+                        checks.push(Check::new(
+                            CheckKind::MultiValueRepeatedKeyVariable((*v2).to_string()),
+                            locator.locate_check(Range::from_located(k2)),
+                        ))
+                    }
+                }
+                _ => {}
+            }
+        }
+    }
+
+    checks
+}
+
+/// Check TrueFalseComparison and NoneComparison compliance.
+pub fn check_literal_comparisons(
+    left: &Expr,
+    ops: &Vec<Cmpop>,
+    comparators: &Vec<Expr>,
+    check_none_comparisons: bool,
+    check_true_false_comparisons: bool,
+    locator: &dyn CheckLocator,
+) -> Vec<Check> {
+    let mut checks: Vec<Check> = vec![];
+
+    let op = ops.first().unwrap();
+    let comparator = left;
+
+    // Check `left`.
+    if check_none_comparisons
+        && matches!(
+            comparator.node,
+            ExprKind::Constant {
+                value: Constant::None,
+                kind: None
+            }
+        )
+    {
+        if matches!(op, Cmpop::Eq) {
+            checks.push(Check::new(
+                CheckKind::NoneComparison(RejectedCmpop::Eq),
+                locator.locate_check(Range::from_located(comparator)),
+            ));
+        }
+        if matches!(op, Cmpop::NotEq) {
+            checks.push(Check::new(
+                CheckKind::NoneComparison(RejectedCmpop::NotEq),
+                locator.locate_check(Range::from_located(comparator)),
+            ));
+        }
+    }
+
+    if check_true_false_comparisons {
+        if let ExprKind::Constant {
+            value: Constant::Bool(value),
+            kind: None,
+        } = comparator.node
+        {
+            if matches!(op, Cmpop::Eq) {
+                checks.push(Check::new(
+                    CheckKind::TrueFalseComparison(value, RejectedCmpop::Eq),
+                    locator.locate_check(Range::from_located(comparator)),
+                ));
+            }
+            if matches!(op, Cmpop::NotEq) {
+                checks.push(Check::new(
+                    CheckKind::TrueFalseComparison(value, RejectedCmpop::NotEq),
+                    locator.locate_check(Range::from_located(comparator)),
+                ));
+            }
+        }
+    }
+
+    // Check each comparator in order.
+    for (op, comparator) in izip!(ops, comparators) {
+        if check_none_comparisons
+            && matches!(
+                comparator.node,
+                ExprKind::Constant {
+                    value: Constant::None,
+                    kind: None
+                }
+            )
+        {
+            if matches!(op, Cmpop::Eq) {
+                checks.push(Check::new(
+                    CheckKind::NoneComparison(RejectedCmpop::Eq),
+                    locator.locate_check(Range::from_located(comparator)),
+                ));
+            }
+            if matches!(op, Cmpop::NotEq) {
+                checks.push(Check::new(
+                    CheckKind::NoneComparison(RejectedCmpop::NotEq),
+                    locator.locate_check(Range::from_located(comparator)),
+                ));
+            }
+        }
+
+        if check_true_false_comparisons {
+            if let ExprKind::Constant {
+                value: Constant::Bool(value),
+                kind: None,
+            } = comparator.node
+            {
+                if matches!(op, Cmpop::Eq) {
+                    checks.push(Check::new(
+                        CheckKind::TrueFalseComparison(value, RejectedCmpop::Eq),
+                        locator.locate_check(Range::from_located(comparator)),
+                    ));
+                }
+                if matches!(op, Cmpop::NotEq) {
+                    checks.push(Check::new(
+                        CheckKind::TrueFalseComparison(value, RejectedCmpop::NotEq),
+                        locator.locate_check(Range::from_located(comparator)),
+                    ));
+                }
+            }
+        }
+    }
+
+    checks
+}
+
+fn is_constant(expr: &Expr) -> bool {
+    match &expr.node {
+        ExprKind::Constant { .. } => true,
+        ExprKind::Tuple { elts, .. } => elts.iter().all(is_constant),
+        _ => false,
+    }
+}
+
+fn is_singleton(expr: &Expr) -> bool {
+    matches!(
+        expr.node,
+        ExprKind::Constant {
+            value: Constant::None | Constant::Bool(_) | Constant::Ellipsis,
+            ..
+        }
+    )
+}
+
+fn is_constant_non_singleton(expr: &Expr) -> bool {
+    is_constant(expr) && !is_singleton(expr)
+}
+
+/// Check IsLiteral compliance.
+pub fn check_is_literal(
+    left: &Expr,
+    ops: &Vec<Cmpop>,
+    comparators: &Vec<Expr>,
+    location: Range,
+) -> Vec<Check> {
+    let mut checks: Vec<Check> = vec![];
+
+    let mut left = left;
+    for (op, right) in izip!(ops, comparators) {
+        if matches!(op, Cmpop::Is | Cmpop::IsNot)
+            && (is_constant_non_singleton(left) || is_constant_non_singleton(right))
+        {
+            checks.push(Check::new(CheckKind::IsLiteral, location));
+        }
+        left = right;
+    }
+
+    checks
+}
+
+/// Check TypeComparison compliance.
+pub fn check_type_comparison(
+    ops: &Vec<Cmpop>,
+    comparators: &Vec<Expr>,
+    location: Range,
+) -> Vec<Check> {
+    let mut checks: Vec<Check> = vec![];
+
+    for (op, right) in izip!(ops, comparators) {
+        if matches!(op, Cmpop::Is | Cmpop::IsNot | Cmpop::Eq | Cmpop::NotEq) {
+            match &right.node {
+                ExprKind::Call { func, args, .. } => {
+                    if let ExprKind::Name { id, .. } = &func.node {
+                        // Ex) type(False)
+                        if id == "type" {
+                            if let Some(arg) = args.first() {
+                                // Allow comparison for types which are not obvious.
+                                if !matches!(arg.node, ExprKind::Name { .. }) {
+                                    checks.push(Check::new(CheckKind::TypeComparison, location));
+                                }
+                            }
+                        }
+                    }
+                }
+                ExprKind::Attribute { value, .. } => {
+                    if let ExprKind::Name { id, .. } = &value.node {
+                        // Ex) types.IntType
+                        if id == "types" {
+                            checks.push(Check::new(CheckKind::TypeComparison, location));
+                        }
+                    }
+                }
+                _ => {}
+            }
+        }
+    }
+
+    checks
+}
+
+/// Check TwoStarredExpressions and TooManyExpressionsInStarredAssignment compliance.
+pub fn check_starred_expressions(
+    elts: &[Expr],
+    check_too_many_expressions: bool,
+    check_two_starred_expressions: bool,
+    location: Range,
+) -> Option<Check> {
+    let mut has_starred: bool = false;
+    let mut starred_index: Option<usize> = None;
+    for (index, elt) in elts.iter().enumerate() {
+        if matches!(elt.node, ExprKind::Starred { .. }) {
+            if has_starred && check_two_starred_expressions {
+                return Some(Check::new(CheckKind::TwoStarredExpressions, location));
+            }
+            has_starred = true;
+            starred_index = Some(index);
+        }
+    }
+
+    if check_too_many_expressions {
+        if let Some(starred_index) = starred_index {
+            if starred_index >= 1 << 8 || elts.len() - starred_index > 1 << 24 {
+                return Some(Check::new(
+                    CheckKind::TooManyExpressionsInStarredAssignment,
+                    location,
+                ));
+            }
+        }
+    }
+
+    None
+}
+
+/// Check BreakOutsideLoop compliance.
+pub fn check_break_outside_loop(
+    stmt: &Stmt,
+    parents: &[&Stmt],
+    parent_stack: &[usize],
+    locator: &dyn CheckLocator,
+) -> Option<Check> {
+    let mut allowed: bool = false;
+    let mut parent = stmt;
+    for index in parent_stack.iter().rev() {
+        let child = parent;
+        parent = parents[*index];
+        match &parent.node {
+            StmtKind::For { orelse, .. }
+            | StmtKind::AsyncFor { orelse, .. }
+            | StmtKind::While { orelse, .. } => {
+                if !orelse.contains(child) {
+                    allowed = true;
+                    break;
+                }
+            }
+
+            StmtKind::FunctionDef { .. }
+            | StmtKind::AsyncFunctionDef { .. }
+            | StmtKind::ClassDef { .. } => {
+                break;
+            }
+            _ => {}
+        }
+    }
+
+    if !allowed {
+        Some(Check::new(
+            CheckKind::BreakOutsideLoop,
+            locator.locate_check(Range::from_located(stmt)),
+        ))
+    } else {
+        None
+    }
+}
+
+/// Check ContinueOutsideLoop compliance.
+pub fn check_continue_outside_loop(
+    stmt: &Stmt,
+    parents: &[&Stmt],
+    parent_stack: &[usize],
+    locator: &dyn CheckLocator,
+) -> Option<Check> {
+    let mut allowed: bool = false;
+    let mut parent = stmt;
+    for index in parent_stack.iter().rev() {
+        let child = parent;
+        parent = parents[*index];
+        match &parent.node {
+            StmtKind::For { orelse, .. }
+            | StmtKind::AsyncFor { orelse, .. }
+            | StmtKind::While { orelse, .. } => {
+                if !orelse.contains(child) {
+                    allowed = true;
+                    break;
+                }
+            }
+
+            StmtKind::FunctionDef { .. }
+            | StmtKind::AsyncFunctionDef { .. }
+            | StmtKind::ClassDef { .. } => {
+                break;
+            }
+            _ => {}
+        }
+    }
+
+    if !allowed {
+        Some(Check::new(
+            CheckKind::ContinueOutsideLoop,
+            locator.locate_check(Range::from_located(stmt)),
+        ))
+    } else {
+        None
+    }
+}
+
+// flake8-builtins
+pub enum ShadowingType {
+    Variable,
+    Argument,
+    Attribute,
+}
+
+/// Check builtin name shadowing
+pub fn check_builtin_shadowing(
+    name: &str,
+    location: Range,
+    node_type: ShadowingType,
+) -> Option<Check> {
+    if BUILTINS.contains(&name) {
+        Some(Check::new(
+            match node_type {
+                ShadowingType::Variable => CheckKind::BuiltinVariableShadowing(name.to_string()),
+                ShadowingType::Argument => CheckKind::BuiltinArgumentShadowing(name.to_string()),
+                ShadowingType::Attribute => CheckKind::BuiltinAttributeShadowing(name.to_string()),
+            },
+            location,
+        ))
+    } else {
+        None
+    }
+}
+
+// flake8-super
+/// Check that `super()` has no args
+pub fn check_super_args(
+    expr: &Expr,
+    func: &Expr,
+    args: &Vec<Expr>,
+    locator: &mut SourceCodeLocator,
+    autofix: &fixer::Mode,
+) -> Option<Check> {
+    if let ExprKind::Name { id, .. } = &func.node {
+        if id == "super" && !args.is_empty() {
+            let mut check = Check::new(
+                CheckKind::SuperCallWithParameters,
+                Range::from_located(expr),
+            );
+            if matches!(autofix, fixer::Mode::Generate | fixer::Mode::Apply) {
+                if let Some(fix) = fixes::remove_super_arguments(locator, expr) {
+                    check.amend(fix);
+                }
+            }
+            return Some(check);
+        }
+    }
+    None
+}

src/ast/operations.rs

@@ -0,0 +1,165 @@
+use rustpython_parser::ast::{Constant, Expr, ExprKind, Location, Stmt, StmtKind};
+
+use crate::ast::types::{BindingKind, Scope};
+
+/// Extract the names bound to a given __all__ assignment.
+pub fn extract_all_names(stmt: &Stmt, scope: &Scope) -> Vec<String> {
+    let mut names: Vec<String> = vec![];
+
+    fn add_to_names(names: &mut Vec<String>, elts: &[Expr]) {
+        for elt in elts {
+            if let ExprKind::Constant {
+                value: Constant::Str(value),
+                ..
+            } = &elt.node
+            {
+                names.push(value.to_string())
+            }
+        }
+    }
+
+    // Grab the existing bound __all__ values.
+    if let StmtKind::AugAssign { .. } = &stmt.node {
+        if let Some(binding) = scope.values.get("__all__") {
+            if let BindingKind::Export(existing) = &binding.kind {
+                names.extend_from_slice(existing);
+            }
+        }
+    }
+
+    if let Some(value) = match &stmt.node {
+        StmtKind::Assign { value, .. } => Some(value),
+        StmtKind::AnnAssign { value, .. } => value.as_ref(),
+        StmtKind::AugAssign { value, .. } => Some(value),
+        _ => None,
+    } {
+        match &value.node {
+            ExprKind::List { elts, .. } | ExprKind::Tuple { elts, .. } => {
+                add_to_names(&mut names, elts)
+            }
+            ExprKind::BinOp { left, right, .. } => {
+                let mut current_left = left;
+                let mut current_right = right;
+                while let Some(elts) = match &current_right.node {
+                    ExprKind::List { elts, .. } => Some(elts),
+                    ExprKind::Tuple { elts, .. } => Some(elts),
+                    _ => None,
+                } {
+                    add_to_names(&mut names, elts);
+                    match &current_left.node {
+                        ExprKind::BinOp { left, right, .. } => {
+                            current_left = left;
+                            current_right = right;
+                        }
+                        ExprKind::List { elts, .. } | ExprKind::Tuple { elts, .. } => {
+                            add_to_names(&mut names, elts);
+                            break;
+                        }
+                        _ => break,
+                    }
+                }
+            }
+            _ => {}
+        }
+    }
+
+    names
+}
+
+/// Check if a node is parent of a conditional branch.
+pub fn on_conditional_branch(parent_stack: &[usize], parents: &[&Stmt]) -> bool {
+    for index in parent_stack.iter().rev() {
+        let parent = parents[*index];
+        if matches!(parent.node, StmtKind::If { .. } | StmtKind::While { .. }) {
+            return true;
+        }
+        if let StmtKind::Expr { value } = &parent.node {
+            if matches!(value.node, ExprKind::IfExp { .. }) {
+                return true;
+            }
+        }
+    }
+
+    false
+}
+
+/// Check if a node is in a nested block.
+pub fn in_nested_block(parent_stack: &[usize], parents: &[&Stmt]) -> bool {
+    for index in parent_stack.iter().rev() {
+        let parent = parents[*index];
+        if matches!(
+            parent.node,
+            StmtKind::Try { .. } | StmtKind::If { .. } | StmtKind::With { .. }
+        ) {
+            return true;
+        }
+    }
+
+    false
+}
+
+/// Check if a node represents an unpacking assignment.
+pub fn is_unpacking_assignment(stmt: &Stmt) -> bool {
+    if let StmtKind::Assign { targets, value, .. } = &stmt.node {
+        if !targets.iter().any(|child| {
+            matches!(
+                child.node,
+                ExprKind::Set { .. } | ExprKind::List { .. } | ExprKind::Tuple { .. }
+            )
+        }) {
+            return false;
+        }
+        match &value.node {
+            ExprKind::Set { .. } | ExprKind::List { .. } | ExprKind::Tuple { .. } => return false,
+            _ => {}
+        }
+        return true;
+    }
+    false
+}
+
+/// Struct used to efficiently slice source code at (row, column) Locations.
+pub struct SourceCodeLocator<'a> {
+    content: &'a str,
+    offsets: Vec<usize>,
+    initialized: bool,
+}
+
+impl<'a> SourceCodeLocator<'a> {
+    pub fn new(content: &'a str) -> Self {
+        SourceCodeLocator {
+            content,
+            offsets: vec![],
+            initialized: false,
+        }
+    }
+
+    pub fn slice_source_code_at(&mut self, location: &Location) -> &'a str {
+        if !self.initialized {
+            let mut offset = 0;
+            for i in self.content.lines() {
+                self.offsets.push(offset);
+                offset += i.len();
+                offset += 1;
+            }
+            self.initialized = true;
+        }
+        let offset = self.offsets[location.row() - 1] + location.column() - 1;
+        &self.content[offset..]
+    }
+
+    pub fn slice_source_code_range(&mut self, start: &Location, end: &Location) -> &'a str {
+        if !self.initialized {
+            let mut offset = 0;
+            for i in self.content.lines() {
+                self.offsets.push(offset);
+                offset += i.len();
+                offset += 1;
+            }
+            self.initialized = true;
+        }
+        let start = self.offsets[start.row() - 1] + start.column() - 1;
+        let end = self.offsets[end.row() - 1] + end.column() - 1;
+        &self.content[start..end]
+    }
+}

src/ast/relocate.rs

@@ -0,0 +1,141 @@
+use rustpython_parser::ast::{Expr, ExprKind, Keyword};
+
+use crate::ast::types::Range;
+
+fn relocate_keyword(keyword: &mut Keyword, location: Range) {
+    keyword.location = location.location;
+    keyword.end_location = location.end_location;
+    relocate_expr(&mut keyword.node.value, location);
+}
+
+/// Change an expression's location (recursively) to match a desired, fixed location.
+pub fn relocate_expr(expr: &mut Expr, location: Range) {
+    expr.location = location.location;
+    expr.end_location = location.end_location;
+    match &mut expr.node {
+        ExprKind::BoolOp { values, .. } => {
+            for expr in values {
+                relocate_expr(expr, location);
+            }
+        }
+        ExprKind::NamedExpr { target, value } => {
+            relocate_expr(target, location);
+            relocate_expr(value, location);
+        }
+        ExprKind::BinOp { left, right, .. } => {
+            relocate_expr(left, location);
+            relocate_expr(right, location);
+        }
+        ExprKind::UnaryOp { operand, .. } => {
+            relocate_expr(operand, location);
+        }
+        ExprKind::Lambda { body, .. } => {
+            relocate_expr(body, location);
+        }
+        ExprKind::IfExp { test, body, orelse } => {
+            relocate_expr(test, location);
+            relocate_expr(body, location);
+            relocate_expr(orelse, location);
+        }
+        ExprKind::Dict { keys, values } => {
+            for expr in keys {
+                relocate_expr(expr, location);
+            }
+            for expr in values {
+                relocate_expr(expr, location);
+            }
+        }
+        ExprKind::Set { elts } => {
+            for expr in elts {
+                relocate_expr(expr, location);
+            }
+        }
+        ExprKind::ListComp { elt, .. } => {
+            relocate_expr(elt, location);
+        }
+        ExprKind::SetComp { elt, .. } => {
+            relocate_expr(elt, location);
+        }
+        ExprKind::DictComp { key, value, .. } => {
+            relocate_expr(key, location);
+            relocate_expr(value, location);
+        }
+        ExprKind::GeneratorExp { elt, .. } => {
+            relocate_expr(elt, location);
+        }
+        ExprKind::Await { value } => relocate_expr(value, location),
+        ExprKind::Yield { value } => {
+            if let Some(expr) = value {
+                relocate_expr(expr, location);
+            }
+        }
+        ExprKind::YieldFrom { value } => relocate_expr(value, location),
+        ExprKind::Compare {
+            left, comparators, ..
+        } => {
+            relocate_expr(left, location);
+            for expr in comparators {
+                relocate_expr(expr, location);
+            }
+        }
+        ExprKind::Call {
+            func,
+            args,
+            keywords,
+        } => {
+            relocate_expr(func, location);
+            for expr in args {
+                relocate_expr(expr, location);
+            }
+            for keyword in keywords {
+                relocate_keyword(keyword, location);
+            }
+        }
+        ExprKind::FormattedValue {
+            value, format_spec, ..
+        } => {
+            relocate_expr(value, location);
+            if let Some(expr) = format_spec {
+                relocate_expr(expr, location);
+            }
+        }
+        ExprKind::JoinedStr { values } => {
+            for expr in values {
+                relocate_expr(expr, location);
+            }
+        }
+        ExprKind::Constant { .. } => {}
+        ExprKind::Attribute { value, .. } => {
+            relocate_expr(value, location);
+        }
+        ExprKind::Subscript { value, slice, .. } => {
+            relocate_expr(value, location);
+            relocate_expr(slice, location);
+        }
+        ExprKind::Starred { value, .. } => {
+            relocate_expr(value, location);
+        }
+        ExprKind::Name { .. } => {}
+        ExprKind::List { elts, .. } => {
+            for expr in elts {
+                relocate_expr(expr, location);
+            }
+        }
+        ExprKind::Tuple { elts, .. } => {
+            for expr in elts {
+                relocate_expr(expr, location);
+            }
+        }
+        ExprKind::Slice { lower, upper, step } => {
+            if let Some(expr) = lower {
+                relocate_expr(expr, location);
+            }
+            if let Some(expr) = upper {
+                relocate_expr(expr, location);
+            }
+            if let Some(expr) = step {
+                relocate_expr(expr, location);
+            }
+        }
+    }
+}

src/ast/types.rs

@@ -0,0 +1,86 @@
+use std::collections::BTreeMap;
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+use rustpython_parser::ast::{Located, Location};
+
+fn id() -> usize {
+    static COUNTER: AtomicUsize = AtomicUsize::new(1);
+    COUNTER.fetch_add(1, Ordering::Relaxed)
+}
+
+#[derive(Clone, Copy, Debug, Default)]
+pub struct Range {
+    pub location: Location,
+    pub end_location: Location,
+}
+
+impl Range {
+    pub fn from_located<T>(located: &Located<T>) -> Self {
+        Range {
+            location: located.location,
+            end_location: located.end_location,
+        }
+    }
+}
+
+#[derive(Clone, Debug, Default)]
+pub struct FunctionScope {
+    pub uses_locals: bool,
+}
+
+#[derive(Clone, Debug)]
+pub enum ScopeKind {
+    Class,
+    Function(FunctionScope),
+    Generator,
+    Module,
+}
+
+#[derive(Clone, Debug)]
+pub struct Scope {
+    pub id: usize,
+    pub kind: ScopeKind,
+    pub import_starred: bool,
+    pub values: BTreeMap<String, Binding>,
+}
+
+impl Scope {
+    pub fn new(kind: ScopeKind) -> Self {
+        Scope {
+            id: id(),
+            kind,
+            import_starred: false,
+            values: BTreeMap::new(),
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub enum BindingKind {
+    Annotation,
+    Argument,
+    Assignment,
+    Binding,
+    LoopVar,
+    Builtin,
+    ClassDefinition,
+    Definition,
+    Export(Vec<String>),
+    FutureImportation,
+    Importation(String),
+    StarImportation,
+    SubmoduleImportation(String),
+}
+
+#[derive(Clone, Debug)]
+pub struct Binding {
+    pub kind: BindingKind,
+    pub location: Range,
+    /// Tuple of (scope index, range) indicating the scope and range at which the binding was
+    /// last used.
+    pub used: Option<(usize, Range)>,
+}
+
+pub trait CheckLocator {
+    fn locate_check(&self, default: Range) -> Range;
+}

src/ast/visitor.rs

@@ -4,144 +4,136 @@ use rustpython_parser::ast::{
     PatternKind, Stmt, StmtKind, Unaryop, Withitem,
 };
 
