Bump version to 0.0.84

This reverts commit 77e5564f4b.

.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

.pre-commit-config.yaml

@@ -3,3 +3,8 @@ repos:
     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 +1,111 @@
+# 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.
+
+You'll also need [Insta](https://insta.rs/docs/) to update snapshot tests:
+
+```shell
+cargo install cargo-insta
+```
+
+### 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 satisfied 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.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ruff"
-version = "0.0.44"
+version = "0.0.84"
 edition = "2021"
 
 [lib]
@@ -9,32 +9,49 @@ name = "ruff"
 [dependencies]
 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"] }
-clearscreen = { version = "1.0.10" }
+clap = { version = "4.0.1", features = ["derive"] }
 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 = "0.10.3" }
+itertools = { version = "0.10.5" }
+libcst = { git = "https://github.com/charliermarsh/LibCST", rev = "32a044c127668df44582f85699358e67803b0d73" }
 log = { version = "0.4.17" }
 notify = { version = "4.0.17" }
+num-bigint = { version = "0.4.3" }
 once_cell = { version = "1.13.1" }
-path-absolutize = { version = "3.0.13", features = ["once_cell_cache"] }
+path-absolutize = { version = "3.0.14", features = ["once_cell_cache", "use_unix_paths_on_wasm"] }
 rayon = { version = "1.5.3" }
 regex = { version = "1.6.0" }
-rustpython-parser = { features = ["lalrpop"], git = "https://github.com/charliermarsh/RustPython.git", rev = "7d21c6923a506e79cc041708d83cef925efd33f4" }
+rustpython-ast = { features = ["unparse"], git = "https://github.com/charliermarsh/RustPython.git", rev = "1b253a12705f84972cd76e8dc1cdaaccb233e5a5" }
+rustpython-common = { git = "https://github.com/charliermarsh/RustPython.git", rev = "1b253a12705f84972cd76e8dc1cdaaccb233e5a5" }
+rustpython-parser = { features = ["lalrpop"], git = "https://github.com/charliermarsh/RustPython.git", rev = "1b253a12705f84972cd76e8dc1cdaaccb233e5a5" }
 serde = { version = "1.0.143", features = ["derive"] }
 serde_json = { version = "1.0.83" }
+strum = { version = "0.24.1", features = ["strum_macros"] }
+strum_macros = { version = "0.24.3" }
+textwrap = { version = "0.15.1" }
+titlecase = { version = "2.2.1" }
 toml = { version = "0.5.9" }
 update-informer = { version = "0.5.0", default_features = false, features = ["pypi"], optional = true }
 walkdir = { version = "2.3.2" }
 
+[target.'cfg(not(target_family = "wasm"))'.dependencies]
+cacache = { version = "10.0.1" } # uses async-std
+clearscreen = { version = "1.0.10" } # uses which
+
+# https://docs.rs/getrandom/0.2.7/getrandom/#webassembly-support
+# For (future) wasm-pack support
+[target.'cfg(all(target_family = "wasm", target_os = "unknown"))'.dependencies]
+getrandom = { version = "0.2.7", features = ["js"] }
+
 [dev-dependencies]
+assert_cmd = { version = "2.0.4" }
 insta = { version = "1.19.1", features = ["yaml"] }
+test-case = { version = "2.2.2" }
 
 [features]
 default = ["update-informer"]

README.md

@@ -1,4 +1,4 @@
-# ruff
+# 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)
@@ -20,17 +20,37 @@ An extremely fast Python linter, written in Rust.
 - 🤝 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#caching)-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
+- 🔧 [ESLint](https://eslint.org/docs/latest/user-guide/command-line-interface#--fix)-inspired autofix support (e.g., automatically remove unused imports)
+- 👀 [TypeScript](https://www.typescriptlang.org/docs/handbook/configuring-watch.html)-inspired `--watch` support, for continuous file monitoring
+- ⚖️ [Near-parity](#how-does-ruff-compare-to-flake8) with the built-in Flake8 rule set
+- 🔌 Native re-implementations of popular Flake8 plugins, like [`flake8-docstrings`](https://pypi.org/project/flake8-docstrings/) ([`pydocstyle`](https://pypi.org/project/pydocstyle/))
+
+Ruff aims to be orders of magnitude faster than alternative tools while integrating more
+functionality behind a single, common interface. Ruff can be used to replace Flake8 (plus a variety
+of plugins), [`pydocstyle`](https://pypi.org/project/pydocstyle/), [`yesqa`](https://github.com/asottile/yesqa),
+and even a subset of [`pyupgrade`](https://pypi.org/project/pyupgrade/) and [`autoflake`](https://pypi.org/project/autoflake/)
+all while executing tens or hundreds of times faster than any individual tool.
 
 Read the [launch blog post](https://notes.crmarsh.com/python-tooling-could-be-much-much-faster).
 
-## Installation and usage
+## Table of Contents
+
+1. [Installation and Usage](#installation-and-usage)
+2. [Configuration](#configuration)
+3. [Supported Rules](#supported-rules)
+4. [Editor Integrations](#editor-integrations)
+5. [FAQ](#faq)
+6. [Development](#development)
+7. [Releases](#releases)
+8. [Benchmarks](#benchmarks)
+9. [License](#license)
+10. [Contributing](#contributing)
+
+## Installation and Usage
 
 ### Installation
 
-Available as [ruff](https://pypi.org/project/ruff/) on PyPI:
+Available as [`ruff`](https://pypi.org/project/ruff/) on PyPI:
 
 ```shell
 pip install ruff
@@ -38,7 +58,7 @@ pip install ruff
 
 ### Usage
 
-To run ruff, try any of the following:
+To run Ruff, try any of the following:
 
 ```shell
 ruff path/to/code/to/check.py
@@ -46,27 +66,27 @@ ruff path/to/code/
 ruff path/to/code/*.py
 ```
 
-You can run ruff in `--watch` mode to automatically re-run on-change:
+You can run Ruff in `--watch` mode to automatically re-run on-change:
 
 ```shell
 ruff path/to/code/ --watch
 ```
 
-ruff also works with [pre-commit](https://pre-commit.com):
+Ruff also works with [pre-commit](https://pre-commit.com):
 
 ```yaml
 repos:
   - repo: https://github.com/charliermarsh/ruff-pre-commit
-    rev: v0.0.40
+    rev: v0.0.84
     hooks:
       - id: lint
 ```
 
 ## Configuration
 
-ruff is configurable both via `pyproject.toml` and the command line.
+Ruff is configurable both via `pyproject.toml` and the command line.
 
-For example, you could configure ruff to only enforce a subset of rules with:
+For example, you could configure Ruff to only enforce a subset of rules with:
 
 ```toml
 [tool.ruff]
@@ -80,55 +100,70 @@ 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 (v0.0.44) 0.0.44
-An extremely fast Python linter.
+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
-        --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
-    -f, --fix
-            Attempt to automatically fix lint errors
-        --format <FORMAT>
-            Output serialization format for error messages [default: text] [possible values: text,
-            json]
-    -h, --help
-            Print help information
-        --ignore <IGNORE>...
-            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>...
-            List of error codes to enable
-        --show-files
-            See the files ruff will be run against with the current configuration options
-        --show-settings
-            See ruff's settings
-    -v, --verbose
-            Enable verbose logging
-    -V, --version
-            Print version information
-    -w, --watch
-            Run in watch mode by re-running whenever files change
+Options:
+      --config <CONFIG>
+          Path to the `pyproject.toml` file to use for configuration
+  -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
+      --target-version <TARGET_VERSION>
+          The minimum Python version that should be supported
+      --stdin-filename <STDIN_FILENAME>
+          The name of the file when passing it through stdin
+  -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
@@ -138,81 +173,444 @@ Exclusions are based on globs, and can be either:
   (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`).
 
-### Compatibility with Black
+### Ignoring errors
 
-ruff is compatible with [Black](https://github.com/psf/black) out-of-the-box, as long as
+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 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.**
+
+## Supported Rules
+
+By default, Ruff enables all `E`, `W`, and `F` error codes, which correspond to those built-in to
+Flake8.
+
+The 🛠 emoji indicates that a rule is automatically fixable by the `--fix` command-line option.
+
+### Pyflakes
+
+| Code | Name | Message | Fix |
+| ---- | ---- | ------- | --- |
+| 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 | ExpressionsInStarAssignment | 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 `==` and `!=` 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 | `yield` or `yield from` statement outside of a function/method |  |
+| F706 | ReturnOutsideFunction | `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` |  |
+
+### pycodestyle
+
+| Code | Name | Message | Fix |
+| ---- | ---- | ------- | --- |
+| 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 | IOError: `...` |  |
+| E999 | SyntaxError | SyntaxError: `...` |  |
+| W292 | NoNewLineAtEndOfFile | No newline at end of file |  |
+
+### pydocstyle
+
+| Code | Name | Message | Fix |
+| ---- | ---- | ------- | --- |
+| D100 | PublicModule | Missing docstring in public module |  |
+| D101 | PublicClass | Missing docstring in public class |  |
+| D102 | PublicMethod | Missing docstring in public method |  |
+| D103 | PublicFunction | Missing docstring in public function |  |
+| D104 | PublicPackage | Missing docstring in public package |  |
+| D105 | MagicMethod | Missing docstring in magic method |  |
+| D106 | PublicNestedClass | Missing docstring in public nested class |  |
+| D107 | PublicInit | Missing docstring in `__init__` |  |
+| D200 | FitsOnOneLine | One-line docstring should fit on one line |  |
+| D201 | NoBlankLineBeforeFunction | No blank lines allowed before function docstring (found 1) | 🛠 |
+| D202 | NoBlankLineAfterFunction | No blank lines allowed after function docstring (found 1) | 🛠 |
+| D203 | OneBlankLineBeforeClass | 1 blank line required before class docstring | 🛠 |
+| D204 | OneBlankLineAfterClass | 1 blank line required after class docstring | 🛠 |
+| D205 | BlankLineAfterSummary | 1 blank line required between summary line and description | 🛠 |
+| D206 | IndentWithSpaces | Docstring should be indented with spaces, not tabs |  |
+| D207 | NoUnderIndentation | Docstring is under-indented | 🛠 |
+| D208 | NoOverIndentation | Docstring is over-indented | 🛠 |
+| D209 | NewLineAfterLastParagraph | Multi-line docstring closing quotes should be on a separate line | 🛠 |
+| D210 | NoSurroundingWhitespace | No whitespaces allowed surrounding docstring text | 🛠 |
+| D211 | NoBlankLineBeforeClass | No blank lines allowed before class docstring | 🛠 |
+| D212 | MultiLineSummaryFirstLine | Multi-line docstring summary should start at the first line |  |
+| D213 | MultiLineSummarySecondLine | Multi-line docstring summary should start at the second line |  |
+| D214 | SectionNotOverIndented | Section is over-indented ("Returns") | 🛠 |
+| D215 | SectionUnderlineNotOverIndented | Section underline is over-indented ("Returns") | 🛠 |
+| D300 | UsesTripleQuotes | Use """triple double quotes""" |  |
+| D400 | EndsInPeriod | First line should end with a period |  |
+| D402 | NoSignature | First line should not be the function's signature |  |
+| D403 | FirstLineCapitalized | First word of the first line should be properly capitalized |  |
+| D404 | NoThisPrefix | First word of the docstring should not be `This` |  |
+| D405 | CapitalizeSectionName | Section name should be properly capitalized ("returns") | 🛠 |
+| D406 | NewLineAfterSectionName | Section name should end with a newline ("Returns") | 🛠 |
+| D407 | DashedUnderlineAfterSection | Missing dashed underline after section ("Returns") | 🛠 |
+| D408 | SectionUnderlineAfterName | Section underline should be in the line following the section's name ("Returns") | 🛠 |
+| D409 | SectionUnderlineMatchesSectionLength | Section underline should match the length of its name ("Returns") | 🛠 |
+| D410 | BlankLineAfterSection | Missing blank line after section ("Returns") | 🛠 |
+| D411 | BlankLineBeforeSection | Missing blank line before section ("Returns") | 🛠 |
+| D412 | NoBlankLinesBetweenHeaderAndContent | No blank lines allowed between a section header and its content ("Returns") | 🛠 |
+| D413 | BlankLineAfterLastSection | Missing blank line after last section ("Returns") | 🛠 |
+| D414 | NonEmptySection | Section has no content ("Returns") |  |
+| D415 | EndsInPunctuation | First line should end with a period, question mark, or exclamation point |  |
+| D416 | SectionNameEndsInColon | Section name should end with a colon ("Returns") | 🛠 |
+| D417 | DocumentAllArguments | Missing argument descriptions in the docstring: `x`, `y` |  |
+| D418 | SkipDocstring | Function decorated with @overload shouldn't contain a docstring |  |
+| D419 | NonEmpty | Docstring is empty |  |
+
+### pyupgrade
+
+| Code | Name | Message | Fix |
+| ---- | ---- | ------- | --- |
+| U001 | UselessMetaclassType | `__metaclass__ = type` is implied | 🛠 |
+| U002 | UnnecessaryAbspath | `abspath(__file__)` is unnecessary in Python 3.9 and later | 🛠 |
+| U003 | TypeOfPrimitive | Use `str` instead of `type(...)` | 🛠 |
+| U004 | UselessObjectInheritance | Class `...` inherits from object | 🛠 |
+| U005 | DeprecatedUnittestAlias | `assertEquals` is deprecated, use `assertEqual` instead | 🛠 |
+| U006 | UsePEP585Annotation | Use `list` instead of `List` for type annotations | 🛠 |
+| U007 | UsePEP604Annotation | Use `X \| Y` for type annotations | 🛠 |
+| U008 | SuperCallWithParameters | Use `super()` instead of `super(__class__, self)` | 🛠 |
+
+### pep8-naming
+
+| Code | Name | Message | Fix |
+| ---- | ---- | ------- | --- |
+| N801 | InvalidClassName | Class name `...` should use CapWords convention  |  |
+| N802 | InvalidFunctionName | Function name `...` should be lowercase |  |
+| N803 | InvalidArgumentName | Argument name `...` should be lowercase |  |
+| N804 | InvalidFirstArgumentNameForClassMethod | First argument of a class method should be named `cls` |  |
+| N805 | InvalidFirstArgumentNameForMethod | First argument of a method should be named `self` |  |
+| N807 | DunderFunctionName | Function name should not start and end with `__` |  |
+| N811 | ConstantImportedAsNonConstant | Constant `...` imported as non-constant `...` |  |
+| N812 | LowercaseImportedAsNonLowercase | Lowercase `...` imported as non-lowercase `...` |  |
+| N813 | CamelcaseImportedAsLowercase | Camelcase `...` imported as lowercase `...` |  |
+| N814 | CamelcaseImportedAsConstant | Camelcase `...` imported as constant `...` |  |
+| N817 | CamelcaseImportedAsAcronym | Camelcase `...` imported as acronym `...` |  |
+
+### flake8-comprehensions
+
+| Code | Name | Message | Fix |
+| ---- | ---- | ------- | --- |
+| C400 | UnnecessaryGeneratorList | Unnecessary generator (rewrite as a `list` comprehension) |  |
+| C401 | UnnecessaryGeneratorSet | Unnecessary generator (rewrite as a `set` comprehension) |  |
+| C402 | UnnecessaryGeneratorDict | Unnecessary generator (rewrite as a `dict` comprehension) |  |
+| C403 | UnnecessaryListComprehensionSet | Unnecessary `list` comprehension (rewrite as a `set` comprehension) |  |
+| C404 | UnnecessaryListComprehensionDict | Unnecessary `list` comprehension (rewrite as a `dict` comprehension) |  |
+| C405 | UnnecessaryLiteralSet | Unnecessary `(list\|tuple)` literal (rewrite as a `set` literal) |  |
+| C406 | UnnecessaryLiteralDict | Unnecessary `(list\|tuple)` literal (rewrite as a `dict` literal) |  |
+| C408 | UnnecessaryCollectionCall | Unnecessary `(dict\|list\|tuple)` call (rewrite as a literal) |  |
+| C409 | UnnecessaryLiteralWithinTupleCall | Unnecessary `(list\|tuple)` literal passed to `tuple()` (remove the outer call to `tuple()`) |  |
+| C410 | UnnecessaryLiteralWithinListCall | Unnecessary `(list\|tuple)` literal passed to `list()` (rewrite as a `list` literal) |  |
+| C411 | UnnecessaryListCall | Unnecessary `list` call (remove the outer call to `list()`) |  |
+| C413 | UnnecessaryCallAroundSorted | Unnecessary `(list\|reversed)` call around `sorted()` |  |
+| C414 | UnnecessaryDoubleCastOrProcess | Unnecessary `(list\|reversed\|set\|sorted\|tuple)` call within `(list\|set\|sorted\|tuple)()` |  |
+| C415 | UnnecessarySubscriptReversal | Unnecessary subscript reversal of iterable within `(reversed\|set\|sorted)()` |  |
+| C416 | UnnecessaryComprehension |  Unnecessary `(list\|set)` comprehension (rewrite using `(list\|set)()`) |  |
+| C417 | UnnecessaryMap | Unnecessary `map` usage (rewrite using a `(list\|set\|dict)` comprehension) |  |
+
+### flake8-bugbear
+
+| Code | Name | Message | Fix |
+| ---- | ---- | ------- | --- |
+| B002 | UnaryPrefixIncrement | Python does not support the unary prefix increment. |  |
+| B007 | UnusedLoopControlVariable | Loop control variable `i` not used within the loop body. | 🛠 |
+| B011 | DoNotAssertFalse | Do not `assert False` (`python -O` removes these calls), raise `AssertionError()` | 🛠 |
+| B014 | DuplicateHandlerException | Exception handler with duplicate exception: `ValueError` | 🛠 |
+| B017 | NoAssertRaisesException | `assertRaises(Exception):` should be considered evil. |  |
+| B025 | DuplicateTryBlockException | try-except block with duplicate exception `Exception` |  |
+
+### flake8-builtins
+
+| Code | Name | Message | Fix |
+| ---- | ---- | ------- | --- |
+| 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 |  |
+
+### flake8-print
+
+| Code | Name | Message | Fix |
+| ---- | ---- | ------- | --- |
+| T201 | PrintFound | `print` found | 🛠 |
+| T203 | PPrintFound | `pprint` found | 🛠 |
+
+### Meta rules
+
+| Code | Name | Message | Fix |
+| ---- | ---- | ------- | --- |
+| M001 | UnusedNOQA | Unused `noqa` directive | 🛠 |
+
+## Editor 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@v3
+      - name: Install Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: "3.10"
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install ruff
+      - name: Run Ruff
+        run: ruff .
+```
+
+## FAQ
+
+### Is Ruff compatible with Black?
+
+Yes. 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
+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
+### How does Ruff compare to 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.
+Ruff can be used as a (near) drop-in replacement for Flake8 when used (1) without or with a small
+number of 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.)
+Under those conditions 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:
+Ruff re-implements some of the most popular Flake8 plugins and related code quality tools natively,
+including:
 
