Bump version to 0.0.46

Cargo.lock

@@ -1801,7 +1801,7 @@ dependencies = [
 
 [[package]]
 name = "ruff"
-version = "0.0.44"
+version = "0.0.46"
 dependencies = [
  "anyhow",
  "bincode",
@@ -1846,7 +1846,7 @@ dependencies = [
 [[package]]
 name = "rustpython-ast"
 version = "0.1.0"
-source = "git+https://github.com/charliermarsh/RustPython.git?rev=7d21c6923a506e79cc041708d83cef925efd33f4#7d21c6923a506e79cc041708d83cef925efd33f4"
+source = "git+https://github.com/charliermarsh/RustPython.git?rev=966a80597d626a9a47eaec78471164422d341453#966a80597d626a9a47eaec78471164422d341453"
 dependencies = [
  "num-bigint",
  "rustpython-compiler-core",
@@ -1855,7 +1855,7 @@ dependencies = [
 [[package]]
 name = "rustpython-compiler-core"
 version = "0.1.2"
-source = "git+https://github.com/charliermarsh/RustPython.git?rev=7d21c6923a506e79cc041708d83cef925efd33f4#7d21c6923a506e79cc041708d83cef925efd33f4"
+source = "git+https://github.com/charliermarsh/RustPython.git?rev=966a80597d626a9a47eaec78471164422d341453#966a80597d626a9a47eaec78471164422d341453"
 dependencies = [
  "bincode",
  "bitflags",
@@ -1872,7 +1872,7 @@ dependencies = [
 [[package]]
 name = "rustpython-parser"
 version = "0.1.2"
-source = "git+https://github.com/charliermarsh/RustPython.git?rev=7d21c6923a506e79cc041708d83cef925efd33f4#7d21c6923a506e79cc041708d83cef925efd33f4"
+source = "git+https://github.com/charliermarsh/RustPython.git?rev=966a80597d626a9a47eaec78471164422d341453#966a80597d626a9a47eaec78471164422d341453"
 dependencies = [
  "ahash",
  "anyhow",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ruff"
-version = "0.0.44"
+version = "0.0.46"
 edition = "2021"
 
 [lib]
@@ -26,7 +26,7 @@ once_cell = { version = "1.13.1" }
 path-absolutize = { version = "3.0.13", features = ["once_cell_cache"] }
 rayon = { version = "1.5.3" }
 regex = { version = "1.6.0" }
-rustpython-parser = { features = ["lalrpop"], git = "https://github.com/charliermarsh/RustPython.git", rev = "7d21c6923a506e79cc041708d83cef925efd33f4" }
+rustpython-parser = { features = ["lalrpop"], git = "https://github.com/charliermarsh/RustPython.git", rev = "966a80597d626a9a47eaec78471164422d341453" }
 serde = { version = "1.0.143", features = ["derive"] }
 serde_json = { version = "1.0.83" }
 toml = { version = "0.5.9" }

README.md

@@ -86,7 +86,7 @@ ruff path/to/code/ --select F401 F403
 See `ruff --help` for more:
 
 ```shell
-ruff (v0.0.44) 0.0.44
+ruff (v0.0.46)
 An extremely fast Python linter.
 
 USAGE:
@@ -96,12 +96,20 @@ ARGS:
     <FILES>...
 
 OPTIONS:
-    -e, --exit-zero
-            Exit with status code "0", even upon detecting errors
+        --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
+    -e, --exit-zero
+            Exit with status code "0", even upon detecting errors
     -f, --fix
             Attempt to automatically fix lint errors
         --format <FORMAT>
@@ -109,16 +117,16 @@ OPTIONS:
             json]
     -h, --help
             Print help information
-        --ignore <IGNORE>...
-            List of error codes to ignore
     -n, --no-cache
             Disable cache reads
+        --per-file-ignores <PER_FILE_IGNORES>...
+            List of mappings from file pattern to code to exclude
     -q, --quiet
             Disable all logging (but still exit with status code "1" upon detecting errors)
-        --select <SELECT>...
-            List of error codes to enable
+        --add-noqa
+            Enable automatic additions of noqa directives to failing lines
         --show-files
-            See the files ruff will be run against with the current configuration options
+            See the files ruff will be run against with the current settings
         --show-settings
             See ruff's settings
     -v, --verbose
@@ -129,6 +137,8 @@ OPTIONS:
             Run in watch mode by re-running whenever files change
 ```
 
+### 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
@@ -138,6 +148,50 @@ 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`).
 