-pub trait Visitor {
-    fn visit_stmt(&mut self, stmt: &Stmt) {
+pub trait Visitor<'a> {
+    fn visit_stmt(&mut self, stmt: &'a Stmt) {
         walk_stmt(self, stmt);
     }
-    fn visit_annotation(&mut self, expr: &Expr) {
+    fn visit_annotation(&mut self, expr: &'a Expr) {
         walk_expr(self, expr);
     }
-    fn visit_expr(&mut self, expr: &Expr) {
+    fn visit_expr(&mut self, expr: &'a Expr) {
         walk_expr(self, expr);
     }
-    fn visit_ident(&mut self, ident: &str) {
-        walk_ident(self, ident);
-    }
-    fn visit_constant(&mut self, constant: &Constant) {
+    fn visit_constant(&mut self, constant: &'a Constant) {
         walk_constant(self, constant);
     }
-    fn visit_expr_context(&mut self, expr_content: &ExprContext) {
+    fn visit_expr_context(&mut self, expr_content: &'a ExprContext) {
         walk_expr_context(self, expr_content);
     }
-    fn visit_boolop(&mut self, boolop: &Boolop) {
+    fn visit_boolop(&mut self, boolop: &'a Boolop) {
         walk_boolop(self, boolop);
     }
-    fn visit_operator(&mut self, operator: &Operator) {
+    fn visit_operator(&mut self, operator: &'a Operator) {
         walk_operator(self, operator);
     }
-    fn visit_unaryop(&mut self, unaryop: &Unaryop) {
+    fn visit_unaryop(&mut self, unaryop: &'a Unaryop) {
         walk_unaryop(self, unaryop);
     }
-    fn visit_cmpop(&mut self, cmpop: &Cmpop) {
+    fn visit_cmpop(&mut self, cmpop: &'a Cmpop) {
         walk_cmpop(self, cmpop);
     }
-    fn visit_comprehension(&mut self, comprehension: &Comprehension) {
+    fn visit_comprehension(&mut self, comprehension: &'a Comprehension) {
         walk_comprehension(self, comprehension);
     }
-    fn visit_excepthandler(&mut self, excepthandler: &Excepthandler) {
+    fn visit_excepthandler(&mut self, excepthandler: &'a Excepthandler) {
         walk_excepthandler(self, excepthandler);
     }
-    fn visit_arguments(&mut self, arguments: &Arguments) {
+    fn visit_arguments(&mut self, arguments: &'a Arguments) {
         walk_arguments(self, arguments);
     }
-    fn visit_arg(&mut self, arg: &Arg) {
+    fn visit_arg(&mut self, arg: &'a Arg) {
         walk_arg(self, arg);
     }
-    fn visit_keyword(&mut self, keyword: &Keyword) {
+    fn visit_keyword(&mut self, keyword: &'a Keyword) {
         walk_keyword(self, keyword);
     }
-    fn visit_alias(&mut self, alias: &Alias) {
+    fn visit_alias(&mut self, alias: &'a Alias) {
         walk_alias(self, alias);
     }
-    fn visit_withitem(&mut self, withitem: &Withitem) {
+    fn visit_withitem(&mut self, withitem: &'a Withitem) {
         walk_withitem(self, withitem);
     }
-    fn visit_match_case(&mut self, match_case: &MatchCase) {
+    fn visit_match_case(&mut self, match_case: &'a MatchCase) {
         walk_match_case(self, match_case);
     }
-    fn visit_pattern(&mut self, pattern: &Pattern) {
+    fn visit_pattern(&mut self, pattern: &'a Pattern) {
         walk_pattern(self, pattern);
     }
 }
 
-pub fn walk_stmt<V: Visitor + ?Sized>(visitor: &mut V, stmt: &Stmt) {
+pub fn walk_stmt<'a, V: Visitor<'a> + ?Sized>(visitor: &mut V, stmt: &'a Stmt) {
     match &stmt.node {
         StmtKind::FunctionDef {
-            name,
             args,
             body,
             decorator_list,
             returns,
             ..
         } => {
-            visitor.visit_ident(name);
             visitor.visit_arguments(args);
-            for stmt in body {
-                visitor.visit_stmt(stmt)
-            }
             for expr in decorator_list {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
             for expr in returns {
                 visitor.visit_annotation(expr);
             }
+            for stmt in body {
+                visitor.visit_stmt(stmt);
+            }
         }
         StmtKind::AsyncFunctionDef {
-            name,
             args,
             body,
             decorator_list,
             returns,
             ..
         } => {
-            visitor.visit_ident(name);
             visitor.visit_arguments(args);
-            for stmt in body {
-                visitor.visit_stmt(stmt)
-            }
             for expr in decorator_list {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
             for expr in returns {
                 visitor.visit_annotation(expr);
             }
+            for stmt in body {
+                visitor.visit_stmt(stmt);
+            }
         }
         StmtKind::ClassDef {
-            name,
             bases,
             keywords,
             body,
             decorator_list,
+            ..
         } => {
-            visitor.visit_ident(name);
             for expr in bases {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
             for keyword in keywords {
-                visitor.visit_keyword(keyword)
-            }
-            for stmt in body {
-                visitor.visit_stmt(stmt)
+                visitor.visit_keyword(keyword);
             }
             for expr in decorator_list {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
+            }
+            for stmt in body {
+                visitor.visit_stmt(stmt);
             }
         }
         StmtKind::Return { value } => {
             if let Some(expr) = value {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
         }
         StmtKind::Delete { targets } => {
             for expr in targets {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
         }
         StmtKind::Assign { targets, value, .. } => {
+            visitor.visit_expr(value);
             for expr in targets {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
-            visitor.visit_expr(value)
         }
         StmtKind::AugAssign { target, op, value } => {
             visitor.visit_expr(target);
@@ -154,11 +146,11 @@ pub fn walk_stmt<V: Visitor + ?Sized>(visitor: &mut V, stmt: &Stmt) {
             value,
             ..
         } => {
-            visitor.visit_expr(target);
             visitor.visit_annotation(annotation);
             if let Some(expr) = value {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
+            visitor.visit_expr(target);
         }
         StmtKind::For {
             target,
@@ -170,10 +162,10 @@ pub fn walk_stmt<V: Visitor + ?Sized>(visitor: &mut V, stmt: &Stmt) {
             visitor.visit_expr(target);
             visitor.visit_expr(iter);
             for stmt in body {
-                visitor.visit_stmt(stmt)
+                visitor.visit_stmt(stmt);
             }
             for stmt in orelse {
-                visitor.visit_stmt(stmt)
+                visitor.visit_stmt(stmt);
             }
         }
         StmtKind::AsyncFor {
@@ -186,28 +178,28 @@ pub fn walk_stmt<V: Visitor + ?Sized>(visitor: &mut V, stmt: &Stmt) {
             visitor.visit_expr(target);
             visitor.visit_expr(iter);
             for stmt in body {
-                visitor.visit_stmt(stmt)
+                visitor.visit_stmt(stmt);
             }
             for stmt in orelse {
-                visitor.visit_stmt(stmt)
+                visitor.visit_stmt(stmt);
             }
         }
         StmtKind::While { test, body, orelse } => {
             visitor.visit_expr(test);
             for stmt in body {
-                visitor.visit_stmt(stmt)
+                visitor.visit_stmt(stmt);
             }
             for stmt in orelse {
-                visitor.visit_stmt(stmt)
+                visitor.visit_stmt(stmt);
             }
         }
         StmtKind::If { test, body, orelse } => {
             visitor.visit_expr(test);
             for stmt in body {
-                visitor.visit_stmt(stmt)
+                visitor.visit_stmt(stmt);
             }
             for stmt in orelse {
-                visitor.visit_stmt(stmt)
+                visitor.visit_stmt(stmt);
             }
         }
         StmtKind::With { items, body, .. } => {
@@ -215,7 +207,7 @@ pub fn walk_stmt<V: Visitor + ?Sized>(visitor: &mut V, stmt: &Stmt) {
                 visitor.visit_withitem(withitem);
             }
             for stmt in body {
-                visitor.visit_stmt(stmt)
+                visitor.visit_stmt(stmt);
             }
         }
         StmtKind::AsyncWith { items, body, .. } => {
@@ -223,7 +215,7 @@ pub fn walk_stmt<V: Visitor + ?Sized>(visitor: &mut V, stmt: &Stmt) {
                 visitor.visit_withitem(withitem);
             }
             for stmt in body {
-                visitor.visit_stmt(stmt)
+                visitor.visit_stmt(stmt);
             }
         }
         StmtKind::Match { subject, cases } => {
@@ -235,10 +227,10 @@ pub fn walk_stmt<V: Visitor + ?Sized>(visitor: &mut V, stmt: &Stmt) {
         }
         StmtKind::Raise { exc, cause } => {
             if let Some(expr) = exc {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             };
             if let Some(expr) = cause {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             };
         }
         StmtKind::Try {
@@ -248,22 +240,22 @@ pub fn walk_stmt<V: Visitor + ?Sized>(visitor: &mut V, stmt: &Stmt) {
             finalbody,
         } => {
             for stmt in body {
-                visitor.visit_stmt(stmt)
+                visitor.visit_stmt(stmt);
             }
             for excepthandler in handlers {
                 visitor.visit_excepthandler(excepthandler)
             }
             for stmt in orelse {
-                visitor.visit_stmt(stmt)
+                visitor.visit_stmt(stmt);
             }
             for stmt in finalbody {
-                visitor.visit_stmt(stmt)
+                visitor.visit_stmt(stmt);
             }
         }
         StmtKind::Assert { test, msg } => {
             visitor.visit_expr(test);
             if let Some(expr) = msg {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
         }
         StmtKind::Import { names } => {
@@ -271,24 +263,13 @@ pub fn walk_stmt<V: Visitor + ?Sized>(visitor: &mut V, stmt: &Stmt) {
                 visitor.visit_alias(alias);
             }
         }
-        StmtKind::ImportFrom { module, names, .. } => {
-            if let Some(ident) = module {
-                visitor.visit_ident(ident);
-            }
+        StmtKind::ImportFrom { names, .. } => {
             for alias in names {
                 visitor.visit_alias(alias);
             }
         }
-        StmtKind::Global { names } => {
-            for ident in names {
-                visitor.visit_ident(ident)
-            }
-        }
-        StmtKind::Nonlocal { names } => {
-            for ident in names {
-                visitor.visit_ident(ident)
-            }
-        }
+        StmtKind::Global { .. } => {}
+        StmtKind::Nonlocal { .. } => {}
         StmtKind::Expr { value } => visitor.visit_expr(value),
         StmtKind::Pass => {}
         StmtKind::Break => {}
@@ -296,12 +277,12 @@ pub fn walk_stmt<V: Visitor + ?Sized>(visitor: &mut V, stmt: &Stmt) {
     }
 }
 
-pub fn walk_expr<V: Visitor + ?Sized>(visitor: &mut V, expr: &Expr) {
+pub fn walk_expr<'a, V: Visitor<'a> + ?Sized>(visitor: &mut V, expr: &'a Expr) {
     match &expr.node {
         ExprKind::BoolOp { op, values } => {
             visitor.visit_boolop(op);
             for expr in values {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
         }
         ExprKind::NamedExpr { target, value } => {
@@ -328,50 +309,50 @@ pub fn walk_expr<V: Visitor + ?Sized>(visitor: &mut V, expr: &Expr) {
         }
         ExprKind::Dict { keys, values } => {
             for expr in keys {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
             for expr in values {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
         }
         ExprKind::Set { elts } => {
             for expr in elts {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
         }
         ExprKind::ListComp { elt, generators } => {
-            visitor.visit_expr(elt);
             for comprehension in generators {
-                visitor.visit_comprehension(comprehension)
+                visitor.visit_comprehension(comprehension);
             }
+            visitor.visit_expr(elt);
         }
         ExprKind::SetComp { elt, generators } => {
-            visitor.visit_expr(elt);
             for comprehension in generators {
-                visitor.visit_comprehension(comprehension)
+                visitor.visit_comprehension(comprehension);
             }
+            visitor.visit_expr(elt);
         }
         ExprKind::DictComp {
             key,
             value,
             generators,
         } => {
+            for comprehension in generators {
+                visitor.visit_comprehension(comprehension);
+            }
             visitor.visit_expr(key);
             visitor.visit_expr(value);
-            for comprehension in generators {
-                visitor.visit_comprehension(comprehension)
-            }
         }
         ExprKind::GeneratorExp { elt, generators } => {
-            visitor.visit_expr(elt);
             for comprehension in generators {
-                visitor.visit_comprehension(comprehension)
+                visitor.visit_comprehension(comprehension);
             }
+            visitor.visit_expr(elt);
         }
         ExprKind::Await { value } => visitor.visit_expr(value),
         ExprKind::Yield { value } => {
             if let Some(expr) = value {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
         }
         ExprKind::YieldFrom { value } => visitor.visit_expr(value),
@@ -385,7 +366,7 @@ pub fn walk_expr<V: Visitor + ?Sized>(visitor: &mut V, expr: &Expr) {
                 visitor.visit_cmpop(cmpop);
             }
             for expr in comparators {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
         }
         ExprKind::Call {
@@ -406,12 +387,12 @@ pub fn walk_expr<V: Visitor + ?Sized>(visitor: &mut V, expr: &Expr) {
         } => {
             visitor.visit_expr(value);
             if let Some(expr) = format_spec {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
         }
         ExprKind::JoinedStr { values } => {
             for expr in values {
-                visitor.visit_expr(expr)
+                visitor.visit_expr(expr);
             }
         }
         ExprKind::Constant { value, .. } => visitor.visit_constant(value),
@@ -428,8 +409,7 @@ pub fn walk_expr<V: Visitor + ?Sized>(visitor: &mut V, expr: &Expr) {
             visitor.visit_expr(value);
             visitor.visit_expr_context(ctx);
         }
-        ExprKind::Name { id, ctx } => {
-            visitor.visit_ident(id);
+        ExprKind::Name { ctx, .. } => {
             visitor.visit_expr_context(ctx);
         }
         ExprKind::List { elts, ctx } => {
@@ -458,7 +438,7 @@ pub fn walk_expr<V: Visitor + ?Sized>(visitor: &mut V, expr: &Expr) {
     }
 }
 
-pub fn walk_constant<V: Visitor + ?Sized>(visitor: &mut V, constant: &Constant) {
+pub fn walk_constant<'a, V: Visitor<'a> + ?Sized>(visitor: &mut V, constant: &'a Constant) {
     if let Constant::Tuple(constants) = constant {
         for constant in constants {
             visitor.visit_constant(constant)
@@ -466,7 +446,10 @@ pub fn walk_constant<V: Visitor + ?Sized>(visitor: &mut V, constant: &Constant)
     }
 }
 
-pub fn walk_comprehension<V: Visitor + ?Sized>(visitor: &mut V, comprehension: &Comprehension) {
+pub fn walk_comprehension<'a, V: Visitor<'a> + ?Sized>(
+    visitor: &mut V,
+    comprehension: &'a Comprehension,
+) {
     visitor.visit_expr(&comprehension.target);
     visitor.visit_expr(&comprehension.iter);
     for expr in &comprehension.ifs {
@@ -474,15 +457,15 @@ pub fn walk_comprehension<V: Visitor + ?Sized>(visitor: &mut V, comprehension: &
     }
 }
 
-pub fn walk_excepthandler<V: Visitor + ?Sized>(visitor: &mut V, excepthandler: &Excepthandler) {
+pub fn walk_excepthandler<'a, V: Visitor<'a> + ?Sized>(
+    visitor: &mut V,
+    excepthandler: &'a Excepthandler,
+) {
     match &excepthandler.node {
-        ExcepthandlerKind::ExceptHandler { type_, name, body } => {
+        ExcepthandlerKind::ExceptHandler { type_, body, .. } => {
             if let Some(expr) = type_ {
                 visitor.visit_expr(expr);
             }
-            if let Some(ident) = name {
-                visitor.visit_ident(ident);
-            }
             for stmt in body {
                 visitor.visit_stmt(stmt);
             }
@@ -490,7 +473,7 @@ pub fn walk_excepthandler<V: Visitor + ?Sized>(visitor: &mut V, excepthandler: &
     }
 }
 
-pub fn walk_arguments<V: Visitor + ?Sized>(visitor: &mut V, arguments: &Arguments) {
+pub fn walk_arguments<'a, V: Visitor<'a> + ?Sized>(visitor: &mut V, arguments: &'a Arguments) {
     for arg in &arguments.posonlyargs {
         visitor.visit_arg(arg);
     }
@@ -498,40 +481,40 @@ pub fn walk_arguments<V: Visitor + ?Sized>(visitor: &mut V, arguments: &Argument
         visitor.visit_arg(arg);
     }
     if let Some(arg) = &arguments.vararg {
-        visitor.visit_arg(arg)
+        visitor.visit_arg(arg);
     }
     for arg in &arguments.kwonlyargs {
         visitor.visit_arg(arg);
     }
     for expr in &arguments.kw_defaults {
-        visitor.visit_expr(expr)
+        visitor.visit_expr(expr);
     }
     if let Some(arg) = &arguments.kwarg {
-        visitor.visit_arg(arg)
+        visitor.visit_arg(arg);
     }
     for expr in &arguments.defaults {
-        visitor.visit_expr(expr)
+        visitor.visit_expr(expr);
     }
 }
 