-1. Flake8 has a plugin architecture and supports writing custom lint rules.
-2. Flake8 supports a wider range of `noqa` patterns, such as per-file ignores defined in `.flake8`.
-3. ruff does not yet support parenthesized context managers.
+- [`pydocstyle`](https://pypi.org/project/pydocstyle/)
+- [`yesqa`](https://github.com/asottile/yesqa)
+- [`flake8-docstrings`](https://pypi.org/project/flake8-docstrings/)
+- [`flake8-builtins`](https://pypi.org/project/flake8-builtins/)
+- [`flake8-super`](https://pypi.org/project/flake8-super/)
+- [`flake8-print`](https://pypi.org/project/flake8-print/)
+- [`flake8-comprehensions`](https://pypi.org/project/flake8-comprehensions/)
+- [`flake8-bugbear`](https://pypi.org/project/flake8-bugbear/) (9/32)
+- [`pyupgrade`](https://pypi.org/project/pyupgrade/) (8/34)
+- [`autoflake`](https://pypi.org/project/autoflake/) (1/7)
 
-## Rules
+Beyond rule-set parity, Ruff suffers from the following limitations vis-à-vis Flake8:
 
-| 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` |
-| R001 | UselessObjectInheritance | Class `...` inherits from object |
-| R002 | NoAssertEquals | `assertEquals` is deprecated, use `assertEqual` instead |
+1. Ruff does not yet support a few Python 3.9 and 3.10 language features, including structural
+   pattern matching and parenthesized context managers.
+2. Flake8 has a plugin architecture and supports writing custom lint rules. (To date, popular Flake8
+   plugins have been re-implemented within Ruff directly.)
+
+### Which tools does Ruff replace?
+
+Today, Ruff can be used to replace Flake8 when used with any of the following plugins:
+
+- [`flake8-docstrings`](https://pypi.org/project/flake8-docstrings/)
+- [`flake8-builtins`](https://pypi.org/project/flake8-builtins/)
+- [`flake8-super`](https://pypi.org/project/flake8-super/)
+- [`flake8-print`](https://pypi.org/project/flake8-print/)
+- [`flake8-comprehensions`](https://pypi.org/project/flake8-comprehensions/)
+- [`flake8-bugbear`](https://pypi.org/project/flake8-bugbear/) (9/32)
+
+Ruff also implements the functionality that you get from [`yesqa`](https://github.com/asottile/yesqa),
+and a subset of the rules implemented in [`pyupgrade`](https://pypi.org/project/pyupgrade/) (8/34).
+
+If you're looking to use Ruff, but rely on an unsupported Flake8 plugin, free to file an Issue.
+
+### Do I need to install Rust to use Ruff?
+
+Nope! Ruff is available as [`ruff`](https://pypi.org/project/ruff/) on PyPI:
+
+```shell
+pip install ruff
+```
+
+Ruff ships with wheels for all major platforms, which enables `pip` to install Ruff without relying
+on Rust at all.
+
+### Can I write my own plugins for Ruff?
+
+Ruff does not yet support third-party plugins, though a plugin system is within-scope for the
+project. See [#283](https://github.com/charliermarsh/ruff/issues/283) for more.
+
+### Does Ruff support NumPy- or Google-style docstrings?
+
+Yes! To enable a specific docstring convention, start by enabling all `pydocstyle` error codes, and
+then selectively disabling based on your [preferred convention](https://www.pydocstyle.org/en/latest/error_codes.html#default-conventions).
+
+For example, if you're coming from `flake8-docstrings`, the following configuration is equivalent to
+`--docstring-convention numpy`:
+
+```toml
+[tool.ruff]
+extend-select = [
+    "D100",
+    "D101",
+    "D102",
+    "D103",
+    "D104",
+    "D105",
+    "D106",
+    "D200",
+    "D201",
+    "D202",
+    "D204",
+    "D205",
+    "D206",
+    "D207",
+    "D208",
+    "D209",
+    "D210",
+    "D211",
+    "D214",
+    "D215",
+    "D300",
+    "D400",
+    "D402",
+    "D403",
+    "D404",
+    "D405",
+    "D406",
+    "D407",
+    "D408",
+    "D409",
+    "D410",
+    "D411",
+    "D412",
+    "D413",
+    "D418",
+    "D419",
+]
+```
+
+Similarly, the following is equivalent to `--docstring-convention google`:
+
+```toml
+[tool.ruff]
+extend-select = [
+    "D100",
+    "D101",
+    "D102",
+    "D103",
+    "D104",
+    "D105",
+    "D106",
+    "D107",
+    "D200",
+    "D201",
+    "D202",
+    "D205",
+    "D206",
+    "D207",
+    "D208",
+    "D209",
+    "D210",
+    "D211",
+    "D212",
+    "D214",
+    "D300",
+    "D402",
+    "D403",
+    "D405",
+    "D410",
+    "D411",
+    "D412",
+    "D414",
+    "D415",
+    "D416",
+    "D417",
+    "D418",
+    "D419",
+]
+```
 
 ## Development
 
-ruff is written in Rust (1.63.0). You'll need to install the [Rust toolchain](https://www.rust-lang.org/tools/install)
+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.
 