+### Ignoring errors
+
+To omit a lint check entirely, add it to the "ignore" list via `--ignore` or `--extend-ignore`,
+either  on the command-line or in your `project.toml` file.
+
+To ignore an error in-line, ruff uses a `noqa` system similar to [Flake8](https://flake8.pycqa.org/en/3.1.1/user/ignoring-errors.html).
+To ignore an individual error, add `# noqa: {code}` to the end of the line, like so:
+
+```python
+# Ignore F841.
+x = 1  # noqa: F841
+
+# Ignore E741 and F841.
+i = 1  # noqa: E741, F841
+
+# Ignore _all_ errors.
+x = 1  # noqa
+```
+
+Note that, for multi-line strings, the `noqa` directive should come at the end of the string, and
+will apply to the entire body, like so:
+
+```python
+"""Lorem ipsum dolor sit amet.
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
+"""  # noqa: E501
+```
+
+ruff supports several (experimental) workflows to aid in `noqa` management.
+
+First, ruff provides a special error code, `M001`, to enforce that your `noqa` directives are
+"valid", in that the errors they _say_ they ignore are actually being triggered on that line (and
+thus suppressed). **You can run `ruff /path/to/file.py --extend-select M001` to flag unused `noqa`
+directives.**
+
+Second, ruff can _automatically remove_ unused `noqa` directives via its autofix functionality.
+**You can run `ruff /path/to/file.py --extend-select M001 --fix` to automatically remove unused
+`noqa` directives.**
+
+Third, ruff can _automatically add_ `noqa` directives to all failing lines. This is useful when
+migrating a new codebase to ruff. **You can run `ruff /path/to/file.py --add-noqa` to automatically
+add `noqa` directives to all failing lines, with the appropriate error codes.**
+
 ### Compatibility with Black
 
 ruff is compatible with [Black](https://github.com/psf/black) out-of-the-box, as long as
@@ -158,8 +212,7 @@ variables.)
 Beyond rule-set parity, ruff suffers from the following limitations vis-à-vis Flake8:
 
 1. Flake8 has a plugin architecture and supports writing custom lint rules.
-2. 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.
+2. ruff does not yet support parenthesized context managers.
 
 ## Rules
 
@@ -209,6 +262,7 @@ Beyond rule-set parity, ruff suffers from the following limitations vis-à-vis F
 | F901 | RaiseNotImplemented | `raise NotImplemented` should be `raise NotImplementedError` |
 | R001 | UselessObjectInheritance | Class `...` inherits from object |
 | R002 | NoAssertEquals | `assertEquals` is deprecated, use `assertEqual` instead |
+| M001 | UnusedNOQA | Unused `noqa` directive |
 
 ## Development
 

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

src/ast/checks.rs

@@ -1,6 +1,7 @@
 use std::collections::BTreeSet;
 
 use itertools::izip;
+use regex::Regex;
 use rustpython_parser::ast::{
     Arg, Arguments, Cmpop, Constant, Excepthandler, ExcepthandlerKind, Expr, ExprKind, Keyword,
     Location, Stmt, StmtKind, Unaryop,
@@ -71,7 +72,11 @@ pub fn check_not_tests(
 }
 
 /// Check UnusedVariable compliance.
-pub fn check_unused_variables(scope: &Scope, locator: &dyn CheckLocator) -> Vec<Check> {
+pub fn check_unused_variables(
+    scope: &Scope,
+    locator: &dyn CheckLocator,
+    dummy_variable_rgx: &Regex,
+) -> Vec<Check> {
     let mut checks: Vec<Check> = vec![];
 
     if matches!(
@@ -82,13 +87,12 @@ pub fn check_unused_variables(scope: &Scope, locator: &dyn CheckLocator) -> Vec<
     }
 
     for (name, binding) in scope.values.iter() {
-        // TODO(charlie): Ignore if using `locals`.
         if binding.used.is_none()
-            && name != "_"
+            && matches!(binding.kind, BindingKind::Assignment)
+            && !dummy_variable_rgx.is_match(name)
             && name != "__tracebackhide__"
             && name != "__traceback_info__"
             && name != "__traceback_supplement__"
-            && matches!(binding.kind, BindingKind::Assignment)
         {
             checks.push(Check::new(
                 CheckKind::UnusedVariable(name.to_string()),

src/check_ast.rs

@@ -1415,8 +1415,11 @@ impl<'a> Checker<'a> {
     fn check_deferred_assignments(&mut self) {
         if self.settings.select.contains(&CheckCode::F841) {
             while let Some(index) = self.deferred_assignments.pop() {
-                self.checks
-                    .extend(checks::check_unused_variables(&self.scopes[index], self));
+                self.checks.extend(checks::check_unused_variables(
+                    &self.scopes[index],
+                    self,
+                    &self.settings.dummy_variable_rgx,
+                ));
             }
         }
     }

src/check_lines.rs

@@ -1,6 +1,11 @@
+use std::collections::BTreeMap;
+
 use rustpython_parser::ast::Location;
 