-pub fn walk_arg<V: Visitor + ?Sized>(visitor: &mut V, arg: &Arg) {
+pub fn walk_arg<'a, V: Visitor<'a> + ?Sized>(visitor: &mut V, arg: &'a Arg) {
     if let Some(expr) = &arg.node.annotation {
-        visitor.visit_annotation(expr)
+        visitor.visit_annotation(expr);
     }
 }
 
-pub fn walk_keyword<V: Visitor + ?Sized>(visitor: &mut V, keyword: &Keyword) {
+pub fn walk_keyword<'a, V: Visitor<'a> + ?Sized>(visitor: &mut V, keyword: &'a Keyword) {
     visitor.visit_expr(&keyword.node.value);
 }
 
-pub fn walk_withitem<V: Visitor + ?Sized>(visitor: &mut V, withitem: &Withitem) {
+pub fn walk_withitem<'a, V: Visitor<'a> + ?Sized>(visitor: &mut V, withitem: &'a Withitem) {
     visitor.visit_expr(&withitem.context_expr);
     if let Some(expr) = &withitem.optional_vars {
         visitor.visit_expr(expr);
     }
 }
 
-pub fn walk_match_case<V: Visitor + ?Sized>(visitor: &mut V, match_case: &MatchCase) {
+pub fn walk_match_case<'a, V: Visitor<'a> + ?Sized>(visitor: &mut V, match_case: &'a MatchCase) {
     visitor.visit_pattern(&match_case.pattern);
     if let Some(expr) = &match_case.guard {
         visitor.visit_expr(expr);
@@ -541,58 +524,42 @@ pub fn walk_match_case<V: Visitor + ?Sized>(visitor: &mut V, match_case: &MatchC
     }
 }
 
-pub fn walk_pattern<V: Visitor + ?Sized>(visitor: &mut V, pattern: &Pattern) {
+pub fn walk_pattern<'a, V: Visitor<'a> + ?Sized>(visitor: &mut V, pattern: &'a Pattern) {
     match &pattern.node {
         PatternKind::MatchValue { value } => visitor.visit_expr(value),
         PatternKind::MatchSingleton { value } => visitor.visit_constant(value),
         PatternKind::MatchSequence { patterns } => {
             for pattern in patterns {
-                visitor.visit_pattern(pattern)
+                visitor.visit_pattern(pattern);
             }
         }
-        PatternKind::MatchMapping {
-            keys,
-            patterns,
-            rest,
-        } => {
+        PatternKind::MatchMapping { keys, patterns, .. } => {
             for expr in keys {
                 visitor.visit_expr(expr);
             }
             for pattern in patterns {
                 visitor.visit_pattern(pattern);
             }
-            if let Some(ident) = rest {
-                visitor.visit_ident(ident);
-            }
         }
         PatternKind::MatchClass {
             cls,
             patterns,
-            kwd_attrs,
             kwd_patterns,
+            ..
         } => {
             visitor.visit_expr(cls);
             for pattern in patterns {
                 visitor.visit_pattern(pattern);
             }
-            for ident in kwd_attrs {
-                visitor.visit_ident(ident);
-            }
+
             for pattern in kwd_patterns {
                 visitor.visit_pattern(pattern);
             }
         }
-        PatternKind::MatchStar { name } => {
-            if let Some(ident) = name {
-                visitor.visit_ident(ident)
-            }
-        }
-        PatternKind::MatchAs { pattern, name } => {
+        PatternKind::MatchStar { .. } => {}
+        PatternKind::MatchAs { pattern, .. } => {
             if let Some(pattern) = pattern {
-                visitor.visit_pattern(pattern)
-            }
-            if let Some(ident) = name {
-                visitor.visit_ident(ident)
+                visitor.visit_pattern(pattern);
             }
         }
         PatternKind::MatchOr { patterns } => {
@@ -604,22 +571,29 @@ pub fn walk_pattern<V: Visitor + ?Sized>(visitor: &mut V, pattern: &Pattern) {
 }
 
 #[allow(unused_variables)]
-pub fn walk_ident<V: Visitor + ?Sized>(visitor: &mut V, ident: &str) {}
+#[inline(always)]
+pub fn walk_expr_context<'a, V: Visitor<'a> + ?Sized>(
+    visitor: &mut V,
+    expr_context: &'a ExprContext,
+) {
+}
 
 #[allow(unused_variables)]
-pub fn walk_expr_context<V: Visitor + ?Sized>(visitor: &mut V, expr_context: &ExprContext) {}
+#[inline(always)]
+pub fn walk_boolop<'a, V: Visitor<'a> + ?Sized>(visitor: &mut V, boolop: &'a Boolop) {}
 
 #[allow(unused_variables)]
-pub fn walk_boolop<V: Visitor + ?Sized>(visitor: &mut V, boolop: &Boolop) {}
+#[inline(always)]
+pub fn walk_operator<'a, V: Visitor<'a> + ?Sized>(visitor: &mut V, operator: &'a Operator) {}
 
 #[allow(unused_variables)]
-pub fn walk_operator<V: Visitor + ?Sized>(visitor: &mut V, operator: &Operator) {}
+#[inline(always)]
+pub fn walk_unaryop<'a, V: Visitor<'a> + ?Sized>(visitor: &mut V, unaryop: &'a Unaryop) {}
 
 #[allow(unused_variables)]
-pub fn walk_unaryop<V: Visitor + ?Sized>(visitor: &mut V, unaryop: &Unaryop) {}
+#[inline(always)]
+pub fn walk_cmpop<'a, V: Visitor<'a> + ?Sized>(visitor: &mut V, cmpop: &'a Cmpop) {}
 
 #[allow(unused_variables)]
-pub fn walk_cmpop<V: Visitor + ?Sized>(visitor: &mut V, cmpop: &Cmpop) {}
-
-#[allow(unused_variables)]
-pub fn walk_alias<V: Visitor + ?Sized>(visitor: &mut V, alias: &Alias) {}
+#[inline(always)]
+pub fn walk_alias<'a, V: Visitor<'a> + ?Sized>(visitor: &mut V, alias: &'a Alias) {}

src/autofix.rs

@@ -0,0 +1,2 @@
+pub mod fixer;
+pub mod fixes;

src/autofix/fixer.rs

@@ -0,0 +1,216 @@
+use std::fs;
+use std::path::Path;
+
+use anyhow::Result;
+use rustpython_parser::ast::Location;
+
+use crate::checks::{Check, Fix};
+
+#[derive(Hash)]
+pub enum Mode {
+    Generate,
+    Apply,
+    None,
+}
+
+impl From<bool> for Mode {
+    fn from(value: bool) -> Self {
+        match value {
+            true => Mode::Apply,
+            false => Mode::None,
+        }
+    }
+}
+
+/// Auto-fix errors in a file, and write the fixed source code to disk.
+pub fn fix_file(checks: &mut [Check], contents: &str, path: &Path) -> Result<()> {
+    if checks.iter().all(|check| check.fix.is_none()) {
+        return Ok(());
+    }
+
+    let output = apply_fixes(
+        checks.iter_mut().filter_map(|check| check.fix.as_mut()),
+        contents,
+    );
+
+    fs::write(path, output).map_err(|e| e.into())
+}
+
+/// Apply a series of fixes.
+fn apply_fixes<'a>(fixes: impl Iterator<Item = &'a mut Fix>, contents: &str) -> String {
+    let lines: Vec<&str> = contents.lines().collect();
+
+    let mut output = "".to_string();
+    let mut last_pos: Location = Location::new(0, 0);
+
+    for fix in fixes {
+        // Best-effort approach: if this fix overlaps with a fix we've already applied, skip it.
+        if last_pos > fix.location {
+            continue;
+        }
+
+        if fix.location.row() > last_pos.row() {
+            if last_pos.row() > 0 || last_pos.column() > 0 {
+                output.push_str(&lines[last_pos.row() - 1][last_pos.column() - 1..]);
+                output.push('\n');
+            }
+            for line in &lines[last_pos.row()..fix.location.row() - 1] {
+                output.push_str(line);
+                output.push('\n');
+            }
+            output.push_str(&lines[fix.location.row() - 1][..fix.location.column() - 1]);
+            output.push_str(&fix.content);
+        } else {
+            output.push_str(
+                &lines[last_pos.row() - 1][last_pos.column() - 1..fix.location.column() - 1],
+            );
+            output.push_str(&fix.content);
+        }
+
+        last_pos = fix.end_location;
+        fix.applied = true;
+    }
+
+    if last_pos.row() > 0 || last_pos.column() > 0 {
+        output.push_str(&lines[last_pos.row() - 1][last_pos.column() - 1..]);
+        output.push('\n');
+    }
+    for line in &lines[last_pos.row()..] {
+        output.push_str(line);
+        output.push('\n');
+    }
+
+    output
+}
+
+#[cfg(test)]
+mod tests {
+    use anyhow::Result;
+    use rustpython_parser::ast::Location;
+
+    use crate::autofix::fixer::apply_fixes;
+    use crate::checks::Fix;
+
+    #[test]
+    fn empty_file() -> Result<()> {
+        let mut fixes = vec![];
+        let actual = apply_fixes(fixes.iter_mut(), "");
+        let expected = "";
+
+        assert_eq!(actual, expected);
+
+        Ok(())
+    }
+
+    #[test]
+    fn apply_single_replacement() -> Result<()> {
+        let mut fixes = vec![Fix {
+            content: "Bar".to_string(),
+            location: Location::new(1, 9),
+            end_location: Location::new(1, 15),
+            applied: false,
+        }];
+        let actual = apply_fixes(
+            fixes.iter_mut(),
+            "class A(object):
+        ...
+",
+        );
+
+        let expected = "class A(Bar):
+        ...
+";
+
+        assert_eq!(actual, expected);
+
+        Ok(())
+    }
+
+    #[test]
+    fn apply_single_removal() -> Result<()> {
+        let mut fixes = vec![Fix {
+            content: "".to_string(),
+            location: Location::new(1, 8),
+            end_location: Location::new(1, 16),
+            applied: false,
+        }];
+        let actual = apply_fixes(
+            fixes.iter_mut(),
+            "class A(object):
+        ...
+",
+        );
+
+        let expected = "class A:
+        ...
+";
+
+        assert_eq!(actual, expected);
+
+        Ok(())
+    }
+
+    #[test]
+    fn apply_double_removal() -> Result<()> {
+        let mut fixes = vec![
+            Fix {
+                content: "".to_string(),
+                location: Location::new(1, 8),
+                end_location: Location::new(1, 17),
+                applied: false,
+            },
+            Fix {
+                content: "".to_string(),
+                location: Location::new(1, 17),
+                end_location: Location::new(1, 24),
+                applied: false,
+            },
+        ];
+        let actual = apply_fixes(
+            fixes.iter_mut(),
+            "class A(object, object):
+        ...
+",
+        );
+
+        let expected = "class A:
+        ...
+";
+
+        assert_eq!(actual, expected);
+
+        Ok(())
+    }
+
+    #[test]
+    fn ignore_overlapping_fixes() -> Result<()> {
+        let mut fixes = vec![
+            Fix {
+                content: "".to_string(),
+                location: Location::new(1, 8),
+                end_location: Location::new(1, 16),
+                applied: false,
+            },
+            Fix {
+                content: "ignored".to_string(),
+                location: Location::new(1, 10),
+                end_location: Location::new(1, 12),
+                applied: false,
+            },
+        ];
+        let actual = apply_fixes(
+            fixes.iter_mut(),
+            "class A(object):
+    ...
+",
+        );
+
+        let expected = "class A:
+    ...
+";
+
+        assert_eq!(actual, expected);
+
+        Ok(())
+    }
+}

src/autofix/fixes.rs

@@ -0,0 +1,158 @@
+use libcst_native::{Codegen, Expression, SmallStatement, Statement};
+use rustpython_parser::ast::{Expr, Keyword, Location};
+use rustpython_parser::lexer;
+use rustpython_parser::token::Tok;
+
+use crate::ast::operations::SourceCodeLocator;
+use crate::checks::Fix;
+
+/// Convert a location within a file (relative to `base`) to an absolute position.
+fn to_absolute(relative: &Location, base: &Location) -> Location {
+    if relative.row() == 1 {
+        Location::new(
+            relative.row() + base.row() - 1,
+            relative.column() + base.column() - 1,
+        )
+    } else {
+        Location::new(relative.row() + base.row() - 1, relative.column())
+    }
+}
+
+/// Generate a fix to remove a base from a ClassDef statement.
+pub fn remove_class_def_base(
+    locator: &mut SourceCodeLocator,
+    stmt_at: &Location,
+    expr_at: Location,
+    bases: &[Expr],
+    keywords: &[Keyword],
+) -> Option<Fix> {
+    let content = locator.slice_source_code_at(stmt_at);
+
+    // Case 1: `object` is the only base.
+    if bases.len() == 1 && keywords.is_empty() {
+        let mut fix_start = None;
+        let mut fix_end = None;
+        let mut count: usize = 0;
+        for (start, tok, end) in lexer::make_tokenizer(content).flatten() {
+            if matches!(tok, Tok::Lpar) {
+                if count == 0 {
+                    fix_start = Some(to_absolute(&start, stmt_at));
+                }
+                count += 1;
+            }
+
+            if matches!(tok, Tok::Rpar) {
+                count -= 1;
+                if count == 0 {
+                    fix_end = Some(to_absolute(&end, stmt_at));
+                    break;
+                }
+            }
+        }
+
+        return match (fix_start, fix_end) {
+            (Some(start), Some(end)) => Some(Fix {
+                content: "".to_string(),
+                location: start,
+                end_location: end,
+                applied: false,
+            }),
+            _ => None,
+        };
+    }
+
+    if bases
+        .iter()
+        .map(|node| node.location)
+        .chain(keywords.iter().map(|node| node.location))
+        .any(|location| location > expr_at)
+    {
+        // Case 2: `object` is _not_ the last node.
+        let mut fix_start: Option<Location> = None;
+        let mut fix_end: Option<Location> = None;
+        let mut seen_comma = false;
+        for (start, tok, end) in lexer::make_tokenizer(content).flatten() {
+            let start = to_absolute(&start, stmt_at);
+            if seen_comma {
+                if matches!(tok, Tok::Newline) {
+                    fix_end = Some(end);
+                } else {
+                    fix_end = Some(start);
+                }
+                break;
+            }
+            if start == expr_at {
+                fix_start = Some(start);
+            }
+            if fix_start.is_some() && matches!(tok, Tok::Comma) {
+                seen_comma = true;
+            }
+        }
+
+        match (fix_start, fix_end) {
+            (Some(start), Some(end)) => Some(Fix {
+                content: "".to_string(),
+                location: start,
+                end_location: end,
+                applied: false,
+            }),
+            _ => None,
+        }
+    } else {
+        // Case 3: `object` is the last node, so we have to find the last token that isn't a comma.
+        let mut fix_start: Option<Location> = None;
+        let mut fix_end: Option<Location> = None;
+        for (start, tok, end) in lexer::make_tokenizer(content).flatten() {
+            let start = to_absolute(&start, stmt_at);
+            let end = to_absolute(&end, stmt_at);
+            if start == expr_at {
+                fix_end = Some(end);
+                break;
+            }
+            if matches!(tok, Tok::Comma) {
+                fix_start = Some(start);
+            }
+        }
+
+        match (fix_start, fix_end) {
+            (Some(start), Some(end)) => Some(Fix {
+                content: "".to_string(),
+                location: start,
+                end_location: end,
+                applied: false,
+            }),
+            _ => None,
+        }
+    }
+}
+
+pub fn remove_super_arguments(locator: &mut SourceCodeLocator, expr: &Expr) -> Option<Fix> {
+    let contents = locator.slice_source_code_range(&expr.location, &expr.end_location);
+
+    let mut tree = match libcst_native::parse_module(contents, None) {
+        Ok(m) => m,
+        Err(_) => return None,
+    };
+
+    if let Some(Statement::Simple(body)) = tree.body.first_mut() {
+        if let Some(SmallStatement::Expr(body)) = body.body.first_mut() {
+            if let Expression::Call(body) = &mut body.value {
+                body.args = vec![];
+                body.whitespace_before_args = Default::default();
+                body.whitespace_after_func = Default::default();
+
+                let mut state = Default::default();
+                tree.codegen(&mut state);
+
+                return Some(Fix {
+                    content: state.to_string(),
+                    location: expr.location,
+                    end_location: expr.end_location,
+                    applied: false,
+                });
+            }
+        }
+    }
+
+    None
+}

src/cache.rs

@@ -1,12 +1,17 @@
 use std::collections::hash_map::DefaultHasher;
+use std::fs::{create_dir_all, File, Metadata};
 use std::hash::{Hash, Hasher};
+use std::io::Write;
 use std::path::Path;
 
+use anyhow::Result;
 use cacache::Error::EntryNotFound;
 use filetime::FileTime;
 use log::error;
+use path_absolutize::Absolutize;
 use serde::{Deserialize, Serialize};
 
+use crate::autofix::fixer;
 use crate::message::Message;
 use crate::settings::Settings;
 
@@ -60,42 +65,59 @@ impl From<bool> for Mode {
     fn from(value: bool) -> Self {
         match value {
             true => Mode::ReadWrite,
-            false => Mode::WriteOnly,
+            false => Mode::None,
         }
     }
 }
 
 fn cache_dir() -> &'static str {
-    "./.cache"
+    "./.ruff_cache"
 }
 
-fn cache_key(path: &Path, settings: &Settings) -> String {
+fn cache_key(path: &Path, settings: &Settings, autofix: &fixer::Mode) -> String {
     let mut hasher = DefaultHasher::new();
     settings.hash(&mut hasher);
+    autofix.hash(&mut hasher);
     format!(
         "{}@{}@{}",
-        path.canonicalize().unwrap().to_string_lossy(),
+        path.absolutize().unwrap().to_string_lossy(),
         VERSION,
         hasher.finish()
     )
 }
 
-pub fn get(path: &Path, settings: &Settings, mode: &Mode) -> Option<Vec<Message>> {
+pub fn init() -> Result<()> {
+    let gitignore_path = Path::new(cache_dir()).join(".gitignore");
+    if gitignore_path.exists() {
+        return Ok(());
+    }
+    create_dir_all(cache_dir())?;
+    let mut file = File::create(gitignore_path)?;
+    file.write_all(b"*").map_err(|e| e.into())
+}
+
+pub fn get(
+    path: &Path,
+    metadata: &Metadata,
+    settings: &Settings,
+    autofix: &fixer::Mode,
+    mode: &Mode,
+) -> Option<Vec<Message>> {
     if !mode.allow_read() {
         return None;
     };
 
-    match cacache::read_sync(cache_dir(), cache_key(path, settings)) {
-        Ok(encoded) => match path.metadata() {
-            Ok(m) => match bincode::deserialize::<CheckResult>(&encoded[..]) {
-                Ok(CheckResult { metadata, messages }) => {
-                    if FileTime::from_last_modification_time(&m).unix_seconds() == metadata.mtime {
-                        return Some(messages);
-                    }
+    match cacache::read_sync(cache_dir(), cache_key(path, settings, autofix)) {
+        Ok(encoded) => match bincode::deserialize::<CheckResult>(&encoded[..]) {
+            Ok(CheckResult {
+                metadata: CacheMetadata { mtime },
+                messages,
+            }) => {
+                if FileTime::from_last_modification_time(metadata).unix_seconds() == mtime {
+                    return Some(messages);
                 }
-                Err(e) => error!("Failed to deserialize encoded cache entry: {e:?}"),
-            },
-            Err(e) => error!("Failed to read metadata from path: {e:?}"),
+            }
+            Err(e) => error!("Failed to deserialize encoded cache entry: {e:?}"),
         },
         Err(EntryNotFound(_, _)) => {}
         Err(e) => error!("Failed to read from cache: {e:?}"),
@@ -103,24 +125,29 @@ pub fn get(path: &Path, settings: &Settings, mode: &Mode) -> Option<Vec<Message>
     None
 }
 
-pub fn set(path: &Path, settings: &Settings, messages: &[Message], mode: &Mode) {
+pub fn set(
+    path: &Path,
+    metadata: &Metadata,
+    settings: &Settings,
+    autofix: &fixer::Mode,
+    messages: &[Message],
+    mode: &Mode,
+) {
     if !mode.allow_write() {
         return;
     };
 