 Assuming you have `cargo` installed, you can run:
@@ -224,13 +622,13 @@ cargo clippy
 cargo test
 ```
 
-## Deployment
+## Releases
 
-ruff is distributed on [PyPI](https://pypi.org/project/ruff/), and published via [`maturin`](https://github.com/PyO3/maturin).
+Ruff is distributed on [PyPI](https://pypi.org/project/ruff/), and published via [`maturin`](https://github.com/PyO3/maturin).
 
 See: `.github/workflows/release.yaml`.
 
-## Benchmarking
+## Benchmarks
 
 First, clone [CPython](https://github.com/python/cpython). It's a large and diverse Python codebase,
 which makes it a good target for benchmarking.
@@ -307,9 +705,9 @@ hyperfine --ignore-failure --warmup 5 \
 
 In order, these evaluate:
 
-- ruff
+- Ruff
 - Pylint
-- PyFlakes
+- Pyflakes
 - autoflake
 - pycodestyle
 - Flake8
@@ -369,3 +767,8 @@ Summary
 ## License
 
 MIT
+
+## Contributing
+
+Contributions are welcome and hugely appreciated. To get started, check out the
+[contributing guidelines](https://github.com/charliermarsh/ruff/blob/main/CONTRIBUTING.md).

examples/generate_rules_table.rs

@@ -1,19 +1,29 @@
-/// Generate a Markdown-compatible table of supported lint rules.
-use ruff::checks::{CheckCode, ALL_CHECK_CODES};
+//! Generate a Markdown-compatible table of supported lint rules.
+
+use strum::IntoEnumIterator;
+
+use ruff::checks::{CheckCategory, CheckCode};
 
 fn main() {
-    let mut check_codes: Vec<CheckCode> = ALL_CHECK_CODES.to_vec();
-    check_codes.sort();
+    for check_category in CheckCategory::iter() {
+        println!("### {}", check_category.title());
+        println!();
 
-    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()
-        );
+        println!("| Code | Name | Message | Fix |");
+        println!("| ---- | ---- | ------- | --- |");
+        for check_code in CheckCode::iter() {
+            if check_code.category() == check_category {
+                let check_kind = check_code.kind();
+                let fix_token = if check_kind.fixable() { "🛠" } else { "" };
+                println!(
+                    "| {} | {} | {} | {} |",
+                    check_kind.code().as_ref(),
+                    check_kind.as_ref(),
+                    check_kind.summary().replace("|", r"\|"),
+                    fix_token
+                );
+            }
+        }
+        println!();
     }
 }

examples/generate_source_code.rs

@@ -0,0 +1,26 @@
+use std::path::PathBuf;
+
+use anyhow::Result;
+use clap::Parser;
+use rustpython_parser::parser;
+
+use ruff::code_gen::SourceGenerator;
+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())?;
+    let mut generator = SourceGenerator::new();
+    generator.unparse_suite(&python_ast)?;
+    println!("{}", generator.generate()?);
+
+    Ok(())
+}

examples/print_ast.rs

@@ -1,15 +1,16 @@
-/// Print the AST for a given Python file.
+//! Print the AST for a given Python file.
+
 use std::path::PathBuf;
 
 use anyhow::Result;
-use clap::{Parser, ValueHint};
+use clap::Parser;
 use rustpython_parser::parser;
 
 use ruff::fs;
 
 #[derive(Debug, Parser)]
 struct Cli {
-    #[clap(parse(from_os_str), value_hint = ValueHint::FilePath, required = true)]
+    #[arg(required = true)]
     file: PathBuf,
 }
 

examples/print_tokens.rs

@@ -1,15 +1,16 @@
-/// Print the token stream for a given Python file.
+//! Print the token stream for a given Python file.
+
 use std::path::PathBuf;
 
 use anyhow::Result;
-use clap::{Parser, ValueHint};
+use clap::Parser;
 use rustpython_parser::lexer;
 
 use ruff::fs;
 
 #[derive(Debug, Parser)]
 struct Cli {
-    #[clap(parse(from_os_str), value_hint = ValueHint::FilePath, required = true)]
+    #[arg(required = true)]
     file: PathBuf,
 }
 

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",

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/B002.py

@@ -0,0 +1,20 @@
+"""
+Should emit:
+B002 - on lines 15 and 20
+"""
+
+
+def this_is_all_fine(n):
+    x = n + 1
+    y = 1 + n
+    z = +x + y
+    return +z
+
+
+def this_is_buggy(n):
+    x = ++n
+    return x
+
+
+def this_is_buggy_too(n):
+    return ++n

resources/test/fixtures/B007.py

@@ -0,0 +1,31 @@
+for i in range(10):
+    print(i)
+
+print(i)  # name no longer defined on Python 3; no warning yet
+
+for i in range(10):  # name not used within the loop; B007
+    print(10)
+
+print(i)  # name no longer defined on Python 3; no warning yet
+
+
+for _ in range(10):  # _ is okay for a throw-away variable
+    print(10)
+
+
+for i in range(10):
+    for j in range(10):
+        for k in range(10):  # k not used, i and j used transitively
+            print(i + j)
+
+
+def strange_generator():
+    for i in range(10):
+        for j in range(10):
+            for k in range(10):
+                for l in range(10):
+                    yield i, (j, (k, l))
+
+
+for i, (j, (k, l)) in strange_generator():  # i, k not used
+    print(j, l)

resources/test/fixtures/B011.py

@@ -0,0 +1,10 @@
+"""
+Should emit:
+B011 - on line 8
+B011 - on line 10
+"""
+
+assert 1 != 2
+assert False
+assert 1 != 2, "message"
+assert False, "message"

resources/test/fixtures/B014.py

@@ -0,0 +1,76 @@
+"""
+Should emit:
+B014 - on lines 11, 17, 28, 42, 49, 56, and 74.
+"""
+
+import binascii
+import re
+
+try:
+    pass
+except (Exception, TypeError):
+    # TypeError is a subclass of Exception, so it doesn't add anything
+    pass
+
+try:
+    pass
+except (OSError, OSError) as err:
+    # Duplicate exception types are useless
+    pass
+
+
+class MyError(Exception):
+    pass
+
+
+try:
+    pass
+except (MyError, MyError):
+    # Detect duplicate non-builtin errors
+    pass
+
+
+try:
+    pass
+except (MyError, Exception) as e:
+    # Don't assume that we're all subclasses of Exception
+    pass
+
+
+try:
+    pass
+except (MyError, BaseException) as e:
+    # But we *can* assume that everything is a subclass of BaseException
+    pass
+
+
+try:
+    pass
+except (re.error, re.error):
+    # Duplicate exception types as attributes
+    pass
+
+
+try:
+    pass
+except (IOError, EnvironmentError, OSError):
+    # Detect if a primary exception and any its aliases are present.
+    #
+    # Since Python 3.3, IOError, EnvironmentError, WindowsError, mmap.error,
+    # socket.error and select.error are aliases of OSError. See PEP 3151 for
+    # more info.
+    pass
+
+
+try:
+    pass
+except (MyException, NotImplemented):
+    # NotImplemented is not an exception, let's not crash on it.
+    pass
+
+
+try:
+    pass
+except (ValueError, binascii.Error):
+    # binascii.Error is a subclass of ValueError.
+    pass

resources/test/fixtures/B017.py

@@ -0,0 +1,36 @@
+"""
+Should emit:
+B017 - on lines 20
+"""
+import asyncio
+import unittest
+
+CONSTANT = True
+
+
+def something_else() -> None:
+    for i in (1, 2, 3):
+        print(i)
+
+
+class Foo:
+    pass
+
+
+class Foobar(unittest.TestCase):
+    def evil_raises(self) -> None:
+        with self.assertRaises(Exception):
+            raise Exception("Evil I say!")
+
+    def context_manager_raises(self) -> None:
+        with self.assertRaises(Exception) as ex:
+            raise Exception("Context manager is good")
+        self.assertEqual("Context manager is good", str(ex.exception))
+
+    def regex_raises(self) -> None:
+        with self.assertRaisesRegex(Exception, "Regex is good"):
+            raise Exception("Regex is good")
+
+    def raises_with_absolute_reference(self):
+        with self.assertRaises(asyncio.CancelledError):
+            Foo()

resources/test/fixtures/B025.py

@@ -0,0 +1,38 @@
+"""
+Should emit:
+B025 - on lines 15, 22, 31
+"""
+
+import pickle
+
+try:
+    a = 1
+except ValueError:
+    a = 2
+finally:
+    a = 3
+
+try:
+    a = 1
+except ValueError:
+    a = 2
+except ValueError:
+    a = 2
+
+try:
+    a = 1
+except pickle.PickleError:
+    a = 2
+except ValueError:
+    a = 2
+except pickle.PickleError:
+    a = 2
+
+try:
+    a = 1
+except (ValueError, TypeError):
+    a = 2
+except ValueError:
+    a = 2
+except (OSError, TypeError):
+    a = 2

resources/test/fixtures/C400.py

@@ -0,0 +1 @@
+x = list(x for x in range(3))

resources/test/fixtures/C401.py

@@ -0,0 +1 @@
+x = set(x for x in range(3))

resources/test/fixtures/C402.py

@@ -0,0 +1 @@
+d = dict((x, x) for x in range(3))

resources/test/fixtures/C403.py

@@ -0,0 +1 @@
+s = set([x for x in range(3)])

resources/test/fixtures/C404.py

@@ -0,0 +1 @@
+d = dict([(i, i) for i in range(3)])

resources/test/fixtures/C405.py

@@ -0,0 +1,5 @@
+s1 = set([1, 2])
+s2 = set((1, 2))
+s3 = set([])
+s4 = set(())
+s5 = set()

resources/test/fixtures/C406.py

@@ -0,0 +1,5 @@
+d1 = dict([(1, 2)])
+d2 = dict(((1, 2),))
+d3 = dict([])
+d4 = dict(())
+d5 = dict()

resources/test/fixtures/C408.py

@@ -0,0 +1,5 @@
+t = tuple()
+l = list()
+d1 = dict()
+d2 = dict(a=1)
+d3 = dict(**d2)

resources/test/fixtures/C409.py

@@ -0,0 +1,3 @@
+t1 = tuple([1, 2])
+t2 = tuple((1, 2))
+t3 = tuple([])

resources/test/fixtures/C410.py

@@ -0,0 +1,4 @@
+l1 = list([1, 2])
+l2 = list((1, 2))
+l3 = list([])
+l4 = list(())

resources/test/fixtures/C411.py

@@ -0,0 +1,2 @@
+x = [1, 2, 3]
+list([i for i in x])

resources/test/fixtures/C413.py

@@ -0,0 +1,4 @@
+x = [2, 3, 1]
+list(sorted(x))
+reversed(sorted(x))
+reversed(sorted(x, reverse=True))

resources/test/fixtures/C414.py

@@ -0,0 +1,14 @@
+x = [1, 2, 3]
+list(list(x))
+list(tuple(x))
+tuple(list(x))
+tuple(tuple(x))
+set(set(x))
+set(list(x))
+set(tuple(x))
+set(sorted(x))
+set(reversed(x))
+sorted(list(x))
+sorted(tuple(x))
+sorted(sorted(x))
+sorted(reversed(x))

resources/test/fixtures/C415.py

@@ -0,0 +1,9 @@
+lst = [2, 1, 3]
+a = set(lst[::-1])
+b = reversed(lst[::-1])
+c = sorted(lst[::-1])
+d = sorted(lst[::-1], reverse=True)
+e = set(lst[2:-1])
+f = set(lst[:1:-1])
+g = set(lst[::1])
+h = set(lst[::-2])

resources/test/fixtures/C416.py

@@ -0,0 +1,6 @@
+x = [1, 2, 3]
+[i for i in x]
+{i for i in x}
+
+[i for i in x if i > 1]
+[i for i in x for j in x]

resources/test/fixtures/C417.py

@@ -0,0 +1,6 @@
+nums = [1, 2, 3]
+map(lambda x: x + 1, nums)
+map(lambda x: str(x), nums)
+list(map(lambda x: x * 2, nums))
+set(map(lambda x: x % 2 == 0, nums))
+dict(map(lambda v: (v, v**2), nums))

resources/test/fixtures/D.py

@@ -0,0 +1,534 @@
+# No docstring, so we can test D100
+from functools import wraps
+import os
+from .expected import Expectation
+from typing import overload
+
+
+expectation = Expectation()
+expect = expectation.expect
+
+expect('class_', 'D101: Missing docstring in public class')
+
+
+class class_:
+
+    expect('meta', 'D419: Docstring is empty')
+
+    class meta:
+        """"""
+
+    @expect('D102: Missing docstring in public method')
+    def method(self=None):
+        pass
+
+    def _ok_since_private(self=None):
+        pass
+
+    @overload
+    def overloaded_method(self, a: int) -> str:
+        ...
+
+    @overload
+    def overloaded_method(self, a: str) -> str:
+        """Foo bar documentation."""
+        ...
+
+    def overloaded_method(a):
+        """Foo bar documentation."""
+        return str(a)
+
+    expect('overloaded_method',
+           "D418: Function/ Method decorated with @overload"
+           " shouldn't contain a docstring")
+
+    @property
+    def foo(self):
+        """The foo of the thing, which isn't in imperitive mood."""
+        return "hello"
+
+    @expect('D102: Missing docstring in public method')
+    def __new__(self=None):
+        pass
+
+    @expect('D107: Missing docstring in __init__')
+    def __init__(self=None):
+        pass
+
+    @expect('D105: Missing docstring in magic method')
+    def __str__(self=None):
+        pass
+
+    @expect('D102: Missing docstring in public method')
+    def __call__(self=None, x=None, y=None, z=None):
+        pass
+
+
+@expect('D419: Docstring is empty')
+def function():
+    """ """
+    def ok_since_nested():
+        pass
+
+    @expect('D419: Docstring is empty')
+    def nested():
+        ''
+
+
+def function_with_nesting():
+    """Foo bar documentation."""
+    @overload
+    def nested_overloaded_func(a: int) -> str:
+        ...
+
+    @overload
+    def nested_overloaded_func(a: str) -> str:
+        """Foo bar documentation."""
+        ...
+
+    def nested_overloaded_func(a):
+        """Foo bar documentation."""
+        return str(a)
+
+
+expect('nested_overloaded_func',
+       "D418: Function/ Method decorated with @overload"
+       " shouldn't contain a docstring")
+
+
+@overload
+def overloaded_func(a: int) -> str:
+    ...
+
+
+@overload
+def overloaded_func(a: str) -> str:
+    """Foo bar documentation."""
+    ...
+
+
+def overloaded_func(a):
+    """Foo bar documentation."""
+    return str(a)
+
+
+expect('overloaded_func',
+       "D418: Function/ Method decorated with @overload"
+       " shouldn't contain a docstring")
+
+
+@expect('D200: One-line docstring should fit on one line with quotes '
+        '(found 3)')
+@expect('D212: Multi-line docstring summary should start at the first line')
+def asdlkfasd():
+    """
+    Wrong.
+    """
+
+
+@expect('D201: No blank lines allowed before function docstring (found 1)')
+def leading_space():
+
+    """Leading space."""
+
+
+@expect('D202: No blank lines allowed after function docstring (found 1)')
+def trailing_space():
+    """Leading space."""
+
+    pass
+
+
+@expect('D201: No blank lines allowed before function docstring (found 1)')
+@expect('D202: No blank lines allowed after function docstring (found 1)')
+def trailing_and_leading_space():
+
+    """Trailing and leading space."""
+
+    pass
+
+
+expect('LeadingSpaceMissing',
+       'D203: 1 blank line required before class docstring (found 0)')
+
+
+class LeadingSpaceMissing:
+    """Leading space missing."""
+
+
+expect('WithLeadingSpace',
+       'D211: No blank lines allowed before class docstring (found 1)')
+
+
+class WithLeadingSpace:
+
+    """With leading space."""
+
+
+expect('TrailingSpace',
+       'D204: 1 blank line required after class docstring (found 0)')
+expect('TrailingSpace',
+       'D211: No blank lines allowed before class docstring (found 1)')
+
+
+class TrailingSpace:
+
+    """TrailingSpace."""
+    pass
+
+
+expect('LeadingAndTrailingSpaceMissing',
+       'D203: 1 blank line required before class docstring (found 0)')
+expect('LeadingAndTrailingSpaceMissing',
+       'D204: 1 blank line required after class docstring (found 0)')
+
+
+class LeadingAndTrailingSpaceMissing:
+    """Leading and trailing space missing."""
+    pass
+
+
+@expect('D205: 1 blank line required between summary line and description '
+        '(found 0)')
+@expect('D213: Multi-line docstring summary should start at the second line')
+def multi_line_zero_separating_blanks():
+    """Summary.
+    Description.
+
+    """
+
+
+@expect('D205: 1 blank line required between summary line and description '
+        '(found 2)')
+@expect('D213: Multi-line docstring summary should start at the second line')
+def multi_line_two_separating_blanks():
+    """Summary.
+
+
+    Description.
+
+    """
+
+
+@expect('D213: Multi-line docstring summary should start at the second line')
+def multi_line_one_separating_blanks():
+    """Summary.
+
+    Description.
+
+    """
+
+
+@expect('D207: Docstring is under-indented')
+@expect('D213: Multi-line docstring summary should start at the second line')
+def asdfsdf():
+    """Summary.
+
+Description.
+
+    """
+
+
+@expect('D207: Docstring is under-indented')
+@expect('D213: Multi-line docstring summary should start at the second line')
+def asdsdfsdffsdf():
+    """Summary.
+
+    Description.
+
+"""
+
+
+@expect('D208: Docstring is over-indented')
+@expect('D213: Multi-line docstring summary should start at the second line')
+def asdfsdsdf24():
+    """Summary.
+
+       Description.
+
+    """
+
+
+@expect('D208: Docstring is over-indented')
+@expect('D213: Multi-line docstring summary should start at the second line')
+def asdfsdsdfsdf24():
+    """Summary.
+
+    Description.
+
+        """
+
+
+@expect('D208: Docstring is over-indented')
+@expect('D213: Multi-line docstring summary should start at the second line')
+def asdfsdfsdsdsdfsdf24():
+    """Summary.
+
+        Description.
+
+    """
+
+
+@expect('D209: Multi-line docstring closing quotes should be on a separate '
+        'line')
+@expect('D213: Multi-line docstring summary should start at the second line')
+def asdfljdf24():
+    """Summary.
+
+    Description."""
+
+
+@expect('D210: No whitespaces allowed surrounding docstring text')
+def endswith():
+    """Whitespace at the end. """
+
+
+@expect('D210: No whitespaces allowed surrounding docstring text')
+def around():
+    """ Whitespace at everywhere. """
+
+
+@expect('D210: No whitespaces allowed surrounding docstring text')
+@expect('D213: Multi-line docstring summary should start at the second line')
+def multiline():
+    """ Whitespace at the beginning.
+
+    This is the end.
+    """
+
+
+@expect('D300: Use """triple double quotes""" (found \'\'\'-quotes)')
+def triple_single_quotes_raw():
+    r'''Summary.'''
+
+
+@expect('D300: Use """triple double quotes""" (found \'\'\'-quotes)')