-    if let Ok(metadata) = path.metadata() {
-        let check_result = CheckResultRef {
-            metadata: &CacheMetadata {
-                mtime: FileTime::from_last_modification_time(&metadata).unix_seconds(),
-            },
-            messages,
-        };
-        if let Err(e) = cacache::write_sync(
-            cache_dir(),
-            cache_key(path, settings),
-            bincode::serialize(&check_result).unwrap(),
-        ) {
-            error!("Failed to write to cache: {e:?}")
-        }
+    let check_result = CheckResultRef {
+        metadata: &CacheMetadata {
+            mtime: FileTime::from_last_modification_time(metadata).unix_seconds(),
+        },
+        messages,
+    };
+    if let Err(e) = cacache::write_sync(
+        cache_dir(),
+        cache_key(path, settings, autofix),
+        bincode::serialize(&check_result).unwrap(),
+    ) {
+        error!("Failed to write to cache: {e:?}")
     }
 }

src/check_lines.rs

@@ -1,26 +1,229 @@
+use std::collections::BTreeMap;
+
+use crate::ast::types::Range;
 use rustpython_parser::ast::Location;
 
-use crate::checks::{Check, CheckKind};
+use crate::autofix::fixer;
+use crate::checks::{Check, CheckCode, CheckKind, Fix};
+use crate::noqa;
+use crate::noqa::Directive;
 use crate::settings::Settings;
 
-pub fn check_lines(contents: &str, settings: &Settings) -> Vec<Check> {
-    contents
-        .lines()
-        .enumerate()
-        .filter_map(|(row, line)| {
-            if settings.select.contains(CheckKind::LineTooLong.code())
-                && line.len() > settings.line_length
-            {
-                let chunks: Vec<&str> = line.split_whitespace().collect();
-                if !(chunks.len() == 1 || (chunks.len() == 2 && chunks[0] == "#")) {
-                    return Some(Check {
-                        kind: CheckKind::LineTooLong,
-                        location: Location::new(row + 1, settings.line_length + 1),
-                    });
+/// Whether the given line is too long and should be reported.
+fn should_enforce_line_length(line: &str, length: usize, limit: usize) -> bool {
+    if length > limit {
+        let mut chunks = line.split_whitespace();
+        if let (Some(first), Some(_)) = (chunks.next(), chunks.next()) {
+            // Do not enforce the line length for commented lines with a single word
+            !(first == "#" && chunks.next().is_none())
+        } else {
+            // Single word / no printable chars - no way to make the line shorter
+            false
+        }
+    } else {
+        false
+    }
+}
+
+pub fn check_lines(
+    checks: &mut Vec<Check>,
+    contents: &str,
+    noqa_line_for: &[usize],
+    settings: &Settings,
+    autofix: &fixer::Mode,
+) {
+    let enforce_line_too_long = settings.select.contains(&CheckCode::E501);
+    let enforce_noqa = settings.select.contains(&CheckCode::M001);
+
+    let mut noqa_directives: BTreeMap<usize, (Directive, Vec<&str>)> = BTreeMap::new();
+
+    let mut line_checks = vec![];
+    let mut ignored = vec![];
+
+    let lines: Vec<&str> = contents.lines().collect();
+    for (lineno, line) in lines.iter().enumerate() {
+        // Grab the noqa (logical) line number for the current (physical) line.
+        // If there are newlines at the end of the file, they won't be represented in
+        // `noqa_line_for`, so fallback to the current line.
+        let noqa_lineno = noqa_line_for
+            .get(lineno)
+            .map(|lineno| lineno - 1)
+            .unwrap_or(lineno);
+
+        if enforce_noqa {
+            noqa_directives
+                .entry(noqa_lineno)
+                .or_insert_with(|| (noqa::extract_noqa_directive(lines[noqa_lineno]), vec![]));
+        }
+
+        // Remove any ignored checks.
+        // TODO(charlie): Only validate checks for the current line.
+        for (index, check) in checks.iter().enumerate() {
+            if check.location.row() == lineno + 1 {
+                let noqa = noqa_directives
+                    .entry(noqa_lineno)
+                    .or_insert_with(|| (noqa::extract_noqa_directive(lines[noqa_lineno]), vec![]));
+
+                match noqa {
+                    (Directive::All(_, _), matches) => {
+                        matches.push(check.kind.code().as_str());
+                        ignored.push(index)
+                    }
+                    (Directive::Codes(_, _, codes), matches) => {
+                        if codes.contains(&check.kind.code().as_str()) {
+                            matches.push(check.kind.code().as_str());
+                            ignored.push(index);
+                        }
+                    }
+                    (Directive::None, _) => {}
                 }
             }
+        }
 
-            None
-        })
-        .collect()
+        // Enforce line length.
+        if enforce_line_too_long {
+            let line_length = line.chars().count();
+            if should_enforce_line_length(line, line_length, settings.line_length) {
+                let noqa = noqa_directives
+                    .entry(noqa_lineno)
+                    .or_insert_with(|| (noqa::extract_noqa_directive(lines[noqa_lineno]), vec![]));
+
+                let check = Check::new(
+                    CheckKind::LineTooLong(line_length, settings.line_length),
+                    Range {
+                        location: Location::new(lineno + 1, 1),
+                        end_location: Location::new(lineno + 1, line_length + 1),
+                    },
+                );
+
+                match noqa {
+                    (Directive::All(_, _), matches) => {
+                        matches.push(check.kind.code().as_str());
+                    }
+                    (Directive::Codes(_, _, codes), matches) => {
+                        if codes.contains(&check.kind.code().as_str()) {
+                            matches.push(check.kind.code().as_str());
+                        } else {
+                            line_checks.push(check);
+                        }
+                    }
+                    (Directive::None, _) => line_checks.push(check),
+                }
+            }
+        }
+    }
+
+    // Enforce that the noqa directive was actually used.
+    if enforce_noqa {
+        for (row, (directive, matches)) in noqa_directives {
+            match directive {
+                Directive::All(start, end) => {
+                    if matches.is_empty() {
+                        let mut check = Check::new(
+                            CheckKind::UnusedNOQA(None),
+                            Range {
+                                location: Location::new(row + 1, start + 1),
+                                end_location: Location::new(row + 1, end + 1),
+                            },
+                        );
+                        if matches!(autofix, fixer::Mode::Generate | fixer::Mode::Apply) {
+                            check.amend(Fix {
+                                content: "".to_string(),
+                                location: Location::new(row + 1, start + 1),
+                                end_location: Location::new(
+                                    row + 1,
+                                    lines[row].chars().count() + 1,
+                                ),
+                                applied: false,
+                            });
+                        }
+                        line_checks.push(check);
+                    }
+                }
+                Directive::Codes(start, end, codes) => {
+                    let mut invalid_codes = vec![];
+                    let mut valid_codes = vec![];
+                    for code in codes {
+                        if !matches.contains(&code) {
+                            invalid_codes.push(code);
+                        } else {
+                            valid_codes.push(code);
+                        }
+                    }
+
+                    if !invalid_codes.is_empty() {
+                        let mut check = Check::new(
+                            CheckKind::UnusedNOQA(Some(invalid_codes.join(", "))),
+                            Range {
+                                location: Location::new(row + 1, start + 1),
+                                end_location: Location::new(row + 1, end + 1),
+                            },
+                        );
+                        if matches!(autofix, fixer::Mode::Generate | fixer::Mode::Apply) {
+                            if valid_codes.is_empty() {
+                                check.amend(Fix {
+                                    content: "".to_string(),
+                                    location: Location::new(row + 1, start + 1),
+                                    end_location: Location::new(
+                                        row + 1,
+                                        lines[row].chars().count() + 1,
+                                    ),
+                                    applied: false,
+                                });
+                            } else {
+                                check.amend(Fix {
+                                    content: format!("  # noqa: {}", valid_codes.join(", ")),
+                                    location: Location::new(row + 1, start + 1),
+                                    end_location: Location::new(
+                                        row + 1,
+                                        lines[row].chars().count() + 1,
+                                    ),
+                                    applied: false,
+                                });
+                            }
+                        }
+                        line_checks.push(check);
+                    }
+                }
+                Directive::None => {}
+            }
+        }
+    }
+
+    ignored.sort();
+    for index in ignored.iter().rev() {
+        checks.swap_remove(*index);
+    }
+    checks.extend(line_checks);
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::autofix::fixer;
+    use crate::checks::{Check, CheckCode};
+    use crate::settings;
+
+    use super::check_lines;
+
+    #[test]
+    fn e501_non_ascii_char() {
+        let line = "'\u{4e9c}' * 2"; // 7 in UTF-32, 9 in UTF-8.
+        let noqa_line_for: Vec<usize> = vec![1];
+        let check_with_max_line_length = |line_length: usize| {
+            let mut checks: Vec<Check> = vec![];
+            check_lines(
+                &mut checks,
+                line,
+                &noqa_line_for,
+                &settings::Settings {
+                    line_length,
+                    ..settings::Settings::for_rule(CheckCode::E501)
+                },
+                &fixer::Mode::Generate,
+            );
+            return checks;
+        };
+        assert!(!check_with_max_line_length(6).is_empty());
+        assert!(check_with_max_line_length(7).is_empty());
+    }
 }

src/checks.rs

@@ -1,18 +1,178 @@
+use std::str::FromStr;
+
+use crate::ast::types::Range;
 use anyhow::Result;
 use rustpython_parser::ast::Location;
 use serde::{Deserialize, Serialize};
-use std::str::FromStr;
 
-#[derive(Debug, PartialEq, Eq, Serialize, Deserialize, Hash, PartialOrd, Ord)]
+pub const DEFAULT_CHECK_CODES: [CheckCode; 46] = [
+    // pycodestyle
+    CheckCode::E402,
+    CheckCode::E501,
+    CheckCode::E711,
+    CheckCode::E712,
+    CheckCode::E713,
+    CheckCode::E714,
+    CheckCode::E721,
+    CheckCode::E722,
+    CheckCode::E731,
+    CheckCode::E741,
+    CheckCode::E742,
+    CheckCode::E743,
+    CheckCode::E902,
+    CheckCode::E999,
+    // pyflakes
+    CheckCode::F401,
+    CheckCode::F402,
+    CheckCode::F403,
+    CheckCode::F404,
+    CheckCode::F405,
+    CheckCode::F406,
+    CheckCode::F407,
+    CheckCode::F541,
+    CheckCode::F601,
+    CheckCode::F602,
+    CheckCode::F621,
+    CheckCode::F622,
+    CheckCode::F631,
+    CheckCode::F632,
+    CheckCode::F633,
+    CheckCode::F634,
+    CheckCode::F701,
+    CheckCode::F702,
+    CheckCode::F704,
+    CheckCode::F706,
+    CheckCode::F707,
+    CheckCode::F722,
+    CheckCode::F821,
+    CheckCode::F822,
+    CheckCode::F823,
+    CheckCode::F831,
+    CheckCode::F841,
+    CheckCode::F901,
+    // flake8-builtins
+    CheckCode::A001,
+    CheckCode::A002,
+    CheckCode::A003,
+    // flake8-super
+    CheckCode::SPR001,
+];
+
+pub const ALL_CHECK_CODES: [CheckCode; 49] = [
+    // pycodestyle
+    CheckCode::E402,
+    CheckCode::E501,
+    CheckCode::E711,
+    CheckCode::E712,
+    CheckCode::E713,
+    CheckCode::E714,
+    CheckCode::E721,
+    CheckCode::E722,
+    CheckCode::E731,
+    CheckCode::E741,
+    CheckCode::E742,
+    CheckCode::E743,
+    CheckCode::E902,
+    CheckCode::E999,
+    // pyflakes
+    CheckCode::F401,
+    CheckCode::F402,
+    CheckCode::F403,
+    CheckCode::F404,
+    CheckCode::F405,
+    CheckCode::F406,
+    CheckCode::F407,
+    CheckCode::F541,
+    CheckCode::F601,
+    CheckCode::F602,
+    CheckCode::F621,
+    CheckCode::F622,
+    CheckCode::F631,
+    CheckCode::F632,
+    CheckCode::F633,
+    CheckCode::F634,
+    CheckCode::F701,
+    CheckCode::F702,
+    CheckCode::F704,
+    CheckCode::F706,
+    CheckCode::F707,
+    CheckCode::F722,
+    CheckCode::F821,
+    CheckCode::F822,
+    CheckCode::F823,
+    CheckCode::F831,
+    CheckCode::F841,
+    CheckCode::F901,
+    // flake8-builtins
+    CheckCode::A001,
+    CheckCode::A002,
+    CheckCode::A003,
+    // flake8-super
+    CheckCode::SPR001,
+    // Meta
+    CheckCode::M001,
+    // Refactor
+    CheckCode::R001,
+    CheckCode::R002,
+];
+
+#[derive(Debug, PartialEq, Eq, Clone, Serialize, Deserialize, Hash, PartialOrd, Ord)]
 pub enum CheckCode {
+    // pycodestyle
+    E402,
     E501,
+    E711,
+    E712,
+    E713,
+    E714,
+    E721,
+    E722,
+    E731,
+    E741,
+    E742,
+    E743,
+    E902,
+    E999,
+    // pyflakes
     F401,
+    F402,
     F403,
+    F404,
+    F405,
+    F406,
+    F407,
     F541,
+    F601,
+    F602,
+    F621,
+    F622,
+    F631,
+    F632,
+    F633,
     F634,
+    F701,
+    F702,
+    F704,
     F706,
+    F707,
+    F722,
+    F821,
+    F822,
+    F823,
     F831,
+    F841,
     F901,
+    // flake8-builtins
+    A001,
+    A002,
+    A003,
+    // flake8-super
+    SPR001,
+    // Refactor
+    R001,
+    R002,
+    // Meta
+    M001,
 }
 
 impl FromStr for CheckCode {
@@ -20,14 +180,61 @@ impl FromStr for CheckCode {
 
     fn from_str(s: &str) -> Result<Self> {
         match s {
+            // pycodestyle
+            "E402" => Ok(CheckCode::E402),
             "E501" => Ok(CheckCode::E501),
+            "E711" => Ok(CheckCode::E711),
+            "E712" => Ok(CheckCode::E712),
+            "E713" => Ok(CheckCode::E713),
+            "E714" => Ok(CheckCode::E714),
+            "E721" => Ok(CheckCode::E721),
+            "E722" => Ok(CheckCode::E722),
+            "E731" => Ok(CheckCode::E731),
+            "E741" => Ok(CheckCode::E741),
+            "E742" => Ok(CheckCode::E742),
+            "E743" => Ok(CheckCode::E743),
+            "E902" => Ok(CheckCode::E902),
+            "E999" => Ok(CheckCode::E999),
+            // pyflakes
             "F401" => Ok(CheckCode::F401),
+            "F402" => Ok(CheckCode::F402),
             "F403" => Ok(CheckCode::F403),
+            "F404" => Ok(CheckCode::F404),
+            "F405" => Ok(CheckCode::F405),
+            "F406" => Ok(CheckCode::F406),
+            "F407" => Ok(CheckCode::F407),
             "F541" => Ok(CheckCode::F541),
+            "F601" => Ok(CheckCode::F601),
+            "F602" => Ok(CheckCode::F602),
+            "F621" => Ok(CheckCode::F621),
+            "F622" => Ok(CheckCode::F622),
+            "F631" => Ok(CheckCode::F631),
+            "F632" => Ok(CheckCode::F632),
+            "F633" => Ok(CheckCode::F633),
             "F634" => Ok(CheckCode::F634),
+            "F701" => Ok(CheckCode::F701),
+            "F702" => Ok(CheckCode::F702),
+            "F704" => Ok(CheckCode::F704),
             "F706" => Ok(CheckCode::F706),
+            "F707" => Ok(CheckCode::F707),
+            "F722" => Ok(CheckCode::F722),
+            "F821" => Ok(CheckCode::F821),
+            "F822" => Ok(CheckCode::F822),
+            "F823" => Ok(CheckCode::F823),
             "F831" => Ok(CheckCode::F831),
+            "F841" => Ok(CheckCode::F841),
             "F901" => Ok(CheckCode::F901),
+            // flake8-builtins
+            "A001" => Ok(CheckCode::A001),
+            "A002" => Ok(CheckCode::A002),
+            "A003" => Ok(CheckCode::A003),
+            // flake8-super
+            "SPR001" => Ok(CheckCode::SPR001),
+            // Refactor
+            "R001" => Ok(CheckCode::R001),
+            "R002" => Ok(CheckCode::R002),
+            // Meta
+            "M001" => Ok(CheckCode::M001),
             _ => Err(anyhow::anyhow!("Unknown check code: {s}")),
         }
     }
@@ -36,28 +243,131 @@ impl FromStr for CheckCode {
 impl CheckCode {
     pub fn as_str(&self) -> &str {
         match self {
+            // pycodestyle
+            CheckCode::E402 => "E402",
             CheckCode::E501 => "E501",
+            CheckCode::E711 => "E711",
+            CheckCode::E712 => "E712",
+            CheckCode::E713 => "E713",
+            CheckCode::E714 => "E714",
+            CheckCode::E721 => "E721",
+            CheckCode::E722 => "E722",
+            CheckCode::E731 => "E731",
+            CheckCode::E741 => "E741",
+            CheckCode::E742 => "E742",
+            CheckCode::E743 => "E743",
+            CheckCode::E902 => "E902",
+            CheckCode::E999 => "E999",
+            // pyflakes
             CheckCode::F401 => "F401",
+            CheckCode::F402 => "F402",
             CheckCode::F403 => "F403",
+            CheckCode::F404 => "F404",
+            CheckCode::F405 => "F405",
+            CheckCode::F406 => "F406",
+            CheckCode::F407 => "F407",
             CheckCode::F541 => "F541",
+            CheckCode::F601 => "F601",
+            CheckCode::F602 => "F602",
+            CheckCode::F621 => "F621",
+            CheckCode::F622 => "F622",
+            CheckCode::F631 => "F631",
+            CheckCode::F632 => "F632",
+            CheckCode::F633 => "F633",
             CheckCode::F634 => "F634",
+            CheckCode::F701 => "F701",
+            CheckCode::F702 => "F702",
+            CheckCode::F704 => "F704",
             CheckCode::F706 => "F706",
+            CheckCode::F707 => "F707",
+            CheckCode::F722 => "F722",
+            CheckCode::F821 => "F821",
+            CheckCode::F822 => "F822",
+            CheckCode::F823 => "F823",
             CheckCode::F831 => "F831",
+            CheckCode::F841 => "F841",
             CheckCode::F901 => "F901",
+            // flake8-builtins
+            CheckCode::A001 => "A001",
+            CheckCode::A002 => "A002",
+            CheckCode::A003 => "A003",
+            // flake8-super
+            CheckCode::SPR001 => "SPR001",
+            // Refactor
+            CheckCode::R001 => "R001",
+            CheckCode::R002 => "R002",
+            // Meta
+            CheckCode::M001 => "M001",
         }
     }
 
-    /// The source for the check (either the AST, or the physical lines).
+    /// The source for the check (either the AST, the filesystem, or the physical lines).
     pub fn lint_source(&self) -> &'static LintSource {
         match self {
-            CheckCode::E501 => &LintSource::Lines,
-            CheckCode::F401 => &LintSource::AST,
-            CheckCode::F403 => &LintSource::AST,
-            CheckCode::F541 => &LintSource::AST,
-            CheckCode::F634 => &LintSource::AST,
-            CheckCode::F706 => &LintSource::AST,
-            CheckCode::F831 => &LintSource::AST,
-            CheckCode::F901 => &LintSource::AST,
+            CheckCode::E501 | CheckCode::M001 => &LintSource::Lines,
+            CheckCode::E902 => &LintSource::FileSystem,
+            _ => &LintSource::AST,
+        }
+    }
+
+    /// A placeholder representation of the CheckKind for the check.
+    pub fn kind(&self) -> CheckKind {
+        match self {
+            // pycodestyle
+            CheckCode::E402 => CheckKind::ModuleImportNotAtTopOfFile,
+            CheckCode::E501 => CheckKind::LineTooLong(89, 88),
+            CheckCode::E711 => CheckKind::NoneComparison(RejectedCmpop::Eq),
+            CheckCode::E712 => CheckKind::TrueFalseComparison(true, RejectedCmpop::Eq),
+            CheckCode::E713 => CheckKind::NotInTest,
+            CheckCode::E714 => CheckKind::NotIsTest,
+            CheckCode::E721 => CheckKind::TypeComparison,
+            CheckCode::E722 => CheckKind::DoNotUseBareExcept,
+            CheckCode::E731 => CheckKind::DoNotAssignLambda,
+            CheckCode::E741 => CheckKind::AmbiguousVariableName("...".to_string()),
+            CheckCode::E742 => CheckKind::AmbiguousClassName("...".to_string()),
+            CheckCode::E743 => CheckKind::AmbiguousFunctionName("...".to_string()),
+            CheckCode::E902 => CheckKind::IOError("...".to_string()),
+            CheckCode::E999 => CheckKind::SyntaxError("...".to_string()),
+            // pyflakes
+            CheckCode::F401 => CheckKind::UnusedImport("...".to_string()),
+            CheckCode::F402 => CheckKind::ImportShadowedByLoopVar("...".to_string(), 1),
+            CheckCode::F403 => CheckKind::ImportStarUsed("...".to_string()),
+            CheckCode::F404 => CheckKind::LateFutureImport,
+            CheckCode::F405 => CheckKind::ImportStarUsage("...".to_string(), "...".to_string()),
+            CheckCode::F406 => CheckKind::ImportStarNotPermitted("...".to_string()),
+            CheckCode::F407 => CheckKind::FutureFeatureNotDefined("...".to_string()),
+            CheckCode::F541 => CheckKind::FStringMissingPlaceholders,
+            CheckCode::F601 => CheckKind::MultiValueRepeatedKeyLiteral,
+            CheckCode::F602 => CheckKind::MultiValueRepeatedKeyVariable("...".to_string()),
+            CheckCode::F621 => CheckKind::TooManyExpressionsInStarredAssignment,
+            CheckCode::F622 => CheckKind::TwoStarredExpressions,
+            CheckCode::F631 => CheckKind::AssertTuple,
+            CheckCode::F632 => CheckKind::IsLiteral,
+            CheckCode::F633 => CheckKind::InvalidPrintSyntax,
+            CheckCode::F634 => CheckKind::IfTuple,
+            CheckCode::F701 => CheckKind::BreakOutsideLoop,
+            CheckCode::F702 => CheckKind::ContinueOutsideLoop,
+            CheckCode::F704 => CheckKind::YieldOutsideFunction,
+            CheckCode::F706 => CheckKind::ReturnOutsideFunction,
+            CheckCode::F707 => CheckKind::DefaultExceptNotLast,
+            CheckCode::F722 => CheckKind::ForwardAnnotationSyntaxError("...".to_string()),
+            CheckCode::F821 => CheckKind::UndefinedName("...".to_string()),
+            CheckCode::F822 => CheckKind::UndefinedExport("...".to_string()),
+            CheckCode::F823 => CheckKind::UndefinedLocal("...".to_string()),
+            CheckCode::F831 => CheckKind::DuplicateArgumentName,
+            CheckCode::F841 => CheckKind::UnusedVariable("...".to_string()),
+            CheckCode::F901 => CheckKind::RaiseNotImplemented,
+            // flake8-builtins
+            CheckCode::A001 => CheckKind::BuiltinVariableShadowing("...".to_string()),
+            CheckCode::A002 => CheckKind::BuiltinArgumentShadowing("...".to_string()),
+            CheckCode::A003 => CheckKind::BuiltinAttributeShadowing("...".to_string()),
+            // flake8-super
+            CheckCode::SPR001 => CheckKind::SuperCallWithParameters,
+            // Refactor
+            CheckCode::R001 => CheckKind::UselessObjectInheritance("...".to_string()),
+            CheckCode::R002 => CheckKind::NoAssertEquals,
+            // Meta
+            CheckCode::M001 => CheckKind::UnusedNOQA(None),
         }
     }
 }
@@ -66,62 +376,374 @@ impl CheckCode {
 pub enum LintSource {
     AST,
     Lines,
+    FileSystem,
+}
+
+#[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub enum RejectedCmpop {
+    Eq,
+    NotEq,
 }
 
 #[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]
 pub enum CheckKind {
+    UnusedNOQA(Option<String>),
+    AmbiguousClassName(String),
+    AmbiguousFunctionName(String),
+    AmbiguousVariableName(String),
+    AssertTuple,
+    BreakOutsideLoop,
+    ContinueOutsideLoop,
+    DefaultExceptNotLast,
+    DoNotAssignLambda,
+    DoNotUseBareExcept,
     DuplicateArgumentName,
+    ForwardAnnotationSyntaxError(String),
     FStringMissingPlaceholders,
+    FutureFeatureNotDefined(String),
+    IOError(String),
     IfTuple,
-    ImportStarUsage,
-    LineTooLong,
+    ImportShadowedByLoopVar(String, usize),
+    ImportStarNotPermitted(String),
+    ImportStarUsage(String, String),
+    ImportStarUsed(String),
+    InvalidPrintSyntax,
+    IsLiteral,
+    LateFutureImport,
+    LineTooLong(usize, usize),
+    ModuleImportNotAtTopOfFile,
+    MultiValueRepeatedKeyLiteral,
+    MultiValueRepeatedKeyVariable(String),
+    NoAssertEquals,
+    NoneComparison(RejectedCmpop),
+    NotInTest,
+    NotIsTest,
     RaiseNotImplemented,
     ReturnOutsideFunction,
+    SyntaxError(String),
+    TooManyExpressionsInStarredAssignment,
+    TrueFalseComparison(bool, RejectedCmpop),
+    TwoStarredExpressions,
+    TypeComparison,
+    UndefinedExport(String),
+    UndefinedLocal(String),
+    UndefinedName(String),
     UnusedImport(String),
+    UnusedVariable(String),
+    UselessObjectInheritance(String),
+    YieldOutsideFunction,
+    // flake8-builtin
+    BuiltinVariableShadowing(String),
+    BuiltinArgumentShadowing(String),
+    BuiltinAttributeShadowing(String),
+    // flake8-super
+    SuperCallWithParameters,
 }
 
 impl CheckKind {
+    /// The name of the check.
+    pub fn name(&self) -> &'static str {
+        match self {
+            CheckKind::AmbiguousClassName(_) => "AmbiguousClassName",
+            CheckKind::AmbiguousFunctionName(_) => "AmbiguousFunctionName",
+            CheckKind::AmbiguousVariableName(_) => "AmbiguousVariableName",
+            CheckKind::AssertTuple => "AssertTuple",
+            CheckKind::BreakOutsideLoop => "BreakOutsideLoop",
+            CheckKind::ContinueOutsideLoop => "ContinueOutsideLoop",
+            CheckKind::DefaultExceptNotLast => "DefaultExceptNotLast",
+            CheckKind::DoNotAssignLambda => "DoNotAssignLambda",
+            CheckKind::DoNotUseBareExcept => "DoNotUseBareExcept",
+            CheckKind::DuplicateArgumentName => "DuplicateArgumentName",
+            CheckKind::FStringMissingPlaceholders => "FStringMissingPlaceholders",
+            CheckKind::ForwardAnnotationSyntaxError(_) => "ForwardAnnotationSyntaxError",
+            CheckKind::FutureFeatureNotDefined(_) => "FutureFeatureNotDefined",
+            CheckKind::IOError(_) => "IOError",
+            CheckKind::IfTuple => "IfTuple",
+            CheckKind::ImportShadowedByLoopVar(_, _) => "ImportShadowedByLoopVar",
+            CheckKind::ImportStarNotPermitted(_) => "ImportStarNotPermitted",
+            CheckKind::ImportStarUsage(_, _) => "ImportStarUsage",
+            CheckKind::ImportStarUsed(_) => "ImportStarUsed",
+            CheckKind::InvalidPrintSyntax => "InvalidPrintSyntax",
+            CheckKind::IsLiteral => "IsLiteral",
+            CheckKind::LateFutureImport => "LateFutureImport",
+            CheckKind::LineTooLong(_, _) => "LineTooLong",
+            CheckKind::ModuleImportNotAtTopOfFile => "ModuleImportNotAtTopOfFile",
+            CheckKind::MultiValueRepeatedKeyLiteral => "MultiValueRepeatedKeyLiteral",
+            CheckKind::MultiValueRepeatedKeyVariable(_) => "MultiValueRepeatedKeyVariable",
+            CheckKind::NoAssertEquals => "NoAssertEquals",
+            CheckKind::NoneComparison(_) => "NoneComparison",
+            CheckKind::NotInTest => "NotInTest",
+            CheckKind::NotIsTest => "NotIsTest",
+            CheckKind::RaiseNotImplemented => "RaiseNotImplemented",
+            CheckKind::ReturnOutsideFunction => "ReturnOutsideFunction",
+            CheckKind::SyntaxError(_) => "SyntaxError",
+            CheckKind::TooManyExpressionsInStarredAssignment => {
+                "TooManyExpressionsInStarredAssignment"
+            }
+            CheckKind::TrueFalseComparison(_, _) => "TrueFalseComparison",
+            CheckKind::TwoStarredExpressions => "TwoStarredExpressions",
+            CheckKind::TypeComparison => "TypeComparison",
+            CheckKind::UndefinedExport(_) => "UndefinedExport",
+            CheckKind::UndefinedLocal(_) => "UndefinedLocal",
+            CheckKind::UndefinedName(_) => "UndefinedName",
+            CheckKind::UnusedImport(_) => "UnusedImport",
+            CheckKind::UnusedVariable(_) => "UnusedVariable",
+            CheckKind::UselessObjectInheritance(_) => "UselessObjectInheritance",
+            CheckKind::YieldOutsideFunction => "YieldOutsideFunction",
+            CheckKind::UnusedNOQA(_) => "UnusedNOQA",
+            // flake8-builtins
+            CheckKind::BuiltinVariableShadowing(_) => "BuiltinVariableShadowing",
+            CheckKind::BuiltinArgumentShadowing(_) => "BuiltinArgumentShadowing",
+            CheckKind::BuiltinAttributeShadowing(_) => "BuiltinAttributeShadowing",
+            // flake8-super
+            CheckKind::SuperCallWithParameters => "SuperCallWithParameters",
+        }
+    }
+
     /// A four-letter shorthand code for the check.
     pub fn code(&self) -> &'static CheckCode {
         match self {
+            CheckKind::AmbiguousClassName(_) => &CheckCode::E742,
+            CheckKind::AmbiguousFunctionName(_) => &CheckCode::E743,
+            CheckKind::AmbiguousVariableName(_) => &CheckCode::E741,
+            CheckKind::AssertTuple => &CheckCode::F631,
+            CheckKind::BreakOutsideLoop => &CheckCode::F701,
+            CheckKind::ContinueOutsideLoop => &CheckCode::F702,
+            CheckKind::DefaultExceptNotLast => &CheckCode::F707,
+            CheckKind::DoNotAssignLambda => &CheckCode::E731,
+            CheckKind::DoNotUseBareExcept => &CheckCode::E722,
             CheckKind::DuplicateArgumentName => &CheckCode::F831,
             CheckKind::FStringMissingPlaceholders => &CheckCode::F541,
+            CheckKind::ForwardAnnotationSyntaxError(_) => &CheckCode::F722,
+            CheckKind::FutureFeatureNotDefined(_) => &CheckCode::F407,
+            CheckKind::IOError(_) => &CheckCode::E902,
             CheckKind::IfTuple => &CheckCode::F634,
-            CheckKind::ImportStarUsage => &CheckCode::F403,
-            CheckKind::LineTooLong => &CheckCode::E501,
+            CheckKind::ImportShadowedByLoopVar(_, _) => &CheckCode::F402,
+            CheckKind::ImportStarNotPermitted(_) => &CheckCode::F406,
+            CheckKind::ImportStarUsage(_, _) => &CheckCode::F405,
+            CheckKind::ImportStarUsed(_) => &CheckCode::F403,
+            CheckKind::InvalidPrintSyntax => &CheckCode::F633,
+            CheckKind::IsLiteral => &CheckCode::F632,
+            CheckKind::LateFutureImport => &CheckCode::F404,
+            CheckKind::LineTooLong(_, _) => &CheckCode::E501,
+            CheckKind::ModuleImportNotAtTopOfFile => &CheckCode::E402,
+            CheckKind::MultiValueRepeatedKeyLiteral => &CheckCode::F601,
+            CheckKind::MultiValueRepeatedKeyVariable(_) => &CheckCode::F602,
+            CheckKind::NoAssertEquals => &CheckCode::R002,
+            CheckKind::NoneComparison(_) => &CheckCode::E711,
+            CheckKind::NotInTest => &CheckCode::E713,
+            CheckKind::NotIsTest => &CheckCode::E714,
             CheckKind::RaiseNotImplemented => &CheckCode::F901,
             CheckKind::ReturnOutsideFunction => &CheckCode::F706,
+            CheckKind::SyntaxError(_) => &CheckCode::E999,
+            CheckKind::TooManyExpressionsInStarredAssignment => &CheckCode::F621,
+            CheckKind::TrueFalseComparison(_, _) => &CheckCode::E712,
+            CheckKind::TwoStarredExpressions => &CheckCode::F622,
+            CheckKind::TypeComparison => &CheckCode::E721,
+            CheckKind::UndefinedExport(_) => &CheckCode::F822,
+            CheckKind::UndefinedLocal(_) => &CheckCode::F823,
+            CheckKind::UndefinedName(_) => &CheckCode::F821,
             CheckKind::UnusedImport(_) => &CheckCode::F401,
+            CheckKind::UnusedNOQA(_) => &CheckCode::M001,
+            CheckKind::UnusedVariable(_) => &CheckCode::F841,
+            CheckKind::UselessObjectInheritance(_) => &CheckCode::R001,
+            CheckKind::YieldOutsideFunction => &CheckCode::F704,
+            // flake8-builtins
+            CheckKind::BuiltinVariableShadowing(_) => &CheckCode::A001,
+            CheckKind::BuiltinArgumentShadowing(_) => &CheckCode::A002,
+            CheckKind::BuiltinAttributeShadowing(_) => &CheckCode::A003,
+            // flake8-super
+            CheckKind::SuperCallWithParameters => &CheckCode::SPR001,
         }
     }
 
     /// The body text for the check.
     pub fn body(&self) -> String {
         match self {
+            CheckKind::AmbiguousClassName(name) => {
+                format!("ambiguous class name '{}'", name)
+            }
+            CheckKind::AmbiguousFunctionName(name) => {
+                format!("ambiguous function name '{}'", name)
+            }
+            CheckKind::AmbiguousVariableName(name) => {
+                format!("ambiguous variable name '{}'", name)
+            }
+            CheckKind::AssertTuple => {
+                "Assert test is a non-empty tuple, which is always `True`".to_string()
+            }
+            CheckKind::BreakOutsideLoop => "`break` outside loop".to_string(),
+            CheckKind::ContinueOutsideLoop => "`continue` not properly in loop".to_string(),
+            CheckKind::DefaultExceptNotLast => {
+                "an `except:` block as not the last exception handler".to_string()
+            }
+            CheckKind::DoNotAssignLambda => {
+                "Do not assign a lambda expression, use a def".to_string()
+            }
+            CheckKind::DoNotUseBareExcept => "Do not use bare `except`".to_string(),
             CheckKind::DuplicateArgumentName => {
                 "Duplicate argument name in function definition".to_string()
             }
+            CheckKind::ForwardAnnotationSyntaxError(body) => {
+                format!("syntax error in forward annotation '{body}'")
+            }
             CheckKind::FStringMissingPlaceholders => {
                 "f-string without any placeholders".to_string()
             }
-            CheckKind::IfTuple => {
-                "If test is a tuple.to_string(), which is always `True`".to_string()
+            CheckKind::FutureFeatureNotDefined(name) => {
+                format!("future feature '{name}' is not defined")
             }
-            CheckKind::ImportStarUsage => "Unable to detect undefined names".to_string(),
-            CheckKind::LineTooLong => "Line too long".to_string(),
+            CheckKind::IOError(message) => message.clone(),
+            CheckKind::IfTuple => "If test is a tuple, which is always `True`".to_string(),
+            CheckKind::InvalidPrintSyntax => "use of >> is invalid with print function".to_string(),
+            CheckKind::ImportShadowedByLoopVar(name, line) => {
+                format!("import '{name}' from line {line} shadowed by loop variable")
+            }
+            CheckKind::ImportStarNotPermitted(name) => {
+                format!("`from {name} import *` only allowed at module level")
+            }
+            CheckKind::ImportStarUsed(name) => {
+                format!("`from {name} import *` used; unable to detect undefined names")
+            }
+            CheckKind::ImportStarUsage(name, sources) => {
+                format!("'{name}' may be undefined, or defined from star imports: {sources}")
+            }
+            CheckKind::IsLiteral => "use ==/!= to compare constant literals".to_string(),
+            CheckKind::LateFutureImport => {
+                "from __future__ imports must occur at the beginning of the file".to_string()
+            }
+            CheckKind::LineTooLong(length, limit) => {
+                format!("Line too long ({length} > {limit} characters)")
+            }
+            CheckKind::ModuleImportNotAtTopOfFile => {
+                "Module level import not at top of file".to_string()
+            }
+            CheckKind::MultiValueRepeatedKeyLiteral => {
+                "Dictionary key literal repeated".to_string()
+            }
+            CheckKind::MultiValueRepeatedKeyVariable(name) => {
+                format!("Dictionary key `{name}` repeated")
+            }
+            CheckKind::NoAssertEquals => {
+                "`assertEquals` is deprecated, use `assertEqual` instead".to_string()
+            }
+            CheckKind::NoneComparison(op) => match op {
+                RejectedCmpop::Eq => "Comparison to `None` should be `cond is None`".to_string(),
+                RejectedCmpop::NotEq => {
+                    "Comparison to `None` should be `cond is not None`".to_string()
+                }
+            },
+            CheckKind::NotInTest => "Test for membership should be `not in`".to_string(),
+            CheckKind::NotIsTest => "Test for object identity should be `is not`".to_string(),
             CheckKind::RaiseNotImplemented => {
-                "'raise NotImplemented' should be 'raise NotImplementedError".to_string()
+                "`raise NotImplemented` should be `raise NotImplementedError`".to_string()
             }
             CheckKind::ReturnOutsideFunction => {
                 "a `return` statement outside of a function/method".to_string()
             }
+            CheckKind::SyntaxError(message) => format!("SyntaxError: {message}"),
+            CheckKind::TooManyExpressionsInStarredAssignment => {
+                "too many expressions in star-unpacking assignment".to_string()
+            }
+            CheckKind::TrueFalseComparison(value, op) => match *value {
+                true => match op {
+                    RejectedCmpop::Eq => {
+                        "Comparison to `True` should be `cond is True`".to_string()
+                    }
+                    RejectedCmpop::NotEq => {
+                        "Comparison to `True` should be `cond is not True`".to_string()
+                    }
+                },
+                false => match op {
+                    RejectedCmpop::Eq => {
+                        "Comparison to `False` should be `cond is False`".to_string()
+                    }
+                    RejectedCmpop::NotEq => {
+                        "Comparison to `False` should be `cond is not False`".to_string()
+                    }
+                },
+            },
+            CheckKind::TwoStarredExpressions => "two starred expressions in assignment".to_string(),
+            CheckKind::TypeComparison => "do not compare types, use `isinstance()`".to_string(),
+            CheckKind::UndefinedExport(name) => {
+                format!("Undefined name `{name}` in `__all__`")
+            }
+            CheckKind::UndefinedLocal(name) => {
+                format!("Local variable `{name}` referenced before assignment")
+            }
+            CheckKind::UndefinedName(name) => {
+                format!("Undefined name `{name}`")
+            }
             CheckKind::UnusedImport(name) => format!("`{name}` imported but unused"),
+            CheckKind::UnusedVariable(name) => {
+                format!("Local variable `{name}` is assigned to but never used")
+            }
+            CheckKind::UselessObjectInheritance(name) => {
+                format!("Class `{name}` inherits from object")
+            }
+            CheckKind::YieldOutsideFunction => {
+                "a `yield` or `yield from` statement outside of a function/method".to_string()
+            }
+            CheckKind::UnusedNOQA(code) => match code {
+                None => "Unused `noqa` directive".to_string(),
+                Some(code) => format!("Unused `noqa` directive for: {code}"),
+            },
+            // flake8-builtins
+            CheckKind::BuiltinVariableShadowing(name) => {
+                format!("Variable `{name}` is shadowing a python builtin")
+            }
+            CheckKind::BuiltinArgumentShadowing(name) => {
+                format!("Argument `{name}` is shadowing a python builtin")
+            }
+            CheckKind::BuiltinAttributeShadowing(name) => {
+                format!("class attribute `{name}` is shadowing a python builtin")
+            }
+            // flake8-super
+            CheckKind::SuperCallWithParameters => {
+                "Use `super()` instead of `super(__class__, self)`".to_string()
+            }
         }
     }
+
+    /// Whether the check kind is (potentially) fixable.
+    pub fn fixable(&self) -> bool {
+        matches!(
+            self,
+            CheckKind::NoAssertEquals
+                | CheckKind::UselessObjectInheritance(_)
+                | CheckKind::UnusedNOQA(_)
+                | CheckKind::SuperCallWithParameters
+        )
+    }
 }
 