+def triple_single_quotes_raw_uppercase():
+    R'''Summary.'''
+
+
+@expect('D300: Use """triple double quotes""" (found \'-quotes)')
+def single_quotes_raw():
+    r'Summary.'
+
+
+@expect('D300: Use """triple double quotes""" (found \'-quotes)')
+def single_quotes_raw_uppercase():
+    R'Summary.'
+
+
+@expect('D300: Use """triple double quotes""" (found \'-quotes)')
+@expect('D301: Use r""" if any backslashes in a docstring')
+def single_quotes_raw_uppercase_backslash():
+    R'Sum\mary.'
+
+
+@expect('D301: Use r""" if any backslashes in a docstring')
+def double_quotes_backslash():
+    """Sum\\mary."""
+
+
+@expect('D301: Use r""" if any backslashes in a docstring')
+def double_quotes_backslash_uppercase():
+    R"""Sum\\mary."""
+
+
+@expect('D213: Multi-line docstring summary should start at the second line')
+def exceptions_of_D301():
+    """Exclude some backslashes from D301.
+
+    In particular, line continuations \
+    and unicode literals \u0394 and \N{GREEK CAPITAL LETTER DELTA}.
+    They are considered to be intentionally unescaped.
+    """
+
+
+@expect("D400: First line should end with a period (not 'y')")
+@expect("D415: First line should end with a period, question mark, "
+        "or exclamation point (not 'y')")
+def lwnlkjl():
+    """Summary"""
+
+
+@expect("D401: First line should be in imperative mood "
+        "(perhaps 'Return', not 'Returns')")
+def liouiwnlkjl():
+    """Returns foo."""
+
+
+@expect("D401: First line should be in imperative mood; try rephrasing "
+        "(found 'Constructor')")
+def sdgfsdg23245():
+    """Constructor for a foo."""
+
+
+@expect("D401: First line should be in imperative mood; try rephrasing "
+        "(found 'Constructor')")
+def sdgfsdg23245777():
+    """Constructor."""
+
+
+@expect('D402: First line should not be the function\'s "signature"')
+def foobar():
+    """Signature: foobar()."""
+
+
+@expect('D213: Multi-line docstring summary should start at the second line')
+def new_209():
+    """First line.
+
+    More lines.
+    """
+    pass
+
+
+@expect('D213: Multi-line docstring summary should start at the second line')
+def old_209():
+    """One liner.
+
+    Multi-line comments. OK to have extra blank line
+
+    """
+
+
+@expect("D103: Missing docstring in public function")
+def oneliner_d102(): return
+
+
+@expect("D400: First line should end with a period (not 'r')")
+@expect("D415: First line should end with a period, question mark,"
+        " or exclamation point (not 'r')")
+def oneliner_withdoc(): """One liner"""
+
+
+def ignored_decorator(func):   # noqa: D400,D401,D415
+    """Runs something"""
+    func()
+    pass
+
+
+def decorator_for_test(func):   # noqa: D400,D401,D415
+    """Runs something"""
+    func()
+    pass
+
+
+@ignored_decorator
+def oneliner_ignored_decorator(): """One liner"""
+
+
+@decorator_for_test
+@expect("D400: First line should end with a period (not 'r')")
+@expect("D415: First line should end with a period, question mark,"
+        " or exclamation point (not 'r')")
+def oneliner_with_decorator_expecting_errors(): """One liner"""
+
+
+@decorator_for_test
+def valid_oneliner_with_decorator(): """One liner."""
+
+
+@expect("D207: Docstring is under-indented")
+@expect('D213: Multi-line docstring summary should start at the second line')
+def docstring_start_in_same_line(): """First Line.
+
+    Second Line
+    """
+
+
+def function_with_lambda_arg(x=lambda y: y):
+    """Wrap the given lambda."""
+
+
+@expect('D213: Multi-line docstring summary should start at the second line')
+def a_following_valid_function(x=None):
+    """Check for a bug where the previous function caused an assertion.
+
+    The assertion was caused in the next function, so this one is necessary.
+
+    """
+
+
+def outer_function():
+    """Do something."""
+    def inner_function():
+        """Do inner something."""
+        return 0
+
+
+@expect("D400: First line should end with a period (not 'g')")
+@expect("D401: First line should be in imperative mood "
+        "(perhaps 'Run', not 'Runs')")
+@expect("D415: First line should end with a period, question mark, "
+        "or exclamation point (not 'g')")
+def docstring_bad():
+    """Runs something"""
+    pass
+
+
+def docstring_bad_ignore_all():  # noqa
+    """Runs something"""
+    pass
+
+
+def docstring_bad_ignore_one():  # noqa: D400,D401,D415
+    """Runs something"""
+    pass
+
+
+@expect("D401: First line should be in imperative mood "
+        "(perhaps 'Run', not 'Runs')")
+def docstring_ignore_some_violations_but_catch_D401():  # noqa: E501,D400,D415
+    """Runs something"""
+    pass
+
+
+@expect(
+    "D401: First line should be in imperative mood "
+    "(perhaps 'Initiate', not 'Initiates')"
+)
+def docstring_initiates():
+    """Initiates the process."""
+
+
+@expect(
+    "D401: First line should be in imperative mood "
+    "(perhaps 'Initialize', not 'Initializes')"
+)
+def docstring_initializes():
+    """Initializes the process."""
+
+
+@wraps(docstring_bad_ignore_one)
+def bad_decorated_function():
+    """Bad (E501) but decorated"""
+    pass
+
+
+def valid_google_string():  # noqa: D400
+    """Test a valid something!"""
+
+
+@expect("D415: First line should end with a period, question mark, "
+        "or exclamation point (not 'g')")
+def bad_google_string():  # noqa: D400
+    """Test a valid something"""
+
+
+# This is reproducing a bug where AttributeError is raised when parsing class
+# parameters as functions for Google / Numpy conventions.
+class Blah:  # noqa: D203,D213
+    """A Blah.
+
+    Parameters
+    ----------
+    x : int
+
+    """
+
+    def __init__(self, x):
+        pass
+
+
+expect(os.path.normcase(__file__ if __file__[-1] != 'c' else __file__[:-1]),
+       'D100: Missing docstring in public module')

resources/test/fixtures/E402.py

@@ -1,4 +1,8 @@
 """Top-level docstring."""
+
+__all__ = ["y"]
+__version__: str = "0.1.0"
+
 import a
 
 try:

resources/test/fixtures/E501.py

@@ -5,5 +5,12 @@
 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/F401.py

@@ -1,41 +0,0 @@
-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/F401_0.py

@@ -0,0 +1,88 @@
+from __future__ import all_feature_names
+import functools, os
+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 (
+    TYPE_CHECKING,
+    NamedTuple,
+    Dict,
+    Type,
+    TypeVar,
+    List,
+    Set,
+    Union,
+    cast,
+)
+from dataclasses import MISSING, field
+
+from blah import ClassA, ClassB, ClassC
+
+if TYPE_CHECKING:
+    from models import Fruit, Nut, Vegetable
+
+
+if TYPE_CHECKING:
+    import shelve
+    import importlib
+
+if TYPE_CHECKING:
+    """Hello, world!"""
+    import pathlib
+
+    z = 1
+
+
+class X:
+    datetime: datetime
+    foo: Type["NamedTuple"]
+
+    def a(self) -> "namedtuple":
+        x = os.environ["1"]
+        y = Counter()
+        z = multiprocessing.pool.ThreadPool()
+
+    def b(self) -> None:
+        import pickle
+
+
+__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)
+
+Field = lambda default=MISSING: field(default=default)
+
+
+# Test: access a sub-importation via an alias.
+import pyarrow as pa
+import pyarrow.csv
+
+print(pa.csv.read_csv("test.csv"))
+
+
+# Test: referencing an import via TypeAlias.
+import sys
+
+import numpy as np
+
+if sys.version_info >= (3, 10):
+    from typing import TypeAlias
+else:
+    from typing_extensions import TypeAlias
+
+
+CustomInt: TypeAlias = "np.int8 | np.int16"

resources/test/fixtures/F401_1.py

@@ -0,0 +1,5 @@
+"""Access a sub-importation via an alias."""
+import pyarrow as pa
+import pyarrow.csv
+
+print(pa.csv.read_csv("test.csv"))

resources/test/fixtures/F401_2.py

@@ -0,0 +1,12 @@
+"""Test: referencing an import via TypeAlias."""
+import sys
+
+import numpy as np
+
+if sys.version_info >= (3, 10):
+    from typing import TypeAlias
+else:
+    from typing_extensions import TypeAlias
+
+
+CustomInt: TypeAlias = "np.int8 | np.int16"

resources/test/fixtures/F401_3.py

@@ -0,0 +1,14 @@
+"""Test: referencing an import via TypeAlias (with future annotations)."""
+from __future__ import annotations
+
+import sys
+
+import numpy as np
+
+if sys.version_info >= (3, 10):
+    from typing import TypeAlias
+else:
+    from typing_extensions import TypeAlias
+
+
+CustomInt: TypeAlias = np.int8 | np.int16

resources/test/fixtures/F401_4.py

@@ -0,0 +1,14 @@
+"""Test: referencing an import via TypeAlias (with future annotations and quotes)."""
+from __future__ import annotations
+
+import sys
+
+import numpy as np
+
+if sys.version_info >= (3, 10):
+    from typing import TypeAlias
+else:
+    from typing_extensions import TypeAlias
+
+
+CustomInt: TypeAlias = "np.int8 | np.int16"

resources/test/fixtures/F404.py

@@ -1,4 +1,3 @@
-from __future__ import print_function
 """Docstring"""
 from __future__ import absolute_import
 

resources/test/fixtures/F821.py

@@ -89,3 +89,45 @@ A = (
     f'B'
     f'{B}'
 )
+
+
+from typing import Annotated, Literal
+
+
+def arbitrary_callable() -> None:
+    ...
+
+
+class PEP593Test:
+    field: Annotated[
+        int,
+        "base64",
+        arbitrary_callable(),
+        123,
+        (1, 2, 3),
+    ]
+    field_with_stringified_type: Annotated[
+        "PEP593Test",
+        123,
+    ]
+    field_with_undefined_stringified_type: Annotated[
+        "PEP593Test123",
+        123,
+    ]
+    field_with_nested_subscript: Annotated[
+        dict[Literal["foo"], str],
+        123,
+    ]
+    field_with_undefined_nested_subscript: Annotated[
+        dict["foo", "bar"],  # Expected to fail as undefined.
+        123,
+    ]
+
+
+def in_ipython_notebook() -> bool:
+    try:
+        # autoimported by notebooks
+        get_ipython()  # type: ignore[name-defined]
+    except NameError:
+        return False  # not in notebook
+    return True

resources/test/fixtures/F841.py

@@ -10,13 +10,13 @@ except ValueError as e:
     print(e)
 
 
-def f():
+def f1():
     x = 1
     y = 2
     z = x + y
 
 
-def g():
+def f2():
     foo = (1, 2)
     (a, b) = (1, 2)
 
@@ -26,6 +26,12 @@ def g():
     (x, y) = baz = bar
 
 
-def h():
+def f3():
     locals()
     x = 1
+
+
+def f4():
+    _ = 1
+    __ = 1
+    _discarded = 1

resources/test/fixtures/M001.py

@@ -0,0 +1,60 @@
+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
+
+    # Invalid (and unimplemented)
+    d = 1  # noqa: F841, W191
+
+
+# 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/N801.py

@@ -0,0 +1,34 @@
+class bad:
+    pass
+
+
+class _bad:
+    pass
+
+
+class bad_class:
+    pass
+
+
+class Bad_Class:
+    pass
+
+
+class BAD_CLASS:
+    pass
+
+
+class Good:
+    pass
+
+
+class _Good:
+    pass
+
+
+class GoodClass:
+    pass
+
+
+class GOOD:
+    pass

resources/test/fixtures/N802.py

@@ -0,0 +1,26 @@
+def Bad():
+    pass
+
+
+def _Bad():
+    pass
+
+
+def BAD():
+    pass
+
+
+def BAD_FUNC():
+    pass
+
+
+def good():
+    pass
+
+
+def _good():
+    pass
+
+
+def good_func():
+    pass

resources/test/fixtures/N803.py

@@ -0,0 +1,7 @@
+def func(a, A):
+    return a, A
+
+
+class Class:
+    def method(self, a, A):
+        return a, A

resources/test/fixtures/N804.py

@@ -0,0 +1,19 @@
+class Class:
+    @classmethod
+    def bad_class_method(this):
+        pass
+
+    @classmethod
+    def good_class_method(cls):
+        pass
+
+    def method(self):
+        pass
+
+    @staticmethod
+    def static_method(x):
+        return x
+
+
+def func(x):
+    return x

resources/test/fixtures/N805.py

@@ -0,0 +1,26 @@
+import random
+
+
+class Class:
+    def bad_method(this):
+        pass
+
+    if random.random(0, 2) == 0:
+
+        def extra_bad_method(this):
+            pass
+
+    def good_method(self):
+        pass
+
+    @classmethod
+    def class_method(cls):
+        pass
+
+    @staticmethod
+    def static_method(x):
+        return x
+
+
+def func(x):
+    return x

resources/test/fixtures/N807.py

@@ -0,0 +1,15 @@
+def __bad__():
+    pass
+
+
+def __good():
+    pass
+
+
+def good__():
+    pass
+
+
+class Class:
+    def __good__(self):
+        pass

resources/test/fixtures/N811.py

@@ -0,0 +1,3 @@
+import mod.CONST as const
+from mod import CONSTANT as constant
+from mod import ANOTHER_CONSTANT as another_constant

resources/test/fixtures/N812.py

@@ -0,0 +1,3 @@
+import modl.lowercase as Lower
+from mod import lowercase as Lowercase
+from mod import another_lowercase as AnotherLowercase

resources/test/fixtures/N813.py

@@ -0,0 +1,3 @@
+import mod.Camel as camel
+from mod import CamelCase as camelcase
+from mod import AnotherCamelCase as another_camelcase

resources/test/fixtures/N814.py

@@ -0,0 +1,3 @@
+import mod.Camel as CAMEL
+from mod import CamelCase as CAMELCASE
+from mod import AnotherCamelCase as ANOTHER_CAMELCASE

resources/test/fixtures/N817.py

@@ -0,0 +1,2 @@
+import mod.CaMel as CM
+from mod import CamelCase as CC

resources/test/fixtures/R002.py

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

resources/test/fixtures/T201.py

@@ -0,0 +1 @@
+print("Hello, world!")  # T201

resources/test/fixtures/T203.py

@@ -0,0 +1,10 @@
+from pprint import pprint
+
+pprint("Hello, world!")  # T203
+
+
+import pprint
+
+pprint.pprint("Hello, world!")  # T203
+
+pprint.pformat("Hello, world!")

resources/test/fixtures/U001.py

@@ -0,0 +1,13 @@
+class A:
+    __metaclass__ = type
+
+
+class B:
+    __metaclass__ = type
+
+    def __init__(self) -> None:
+        pass
+
+
+class C(metaclass=type):
+    pass

resources/test/fixtures/U002.py

@@ -0,0 +1,15 @@
+from os.path import abspath
+
+x = abspath(__file__)
+
+
+import os
+
+
+y = os.path.abspath(__file__)
+
+
+from os import path
+
+
+z = path.abspath(__file__)

resources/test/fixtures/U003.py

@@ -0,0 +1,5 @@
+type('')
+type(b'')
+type(0)
+type(0.)
+type(0j)

resources/test/fixtures/U005.py

@@ -0,0 +1,10 @@
+import unittest
+
+
+class Suite(unittest.TestCase):
+    def test(self) -> None:
+        self.assertEquals (1, 2)
+        self.assertEquals(1, 2)
+        self.assertEqual(3, 4)
+        self.failUnlessAlmostEqual(1, 1.1)
+        self.assertNotRegexpMatches("a", "b")

resources/test/fixtures/U006.py

@@ -0,0 +1,12 @@
+from typing import List
+
+
+def f(x: List[str]) -> None:
+    ...
+
+
+import typing
+
+
+def f(x: typing.List[str]) -> None:
+    ...

resources/test/fixtures/U007.py

@@ -0,0 +1,40 @@
+from typing import Optional
+
+
+def f(x: Optional[str]) -> None:
+    ...
+
+
+import typing
+
+
+def f(x: typing.Optional[str]) -> None:
+    ...
+
+
+from typing import Union
+
+
+def f(x: Union[str, int, Union[float, bytes]]) -> None:
+    ...
+
+
+import typing
+
+
+def f(x: typing.Union[str, int]) -> None:
+    ...
+
+
+from typing import Union
+
+
+def f(x: "Union[str, int, Union[float, bytes]]") -> None:
+    ...
+
+
+import typing
+
+
+def f(x: "typing.Union[str, int]") -> None:
+    ...

resources/test/fixtures/U008.py

@@ -0,0 +1,65 @@
+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
+
+
+class BaseClass:
+    def f(self):
+        print("f")
+
+
+def defined_outside(self):
+    super(MyClass, self).f()  # CANNOT use super()
+
+
+class MyClass(BaseClass):
+    def normal(self):
+        super(MyClass, self).f()  # can use super()
+        super().f()
+
+    def different_argument(self, other):
+        super(MyClass, other).f()  # CANNOT use super()
+
+    def comprehension_scope(self):
+        [super(MyClass, self).f() for x in [1]]  # CANNOT use super()
+
+    def inner_functions(self):
+        def outer_argument():
+            super(MyClass, self).f()  # CANNOT use super()
+
+        def inner_argument(self):
+            super(MyClass, self).f()  # can use super()
+            super().f()
+
+        outer_argument()
+        inner_argument(self)
+
+    def inner_class(self):
+        class InnerClass:
+            super(MyClass, self).f()  # CANNOT use super()
+
+            def method(inner_self):
+                super(MyClass, self).f()  # CANNOT use super()
+
+        InnerClass().method()
+
+    defined_outside = defined_outside

resources/test/fixtures/W292_0.py

@@ -0,0 +1,2 @@
+def fn() -> None:
+    pass

resources/test/fixtures/W292_1.py

@@ -0,0 +1,2 @@
+def fn() -> None:
+    pass  # noqa: W292

resources/test/fixtures/W292_2.py

@@ -0,0 +1,2 @@
+def fn() -> None:
+    pass

resources/test/fixtures/canonical_google_examples.py

@@ -0,0 +1,108 @@
+"""A one line summary of the module or program, terminated by a period.
+
+Leave one blank line.  The rest of this docstring should contain an
+overall description of the module or program.  Optionally, it may also
+contain a brief description of exported classes and functions and/or usage
+examples.
+
+  Typical usage example:
+
+  foo = ClassFoo()
+  bar = foo.FunctionBar()
+"""
+# above: "2.8.2 Modules" section example
+# https://google.github.io/styleguide/pyguide.html#382-modules
+
+# Examples from the official "Google Python Style Guide" documentation:
+#     * As HTML: https://google.github.io/styleguide/pyguide.html
+#     * Source Markdown:
+#         https://github.com/google/styleguide/blob/gh-pages/pyguide.md
+
+import os
+from .expected import Expectation
+
+expectation = Expectation()
+expect = expectation.expect
+
+# module docstring expected violations:
+expectation.expected.add((
+    os.path.normcase(__file__),
+    "D213: Multi-line docstring summary should start at the second line"))
+
+
+# "3.8.3 Functions and Methods" section example
+# https://google.github.io/styleguide/pyguide.html#383-functions-and-methods
+@expect("D213: Multi-line docstring summary should start at the second line",
+        arg_count=3)
+@expect("D401: First line should be in imperative mood "
+        "(perhaps 'Fetch', not 'Fetches')", arg_count=3)
+@expect("D406: Section name should end with a newline "
+        "('Raises', not 'Raises:')", arg_count=3)
+@expect("D406: Section name should end with a newline "
+        "('Returns', not 'Returns:')", arg_count=3)
+@expect("D407: Missing dashed underline after section ('Raises')", arg_count=3)
+@expect("D407: Missing dashed underline after section ('Returns')",
+        arg_count=3)
+@expect("D413: Missing blank line after last section ('Raises')", arg_count=3)
+def fetch_bigtable_rows(big_table, keys, other_silly_variable=None):
+    """Fetches rows from a Bigtable.
+
+    Retrieves rows pertaining to the given keys from the Table instance
+    represented by big_table.  Silly things may happen if
+    other_silly_variable is not None.
+
+    Args:
+        big_table: An open Bigtable Table instance.
+        keys: A sequence of strings representing the key of each table row
+            to fetch.
+        other_silly_variable: Another optional variable, that has a much
+            longer name than the other args, and which does nothing.
+
+    Returns:
+        A dict mapping keys to the corresponding table row data
+        fetched. Each row is represented as a tuple of strings. For
+        example:
+
+        {'Serak': ('Rigel VII', 'Preparer'),
+         'Zim': ('Irk', 'Invader'),
+         'Lrrr': ('Omicron Persei 8', 'Emperor')}
+
+        If a key from the keys argument is missing from the dictionary,
+        then that row was not found in the table.
+
+    Raises:
+        IOError: An error occurred accessing the bigtable.Table object.
+    """
+
+
+# "3.8.4 Classes" section example
+# https://google.github.io/styleguide/pyguide.html#384-classes
+@expect("D203: 1 blank line required before class docstring (found 0)")
+@expect("D213: Multi-line docstring summary should start at the second line")
+@expect("D406: Section name should end with a newline "
+        "('Attributes', not 'Attributes:')")
+@expect("D407: Missing dashed underline after section ('Attributes')")
+@expect("D413: Missing blank line after last section ('Attributes')")
+class SampleClass:
+    """Summary of class here.
+
+    Longer class information....
+    Longer class information....
+
+    Attributes:
+        likes_spam: A boolean indicating if we like SPAM or not.
+        eggs: An integer count of the eggs we have laid.
+    """
+
+    @expect("D401: First line should be in imperative mood "
+            "(perhaps 'Init', not 'Inits')", arg_count=2)
+    def __init__(self, likes_spam=False):
+        """Inits SampleClass with blah."""
+        if self:  # added to avoid NameError when run via @expect decorator
+            self.likes_spam = likes_spam
+            self.eggs = 0
+
+    @expect("D401: First line should be in imperative mood "
+            "(perhaps 'Perform', not 'Performs')", arg_count=1)
+    def public_method(self):
+        """Performs operation blah."""

resources/test/fixtures/canonical_numpy_examples.py

@@ -0,0 +1,163 @@
+"""This is the docstring for the example.py module.  Modules names should
+have short, all-lowercase names.  The module name may have underscores if
+this improves readability.
+
+Every module should have a docstring at the very top of the file.  The
+module's docstring may extend over multiple lines.  If your docstring does
+extend over multiple lines, the closing three quotation marks must be on
+a line by itself, preferably preceded by a blank line.
+
+"""
+
+# Example source file from the official "numpydoc docstring guide"
+# documentation (with the modification of commenting out all the original
+# ``import`` lines, plus adding this note and ``Expectation`` code):
+#     * As HTML: https://numpydoc.readthedocs.io/en/latest/example.html
+#     * Source Python:
+#         https://github.com/numpy/numpydoc/blob/master/doc/example.py
+
+# from __future__ import division, absolute_import, print_function
+#
+# import os  # standard library imports first
+#
+# Do NOT import using *, e.g. from numpy import *
+#
+# Import the module using
+#
+#   import numpy
+#
+# instead or import individual functions as needed, e.g
+#
+#  from numpy import array, zeros
+#
+# If you prefer the use of abbreviated module names, we suggest the
+# convention used by NumPy itself::
+#
+# import numpy as np
+# import matplotlib as mpl
+# import matplotlib.pyplot as plt
+#
+# These abbreviated names are not to be used in docstrings; users must
+# be able to paste and execute docstrings after importing only the
+# numpy module itself, unabbreviated.
+
+import os
+from .expected import Expectation
+
+expectation = Expectation()
+expect = expectation.expect
+
+# module docstring expected violations:
+expectation.expected.add((
+    os.path.normcase(__file__),
+    "D205: 1 blank line required between summary line and description "
+    "(found 0)"))
+expectation.expected.add((
+    os.path.normcase(__file__),
+    "D213: Multi-line docstring summary should start at the second line"))
+expectation.expected.add((
+    os.path.normcase(__file__),
+    "D400: First line should end with a period (not 'd')"))
+expectation.expected.add((
+    os.path.normcase(__file__),
+    "D404: First word of the docstring should not be `This`"))
+expectation.expected.add((
+    os.path.normcase(__file__),
+    "D415: First line should end with a period, question mark, or exclamation "
+    "point (not 'd')"))
+
+
+@expect("D213: Multi-line docstring summary should start at the second line",
+        arg_count=3)
+@expect("D401: First line should be in imperative mood; try rephrasing "
+        "(found 'A')", arg_count=3)
+@expect("D413: Missing blank line after last section ('Examples')",
+        arg_count=3)
+def foo(var1, var2, long_var_name='hi'):
+    r"""A one-line summary that does not use variable names.
+
+    Several sentences providing an extended description. Refer to
+    variables using back-ticks, e.g. `var`.
+
+    Parameters
+    ----------
+    var1 : array_like
+        Array_like means all those objects -- lists, nested lists, etc. --
+        that can be converted to an array.  We can also refer to
+        variables like `var1`.
+    var2 : int
+        The type above can either refer to an actual Python type
+        (e.g. ``int``), or describe the type of the variable in more
+        detail, e.g. ``(N,) ndarray`` or ``array_like``.
+    long_var_name : {'hi', 'ho'}, optional
+        Choices in brackets, default first when optional.
+
+    Returns
+    -------
+    type
+        Explanation of anonymous return value of type ``type``.
+    describe : type
+        Explanation of return value named `describe`.
+    out : type
+        Explanation of `out`.
+    type_without_description
+
+    Other Parameters
+    ----------------
+    only_seldom_used_keywords : type
+        Explanation
+    common_parameters_listed_above : type
+        Explanation
+
+    Raises
+    ------
+    BadException
+        Because you shouldn't have done that.
+
+    See Also
+    --------
+    numpy.array : Relationship (optional).
+    numpy.ndarray : Relationship (optional), which could be fairly long, in
+                    which case the line wraps here.
+    numpy.dot, numpy.linalg.norm, numpy.eye
+
+    Notes
+    -----
+    Notes about the implementation algorithm (if needed).
+
+    This can have multiple paragraphs.
+
+    You may include some math:
+
+    .. math:: X(e^{j\omega } ) = x(n)e^{ - j\omega n}
+
+    And even use a Greek symbol like :math:`\omega` inline.
+
+    References
+    ----------
+    Cite the relevant literature, e.g. [1]_.  You may also cite these
+    references in the notes section above.
+
+    .. [1] O. McNoleg, "The integration of GIS, remote sensing,
+       expert systems and adaptive co-kriging for environmental habitat
+       modelling of the Highland Haggis using object-oriented, fuzzy-logic
+       and neural-network techniques," Computers & Geosciences, vol. 22,
+       pp. 585-588, 1996.
+
+    Examples
+    --------
+    These are written in doctest format, and should illustrate how to
+    use the function.
+
+    >>> a = [1, 2, 3]
+    >>> print([x + 3 for x in a])
+    [4, 5, 6]
+    >>> print("a\nb")
+    a
+    b
+    """
+    # After closing class docstring, there should be one blank line to
+    # separate following codes (according to PEP257).
+    # But for function, method and module, there should be no blank lines
+    # after closing the docstring.
+    pass

resources/test/fixtures/future_annotations.py

@@ -2,7 +2,10 @@ from __future__ import annotations
 
 from dataclasses import dataclass
 
-from models import Fruit, Nut
+from models import (
+    Fruit,
+    Nut,
+)
 
 
 @dataclass

resources/test/fixtures/sections.py

@@ -0,0 +1,497 @@
+"""A valid module docstring."""
+
+from .expected import Expectation
+
+expectation = Expectation()
+expect = expectation.expect
+
+
+_D213 = 'D213: Multi-line docstring summary should start at the second line'
+_D400 = "D400: First line should end with a period (not '!')"
+
+
+@expect(_D213)
+@expect("D405: Section name should be properly capitalized "
+        "('Returns', not 'returns')")
+def not_capitalized():  # noqa: D416
+    """Toggle the gizmo.
+
+    returns
+    -------
+    A value of some sort.
+
+    """
+
+
+@expect(_D213)
+@expect("D406: Section name should end with a newline "
+        "('Returns', not 'Returns:')")
+def superfluous_suffix():  # noqa: D416
+    """Toggle the gizmo.
+
+    Returns:
+    -------
+    A value of some sort.
+
+    """
+
+
+@expect(_D213)
+@expect("D407: Missing dashed underline after section ('Returns')")
+def no_underline():  # noqa: D416
+    """Toggle the gizmo.
+
+    Returns
+    A value of some sort.
+
+    """
+
+
+@expect(_D213)
+@expect("D407: Missing dashed underline after section ('Returns')")
+@expect("D414: Section has no content ('Returns')")
+def no_underline_and_no_description():  # noqa: D416
+    """Toggle the gizmo.
+
+    Returns
+
+    """
+
+
+@expect(_D213)
+@expect("D410: Missing blank line after section ('Returns')")
+@expect("D414: Section has no content ('Returns')")
+@expect("D411: Missing blank line before section ('Yields')")
+@expect("D414: Section has no content ('Yields')")
+def consecutive_sections():  # noqa: D416
+    """Toggle the gizmo.
+
+    Returns
+    -------
+    Yields
+    ------
+
+    Raises
+    ------
+    Questions.
+
+    """
+
+
+@expect(_D213)
+@expect("D408: Section underline should be in the line following the "
+        "section's name ('Returns')")
+def blank_line_before_underline():  # noqa: D416
+    """Toggle the gizmo.
+
+    Returns
+
+    -------
+    A value of some sort.
+
+    """
+
+
+@expect(_D213)
+@expect("D409: Section underline should match the length of its name "
+        "(Expected 7 dashes in section 'Returns', got 2)")
+def bad_underline_length():  # noqa: D416
+    """Toggle the gizmo.
+
+    Returns
+    --
+    A value of some sort.
+
+    """
+
+
+@expect(_D213)
+@expect("D413: Missing blank line after last section ('Returns')")
+def no_blank_line_after_last_section():  # noqa: D416
+    """Toggle the gizmo.
+
+    Returns
+    -------
+    A value of some sort.
+    """
+
+
+@expect(_D213)
+@expect("D411: Missing blank line before section ('Returns')")
+def no_blank_line_before_section():  # noqa: D416
+    """Toggle the gizmo.
+
+    The function's description.
+    Returns
+    -------
+    A value of some sort.
+
+    """
+
+
+@expect(_D213)
+@expect("D214: Section is over-indented ('Returns')")
+def section_overindented():  # noqa: D416
+    """Toggle the gizmo.
+
+        Returns
+    -------
+    A value of some sort.
+
+    """
+
+
+@expect(_D213)
+@expect("D215: Section underline is over-indented (in section 'Returns')")
+def section_underline_overindented():  # noqa: D416
+    """Toggle the gizmo.
+
+    Returns
+        -------
+    A value of some sort.
+
+    """
+
+
+@expect(_D213)
+@expect("D215: Section underline is over-indented (in section 'Returns')")
+@expect("D413: Missing blank line after last section ('Returns')")
+@expect("D414: Section has no content ('Returns')")
+def section_underline_overindented_and_contentless():  # noqa: D416
+    """Toggle the gizmo.
+
+    Returns
+        -------
+    """
+
+
+@expect(_D213)
+def ignore_non_actual_section():  # noqa: D416
+    """Toggle the gizmo.
+
+    This is the function's description, which will also specify what it
+    returns
+
+    """
+
+
+@expect(_D213)
+@expect("D401: First line should be in imperative mood "
+        "(perhaps 'Return', not 'Returns')")
+@expect("D400: First line should end with a period (not 's')")
+@expect("D415: First line should end with a period, question "
+        "mark, or exclamation point (not 's')")
+@expect("D205: 1 blank line required between summary line and description "
+        "(found 0)")
+def section_name_in_first_line():  # noqa: D416
+    """Returns
+    -------
+    A value of some sort.
+
+    """
+
+
+@expect(_D213)
+@expect("D405: Section name should be properly capitalized "
+        "('Short Summary', not 'Short summary')")
+@expect("D412: No blank lines allowed between a section header and its "
+        "content ('Short Summary')")
+@expect("D409: Section underline should match the length of its name "
+        "(Expected 7 dashes in section 'Returns', got 6)")
+@expect("D410: Missing blank line after section ('Returns')")
+@expect("D411: Missing blank line before section ('Raises')")
+@expect("D406: Section name should end with a newline "
+        "('Raises', not 'Raises:')")
+@expect("D407: Missing dashed underline after section ('Raises')")
+def multiple_sections():  # noqa: D416
+    """Toggle the gizmo.
+
+    Short summary
+    -------------
+
+    This is the function's description, which will also specify what it
+    returns.
+
+    Returns
+    ------
+    Many many wonderful things.
+    Raises:
+    My attention.
+
+    """
+
+
+@expect(_D213)
+def false_positive_section_prefix():  # noqa: D416
+    """Toggle the gizmo.
+
+    Parameters
+    ----------
+    attributes_are_fun: attributes for the function.
+
+    """
+
+
+@expect(_D213)
+def section_names_as_parameter_names():  # noqa: D416
+    """Toggle the gizmo.
+
+    Parameters
+    ----------
+    notes : list
+        A list of wonderful notes.
+    examples: list
+        A list of horrible examples.
+
+    """
+
+
+@expect(_D213)
+@expect("D414: Section has no content ('Returns')")
+def valid_google_style_section():  # noqa: D406, D407
+    """Toggle the gizmo.
+
+    Args:
+        note: A random string.
+
+    Returns:
+
+    Raises:
+        RandomError: A random error that occurs randomly.
+
+    """
+
+
+@expect(_D213)
+@expect("D416: Section name should end with a colon "
+        "('Args:', not 'Args')")
+def missing_colon_google_style_section():  # noqa: D406, D407
+    """Toggle the gizmo.
+
+    Args
+        note: A random string.
+
+    """
+
+
+@expect("D417: Missing argument descriptions in the docstring "
+        "(argument(s) y are missing descriptions in "
+        "'bar' docstring)", func_name="bar")
+def _test_nested_functions():
+    x = 1
+
+    def bar(y=2):  # noqa: D207, D213, D406, D407
+        """Nested function test for docstrings.
+
+        Will this work when referencing x?
+
+        Args:
+            x: Test something
+that is broken.
+
+        """
+        print(x)
+
+
+@expect(_D213)
+@expect("D417: Missing argument descriptions in the docstring "
+        "(argument(s) y are missing descriptions in "
+        "'test_missing_google_args' docstring)")
+def test_missing_google_args(x=1, y=2, _private=3):  # noqa: D406, D407
+    """Toggle the gizmo.
+
+    Args:
+        x (int): The greatest integer.
+
+    """
+
+
+class TestGoogle:  # noqa: D203
+    """Test class."""
+
+    def test_method(self, test, another_test, _):  # noqa: D213, D407
+        """Test a valid args section.
+
+        Args:
+            test: A parameter.
+            another_test: Another parameter.
+
+        """
+
+    @expect("D417: Missing argument descriptions in the docstring "
+            "(argument(s) test, y, z are missing descriptions in "
+            "'test_missing_args' docstring)", arg_count=5)
+    def test_missing_args(self, test, x, y, z=3, _private_arg=3):  # noqa: D213, D407
+        """Test a valid args section.
+
+        Args:
+            x: Another parameter.
+
+        """
+