-#[derive(Debug, PartialEq, Eq)]
+#[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub struct Fix {
+    pub content: String,
+    pub location: Location,
+    pub end_location: Location,
+    pub applied: bool,
+}
+
+#[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]
 pub struct Check {
     pub kind: CheckKind,
     pub location: Location,
+    pub end_location: Location,
+    pub fix: Option<Fix>,
+}
+
+impl Check {
+    pub fn new(kind: CheckKind, span: Range) -> Self {
+        Self {
+            kind,
+            location: span.location,
+            end_location: span.end_location,
+            fix: None,
+        }
+    }
+
+    pub fn amend(&mut self, fix: Fix) {
+        self.fix = Some(fix);
+    }
 }

src/fs.rs

@@ -1,37 +1,167 @@
+use std::borrow::Cow;
+use std::collections::BTreeSet;
 use std::fs::File;
-use std::io::{BufRead, BufReader, Read};
+use std::io::{BufReader, Read};
+use std::ops::Deref;
 use std::path::{Path, PathBuf};
 
-use anyhow::Result;
+use anyhow::{anyhow, Result};
+use log::debug;
+use path_absolutize::path_dedot;
+use path_absolutize::Absolutize;
 use walkdir::{DirEntry, WalkDir};
 
-fn is_not_hidden(entry: &DirEntry) -> bool {
-    entry
-        .file_name()
+use crate::checks::CheckCode;
+use crate::settings::{FilePattern, PerFileIgnore};
+
+/// Extract the absolute path and basename (as strings) from a Path.
+fn extract_path_names(path: &Path) -> Result<(&str, &str)> {
+    let file_path = path
         .to_str()
-        .map(|s| entry.depth() == 0 || !s.starts_with('.'))
-        .unwrap_or(false)
+        .ok_or_else(|| anyhow!("Unable to parse filename: {:?}", path))?;
+    let file_basename = path
+        .file_name()
+        .ok_or_else(|| anyhow!("Unable to parse filename: {:?}", path))?
+        .to_str()
+        .ok_or_else(|| anyhow!("Unable to parse filename: {:?}", path))?;
+    Ok((file_path, file_basename))
 }
 
-pub fn iter_python_files(path: &PathBuf) -> impl Iterator<Item = DirEntry> {
-    WalkDir::new(path)
-        .follow_links(true)
+fn is_excluded<'a, T>(file_path: &str, file_basename: &str, exclude: T) -> bool
+where
+    T: Iterator<Item = &'a FilePattern>,
+{
+    for pattern in exclude {
+        match pattern {
+            FilePattern::Simple(basename) => {
+                if *basename == file_basename {
+                    return true;
+                }
+            }
+            FilePattern::Complex(absolute, basename) => {
+                if absolute.matches(file_path) {
+                    return true;
+                }
+                if basename
+                    .as_ref()
+                    .map(|pattern| pattern.matches(file_basename))
+                    .unwrap_or_default()
+                {
+                    return true;
+                }
+            }
+        };
+    }
+    false
+}
+
+fn is_included(path: &Path) -> bool {
+    let file_name = path.to_string_lossy();
+    file_name.ends_with(".py") || file_name.ends_with(".pyi")
+}
+
+pub fn iter_python_files<'a>(
+    path: &'a Path,
+    exclude: &'a [FilePattern],
+    extend_exclude: &'a [FilePattern],
+) -> impl Iterator<Item = Result<DirEntry, walkdir::Error>> + 'a {
+    // Run some checks over the provided patterns, to enable optimizations below.
+    let has_exclude = !exclude.is_empty();
+    let has_extend_exclude = !extend_exclude.is_empty();
+    let exclude_simple = exclude
+        .iter()
+        .all(|pattern| matches!(pattern, FilePattern::Simple(_)));
+    let extend_exclude_simple = extend_exclude
+        .iter()
+        .all(|pattern| matches!(pattern, FilePattern::Simple(_)));
+
+    WalkDir::new(normalize_path(path))
         .into_iter()
-        .filter_entry(is_not_hidden)
-        .filter_map(|entry| entry.ok())
-        .filter(|entry| entry.path().to_string_lossy().ends_with(".py"))
+        .filter_entry(move |entry| {
+            if !has_exclude && !has_extend_exclude {
+                return true;
+            }
+
+            let path = entry.path();
+            match extract_path_names(path) {
+                Ok((file_path, file_basename)) => {
+                    let file_type = entry.file_type();
+
+                    if has_exclude
+                        && (!exclude_simple || file_type.is_dir())
+                        && is_excluded(file_path, file_basename, exclude.iter())
+                    {
+                        debug!("Ignored path via `exclude`: {:?}", path);
+                        false
+                    } else if has_extend_exclude
+                        && (!extend_exclude_simple || file_type.is_dir())
+                        && is_excluded(file_path, file_basename, extend_exclude.iter())
+                    {
+                        debug!("Ignored path via `extend-exclude`: {:?}", path);
+                        false
+                    } else {
+                        true
+                    }
+                }
+                Err(_) => {
+                    debug!("Ignored path due to error in parsing: {:?}", path);
+                    true
+                }
+            }
+        })
+        .filter(|entry| {
+            entry.as_ref().map_or(true, |entry| {
+                (entry.depth() == 0 || is_included(entry.path()))
+                    && !entry.file_type().is_dir()
+                    && !(entry.file_type().is_symlink() && entry.path().is_dir())
+            })
+        })
 }
 
-pub fn read_line(path: &Path, row: &usize) -> Result<String> {
-    let file = File::open(path)?;
-    let buf_reader = BufReader::new(file);
-    buf_reader
-        .lines()
-        .nth(*row - 1)
-        .unwrap()
-        .map_err(|e| e.into())
+/// Create tree set with codes matching the pattern/code pairs.
+pub fn ignores_from_path<'a>(
+    path: &Path,
+    pattern_code_pairs: &'a [PerFileIgnore],
+) -> Result<BTreeSet<&'a CheckCode>> {
+    let (file_path, file_basename) = extract_path_names(path)?;
+    Ok(pattern_code_pairs
+        .iter()
+        .filter(|pattern_code_pair| {
+            is_excluded(
+                file_path,
+                file_basename,
+                [&pattern_code_pair.pattern].into_iter(),
+            )
+        })
+        .map(|pattern_code_pair| &pattern_code_pair.code)
+        .collect())
 }
 
+/// Convert any path to an absolute path (based on the current working directory).
+pub fn normalize_path(path: &Path) -> PathBuf {
+    if let Ok(path) = path.absolutize() {
+        return path.to_path_buf();
+    }
+    path.to_path_buf()
+}
+
+/// Convert any path to an absolute path (based on the specified project root).
+pub fn normalize_path_to(path: &Path, project_root: &Path) -> PathBuf {
+    if let Ok(path) = path.absolutize_from(project_root) {
+        return path.to_path_buf();
+    }
+    path.to_path_buf()
+}
+
+/// Convert an absolute path to be relative to the current working directory.
+pub fn relativize_path(path: &Path) -> Cow<str> {
+    if let Ok(path) = path.strip_prefix(path_dedot::CWD.deref()) {
+        return path.to_string_lossy();
+    }
+    path.to_string_lossy()
+}
+
+/// Read a file's contents from disk.
 pub fn read_file(path: &Path) -> Result<String> {
     let file = File::open(path)?;
     let mut buf_reader = BufReader::new(file);
@@ -39,3 +169,100 @@ pub fn read_file(path: &Path) -> Result<String> {
     buf_reader.read_to_string(&mut contents)?;
     Ok(contents)
 }
+
+#[cfg(test)]
+mod tests {
+    use std::path::Path;
+
+    use anyhow::Result;
+    use path_absolutize::Absolutize;
+
+    use crate::fs::{extract_path_names, is_excluded, is_included};
+    use crate::settings::FilePattern;
+
+    #[test]
+    fn inclusions() {
+        let path = Path::new("foo/bar/baz.py").absolutize().unwrap();
+        assert!(is_included(&path));
+
+        let path = Path::new("foo/bar/baz.pyi").absolutize().unwrap();
+        assert!(is_included(&path));
+
+        let path = Path::new("foo/bar/baz.js").absolutize().unwrap();
+        assert!(!is_included(&path));
+
+        let path = Path::new("foo/bar/baz").absolutize().unwrap();
+        assert!(!is_included(&path));
+    }
+
+    #[test]
+    fn exclusions() -> Result<()> {
+        let project_root = Path::new("/tmp/");
+
+        let path = Path::new("foo").absolutize_from(project_root).unwrap();
+        let exclude = vec![FilePattern::from_user(
+            "foo",
+            &Some(project_root.to_path_buf()),
+        )];
+        let (file_path, file_basename) = extract_path_names(&path)?;
+        assert!(is_excluded(file_path, file_basename, exclude.iter()));
+
+        let path = Path::new("foo/bar").absolutize_from(project_root).unwrap();
+        let exclude = vec![FilePattern::from_user(
+            "bar",
+            &Some(project_root.to_path_buf()),
+        )];
+        let (file_path, file_basename) = extract_path_names(&path)?;
+        assert!(is_excluded(file_path, file_basename, exclude.iter()));
+
+        let path = Path::new("foo/bar/baz.py")
+            .absolutize_from(project_root)
+            .unwrap();
+        let exclude = vec![FilePattern::from_user(
+            "baz.py",
+            &Some(project_root.to_path_buf()),
+        )];
+        let (file_path, file_basename) = extract_path_names(&path)?;
+        assert!(is_excluded(file_path, file_basename, exclude.iter()));
+
+        let path = Path::new("foo/bar").absolutize_from(project_root).unwrap();
+        let exclude = vec![FilePattern::from_user(
+            "foo/bar",
+            &Some(project_root.to_path_buf()),
+        )];
+        let (file_path, file_basename) = extract_path_names(&path)?;
+        assert!(is_excluded(file_path, file_basename, exclude.iter()));
+
+        let path = Path::new("foo/bar/baz.py")
+            .absolutize_from(project_root)
+            .unwrap();
+        let exclude = vec![FilePattern::from_user(
+            "foo/bar/baz.py",
+            &Some(project_root.to_path_buf()),
+        )];
+        let (file_path, file_basename) = extract_path_names(&path)?;
+        assert!(is_excluded(file_path, file_basename, exclude.iter()));
+
+        let path = Path::new("foo/bar/baz.py")
+            .absolutize_from(project_root)
+            .unwrap();
+        let exclude = vec![FilePattern::from_user(
+            "foo/bar/*.py",
+            &Some(project_root.to_path_buf()),
+        )];
+        let (file_path, file_basename) = extract_path_names(&path)?;
+        assert!(is_excluded(file_path, file_basename, exclude.iter()));
+
+        let path = Path::new("foo/bar/baz.py")
+            .absolutize_from(project_root)
+            .unwrap();
+        let exclude = vec![FilePattern::from_user(
+            "baz",
+            &Some(project_root.to_path_buf()),
+        )];
+        let (file_path, file_basename) = extract_path_names(&path)?;
+        assert!(!is_excluded(file_path, file_basename, exclude.iter()));
+
+        Ok(())
+    }
+}

src/lib.rs

@@ -1,4 +1,17 @@
-mod cache;
+use std::path::Path;
+
+use anyhow::Result;
+use log::debug;
+use rustpython_parser::lexer::LexResult;
+
+use crate::autofix::fixer::Mode;
+use crate::linter::{check_path, tokenize};
+use crate::message::Message;
+use crate::settings::Settings;
+
+mod ast;
+mod autofix;
+pub mod cache;
 pub mod check_ast;
 mod check_lines;
 pub mod checks;
@@ -6,6 +19,55 @@ pub mod fs;
 pub mod linter;
 pub mod logging;
 pub mod message;
-mod pyproject;
+mod noqa;
+pub mod printer;
+pub mod pyproject;
+mod python;
 pub mod settings;
-mod visitor;
+
+/// Run ruff over Python source code directly.
+pub fn check(path: &Path, contents: &str) -> Result<Vec<Message>> {
+    // Find the project root and pyproject.toml.
+    let project_root = pyproject::find_project_root(&[path.to_path_buf()]);
+    match &project_root {
+        Some(path) => debug!("Found project root at: {:?}", path),
+        None => debug!("Unable to identify project root; assuming current directory..."),
+    };
+    let pyproject = pyproject::find_pyproject_toml(&project_root);
+    match &pyproject {
+        Some(path) => debug!("Found pyproject.toml at: {:?}", path),
+        None => debug!("Unable to find pyproject.toml; using default settings..."),
+    };
+
+    let settings = Settings::from_pyproject(pyproject, project_root)?;
+
+    // Tokenize once.
+    let tokens: Vec<LexResult> = tokenize(contents);
+
+    // Determine the noqa line for every line in the source.
+    let noqa_line_for = noqa::extract_noqa_line_for(&tokens);
+
+    // Generate checks.
+    let checks = check_path(
+        path,
+        contents,
+        tokens,
+        &noqa_line_for,
+        &settings,
+        &Mode::None,
+    )?;
+
+    // Convert to messages.
+    let messages: Vec<Message> = checks
+        .into_iter()
+        .map(|check| Message {
+            kind: check.kind,
+            fixed: check.fix.map(|fix| fix.applied).unwrap_or_default(),
+            location: check.location,
+            end_location: check.end_location,
+            filename: path.to_string_lossy().to_string(),
+        })
+        .collect();
+
+    Ok(messages)
+}

src/main.rs

@@ -1,110 +1,225 @@
+use std::io;
 use std::path::{Path, PathBuf};
 use std::process::ExitCode;
 use std::sync::mpsc::channel;
 use std::time::Instant;
 
 use anyhow::Result;
-use clap::{Parser, ValueHint};
+use clap::{command, Parser};
 use colored::Colorize;
 use log::{debug, error};
 use notify::{raw_watcher, RecursiveMode, Watcher};
 use rayon::prelude::*;
+use regex::Regex;
 use walkdir::DirEntry;
 
+use ::ruff::cache;
 use ::ruff::checks::CheckCode;
+use ::ruff::checks::CheckKind;
 use ::ruff::fs::iter_python_files;
-use ::ruff::linter::check_path;
+use ::ruff::linter::add_noqa_to_path;
+use ::ruff::linter::lint_path;
 use ::ruff::logging::set_up_logging;
 use ::ruff::message::Message;
-use ::ruff::settings::Settings;
+use ::ruff::printer::{Printer, SerializationFormat};
+use ::ruff::pyproject::{self, StrCheckCodePair};
+use ::ruff::settings::CurrentSettings;
+use ::ruff::settings::{FilePattern, PerFileIgnore, Settings};
 use ::ruff::tell_user;
 
+const CARGO_PKG_NAME: &str = env!("CARGO_PKG_NAME");
+const CARGO_PKG_VERSION: &str = env!("CARGO_PKG_VERSION");
+
 #[derive(Debug, Parser)]
-#[clap(name = "ruff")]
-#[clap(about = "A Python linter written in Rust", long_about = None)]
+#[command(author, about = "ruff: An extremely fast Python linter.")]
+#[command(version)]
 struct Cli {
-    #[clap(parse(from_os_str), value_hint = ValueHint::AnyPath, required = true)]
+    #[arg(required = true)]
     files: Vec<PathBuf>,
     /// Enable verbose logging.
-    #[clap(short, long, action)]
+    #[arg(short, long)]
     verbose: bool,
     /// Disable all logging (but still exit with status code "1" upon detecting errors).
-    #[clap(short, long, action)]
+    #[arg(short, long)]
     quiet: bool,
     /// Exit with status code "0", even upon detecting errors.
-    #[clap(short, long, action)]
+    #[arg(short, long)]
     exit_zero: bool,
     /// Run in watch mode by re-running whenever files change.
-    #[clap(short, long, action)]
+    #[arg(short, long)]
     watch: bool,
+    /// Attempt to automatically fix lint errors.
+    #[arg(short, long)]
+    fix: bool,
     /// Disable cache reads.
-    #[clap(short, long, action)]
+    #[arg(short, long)]
     no_cache: bool,
-    /// Comma-separated list of error codes to enable.
-    #[clap(long, multiple = true)]
+    /// List of error codes to enable.
+    #[arg(long, value_delimiter = ',')]
     select: Vec<CheckCode>,
-    /// Comma-separated list of error codes to ignore.
-    #[clap(long, multiple = true)]
+    /// Like --select, but adds additional error codes on top of the selected ones.
+    #[arg(long, value_delimiter = ',')]
+    extend_select: Vec<CheckCode>,
+    /// List of error codes to ignore.
+    #[arg(long, value_delimiter = ',')]
     ignore: Vec<CheckCode>,
+    /// Like --ignore, but adds additional error codes on top of the ignored ones.
+    #[arg(long, value_delimiter = ',')]
+    extend_ignore: Vec<CheckCode>,
+    /// List of paths, used to exclude files and/or directories from checks.
+    #[arg(long, value_delimiter = ',')]
+    exclude: Vec<String>,
+    /// Like --exclude, but adds additional files and directories on top of the excluded ones.
+    #[arg(long, value_delimiter = ',')]
+    extend_exclude: Vec<String>,
+    /// List of mappings from file pattern to code to exclude
+    #[arg(long, value_delimiter = ',')]
+    per_file_ignores: Vec<StrCheckCodePair>,
+    /// Output serialization format for error messages.
+    #[arg(long, value_enum, default_value_t=SerializationFormat::Text)]
+    format: SerializationFormat,
+    /// See the files ruff will be run against with the current settings.
+    #[arg(long)]
+    show_files: bool,
+    /// See ruff's settings.
+    #[arg(long)]
+    show_settings: bool,
+    /// Enable automatic additions of noqa directives to failing lines.
+    #[arg(long)]
+    add_noqa: bool,
+    /// Regular expression matching the name of dummy variables.
+    #[arg(long)]
+    dummy_variable_rgx: Option<Regex>,
 }
 