+    @classmethod
+    @expect("D417: Missing argument descriptions in the docstring "
+            "(argument(s) test, y, z are missing descriptions in "
+            "'test_missing_args_class_method' docstring)", arg_count=5)
+    def test_missing_args_class_method(cls, test, x, y, _, z=3):  # noqa: D213, D407
+        """Test a valid args section.
+
+        Args:
+            x: Another parameter. The parameter below is missing description.
+            y:
+
+        """
+
+    @staticmethod
+    @expect("D417: Missing argument descriptions in the docstring "
+            "(argument(s) a, y, z are missing descriptions in "
+            "'test_missing_args_static_method' docstring)", arg_count=4)
+    def test_missing_args_static_method(a, x, y, _test, z=3):  # noqa: D213, D407
+        """Test a valid args section.
+
+        Args:
+            x: Another parameter.
+
+        """
+
+    @staticmethod
+    @expect("D417: Missing argument descriptions in the docstring "
+            "(argument(s) a, b are missing descriptions in "
+            "'test_missing_docstring' docstring)", arg_count=2)
+    def test_missing_docstring(a, b):  # noqa: D213, D407
+        """Test a valid args section.
+
+        Args:
+            a:
+
+        """
+
+    @staticmethod
+    def test_hanging_indent(skip, verbose):  # noqa: D213, D407
+        """Do stuff.
+
+        Args:
+            skip (:attr:`.Skip`):
+                Lorem ipsum dolor sit amet, consectetur adipiscing elit.
+                Etiam at tellus a tellus faucibus maximus. Curabitur tellus
+                mauris, semper id vehicula ac, feugiat ut tortor.
+            verbose (bool):
+                If True, print out as much infromation as possible.
+                If False, print out concise "one-liner" information.
+
+        """
+
+
+@expect(_D213)
+@expect("D417: Missing argument descriptions in the docstring "
+        "(argument(s) y are missing descriptions in "
+        "'test_missing_numpy_args' docstring)")
+def test_missing_numpy_args(_private_arg=0, x=1, y=2):  # noqa: D406, D407
+    """Toggle the gizmo.
+
+    Parameters
+    ----------
+    x : int
+        The greatest integer in the history \
+of the entire world.
+
+    """
+
+
+class TestNumpy:  # noqa: D203
+    """Test class."""
+
+    def test_method(self, test, another_test, z, _, x=1, y=2, _private_arg=1):  # noqa: D213, D407
+        """Test a valid args section.
+
+        Some long string with a \
+line continuation.
+
+        Parameters
+        ----------
+        test, another_test
+            Some parameters without type.
+        z : some parameter with a very long type description that requires a \
+line continuation.
+            But no further description.
+        x, y : int
+            Some integer parameters.
+
+        """
+
+    @expect("D417: Missing argument descriptions in the docstring "
+            "(argument(s) test, y, z are missing descriptions in "
+            "'test_missing_args' docstring)", arg_count=5)
+    def test_missing_args(self, test, x, y, z=3, t=1, _private=0):  # noqa: D213, D407
+        """Test a valid args section.
+
+        Parameters
+        ----------
+        x, t : int
+            Some parameters.
+
+
+        """
+
+    @classmethod
+    @expect("D417: Missing argument descriptions in the docstring "
+            "(argument(s) test, y, z are missing descriptions in "
+            "'test_missing_args_class_method' docstring)", arg_count=4)
+    def test_missing_args_class_method(cls, test, x, y, z=3):  # noqa: D213, D407
+        """Test a valid args section.
+
+        Parameters
+        ----------
+        z
+        x
+            Another parameter. The parameters y, test below are
+            missing descriptions. The parameter z above is also missing
+            a description.
+        y
+        test
+
+        """
+
+    @staticmethod
+    @expect("D417: Missing argument descriptions in the docstring "
+            "(argument(s) a, z are missing descriptions in "
+            "'test_missing_args_static_method' docstring)", arg_count=3)
+    def test_missing_args_static_method(a, x, y, z=3, t=1):  # noqa: D213, D407
+        """Test a valid args section.
+
+        Parameters
+        ----------
+        x, y
+            Another parameter.
+        t : int
+            Yet another parameter.
+
+        """
+
+    @staticmethod
+    def test_mixing_numpy_and_google(danger):  # noqa: D213
+        """Repro for #388.
+
+        Parameters
+        ----------
+        danger
+            Zoneeeeee!
+
+        """
+
+
+class TestIncorrectIndent:  # noqa: D203
+    """Test class."""
+
+    @expect("D417: Missing argument descriptions in the docstring "
+            "(argument(s) y are missing descriptions in "
+            "'test_incorrect_indent' docstring)", arg_count=3)
+    def test_incorrect_indent(self, x=1, y=2):  # noqa: D207, D213, D407
+        """Reproducing issue #437.
+
+Testing this incorrectly indented docstring.
+
+        Args:
+            x: Test argument.
+
+        """

scripts/.flake8

@@ -0,0 +1,19 @@
+[flake8]
+exclude =
+    # Defaults
+    .svn,
+    CVS,
+    .bzr,
+    .hg,
+    .git,
+    __pycache__,
+    .tox,
+    .idea,
+    .mypy_cache,
+    .venv,
+    node_modules,
+    # Custom
+    _state_machine.py,
+    test_fstring.py,
+    bad_coding2.py,
+    badsyntax_*.py

setup.py

@@ -0,0 +1,23 @@
+import sys
+
+from setuptools import setup
+
+sys.stderr.write(
+    """
+===============================
+Unsupported installation method
+===============================
+ruff no longer supports installation with `python setup.py install`.
+Please use `python -m pip install .` instead.
+"""
+)
+sys.exit(1)
+
+
+# The below code will never execute, however GitHub is particularly
+# picky about where it finds Python packaging metadata.
+# See: https://github.com/github/feedback/discussions/6456
+#
+# To be removed once GitHub catches up.
+
+setup(name="ruff", install_requires=[])

src/ast.rs

@@ -1,4 +1,4 @@
-pub mod checks;
+pub mod helpers;
 pub mod operations;
 pub mod relocate;
 pub mod types;

src/ast/checks.rs

@@ -1,650 +0,0 @@
-use std::collections::BTreeSet;
-
-use itertools::izip;
-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, Scope, ScopeKind};
-use crate::autofix::{fixer, fixes};
-use crate::checks::{Check, CheckKind, Fix, RejectedCmpop};
-
-/// Check IfTuple compliance.
-pub fn check_if_tuple(test: &Expr, location: Location) -> 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: Location) -> 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(operand.location),
-                            ));
-                        }
-                    }
-                    Cmpop::Is => {
-                        if check_not_is {
-                            checks.push(Check::new(
-                                CheckKind::NotIsTest,
-                                locator.locate_check(operand.location),
-                            ));
-                        }
-                    }
-                    _ => {}
-                }
-            }
-        }
-    }
-
-    checks
-}
-
-/// Check UnusedVariable compliance.
-pub fn check_unused_variables(scope: &Scope, locator: &dyn CheckLocator) -> 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() {
-        // TODO(charlie): Ignore if using `locals`.
-        if binding.used.is_none()
-            && name != "_"
-            && name != "__tracebackhide__"
-            && name != "__traceback_info__"
-            && name != "__traceback_supplement__"
-            && matches!(binding.kind, BindingKind::Assignment)
-        {
-            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: Location) -> 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: Location) -> 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: Location) -> 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: Location) -> 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()),
-                            expr.location,
-                        );
-                        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,
-                handler.location,
-            ));
-        }
-    }
-
-    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, expr.location));
-                }
-            }
-        }
-        ExprKind::Name { id, .. } => {
-            if id == "NotImplemented" {
-                return Some(Check::new(CheckKind::RaiseNotImplemented, expr.location));
-            }
-        }
-        _ => {}
-    }
-
-    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, arg.location));
-        }
-        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, expr.location);
-                    if matches!(autofix, fixer::Mode::Generate | fixer::Mode::Apply) {
-                        check.amend(Fix {
-                            content: "assertEqual".to_string(),
-                            start: Location::new(expr.location.row(), expr.location.column() + 1),
-                            end: 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(k2.location),
-                        ))
-                    }
-                }
-                (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(k2.location),
-                        ))
-                    }
-                }
-                _ => {}
-            }
-        }
-    }
-
-    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(comparator.location),
-            ));
-        }
-        if matches!(op, Cmpop::NotEq) {
-            checks.push(Check::new(
-                CheckKind::NoneComparison(RejectedCmpop::NotEq),
-                locator.locate_check(comparator.location),
-            ));
-        }
-    }
-
-    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(comparator.location),
-                ));
-            }
-            if matches!(op, Cmpop::NotEq) {
-                checks.push(Check::new(
-                    CheckKind::TrueFalseComparison(value, RejectedCmpop::NotEq),
-                    locator.locate_check(comparator.location),
-                ));
-            }
-        }
-    }
-
-    // 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(comparator.location),
-                ));
-            }
-            if matches!(op, Cmpop::NotEq) {
-                checks.push(Check::new(
-                    CheckKind::NoneComparison(RejectedCmpop::NotEq),
-                    locator.locate_check(comparator.location),
-                ));
-            }
-        }
-
-        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(comparator.location),
-                    ));
-                }
-                if matches!(op, Cmpop::NotEq) {
-                    checks.push(Check::new(
-                        CheckKind::TrueFalseComparison(value, RejectedCmpop::NotEq),
-                        locator.locate_check(comparator.location),
-                    ));
-                }
-            }
-        }
-    }
-
-    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: Location,
-) -> 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: Location,
-) -> 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: Location,
-) -> 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(stmt.location),
-        ))
-    } 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(stmt.location),
-        ))
-    } else {
-        None
-    }
-}

src/ast/helpers.rs

@@ -0,0 +1,145 @@
+use once_cell::sync::Lazy;
+use regex::Regex;
+use rustpython_ast::{Excepthandler, ExcepthandlerKind, Expr, ExprKind, Location, StmtKind};
+
+use crate::python::typing;
+
+fn compose_call_path_inner<'a>(expr: &'a Expr, parts: &mut Vec<&'a str>) {
+    match &expr.node {
+        ExprKind::Call { func, .. } => {
+            compose_call_path_inner(func, parts);
+        }
+        ExprKind::Attribute { value, attr, .. } => {
+            compose_call_path_inner(value, parts);
+            parts.push(attr);
+        }
+        ExprKind::Name { id, .. } => {
+            parts.push(id);
+        }
+        _ => {}
+    }
+}
+
+pub fn compose_call_path(expr: &Expr) -> Option<String> {
+    let mut segments = vec![];
+    compose_call_path_inner(expr, &mut segments);
+    if segments.is_empty() {
+        None
+    } else {
+        Some(segments.join("."))
+    }
+}
+
+pub fn match_name_or_attr(expr: &Expr, target: &str) -> bool {
+    match &expr.node {
+        ExprKind::Attribute { attr, .. } => target == attr,
+        ExprKind::Name { id, .. } => target == id,
+        _ => false,
+    }
+}
+
+pub enum SubscriptKind {
+    AnnotatedSubscript,
+    PEP593AnnotatedSubscript,
+}
+
+pub fn match_annotated_subscript(expr: &Expr) -> Option<SubscriptKind> {
+    match &expr.node {
+        ExprKind::Attribute { attr, .. } => {
+            if typing::is_annotated_subscript(attr) {
+                Some(SubscriptKind::AnnotatedSubscript)
+            } else if typing::is_pep593_annotated_subscript(attr) {
+                Some(SubscriptKind::PEP593AnnotatedSubscript)
+            } else {
+                None
+            }
+        }
+        ExprKind::Name { id, .. } => {
+            if typing::is_annotated_subscript(id) {
+                Some(SubscriptKind::AnnotatedSubscript)
+            } else if typing::is_pep593_annotated_subscript(id) {
+                Some(SubscriptKind::PEP593AnnotatedSubscript)
+            } else {
+                None
+            }
+        }
+        _ => None,
+    }
+}
+
+static DUNDER_REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"__[^\s]+__").unwrap());
+
+pub fn is_assignment_to_a_dunder(node: &StmtKind) -> bool {
+    // Check whether it's an assignment to a dunder, with or without a type annotation.
+    // This is what pycodestyle (as of 2.9.1) does.
+    match node {
+        StmtKind::Assign {
+            targets,
+            value: _,
+            type_comment: _,
+        } => {
+            if targets.len() != 1 {
+                return false;
+            }
+            match &targets[0].node {
+                ExprKind::Name { id, ctx: _ } => DUNDER_REGEX.is_match(id),
+                _ => false,
+            }
+        }
+        StmtKind::AnnAssign {
+            target,
+            annotation: _,
+            value: _,
+            simple: _,
+        } => match &target.node {
+            ExprKind::Name { id, ctx: _ } => DUNDER_REGEX.is_match(id),
+            _ => false,
+        },
+        _ => false,
+    }
+}
+
+/// Extract the names of all handled exceptions.
+pub fn extract_handler_names(handlers: &[Excepthandler]) -> Vec<String> {
+    let mut handler_names = vec![];
+    for handler in handlers {
+        match &handler.node {
+            ExcepthandlerKind::ExceptHandler { type_, .. } => {
+                if let Some(type_) = type_ {
+                    if let ExprKind::Tuple { elts, .. } = &type_.node {
+                        for type_ in elts {
+                            if let Some(name) = compose_call_path(type_) {
+                                handler_names.push(name);
+                            }
+                        }
+                    } else if let Some(name) = compose_call_path(type_) {
+                        handler_names.push(name);
+                    }
+                }
+            }
+        }
+    }
+    handler_names
+}
+
+/// Returns `true` if a call is an argumented `super` invocation.
+pub fn is_super_call_with_arguments(func: &Expr, args: &[Expr]) -> bool {
+    // Check: is this a `super` call?
+    if let ExprKind::Name { id, .. } = &func.node {
+        id == "super" && !args.is_empty()
+    } else {
+        false
+    }
+}
+
+/// Convert a location within a file (relative to `base`) to an absolute position.
+pub 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())
+    }
+}

src/ast/operations.rs

@@ -1,6 +1,6 @@
 use rustpython_parser::ast::{Constant, Expr, ExprKind, Location, Stmt, StmtKind};
 
-use crate::ast::types::{BindingKind, Scope};
+use crate::ast::types::{BindingKind, Range, Scope};
 
 /// Extract the names bound to a given __all__ assignment.
 pub fn extract_all_names(stmt: &Stmt, scope: &Scope) -> Vec<String> {
@@ -121,30 +121,78 @@ pub fn is_unpacking_assignment(stmt: &Stmt) -> bool {
 /// Struct used to efficiently slice source code at (row, column) Locations.
 pub struct SourceCodeLocator<'a> {
     content: &'a str,
-    offsets: Vec<usize>,
-    initialized: bool,
+    offsets: Vec<Vec<usize>>,
 }
 
 impl<'a> SourceCodeLocator<'a> {
     pub fn new(content: &'a str) -> Self {
         SourceCodeLocator {
             content,
-            offsets: vec![],
-            initialized: false,
+            offsets: Self::compute_offsets(content),
         }
     }
 
-    pub fn slice_source_code(&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;
+    fn compute_offsets(content: &str) -> Vec<Vec<usize>> {
+        let mut offsets = vec![];
+        let mut offset = 0;
+        for line in content.lines() {
+            let mut newline = 0;
+            let mut line_offsets: Vec<usize> = vec![];
+            for (i, char) in line.char_indices() {
+                line_offsets.push(offset + i);
+                newline = i + char.len_utf8();
             }
-            self.initialized = true;
+            line_offsets.push(offset + newline);
+            offsets.push(line_offsets);
+            offset += newline + 1;
         }
-        let offset = self.offsets[location.row() - 1] + location.column() - 1;
+        offsets.push(vec![offset]);
+        offsets
+    }
+
+    pub fn slice_source_code_at(&self, location: &Location) -> &'a str {
+        let offset = self.offsets[location.row() - 1][location.column() - 1];
         &self.content[offset..]
     }
+
+    pub fn slice_source_code_range(&self, range: &Range) -> &'a str {
+        let start = self.offsets[range.location.row() - 1][range.location.column() - 1];
+        let end = self.offsets[range.end_location.row() - 1][range.end_location.column() - 1];
+        &self.content[start..end]
+    }
+
+    pub fn partition_source_code_at(
+        &self,
+        outer: &Range,
+        inner: &Range,
+    ) -> (&'a str, &'a str, &'a str) {
+        let outer_start = self.offsets[outer.location.row() - 1][outer.location.column() - 1];
+        let outer_end = self.offsets[outer.end_location.row() - 1][outer.end_location.column() - 1];
+        let inner_start = self.offsets[inner.location.row() - 1][inner.location.column() - 1];
+        let inner_end = self.offsets[inner.end_location.row() - 1][inner.end_location.column() - 1];
+        (
+            &self.content[outer_start..inner_start],
+            &self.content[inner_start..inner_end],
+            &self.content[inner_end..outer_end],
+        )
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::SourceCodeLocator;
+
+    #[test]
+    fn source_code_locator_init() {
+        let content = "# \u{4e9c}\nclass Foo:\n    \"\"\".\"\"\"";
+        let locator = SourceCodeLocator::new(content);
+        assert_eq!(locator.offsets.len(), 4);
+        assert_eq!(locator.offsets[0], [0, 1, 2, 5]);
+        assert_eq!(locator.offsets[1], [6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]);
+        assert_eq!(
+            locator.offsets[2],
+            [17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28]
+        );
+        assert_eq!(locator.offsets[3], [29]);
+    }
 }

src/ast/relocate.rs

@@ -1,13 +1,17 @@
-use rustpython_parser::ast::{Expr, ExprKind, Keyword, Location};
+use rustpython_parser::ast::{Expr, ExprKind, Keyword};
 
-fn relocate_keyword(keyword: &mut Keyword, location: Location) {
-    keyword.location = location;
+use crate::ast::types::Range;
+
+fn relocate_keyword(keyword: &mut Keyword, location: Range) {
+    keyword.location = location.location;
+    keyword.end_location = Some(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: Location) {
-    expr.location = location;
+pub fn relocate_expr(expr: &mut Expr, location: Range) {
+    expr.location = location.location;
+    expr.end_location = Some(location.end_location);
     match &mut expr.node {
         ExprKind::BoolOp { values, .. } => {
             for expr in values {

src/ast/types.rs

@@ -1,13 +1,30 @@
 use std::collections::BTreeMap;
 use std::sync::atomic::{AtomicUsize, Ordering};
 
-use rustpython_parser::ast::Location;
+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, PartialEq, Eq, PartialOrd, Ord)]
+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
+                .expect("AST nodes should have end_location."),
+        }
+    }
+}
+
 #[derive(Clone, Debug, Default)]
 pub struct FunctionScope {
     pub uses_locals: bool,
@@ -40,6 +57,12 @@ impl Scope {
     }
 }
 
+#[derive(Clone, Debug)]
+pub struct BindingContext {
+    pub defined_by: usize,
+    pub defined_in: Option<usize>,
+}
+
 #[derive(Clone, Debug)]
 pub enum BindingKind {
     Annotation,
@@ -52,20 +75,27 @@ pub enum BindingKind {
     Definition,
     Export(Vec<String>),
     FutureImportation,
-    Importation(String),
     StarImportation,
-    SubmoduleImportation(String),
+    Importation(String, String, BindingContext),
+    FromImportation(String, String, BindingContext),
+    SubmoduleImportation(String, String, BindingContext),
 }
 
 #[derive(Clone, Debug)]
 pub struct Binding {
     pub kind: BindingKind,
-    pub location: Location,
-    /// Tuple of (scope index, location) indicating the scope and location at which the binding was
+    pub range: Range,
+    /// Tuple of (scope index, range) indicating the scope and range at which the binding was
     /// last used.
-    pub used: Option<(usize, Location)>,
+    pub used: Option<(usize, Range)>,
 }
 
 pub trait CheckLocator {
-    fn locate_check(&self, default: Location) -> Location;
+    fn locate_check(&self, default: Range) -> Range;
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub enum ImportKind {
+    Import,
+    ImportFrom,
 }

src/ast/visitor.rs

@@ -4,6 +4,8 @@ use rustpython_parser::ast::{
     PatternKind, Stmt, StmtKind, Unaryop, Withitem,
 };
 
+use crate::ast::helpers::match_name_or_attr;
+
 pub trait Visitor<'a> {
     fn visit_stmt(&mut self, stmt: &'a Stmt) {
         walk_stmt(self, stmt);
@@ -148,7 +150,11 @@ pub fn walk_stmt<'a, V: Visitor<'a> + ?Sized>(visitor: &mut V, stmt: &'a Stmt) {
         } => {
             visitor.visit_annotation(annotation);
             if let Some(expr) = value {
-                visitor.visit_expr(expr);
+                if match_name_or_attr(annotation, "TypeAlias") {
+                    visitor.visit_annotation(expr);
+                } else {
+                    visitor.visit_expr(expr);
+                }
             }
             visitor.visit_expr(target);
         }

src/autofix.rs

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

src/autofix/fixer.rs

@@ -1,10 +1,11 @@
-use std::fs;
-use std::path::Path;
+use std::collections::BTreeSet;
 
-use anyhow::Result;
+use itertools::Itertools;
 use rustpython_parser::ast::Location;
 
-use crate::checks::{Check, Fix};
+use crate::autofix::Fix;
+use crate::autofix::Patch;
+use crate::checks::Check;
 
 #[derive(Hash)]
 pub enum Mode {
@@ -13,6 +14,17 @@ pub enum Mode {
     None,
 }
 
+impl Mode {
+    /// Return `true` if a patch should be generated under the given `Mode`.
+    pub fn patch(&self) -> bool {
+        match &self {
+            Mode::Generate => true,
+            Mode::Apply => true,
+            Mode::None => false,
+        }
+    }
+}
+
 impl From<bool> for Mode {
     fn from(value: bool) -> Self {
         match value {
@@ -23,61 +35,74 @@ impl From<bool> for Mode {
 }
 
 /// 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<()> {
+pub fn fix_file(checks: &mut [Check], contents: &str) -> Option<String> {
     if checks.iter().all(|check| check.fix.is_none()) {
-        return Ok(());
+        return None;
     }
 
-    let output = apply_fixes(
+    Some(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);
+    let mut output: String = Default::default();
+    let mut last_pos: Location = Default::default();
+    let mut applied: BTreeSet<&Patch> = Default::default();
 
-    for fix in fixes {
-        // Best-effort approach: if this fix overlaps with a fix we've already applied, skip it.
-        if last_pos > fix.start {
+    for fix in fixes.sorted_by_key(|fix| fix.patch.location) {
+        // If we already applied an identical fix as part of another correction, skip any
+        // re-application.
+        if applied.contains(&fix.patch) {
+            fix.applied = true;
             continue;
         }
 
-        if fix.start.row() > last_pos.row() {
+        // Best-effort approach: if this fix overlaps with a fix we've already applied, skip it.
+        if last_pos > fix.patch.location {
+            continue;
+        }
+
+        if fix.patch.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.start.row() - 1] {
+            for line in &lines[last_pos.row()..fix.patch.location.row() - 1] {
                 output.push_str(line);
                 output.push('\n');
             }
-            output.push_str(&lines[fix.start.row() - 1][..fix.start.column() - 1]);
-            output.push_str(&fix.content);
+            output
+                .push_str(&lines[fix.patch.location.row() - 1][..fix.patch.location.column() - 1]);
+            output.push_str(&fix.patch.content);
         } else {
             output.push_str(
-                &lines[last_pos.row() - 1][last_pos.column() - 1..fix.start.column() - 1],
+                &lines[last_pos.row() - 1][last_pos.column() - 1..fix.patch.location.column() - 1],
             );
-            output.push_str(&fix.content);
+            output.push_str(&fix.patch.content);
         }
+        last_pos = fix.patch.end_location;
 
-        last_pos = fix.end;
+        applied.insert(&fix.patch);
         fix.applied = true;
     }
 
-    if last_pos.row() > 0 || last_pos.column() > 0 {
+    if last_pos.row() > 0
+        && (last_pos.row() - 1) < lines.len()
+        && (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');
+    if last_pos.row() < lines.len() {
+        for line in &lines[last_pos.row()..] {
+            output.push_str(line);
+            output.push('\n');
+        }
     }
 
     output
@@ -89,7 +114,8 @@ mod tests {
     use rustpython_parser::ast::Location;
 
     use crate::autofix::fixer::apply_fixes;
-    use crate::checks::Fix;
+    use crate::autofix::Fix;
+    use crate::autofix::Patch;
 
     #[test]
     fn empty_file() -> Result<()> {
@@ -105,9 +131,11 @@ mod tests {
     #[test]
     fn apply_single_replacement() -> Result<()> {
         let mut fixes = vec![Fix {
-            content: "Bar".to_string(),
-            start: Location::new(1, 9),
-            end: Location::new(1, 15),
+            patch: Patch {
+                content: "Bar".to_string(),
+                location: Location::new(1, 9),
+                end_location: Location::new(1, 15),
+            },
             applied: false,
         }];
         let actual = apply_fixes(
@@ -129,9 +157,11 @@ mod tests {
     #[test]
     fn apply_single_removal() -> Result<()> {
         let mut fixes = vec![Fix {
-            content: "".to_string(),
-            start: Location::new(1, 8),
-            end: Location::new(1, 16),
+            patch: Patch {
+                content: "".to_string(),
+                location: Location::new(1, 8),
+                end_location: Location::new(1, 16),
+            },
             applied: false,
         }];
         let actual = apply_fixes(
@@ -154,15 +184,19 @@ mod tests {
     fn apply_double_removal() -> Result<()> {
         let mut fixes = vec![
             Fix {
-                content: "".to_string(),
-                start: Location::new(1, 8),
-                end: Location::new(1, 17),
+                patch: Patch {
+                    content: "".to_string(),
+                    location: Location::new(1, 8),
+                    end_location: Location::new(1, 17),
+                },
                 applied: false,
             },
             Fix {
-                content: "".to_string(),
-                start: Location::new(1, 17),
-                end: Location::new(1, 24),
+                patch: Patch {
+                    content: "".to_string(),
+                    location: Location::new(1, 17),
+                    end_location: Location::new(1, 24),
+                },
                 applied: false,
             },
         ];
@@ -186,15 +220,19 @@ mod tests {
     fn ignore_overlapping_fixes() -> Result<()> {
         let mut fixes = vec![
             Fix {
-                content: "".to_string(),
-                start: Location::new(1, 8),
-                end: Location::new(1, 16),
+                patch: Patch {
+                    content: "".to_string(),
+                    location: Location::new(1, 8),
+                    end_location: Location::new(1, 16),
+                },
                 applied: false,
             },
             Fix {
-                content: "ignored".to_string(),
-                start: Location::new(1, 10),
-                end: Location::new(1, 12),
+                patch: Patch {
+                    content: "ignored".to_string(),
+                    location: Location::new(1, 10),
+                    end_location: Location::new(1, 12),
+                },
                 applied: false,
             },
         ];

src/autofix/helpers.rs

@@ -0,0 +1,89 @@
+use anyhow::Result;
+use itertools::Itertools;
+use rustpython_parser::ast::{ExcepthandlerKind, Location, Stmt, StmtKind};
+
+use crate::autofix::Fix;
+
+/// Determine if a body contains only a single statement, taking into account deleted.
+fn has_single_child(body: &[Stmt], deleted: &[&Stmt]) -> bool {
+    body.iter().filter(|child| !deleted.contains(child)).count() == 1
+}
+
+/// Determine if a child is the only statement in its body.
+fn is_lone_child(child: &Stmt, parent: &Stmt, deleted: &[&Stmt]) -> Result<bool> {
+    match &parent.node {
+        StmtKind::FunctionDef { body, .. }
+        | StmtKind::AsyncFunctionDef { body, .. }
+        | StmtKind::ClassDef { body, .. }
+        | StmtKind::With { body, .. }
+        | StmtKind::AsyncWith { body, .. } => {
+            if body.iter().contains(child) {
+                Ok(has_single_child(body, deleted))
+            } else {
+                Err(anyhow::anyhow!("Unable to find child in parent body."))
+            }
+        }
+        StmtKind::For { body, orelse, .. }
+        | StmtKind::AsyncFor { body, orelse, .. }
+        | StmtKind::While { body, orelse, .. }
+        | StmtKind::If { body, orelse, .. } => {
+            if body.iter().contains(child) {
+                Ok(has_single_child(body, deleted))
+            } else if orelse.iter().contains(child) {
+                Ok(has_single_child(orelse, deleted))
+            } else {
+                Err(anyhow::anyhow!("Unable to find child in parent body."))
+            }
+        }
+        StmtKind::Try {
+            body,
+            handlers,
+            orelse,
+            finalbody,
+        } => {
+            if body.iter().contains(child) {
+                Ok(has_single_child(body, deleted))
+            } else if orelse.iter().contains(child) {
+                Ok(has_single_child(orelse, deleted))
+            } else if finalbody.iter().contains(child) {
+                Ok(has_single_child(finalbody, deleted))
+            } else if let Some(body) = handlers.iter().find_map(|handler| match &handler.node {
+                ExcepthandlerKind::ExceptHandler { body, .. } => {
+                    if body.iter().contains(child) {
+                        Some(body)
+                    } else {
+                        None
+                    }
+                }
+            }) {
+                Ok(has_single_child(body, deleted))
+            } else {
+                Err(anyhow::anyhow!("Unable to find child in parent body."))
+            }
+        }
+        _ => Err(anyhow::anyhow!("Unable to find child in parent body.")),
+    }
+}
+
+pub fn remove_stmt(stmt: &Stmt, parent: Option<&Stmt>, deleted: &[&Stmt]) -> Result<Fix> {
+    if parent
+        .map(|parent| is_lone_child(stmt, parent, deleted))
+        .map_or(Ok(None), |v| v.map(Some))?
+        .unwrap_or_default()
+    {
+        // If removing this node would lead to an invalid syntax tree, replace
+        // it with a `pass`.
+        Ok(Fix::replacement(
+            "pass".to_string(),
+            stmt.location,
+            stmt.end_location.unwrap(),
+        ))
+    } else {
+        // Otherwise, nuke the entire line.
+        // TODO(charlie): This logic assumes that there are no multi-statement physical lines.
+        Ok(Fix::deletion(
+            Location::new(stmt.location.row(), 1),
+            Location::new(stmt.end_location.unwrap().row() + 1, 1),
+        ))
+    }
+}

src/autofix/mod.rs

@@ -0,0 +1,53 @@
+use rustpython_ast::Location;
+use serde::{Deserialize, Serialize};
+
+pub mod fixer;
+pub mod helpers;
+
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
+pub struct Patch {
+    pub content: String,
+    pub location: Location,
+    pub end_location: Location,
+}
+
+#[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub struct Fix {
+    pub patch: Patch,
+    pub applied: bool,
+}
+
+impl Fix {
+    pub fn deletion(start: Location, end: Location) -> Self {
+        Self {
+            patch: Patch {
+                content: "".to_string(),
+                location: start,
+                end_location: end,
+            },
+            applied: false,
+        }
+    }
+
+    pub fn replacement(content: String, start: Location, end: Location) -> Self {
+        Self {
+            patch: Patch {
+                content,
+                location: start,
+                end_location: end,
+            },
+            applied: false,
+        }
+    }
+
+    pub fn insertion(content: String, at: Location) -> Self {
+        Self {
+            patch: Patch {