-fn run_once(files: &[PathBuf], settings: &Settings, cache: bool) -> Result<Vec<Message>> {
+#[cfg(feature = "update-informer")]
+fn check_for_updates() {
+    use update_informer::{registry, Check};
+
+    let informer = update_informer::new(registry::PyPI, CARGO_PKG_NAME, CARGO_PKG_VERSION);
+
+    if let Some(new_version) = informer.check_version().ok().flatten() {
+        let msg = format!(
+            "A new version of {pkg_name} is available: v{pkg_version} -> {new_version}",
+            pkg_name = CARGO_PKG_NAME.italic().cyan(),
+            pkg_version = CARGO_PKG_VERSION,
+            new_version = new_version.to_string().green()
+        );
+
+        let cmd = format!(
+            "Run to update: {cmd} {pkg_name}",
+            cmd = "pip3 install --upgrade".green(),
+            pkg_name = CARGO_PKG_NAME.green()
+        );
+
+        println!("\n{msg}\n{cmd}");
+    }
+}
+
+fn show_settings(settings: Settings) {
+    println!("{:#?}", CurrentSettings::from_settings(settings));
+}
+
+fn show_files(files: &[PathBuf], settings: &Settings) {
+    let mut entries: Vec<DirEntry> = files
+        .iter()
+        .flat_map(|path| iter_python_files(path, &settings.exclude, &settings.extend_exclude))
+        .flatten()
+        .collect();
+    entries.sort_by(|a, b| a.path().cmp(b.path()));
+    for entry in entries {
+        println!("{}", entry.path().to_string_lossy());
+    }
+}
+
+fn run_once(
+    files: &[PathBuf],
+    settings: &Settings,
+    cache: bool,
+    autofix: bool,
+) -> Result<Vec<Message>> {
     // Collect all the files to check.
     let start = Instant::now();
-    let files: Vec<DirEntry> = files.iter().flat_map(iter_python_files).collect();
+    let paths: Vec<Result<DirEntry, walkdir::Error>> = files
+        .iter()
+        .flat_map(|path| iter_python_files(path, &settings.exclude, &settings.extend_exclude))
+        .collect();
     let duration = start.elapsed();
     debug!("Identified files to lint in: {:?}", duration);
 
     let start = Instant::now();
-    let messages: Vec<Message> = files
+    let mut messages: Vec<Message> = paths
         .par_iter()
-        .filter(|entry| {
-            !settings
-                .exclude
-                .iter()
-                .any(|exclusion| entry.path().starts_with(exclusion))
-        })
         .map(|entry| {
-            check_path(entry.path(), settings, &cache.into()).unwrap_or_else(|e| {
-                error!("Failed to check {}: {e:?}", entry.path().to_string_lossy());
-                vec![]
+            match entry {
+                Ok(entry) => {
+                    let path = entry.path();
+                    lint_path(path, settings, &cache.into(), &autofix.into())
+                        .map_err(|e| (Some(path.to_owned()), e.to_string()))
+                }
+                Err(e) => Err((
+                    e.path().map(Path::to_owned),
+                    e.io_error()
+                        .map_or_else(|| e.to_string(), io::Error::to_string),
+                )),
+            }
+            .unwrap_or_else(|(path, message)| {
+                if let Some(path) = path {
+                    if settings.select.contains(&CheckCode::E902) {
+                        vec![Message {
+                            kind: CheckKind::IOError(message),
+                            fixed: false,
+                            location: Default::default(),
+                            end_location: Default::default(),
+                            filename: path.to_string_lossy().to_string(),
+                        }]
+                    } else {
+                        error!("Failed to check {}: {message}", path.to_string_lossy());
+                        vec![]
+                    }
+                } else {
+                    error!("{message}");
+                    vec![]
+                }
             })
         })
         .flatten()
         .collect();
+
+    messages.sort_unstable();
     let duration = start.elapsed();
     debug!("Checked files in: {:?}", duration);
 
     Ok(messages)
 }
 
-fn report_once(messages: &[Message]) -> Result<()> {
-    println!("Found {} error(s).", messages.len());
+fn add_noqa(files: &[PathBuf], settings: &Settings) -> Result<usize> {
+    // Collect all the files to check.
+    let start = Instant::now();
+    let paths: Vec<Result<DirEntry, walkdir::Error>> = files
+        .iter()
+        .flat_map(|path| iter_python_files(path, &settings.exclude, &settings.extend_exclude))
+        .collect();
+    let duration = start.elapsed();
+    debug!("Identified files to lint in: {:?}", duration);
 
-    if !messages.is_empty() {
-        println!();
-        for message in messages {
-            println!("{}", message);
-        }
-    }
+    let start = Instant::now();
+    let modifications: usize = paths
+        .par_iter()
+        .map(|entry| match entry {
+            Ok(entry) => {
+                let path = entry.path();
+                add_noqa_to_path(path, settings)
+            }
+            Err(_) => Ok(0),
+        })
+        .flatten()
+        .sum();
 
-    Ok(())
-}
+    let duration = start.elapsed();
+    debug!("Added noqa to files in: {:?}", duration);
 
-fn report_continuously(messages: &[Message]) -> Result<()> {
-    tell_user!(
-        "Found {} error(s). Watching for file changes.",
-        messages.len(),
-    );
-
-    if !messages.is_empty() {
-        println!();
-        for message in messages {
-            println!("{}", message);
-        }
-    }
-
-    Ok(())
+    Ok(modifications)
 }
 
 fn inner_main() -> Result<ExitCode> {
@@ -112,24 +227,98 @@ fn inner_main() -> Result<ExitCode> {
 
     set_up_logging(cli.verbose)?;
 
-    // TODO(charlie): Can we avoid this cast?
-    let paths: Vec<&Path> = cli.files.iter().map(PathBuf::as_path).collect();
-    let mut settings = Settings::from_paths(paths)?;
+    // Find the project root and pyproject.toml.
+    let project_root = pyproject::find_project_root(&cli.files);
+    match &project_root {
+        Some(path) => debug!("Found project root at: {:?}", path),
+        None => debug!("Unable to identify project root; assuming current directory..."),
+    };
+    let pyproject = pyproject::find_pyproject_toml(&project_root);
+    match &pyproject {
+        Some(path) => debug!("Found pyproject.toml at: {:?}", path),
+        None => debug!("Unable to find pyproject.toml; using default settings..."),
+    };
+
+    // Parse the settings from the pyproject.toml and command-line arguments.
+    let exclude: Vec<FilePattern> = cli
+        .exclude
+        .iter()
+        .map(|path| FilePattern::from_user(path, &project_root))
+        .collect();
+    let extend_exclude: Vec<FilePattern> = cli
+        .extend_exclude
+        .iter()
+        .map(|path| FilePattern::from_user(path, &project_root))
+        .collect();
+    let per_file_ignores: Vec<PerFileIgnore> = cli
+        .per_file_ignores
+        .into_iter()
+        .map(|pair| PerFileIgnore::new(pair, &project_root))
+        .collect();
+
+    let mut settings = Settings::from_pyproject(pyproject, project_root)?;
+    if !exclude.is_empty() {
+        settings.exclude = exclude;
+    }
+    if !extend_exclude.is_empty() {
+        settings.extend_exclude = extend_exclude;
+    }
+    if !per_file_ignores.is_empty() {
+        settings.per_file_ignores = per_file_ignores;
+    }
     if !cli.select.is_empty() {
+        settings.clear();
         settings.select(cli.select);
     }
+    if !cli.extend_select.is_empty() {
+        settings.select(cli.extend_select);
+    }
     if !cli.ignore.is_empty() {
         settings.ignore(&cli.ignore);
     }
+    if !cli.extend_ignore.is_empty() {
+        settings.ignore(&cli.extend_ignore);
+    }
+    if let Some(dummy_variable_rgx) = cli.dummy_variable_rgx {
+        settings.dummy_variable_rgx = dummy_variable_rgx;
+    }
 
+    if cli.show_settings && cli.show_files {
+        eprintln!("Error: specify --show-settings or show-files (not both).");
+        return Ok(ExitCode::FAILURE);
+    }
+    if cli.show_files {
+        show_files(&cli.files, &settings);
+        return Ok(ExitCode::SUCCESS);
+    }
+    if cli.show_settings {
+        show_settings(settings);
+        return Ok(ExitCode::SUCCESS);
+    }
+
+    cache::init()?;
+
+    let mut printer = Printer::new(cli.format, cli.verbose);
     if cli.watch {
+        if cli.fix {
+            eprintln!("Warning: --fix is not enabled in watch mode.");
+        }
+
+        if cli.add_noqa {
+            eprintln!("Warning: --no-qa is not enabled in watch mode.");
+        }
+
+        if cli.format != SerializationFormat::Text {
+            eprintln!("Warning: --format 'text' is used in watch mode.");
+        }
+
         // Perform an initial run instantly.
-        clearscreen::clear()?;
+        printer.clear_screen()?;
         tell_user!("Starting linter in watch mode...\n");
 
-        let messages = run_once(&cli.files, &settings, !cli.no_cache)?;
+        let messages = run_once(&cli.files, &settings, !cli.no_cache, false)?;
         if !cli.quiet {
-            report_continuously(&messages)?;
+            printer.write_continuously(&messages)?;
         }
 
         // Configure the file watcher.
@@ -144,12 +333,12 @@ fn inner_main() -> Result<ExitCode> {
                 Ok(e) => {
                     if let Some(path) = e.path {
                         if path.to_string_lossy().ends_with(".py") {
-                            clearscreen::clear()?;
+                            printer.clear_screen()?;
                             tell_user!("File change detected...\n");
 
-                            let messages = run_once(&cli.files, &settings, !cli.no_cache)?;
+                            let messages = run_once(&cli.files, &settings, !cli.no_cache, false)?;
                             if !cli.quiet {
-                                report_continuously(&messages)?;
+                                printer.write_continuously(&messages)?;
                             }
                         }
                     }
@@ -157,11 +346,19 @@ fn inner_main() -> Result<ExitCode> {
                 Err(e) => return Err(e.into()),
             }
         }
-    } else {
-        let messages = run_once(&cli.files, &settings, !cli.no_cache)?;
-        if !cli.quiet {
-            report_once(&messages)?;
+    } else if cli.add_noqa {
+        let modifications = add_noqa(&cli.files, &settings)?;
+        if modifications > 0 {
+            println!("Added {modifications} noqa directives.");
         }
+    } else {
+        let messages = run_once(&cli.files, &settings, !cli.no_cache, cli.fix)?;
+        if !cli.quiet {
+            printer.write_once(&messages)?;
+        }
+
+        #[cfg(feature = "update-informer")]
+        check_for_updates();
 
         if !messages.is_empty() && !cli.exit_zero {
             return Ok(ExitCode::FAILURE);
@@ -174,6 +371,9 @@ fn inner_main() -> Result<ExitCode> {
 fn main() -> ExitCode {
     match inner_main() {
         Ok(code) => code,
-        Err(_) => ExitCode::FAILURE,
+        Err(err) => {
+            eprintln!("{} {:?}", "error".red().bold(), err);
+            ExitCode::FAILURE
+        }
     }
 }

src/message.rs

@@ -1,66 +1,36 @@
+use std::cmp::Ordering;
 use std::fmt;
 use std::path::Path;
 
 use colored::Colorize;
-use regex::Regex;
 use rustpython_parser::ast::Location;
 use serde::{Deserialize, Serialize};
 
 use crate::checks::CheckKind;
-use crate::fs;
-
-#[derive(Serialize, Deserialize)]
-#[serde(remote = "Location")]
-struct LocationDef {
-    #[serde(getter = "Location::row")]
-    row: usize,
-    #[serde(getter = "Location::column")]
-    column: usize,
-}
-
-impl From<LocationDef> for Location {
-    fn from(def: LocationDef) -> Location {
-        Location::new(def.row, def.column)
-    }
-}
+use crate::fs::relativize_path;
 
 #[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]
 pub struct Message {
     pub kind: CheckKind,
-    #[serde(with = "LocationDef")]
+    pub fixed: bool,
     pub location: Location,
+    pub end_location: Location,
     pub filename: String,
 }
 
-impl Message {
-    pub fn is_inline_ignored(&self) -> bool {
-        match fs::read_line(Path::new(&self.filename), &self.location.row()) {
-            Ok(line) => {
-                // https://github.com/PyCQA/flake8/blob/799c71eeb61cf26c7c176aed43e22523e2a6d991/src/flake8/defaults.py#L26
-                let re = Regex::new(r"(?i)# noqa(?::\s?(?P<codes>([A-Z]+[0-9]+(?:[,\s]+)?)+))?")
-                    .unwrap();
-                match re.captures(&line) {
-                    Some(caps) => match caps.name("codes") {
-                        Some(codes) => {
-                            let re = Regex::new(r"[,\s]").unwrap();
-                            for code in re
-                                .split(codes.as_str())
-                                .map(|code| code.trim())
-                                .filter(|code| !code.is_empty())
-                            {
-                                if code == self.kind.code().as_str() {
-                                    return true;
-                                }
-                            }
-                            false
-                        }
-                        None => true,
-                    },
-                    None => false,
-                }
-            }
-            Err(_) => false,
-        }
+impl Ord for Message {
+    fn cmp(&self, other: &Self) -> Ordering {
+        (&self.filename, self.location.row(), self.location.column()).cmp(&(
+            &other.filename,
+            other.location.row(),
+            other.location.column(),
+        ))
+    }
+}
+
+impl PartialOrd for Message {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
     }
 }
 
@@ -69,7 +39,7 @@ impl fmt::Display for Message {
         write!(
             f,
             "{}{}{}{}{}{} {} {}",
-            self.filename.white().bold(),
+            relativize_path(Path::new(&self.filename)).white().bold(),
             ":".cyan(),
             self.location.row(),
             ":".cyan(),

src/noqa.rs

@@ -0,0 +1,298 @@
+use std::cmp::{max, min};
+use std::collections::{BTreeMap, BTreeSet};
+use std::fs;
+use std::path::Path;
+
+use anyhow::Result;
+use once_cell::sync::Lazy;
+use regex::Regex;
+use rustpython_parser::lexer::{LexResult, Tok};
+
+use crate::checks::{Check, CheckCode};
+
+static NO_QA_REGEX: Lazy<Regex> = Lazy::new(|| {
+    Regex::new(r"(?i)(?P<noqa>\s*# noqa(?::\s?(?P<codes>([A-Z]+[0-9]+(?:[,\s]+)?)+))?)")
+        .expect("Invalid regex")
+});
+static SPLIT_COMMA_REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"[,\s]").expect("Invalid regex"));
+
+#[derive(Debug)]
+pub enum Directive<'a> {
+    None,
+    All(usize, usize),
+    Codes(usize, usize, Vec<&'a str>),
+}
+
+pub fn extract_noqa_directive(line: &str) -> Directive {
+    match NO_QA_REGEX.captures(line) {
+        Some(caps) => match caps.name("noqa") {
+            Some(noqa) => match caps.name("codes") {
+                Some(codes) => Directive::Codes(
+                    noqa.start(),
+                    noqa.end(),
+                    SPLIT_COMMA_REGEX
+                        .split(codes.as_str())
+                        .map(|code| code.trim())
+                        .filter(|code| !code.is_empty())
+                        .collect(),
+                ),
+                None => Directive::All(noqa.start(), noqa.end()),
+            },
+            None => Directive::None,
+        },
+        None => Directive::None,
+    }
+}
+
+pub fn extract_noqa_line_for(lxr: &[LexResult]) -> Vec<usize> {
+    let mut noqa_line_for: Vec<usize> = vec![];
+
+    let mut last_is_string = false;
+    let mut last_seen = usize::MIN;
+    let mut min_line = usize::MAX;
+    let mut max_line = usize::MIN;
+
+    for (start, tok, end) in lxr.iter().flatten() {
+        if matches!(tok, Tok::EndOfFile) {
+            break;
+        }
+
+        if matches!(tok, Tok::Newline) {
+            min_line = min(min_line, start.row());
+            max_line = max(max_line, start.row());
+
+            // For now, we only care about preserving noqa directives across multi-line strings.
+            if last_is_string {
+                noqa_line_for.extend(vec![max_line; (max_line + 1) - min_line]);
+            } else {
+                for i in (min_line - 1)..(max_line) {
+                    noqa_line_for.push(i + 1);
+                }
+            }
+
+            min_line = usize::MAX;
+            max_line = usize::MIN;
+        } else {
+            // Handle empty lines.
+            if start.row() > last_seen {
+                for i in last_seen..(start.row() - 1) {
+                    noqa_line_for.push(i + 1);
+                }
+            }
+
+            min_line = min(min_line, start.row());
+            max_line = max(max_line, end.row());
+        }
+        last_seen = start.row();
+        last_is_string = matches!(tok, Tok::String { .. });
+    }
+
+    noqa_line_for
+}
+
+fn add_noqa_inner(
+    checks: &Vec<Check>,
+    contents: &str,
+    noqa_line_for: &[usize],
+) -> Result<(usize, String)> {
+    let lines: Vec<&str> = contents.lines().collect();
+    let mut matches_by_line: BTreeMap<usize, BTreeSet<&CheckCode>> = BTreeMap::new();
+    for lineno in 0..lines.len() {
+        let mut codes: BTreeSet<&CheckCode> = BTreeSet::new();
+        for check in checks {
+            if check.location.row() == lineno + 1 {
+                codes.insert(check.kind.code());
+            }
+        }
+
+        // Grab the noqa (logical) line number for the current (physical) line.
+        // If there are newlines at the end of the file, they won't be represented in
+        // `noqa_line_for`, so fallback to the current line.
+        let noqa_lineno = noqa_line_for
+            .get(lineno)
+            .map(|lineno| lineno - 1)
+            .unwrap_or(lineno);
+
+        if !codes.is_empty() {
+            let matches = matches_by_line
+                .entry(noqa_lineno)
+                .or_insert_with(BTreeSet::new);
+            matches.append(&mut codes);
+        }
+    }
+
+    let mut count: usize = 0;
+    let mut output = "".to_string();
+    for (lineno, line) in lines.iter().enumerate() {
+        match matches_by_line.get(&lineno) {
+            None => {
+                output.push_str(line);
+                output.push('\n');
+            }
+            Some(codes) => {
+                match extract_noqa_directive(line) {
+                    Directive::None => {
+                        output.push_str(line);
+                    }
+                    Directive::All(start, _) => output.push_str(&line[..start]),
+                    Directive::Codes(start, _, _) => output.push_str(&line[..start]),
+                };
+                let codes: Vec<&str> = codes.iter().map(|code| code.as_str()).collect();
+                output.push_str("  # noqa: ");
+                output.push_str(&codes.join(", "));
+                output.push('\n');
+                count += 1;
+            }
+        }
+    }
+
+    Ok((count, output))
+}
+
+pub fn add_noqa(
+    checks: &Vec<Check>,
+    contents: &str,
+    noqa_line_for: &[usize],
+    path: &Path,
+) -> Result<usize> {
+    let (count, output) = add_noqa_inner(checks, contents, noqa_line_for)?;
+    fs::write(path, output)?;
+    Ok(count)
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::ast::types::Range;
+    use anyhow::Result;
+    use rustpython_parser::ast::Location;
+    use rustpython_parser::lexer;
+    use rustpython_parser::lexer::LexResult;
+
+    use crate::checks::{Check, CheckKind};
+    use crate::noqa::{add_noqa_inner, extract_noqa_line_for};
+
+    #[test]
+    fn extraction() -> Result<()> {
+        let lxr: Vec<LexResult> = lexer::make_tokenizer(
+            "x = 1
+y = 2
+z = x + 1",
+        )
+        .collect();
+        println!("{:?}", extract_noqa_line_for(&lxr));
+        assert_eq!(extract_noqa_line_for(&lxr), vec![1, 2, 3]);
+
+        let lxr: Vec<LexResult> = lexer::make_tokenizer(
+            "
+x = 1
+y = 2
+z = x + 1",
+        )
+        .collect();
+        println!("{:?}", extract_noqa_line_for(&lxr));
+        assert_eq!(extract_noqa_line_for(&lxr), vec![1, 2, 3, 4]);
+
+        let lxr: Vec<LexResult> = lexer::make_tokenizer(
+            "x = 1
+y = 2
+z = x + 1
+        ",
+        )
+        .collect();
+        println!("{:?}", extract_noqa_line_for(&lxr));
+        assert_eq!(extract_noqa_line_for(&lxr), vec![1, 2, 3]);
+
+        let lxr: Vec<LexResult> = lexer::make_tokenizer(
+            "x = 1
+
+y = 2
+z = x + 1
+        ",
+        )
+        .collect();
+        println!("{:?}", extract_noqa_line_for(&lxr));
+        assert_eq!(extract_noqa_line_for(&lxr), vec![1, 2, 3, 4]);
+
+        let lxr: Vec<LexResult> = lexer::make_tokenizer(
+            "x = '''abc
+def
+ghi
+'''
+y = 2
+z = x + 1",
+        )
+        .collect();
+        assert_eq!(extract_noqa_line_for(&lxr), vec![4, 4, 4, 4, 5, 6]);
+
+        Ok(())
+    }
+
+    #[test]
+    fn modification() -> Result<()> {
+        let checks = vec![];
+        let contents = "x = 1";
+        let noqa_line_for = vec![1];
+        let (count, output) = add_noqa_inner(&checks, contents, &noqa_line_for)?;
+        assert_eq!(count, 0);
+        assert_eq!(output.trim(), contents.trim());
+
+        let checks = vec![Check::new(
+            CheckKind::UnusedVariable("x".to_string()),
+            Range {
+                location: Location::new(1, 1),
+                end_location: Location::new(1, 1),
+            },
+        )];
+        let contents = "x = 1";
+        let noqa_line_for = vec![1];
+        let (count, output) = add_noqa_inner(&checks, contents, &noqa_line_for)?;
+        assert_eq!(count, 1);
+        assert_eq!(output.trim(), "x = 1  # noqa: F841".trim());
+
+        let checks = vec![
+            Check::new(
+                CheckKind::AmbiguousVariableName("x".to_string()),
+                Range {
+                    location: Location::new(1, 1),
+                    end_location: Location::new(1, 1),
+                },
+            ),
+            Check::new(
+                CheckKind::UnusedVariable("x".to_string()),
+                Range {
+                    location: Location::new(1, 1),
+                    end_location: Location::new(1, 1),
+                },
+            ),
+        ];
+        let contents = "x = 1  # noqa: E741";
+        let noqa_line_for = vec![1];
+        let (count, output) = add_noqa_inner(&checks, contents, &noqa_line_for)?;
+        assert_eq!(count, 1);
+        assert_eq!(output.trim(), "x = 1  # noqa: E741, F841".trim());
+
+        let checks = vec![
+            Check::new(
+                CheckKind::AmbiguousVariableName("x".to_string()),
+                Range {
+                    location: Location::new(1, 1),
+                    end_location: Location::new(1, 1),
+                },
+            ),
+            Check::new(
+                CheckKind::UnusedVariable("x".to_string()),
+                Range {
+                    location: Location::new(1, 1),
+                    end_location: Location::new(1, 1),
+                },
+            ),
+        ];
+        let contents = "x = 1  # noqa";
+        let noqa_line_for = vec![1];
+        let (count, output) = add_noqa_inner(&checks, contents, &noqa_line_for)?;
+        assert_eq!(count, 1);
+        assert_eq!(output.trim(), "x = 1  # noqa: E741, F841".trim());
+
+        Ok(())
+    }
+}

src/printer.rs

@@ -0,0 +1,110 @@
+use anyhow::Result;
+use clap::ValueEnum;
+use colored::Colorize;
+use rustpython_parser::ast::Location;
+use serde::Serialize;
+
+use crate::checks::{CheckCode, CheckKind};
+use crate::message::Message;
+use crate::tell_user;
+
+#[derive(Clone, Copy, ValueEnum, PartialEq, Eq, Debug)]
+pub enum SerializationFormat {
+    Text,
+    Json,
+}
+
+#[derive(Serialize)]
+struct ExpandedMessage<'a> {
+    kind: &'a CheckKind,
+    code: &'a CheckCode,
+    message: String,
+    fixed: bool,
+    location: Location,
+    end_location: Location,
+    filename: &'a String,
+}
+
+pub struct Printer {
+    format: SerializationFormat,
+    verbose: bool,
+}
+
+impl Printer {
+    pub fn new(format: SerializationFormat, verbose: bool) -> Self {
+        Self { format, verbose }
+    }
+
+    pub fn write_once(&mut self, messages: &[Message]) -> Result<()> {
+        let (fixed, outstanding): (Vec<&Message>, Vec<&Message>) =
+            messages.iter().partition(|message| message.fixed);
+        let num_fixable = outstanding
+            .iter()
+            .filter(|message| message.kind.fixable())
+            .count();
+
+        match self.format {
+            SerializationFormat::Json => {
+                println!(
+                    "{}",
+                    serde_json::to_string_pretty(
+                        &messages
+                            .iter()
+                            .map(|m| ExpandedMessage {
+                                kind: &m.kind,
+                                code: m.kind.code(),
+                                message: m.kind.body(),
+                                fixed: m.fixed,
+                                location: m.location,
+                                end_location: m.end_location,
+                                filename: &m.filename,
+                            })
+                            .collect::<Vec<_>>()
+                    )?
+                )
+            }
+            SerializationFormat::Text => {
+                if !fixed.is_empty() {
+                    println!(
+                        "Found {} error(s) ({} fixed).",
+                        outstanding.len(),
+                        fixed.len()
+                    )
+                } else if !outstanding.is_empty() || self.verbose {
+                    println!("Found {} error(s).", outstanding.len())
+                }
+
+                for message in outstanding {
+                    println!("{}", message)
+                }
+
+                if num_fixable > 0 {
+                    println!("{num_fixable} potentially fixable with the --fix option.")
+                }
+            }
+        }
+
+        Ok(())
+    }
+
+    pub fn write_continuously(&mut self, messages: &[Message]) -> Result<()> {
+        tell_user!(
+            "Found {} error(s). Watching for file changes.",
+            messages.len(),
+        );
+
+        if !messages.is_empty() {
+            println!();
+            for message in messages {
+                println!("{}", message)
+            }
+        }
+
+        Ok(())
+    }
+
+    pub fn clear_screen(&mut self) -> Result<()> {
+        clearscreen::clear()?;
+        Ok(())
+    }
+}

src/pyproject.rs

@@ -1,29 +1,26 @@
-use std::collections::BTreeSet;
 use std::path::{Path, PathBuf};
+use std::str::FromStr;
 
-use anyhow::Result;
+use anyhow::{anyhow, Result};
 use common_path::common_path_all;
-use log::debug;
-use serde::Deserialize;
+use path_absolutize::Absolutize;
+use serde::de;
+use serde::{Deserialize, Deserializer};
 
 use crate::checks::CheckCode;
 use crate::fs;
 
-pub fn load_config<'a>(paths: impl IntoIterator<Item = &'a Path>) -> Result<(PathBuf, Config)> {
-    match find_project_root(paths) {
-        Some(project_root) => match find_pyproject_toml(&project_root) {
-            Some(path) => {
-                debug!("Found pyproject.toml at: {}", path.to_string_lossy());
-                let pyproject = parse_pyproject_toml(&path)?;
-                let config = pyproject
-                    .tool
-                    .and_then(|tool| tool.ruff)
-                    .unwrap_or_default();
-                Ok((project_root, config))
-            }
-            None => Ok(Default::default()),
-        },
-        None => Ok(Default::default()),
+pub fn load_config(pyproject: &Option<PathBuf>) -> Result<Config> {
+    match pyproject {
+        Some(pyproject) => Ok(parse_pyproject_toml(pyproject)?
+            .tool
+            .and_then(|tool| tool.ruff)
+            .unwrap_or_default()),
+        None => {
+            eprintln!("No pyproject.toml found.");
+            eprintln!("Falling back to default configuration...");
+            Ok(Default::default())
+        }
     }
 }
 
@@ -31,8 +28,54 @@ pub fn load_config<'a>(paths: impl IntoIterator<Item = &'a Path>) -> Result<(Pat
 #[serde(deny_unknown_fields, rename_all = "kebab-case")]
 pub struct Config {
     pub line_length: Option<usize>,
-    pub exclude: Option<Vec<PathBuf>>,
-    pub select: Option<BTreeSet<CheckCode>>,
+    pub exclude: Option<Vec<String>>,
+    pub extend_exclude: Option<Vec<String>>,
+    pub select: Option<Vec<CheckCode>>,
+    pub ignore: Option<Vec<CheckCode>>,
+    pub per_file_ignores: Option<Vec<StrCheckCodePair>>,
+    pub dummy_variable_rgx: Option<String>,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct StrCheckCodePair {
+    pub pattern: String,
+    pub code: CheckCode,
+}
+
+impl StrCheckCodePair {
+    const EXPECTED_PATTERN: &'static str = "<FilePattern>:<CheckCode> pattern";
+}
+
+impl<'de> Deserialize<'de> for StrCheckCodePair {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let str_result = String::deserialize(deserializer)?;
+        Self::from_str(str_result.as_str()).map_err(|_| {
+            de::Error::invalid_value(
+                de::Unexpected::Str(str_result.as_str()),
+                &Self::EXPECTED_PATTERN,
+            )
+        })
+    }
+}
+
+impl FromStr for StrCheckCodePair {
+    type Err = anyhow::Error;
+
+    fn from_str(string: &str) -> Result<Self, Self::Err> {
+        let (pattern_str, code_string) = {
+            let tokens = string.split(':').collect::<Vec<_>>();
+            if tokens.len() != 2 {
+                return Err(anyhow!("Expected {}", Self::EXPECTED_PATTERN));
+            }
+            (tokens[0], tokens[1])
+        };
+        let code = CheckCode::from_str(code_string)?;
+        let pattern = pattern_str.into();
+        Ok(Self { pattern, code })
+    }
 }
 
 #[derive(Debug, PartialEq, Eq, Deserialize)]
@@ -50,20 +93,34 @@ fn parse_pyproject_toml(path: &Path) -> Result<PyProject> {
     toml::from_str(&contents).map_err(|e| e.into())
 }
 
-fn find_pyproject_toml(path: &Path) -> Option<PathBuf> {
-    let path_pyproject_toml = path.join("pyproject.toml");
-    if path_pyproject_toml.is_file() {
-        return Some(path_pyproject_toml);
+pub fn find_pyproject_toml(path: &Option<PathBuf>) -> Option<PathBuf> {
+    if let Some(path) = path {
+        let path_pyproject_toml = path.join("pyproject.toml");
+        if path_pyproject_toml.is_file() {
+            return Some(path_pyproject_toml);
+        }
     }
+
     find_user_pyproject_toml()
 }
 
 fn find_user_pyproject_toml() -> Option<PathBuf> {
-    dirs::home_dir().map(|path| path.join(".ruff"))
+    let mut path = dirs::config_dir()?;
+    path.push("ruff");
+    path.push("pyproject.toml");
+    if path.is_file() {
+        Some(path)
+    } else {
+        None
+    }
 }
 
-fn find_project_root<'a>(sources: impl IntoIterator<Item = &'a Path>) -> Option<PathBuf> {
-    if let Some(prefix) = common_path_all(sources) {
+pub fn find_project_root(sources: &[PathBuf]) -> Option<PathBuf> {
+    let absolute_sources: Vec<PathBuf> = sources
+        .iter()
+        .flat_map(|source| source.absolutize().map(|path| path.to_path_buf()))
+        .collect();
+    if let Some(prefix) = common_path_all(absolute_sources.iter().map(PathBuf::as_path)) {
         for directory in prefix.ancestors() {
             if directory.join(".git").is_dir() {
                 return Some(directory.to_path_buf());
@@ -82,11 +139,13 @@ fn find_project_root<'a>(sources: impl IntoIterator<Item = &'a Path>) -> Option<
 
 #[cfg(test)]
 mod tests {
-    use std::collections::BTreeSet;
-    use std::path::Path;
+    use std::env::current_dir;
+    use std::path::PathBuf;
+    use std::str::FromStr;
 
     use anyhow::Result;
 
+    use super::StrCheckCodePair;
     use crate::checks::CheckCode;
     use crate::pyproject::{
         find_project_root, find_pyproject_toml, parse_pyproject_toml, Config, PyProject, Tools,
@@ -116,7 +175,11 @@ mod tests {
                 ruff: Some(Config {
                     line_length: None,
                     exclude: None,
+                    extend_exclude: None,
                     select: None,
+                    ignore: None,
+                    per_file_ignores: None,
+                    dummy_variable_rgx: None,
                 })
             })
         );
@@ -134,7 +197,11 @@ line-length = 79
                 ruff: Some(Config {
                     line_length: Some(79),
                     exclude: None,
+                    extend_exclude: None,
                     select: None,
+                    ignore: None,
+                    per_file_ignores: None,
+                    dummy_variable_rgx: None,
                 })
             })
         );
@@ -151,8 +218,12 @@ exclude = ["foo.py"]
             Some(Tools {
                 ruff: Some(Config {
                     line_length: None,
-                    exclude: Some(vec![Path::new("foo.py").to_path_buf()]),
+                    exclude: Some(vec!["foo.py".to_string()]),
+                    extend_exclude: None,
                     select: None,
+                    ignore: None,
+                    per_file_ignores: None,
+                    dummy_variable_rgx: None,
                 })
             })
         );
@@ -170,7 +241,33 @@ select = ["E501"]
                 ruff: Some(Config {
                     line_length: None,
                     exclude: None,
-                    select: Some(BTreeSet::from([CheckCode::E501])),
+                    extend_exclude: None,
+                    select: Some(vec![CheckCode::E501]),
+                    ignore: None,
+                    per_file_ignores: None,
+                    dummy_variable_rgx: None,
+                })
+            })
+        );
+
+        let pyproject: PyProject = toml::from_str(
+            r#"
+[tool.black]
+[tool.ruff]
+ignore = ["E501"]
+"#,
+        )?;
+        assert_eq!(
+            pyproject.tool,
+            Some(Tools {
+                ruff: Some(Config {
+                    line_length: None,
+                    exclude: None,
+                    extend_exclude: None,
+                    select: None,
+                    ignore: Some(vec![CheckCode::E501]),
+                    per_file_ignores: None,
+                    dummy_variable_rgx: None,
                 })
             })
         );
@@ -208,37 +305,56 @@ other-attribute = 1
 
     #[test]
     fn find_and_parse_pyproject_toml() -> Result<()> {
-        let project_root = find_project_root([Path::new("resources/test/src/__init__.py")])
-            .expect("Unable to find project root.");
-        assert_eq!(project_root, Path::new("resources/test/src"));
+        let cwd = current_dir()?;
+        let project_root =
+            find_project_root(&[PathBuf::from("resources/test/fixtures/__init__.py")])
+                .expect("Unable to find project root.");
+        assert_eq!(project_root, cwd.join("resources/test/fixtures"));
 
-        let path = find_pyproject_toml(&project_root).expect("Unable to find pyproject.toml.");
-        assert_eq!(path, Path::new("resources/test/src/pyproject.toml"));
+        let path =
+            find_pyproject_toml(&Some(project_root)).expect("Unable to find pyproject.toml.");
+        assert_eq!(path, cwd.join("resources/test/fixtures/pyproject.toml"));
 
         let pyproject = parse_pyproject_toml(&path)?;
         let config = pyproject
             .tool
-            .map(|tool| tool.ruff)
-            .flatten()
+            .and_then(|tool| tool.ruff)
             .expect("Unable to find tool.ruff.");
         assert_eq!(
             config,
             Config {
                 line_length: Some(88),
-                exclude: Some(vec![Path::new("excluded.py").to_path_buf()]),
-                select: Some(BTreeSet::from([
-                    CheckCode::E501,
-                    CheckCode::F401,
-                    CheckCode::F403,
-                    CheckCode::F541,
-                    CheckCode::F634,
-                    CheckCode::F706,
-                    CheckCode::F831,
-                    CheckCode::F901,
-                ])),
+                exclude: None,
+                extend_exclude: Some(vec![
+                    "excluded.py".to_string(),
+                    "migrations".to_string(),
+                    "directory/also_excluded.py".to_string(),
+                ]),
+                select: None,
+                ignore: None,
+                per_file_ignores: None,
+                dummy_variable_rgx: None,
             }
         );
 
         Ok(())
     }
+
+    #[test]
+    fn str_check_code_pair_strings() {
+        let result = StrCheckCodePair::from_str("foo:E501");
+        assert!(result.is_ok());
+        let result = StrCheckCodePair::from_str("E501:foo");
+        assert!(result.is_err());
+        let result = StrCheckCodePair::from_str("E501");
+        assert!(result.is_err());
+        let result = StrCheckCodePair::from_str("foo");
+        assert!(result.is_err());
+        let result = StrCheckCodePair::from_str("foo:E501:E402");
+        assert!(result.is_err());
+        let result = StrCheckCodePair::from_str("**/bar:E501");
+        assert!(result.is_ok());
+        let result = StrCheckCodePair::from_str("bar:E502");
+        assert!(result.is_err());
+    }
 }

src/python.rs

@@ -0,0 +1,3 @@
+pub mod builtins;
+pub mod future;
+pub mod typing;

src/python/builtins.rs

@@ -0,0 +1,163 @@
+pub const BUILTINS: &[&str] = &[
+    "ArithmeticError",
+    "AssertionError",
+    "AttributeError",
+    "BaseException",
+    "BlockingIOError",
+    "BrokenPipeError",
+    "BufferError",
+    "BytesWarning",
+    "ChildProcessError",
+    "ConnectionAbortedError",
+    "ConnectionError",
+    "ConnectionRefusedError",
+    "ConnectionResetError",
+    "DeprecationWarning",
+    "EOFError",
+    "Ellipsis",
+    "EnvironmentError",
+    "Exception",
+    "False",
+    "FileExistsError",
+    "FileNotFoundError",
+    "FloatingPointError",
+    "FutureWarning",
+    "GeneratorExit",
+    "IOError",
+    "ImportError",
+    "ImportWarning",
+    "IndentationError",
+    "IndexError",
+    "InterruptedError",
+    "IsADirectoryError",
+    "KeyError",
+    "KeyboardInterrupt",
+    "LookupError",
+    "MemoryError",
+    "ModuleNotFoundError",
+    "NameError",
+    "None",
+    "NotADirectoryError",
+    "NotImplemented",
+    "NotImplementedError",
+    "OSError",
+    "OverflowError",
+    "PendingDeprecationWarning",
+    "PermissionError",
+    "ProcessLookupError",
+    "RecursionError",
+    "ReferenceError",
+    "ResourceWarning",
+    "RuntimeError",
+    "RuntimeWarning",
+    "StopAsyncIteration",
+    "StopIteration",
+    "SyntaxError",
+    "SyntaxWarning",
+    "SystemError",
+    "SystemExit",
+    "TabError",
+    "TimeoutError",
+    "True",
+    "TypeError",
+    "UnboundLocalError",
+    "UnicodeDecodeError",
+    "UnicodeEncodeError",
+    "UnicodeError",
+    "UnicodeTranslateError",
+    "UnicodeWarning",
+    "UserWarning",
+    "ValueError",
+    "Warning",
+    "ZeroDivisionError",
+    "__build_class__",
+    "__debug__",
+    "__doc__",
+    "__import__",
+    "__loader__",
+    "__name__",
+    "__package__",
+    "__spec__",
+    "abs",
+    "all",
+    "any",
+    "ascii",
+    "bin",
+    "bool",
+    "breakpoint",
+    "bytearray",
+    "bytes",
+    "callable",
+    "chr",
+    "classmethod",
+    "compile",
+    "complex",
+    "copyright",
+    "credits",
+    "delattr",
+    "dict",
+    "dir",
+    "divmod",
+    "enumerate",
+    "eval",
+    "exec",
+    "exit",
+    "filter",
+    "float",
+    "format",
+    "frozenset",
+    "getattr",
+    "globals",
+    "hasattr",
+    "hash",
+    "help",
+    "hex",
+    "id",
+    "input",
+    "int",
+    "isinstance",
+    "issubclass",
+    "iter",
+    "len",
+    "license",
+    "list",
+    "locals",
+    "map",
+    "max",
+    "memoryview",
+    "min",
+    "next",
+    "object",
+    "oct",
+    "open",
+    "ord",
+    "pow",
+    "print",
+    "property",
+    "quit",
+    "range",
+    "repr",
+    "reversed",
+    "round",
+    "set",
+    "setattr",
+    "slice",
+    "sorted",
+    "staticmethod",
+    "str",
+    "sum",
+    "super",
+    "tuple",
+    "type",
+    "vars",
+    "zip",
+];
+
+// Globally defined names which are not attributes of the builtins module, or are only present on
+// some platforms.
+pub const MAGIC_GLOBALS: &[&str] = &[
+    "WindowsError",
+    "__annotations__",
+    "__builtins__",
+    "__file__",
+];

src/python/future.rs

@@ -0,0 +1,13 @@
+/// A copy of `__future__.all_feature_names`.
+pub const ALL_FEATURE_NAMES: &[&str] = &[
+    "nested_scopes",
+    "generators",
+    "division",
+    "absolute_import",
+    "with_statement",
+    "print_function",
+    "unicode_literals",
+    "barry_as_FLUFL",
+    "generator_stop",
+    "annotations",
+];