+                content,
+                location: at,
+                end_location: at,
+            },
+            applied: false,
+        }
+    }
+}

src/cache.rs

@@ -1,3 +1,9 @@
+// cacache uses asyncd-std which has no wasm support, so currently no caching support on wasm
+#![cfg_attr(
+    target_family = "wasm",
+    allow(unused_imports, unused_variables, dead_code)
+)]
+
 use std::collections::hash_map::DefaultHasher;
 use std::fs::{create_dir_all, File, Metadata};
 use std::hash::{Hash, Hasher};
@@ -5,6 +11,7 @@ use std::io::Write;
 use std::path::Path;
 
 use anyhow::Result;
+#[cfg(not(target_family = "wasm"))]
 use cacache::Error::EntryNotFound;
 use filetime::FileTime;
 use log::error;
@@ -107,6 +114,7 @@ pub fn get(
         return None;
     };
 
+    #[cfg(not(target_family = "wasm"))] // cacache needs async-std which doesn't support wasm
     match cacache::read_sync(cache_dir(), cache_key(path, settings, autofix)) {
         Ok(encoded) => match bincode::deserialize::<CheckResult>(&encoded[..]) {
             Ok(CheckResult {
@@ -137,12 +145,14 @@ pub fn set(
         return;
     };
 
+    #[cfg(not(target_family = "wasm"))] // modification date not supported on wasm
     let check_result = CheckResultRef {
         metadata: &CacheMetadata {
             mtime: FileTime::from_last_modification_time(metadata).unix_seconds(),
         },
         messages,
     };
+    #[cfg(not(target_family = "wasm"))] // cacache needs async-std which doesn't support wasm
     if let Err(e) = cacache::write_sync(
         cache_dir(),
         cache_key(path, settings, autofix),

src/check_lines.rs

@@ -1,6 +1,13 @@
+use std::collections::BTreeMap;
+
 use rustpython_parser::ast::Location;
 
+use crate::ast::types::Range;
+use crate::autofix::fixer;
+use crate::autofix::Fix;
 use crate::checks::{Check, CheckCode, CheckKind};
+use crate::noqa;
+use crate::noqa::Directive;
 use crate::settings::Settings;
 
 /// Whether the given line is too long and should be reported.
@@ -19,17 +26,58 @@ fn should_enforce_line_length(line: &str, length: usize, limit: usize) -> bool {
     }
 }
 
-pub fn check_lines(checks: &mut Vec<Check>, contents: &str, settings: &Settings) {
-    let enforce_line_too_long = settings.select.contains(&CheckCode::E501);
+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.enabled.contains(&CheckCode::E501);
+    let enforce_noqa = settings.enabled.contains(&CheckCode::M001);
+
+    let mut noqa_directives: BTreeMap<usize, (Directive, Vec<&str>)> = BTreeMap::new();
 
     let mut line_checks = vec![];
     let mut ignored = vec![];
-    for (row, line) in contents.lines().enumerate() {
+
+    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() == row + 1 && check.is_inline_ignored(line) {
-                ignored.push(index);
+            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_ref());
+                        ignored.push(index)
+                    }
+                    (Directive::Codes(_, _, codes), matches) => {
+                        if codes.contains(&check.kind.code().as_ref()) {
+                            matches.push(check.kind.code().as_ref());
+                            ignored.push(index);
+                        }
+                    }
+                    (Directive::None, _) => {}
+                }
             }
         }
 
@@ -37,16 +85,137 @@ pub fn check_lines(checks: &mut Vec<Check>, contents: &str, settings: &Settings)
         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),
-                    Location::new(row + 1, settings.line_length + 1),
+                    Range {
+                        location: Location::new(lineno + 1, 1),
+                        end_location: Location::new(lineno + 1, line_length + 1),
+                    },
                 );
-                if !check.is_inline_ignored(line) {
-                    line_checks.push(check);
+
+                match noqa {
+                    (Directive::All(_, _), matches) => {
+                        matches.push(check.kind.code().as_ref());
+                    }
+                    (Directive::Codes(_, _, codes), matches) => {
+                        if codes.contains(&check.kind.code().as_ref()) {
+                            matches.push(check.kind.code().as_ref());
+                        } else {
+                            line_checks.push(check);
+                        }
+                    }
+                    (Directive::None, _) => line_checks.push(check),
                 }
             }
         }
     }
+
+    // Enforce newlines at end of files.
+    if settings.enabled.contains(&CheckCode::W292) && !contents.ends_with('\n') {
+        // Note: if `lines.last()` is `None`, then `contents` is empty (and so we don't want to
+        // raise W292 anyway).
+        if let Some(line) = lines.last() {
+            let lineno = lines.len() - 1;
+            let noqa_lineno = noqa_line_for
+                .get(lineno)
+                .map(|lineno| lineno - 1)
+                .unwrap_or(lineno);
+
+            let noqa = noqa_directives
+                .entry(noqa_lineno)
+                .or_insert_with(|| (noqa::extract_noqa_directive(lines[noqa_lineno]), vec![]));
+
+            let check = Check::new(
+                CheckKind::NoNewLineAtEndOfFile,
+                Range {
+                    location: Location::new(lines.len(), line.len() + 1),
+                    end_location: Location::new(lines.len(), line.len() + 1),
+                },
+            );
+
+            match noqa {
+                (Directive::All(_, _), matches) => {
+                    matches.push(check.kind.code().as_ref());
+                }
+                (Directive::Codes(_, _, codes), matches) => {
+                    if codes.contains(&check.kind.code().as_ref()) {
+                        matches.push(check.kind.code().as_ref());
+                    } 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 autofix.patch() {
+                            check.amend(Fix::deletion(
+                                Location::new(row + 1, start + 1),
+                                Location::new(row + 1, lines[row].chars().count() + 1),
+                            ));
+                        }
+                        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.to_string());
+                        } else {
+                            valid_codes.push(code.to_string());
+                        }
+                    }
+
+                    if !invalid_codes.is_empty() {
+                        let mut check = Check::new(
+                            CheckKind::UnusedNOQA(Some(invalid_codes)),
+                            Range {
+                                location: Location::new(row + 1, start + 1),
+                                end_location: Location::new(row + 1, end + 1),
+                            },
+                        );
+                        if autofix.patch() {
+                            if valid_codes.is_empty() {
+                                check.amend(Fix::deletion(
+                                    Location::new(row + 1, start + 1),
+                                    Location::new(row + 1, lines[row].chars().count() + 1),
+                                ));
+                            } else {
+                                check.amend(Fix::replacement(
+                                    format!("  # noqa: {}", valid_codes.join(", ")),
+                                    Location::new(row + 1, start + 1),
+                                    Location::new(row + 1, lines[row].chars().count() + 1),
+                                ));
+                            }
+                        }
+                        line_checks.push(check);
+                    }
+                }
+                Directive::None => {}
+            }
+        }
+    }
+
     ignored.sort();
     for index in ignored.iter().rev() {
         checks.swap_remove(*index);
@@ -56,25 +225,28 @@ pub fn check_lines(checks: &mut Vec<Check>, contents: &str, settings: &Settings)
 
 #[cfg(test)]
 mod tests {
-    use std::collections::BTreeSet;
+    use crate::autofix::fixer;
+    use crate::checks::{Check, CheckCode};
+    use crate::settings;
 
     use super::check_lines;
-    use super::*;
 
     #[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![];
-            let settings = Settings {
-                pyproject: None,
-                project_root: None,
-                line_length,
-                exclude: vec![],
-                extend_exclude: vec![],
-                select: BTreeSet::from_iter(vec![CheckCode::E501]),
-            };
-            check_lines(&mut checks, line, &settings);
+            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());

src/cli.rs

@@ -0,0 +1,142 @@
+use std::fmt;
+use std::path::PathBuf;
+
+use clap::{command, Parser};
+use log::warn;
+use regex::Regex;
+
+use crate::checks::CheckCode;
+use crate::printer::SerializationFormat;
+use crate::pyproject::StrCheckCodePair;
+use crate::settings::PythonVersion;
+use crate::RawSettings;
+
+#[derive(Debug, Parser)]
+#[command(author, about = "ruff: An extremely fast Python linter.")]
+#[command(version)]
+pub struct Cli {
+    #[arg(required = true)]
+    pub files: Vec<PathBuf>,
+    /// Path to the `pyproject.toml` file to use for configuration.
+    #[arg(long)]
+    pub config: Option<PathBuf>,
+    /// Enable verbose logging.
+    #[arg(short, long)]
+    pub verbose: bool,
+    /// Disable all logging (but still exit with status code "1" upon detecting errors).
+    #[arg(short, long)]
+    pub quiet: bool,
+    /// Exit with status code "0", even upon detecting errors.
+    #[arg(short, long)]
+    pub exit_zero: bool,
+    /// Run in watch mode by re-running whenever files change.
+    #[arg(short, long)]
+    pub watch: bool,
+    /// Attempt to automatically fix lint errors.
+    #[arg(short, long)]
+    pub fix: bool,
+    /// Disable cache reads.
+    #[arg(short, long)]
+    pub no_cache: bool,
+    /// List of error codes to enable.
+    #[arg(long, value_delimiter = ',')]
+    pub select: Vec<CheckCode>,
+    /// Like --select, but adds additional error codes on top of the selected ones.
+    #[arg(long, value_delimiter = ',')]
+    pub extend_select: Vec<CheckCode>,
+    /// List of error codes to ignore.
+    #[arg(long, value_delimiter = ',')]
+    pub ignore: Vec<CheckCode>,
+    /// Like --ignore, but adds additional error codes on top of the ignored ones.
+    #[arg(long, value_delimiter = ',')]
+    pub extend_ignore: Vec<CheckCode>,
+    /// List of paths, used to exclude files and/or directories from checks.
+    #[arg(long, value_delimiter = ',')]
+    pub exclude: Vec<String>,
+    /// Like --exclude, but adds additional files and directories on top of the excluded ones.
+    #[arg(long, value_delimiter = ',')]
+    pub extend_exclude: Vec<String>,
+    /// List of mappings from file pattern to code to exclude
+    #[arg(long, value_delimiter = ',')]
+    pub per_file_ignores: Vec<StrCheckCodePair>,
+    /// Output serialization format for error messages.
+    #[arg(long, value_enum, default_value_t=SerializationFormat::Text)]
+    pub format: SerializationFormat,
+    /// See the files ruff will be run against with the current settings.
+    #[arg(long)]
+    pub show_files: bool,
+    /// See ruff's settings.
+    #[arg(long)]
+    pub show_settings: bool,
+    /// Enable automatic additions of noqa directives to failing lines.
+    #[arg(long)]
+    pub add_noqa: bool,
+    /// Regular expression matching the name of dummy variables.
+    #[arg(long)]
+    pub dummy_variable_rgx: Option<Regex>,
+    /// The minimum Python version that should be supported.
+    #[arg(long)]
+    pub target_version: Option<PythonVersion>,
+    /// Round-trip auto-formatting.
+    // TODO(charlie): This should be a sub-command.
+    #[arg(long, hide = true)]
+    pub autoformat: bool,
+    /// The name of the file when passing it through stdin.
+    #[arg(long)]
+    pub stdin_filename: Option<String>,
+}
+
+pub enum Warnable {
+    Select,
+    ExtendSelect,
+}
+
+impl fmt::Display for Warnable {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Warnable::Select => fmt.write_str("--select"),
+            Warnable::ExtendSelect => fmt.write_str("--extend-select"),
+        }
+    }
+}
+
+/// Warn the user if they attempt to enable a code that won't be respected.
+pub fn warn_on(
+    flag: Warnable,
+    codes: &[CheckCode],
+    cli_ignore: &[CheckCode],
+    cli_extend_ignore: &[CheckCode],
+    pyproject_settings: &RawSettings,
+    pyproject_path: &Option<PathBuf>,
+) {
+    for code in codes {
+        if !cli_ignore.is_empty() {
+            if cli_ignore.contains(code) {
+                warn!("{code:?} was passed to {flag}, but ignored via --ignore")
+            }
+        } else if pyproject_settings.ignore.contains(code) {
+            if let Some(path) = pyproject_path {
+                warn!(
+                    "{code:?} was passed to {flag}, but ignored by the `ignore` field in {}",
+                    path.to_string_lossy()
+                )
+            } else {
+                warn!("{code:?} was passed to {flag}, but ignored by the default `ignore` field",)
+            }
+        }
+        if !cli_extend_ignore.is_empty() {
+            if cli_extend_ignore.contains(code) {
+                warn!("{code:?} was passed to {flag}, but ignored via --extend-ignore")
+            }
+        } else if pyproject_settings.extend_ignore.contains(code) {
+            if let Some(path) = pyproject_path {
+                warn!(
+                    "{code:?} was passed to {flag}, but ignored by the `extend_ignore` field in {}",
+                    path.to_string_lossy()
+                )
+            } else {
+                warn!("{code:?} was passed to {flag}, but ignored by the default `extend_ignore` field")
+            }
+        }
+    }
+}

src/docstrings/definition.rs

@@ -0,0 +1,23 @@
+use rustpython_ast::{Expr, Stmt};
+
+#[derive(Debug)]
+pub enum DefinitionKind<'a> {
+    Module,
+    Package,
+    Class(&'a Stmt),
+    NestedClass(&'a Stmt),
+    Function(&'a Stmt),
+    NestedFunction(&'a Stmt),
+    Method(&'a Stmt),
+}
+
+#[derive(Debug)]
+pub struct Definition<'a> {
+    pub kind: DefinitionKind<'a>,
+    pub docstring: Option<&'a Expr>,
+}
+
+pub enum Documentable {
+    Class,
+    Function,
+}

src/docstrings/extraction.rs

@@ -0,0 +1,82 @@
+//! Extract docstrings from an AST.
+
+use rustpython_ast::{Constant, Expr, ExprKind, Stmt, StmtKind};
+
+use crate::docstrings::definition::{Definition, DefinitionKind, Documentable};
+use crate::visibility::{Modifier, VisibleScope};
+
+/// Extract a docstring from a function or class body.
+pub fn docstring_from(suite: &[Stmt]) -> Option<&Expr> {
+    if let Some(stmt) = suite.first() {
+        if let StmtKind::Expr { value } = &stmt.node {
+            if matches!(
+                &value.node,
+                ExprKind::Constant {
+                    value: Constant::Str(_),
+                    ..
+                }
+            ) {
+                return Some(value);
+            }
+        }
+    }
+    None
+}
+
+/// Extract a `Definition` from the AST node defined by a `Stmt`.
+pub fn extract<'a>(
+    scope: &VisibleScope,
+    stmt: &'a Stmt,
+    body: &'a [Stmt],
+    kind: &Documentable,
+) -> Definition<'a> {
+    let expr = docstring_from(body);
+    match kind {
+        Documentable::Function => match scope {
+            VisibleScope {
+                modifier: Modifier::Module,
+                ..
+            } => Definition {
+                kind: DefinitionKind::Function(stmt),
+                docstring: expr,
+            },
+            VisibleScope {
+                modifier: Modifier::Class,
+                ..
+            } => Definition {
+                kind: DefinitionKind::Method(stmt),
+                docstring: expr,
+            },
+            VisibleScope {
+                modifier: Modifier::Function,
+                ..
+            } => Definition {
+                kind: DefinitionKind::NestedFunction(stmt),
+                docstring: expr,
+            },
+        },
+        Documentable::Class => match scope {
+            VisibleScope {
+                modifier: Modifier::Module,
+                ..
+            } => Definition {
+                kind: DefinitionKind::Class(stmt),
+                docstring: expr,
+            },
+            VisibleScope {
+                modifier: Modifier::Class,
+                ..
+            } => Definition {
+                kind: DefinitionKind::NestedClass(stmt),
+                docstring: expr,
+            },
+            VisibleScope {
+                modifier: Modifier::Function,
+                ..
+            } => Definition {
+                kind: DefinitionKind::NestedClass(stmt),
+                docstring: expr,
+            },
+        },
+    }
+}