-use crate::checks::{Check, CheckCode, CheckKind};
+use crate::autofix::fixer;
+use crate::checks::{Check, CheckCode, CheckKind, Fix};
+use crate::noqa;
+use crate::noqa::Directive;
 use crate::settings::Settings;
 
 /// Whether the given line is too long and should be reported.
@@ -19,17 +24,58 @@ fn should_enforce_line_length(line: &str, length: usize, limit: usize) -> bool {
     }
 }
 
-pub fn check_lines(checks: &mut Vec<Check>, contents: &str, settings: &Settings) {
+pub fn check_lines(
+    checks: &mut Vec<Check>,
+    contents: &str,
+    noqa_line_for: &[usize],
+    settings: &Settings,
+    autofix: &fixer::Mode,
+) {
     let enforce_line_too_long = settings.select.contains(&CheckCode::E501);
+    let enforce_noqa = settings.select.contains(&CheckCode::M001);
+
+    let mut noqa_directives: BTreeMap<usize, (Directive, Vec<&str>)> = BTreeMap::new();
 
     let mut line_checks = vec![];
     let mut ignored = vec![];
-    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_str());
+                        ignored.push(index)
+                    }
+                    (Directive::Codes(_, codes), matches) => {
+                        if codes.contains(&check.kind.code().as_str()) {
+                            matches.push(check.kind.code().as_str());
+                            ignored.push(index);
+                        }
+                    }
+                    (Directive::None, _) => {}
+                }
             }
         }
 
@@ -37,16 +83,94 @@ 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),
+                    Location::new(lineno + 1, settings.line_length + 1),
                 );
-                if !check.is_inline_ignored(line) {
-                    line_checks.push(check);
+
+                match noqa {
+                    (Directive::All(_), matches) => {
+                        matches.push(check.kind.code().as_str());
+                    }
+                    (Directive::Codes(_, codes), matches) => {
+                        if codes.contains(&check.kind.code().as_str()) {
+                            matches.push(check.kind.code().as_str());
+                        } else {
+                            line_checks.push(check);
+                        }
+                    }
+                    (Directive::None, _) => line_checks.push(check),
                 }
             }
         }
     }
+
+    // Enforce that the noqa directive was actually used.
+    if enforce_noqa {
+        for (row, (directive, matches)) in noqa_directives {
+            match directive {
+                Directive::All(column) => {
+                    if matches.is_empty() {
+                        let mut check = Check::new(
+                            CheckKind::UnusedNOQA(None),
+                            Location::new(row + 1, column + 1),
+                        );
+                        if matches!(autofix, fixer::Mode::Generate | fixer::Mode::Apply) {
+                            check.amend(Fix {
+                                content: "".to_string(),
+                                start: Location::new(row + 1, column + 1),
+                                end: Location::new(row + 1, lines[row].chars().count() + 1),
+                                applied: false,
+                            });
+                        }
+                        line_checks.push(check);
+                    }
+                }
+                Directive::Codes(column, codes) => {
+                    let mut invalid_codes = vec![];
+                    let mut valid_codes = vec![];
+                    for code in codes {
+                        if !matches.contains(&code) {
+                            invalid_codes.push(code);
+                        } else {
+                            valid_codes.push(code);
+                        }
+                    }
+
+                    if !invalid_codes.is_empty() {
+                        let mut check = Check::new(
+                            CheckKind::UnusedNOQA(Some(invalid_codes.join(", "))),
+                            Location::new(row + 1, column + 1),
+                        );
+                        if matches!(autofix, fixer::Mode::Generate | fixer::Mode::Apply) {
+                            if valid_codes.is_empty() {
+                                check.amend(Fix {
+                                    content: "".to_string(),
+                                    start: Location::new(row + 1, column + 1),
+                                    end: Location::new(row + 1, lines[row].chars().count() + 1),
+                                    applied: false,
+                                });
+                            } else {
+                                check.amend(Fix {
+                                    content: format!("  # noqa: {}", valid_codes.join(", ")),
+                                    start: Location::new(row + 1, column + 1),
+                                    end: Location::new(row + 1, lines[row].chars().count() + 1),
+                                    applied: false,
+                                });
+                            }
+                        }
+                        line_checks.push(check);
+                    }
+                }
+                Directive::None => {}
+            }
+        }
+    }
+
     ignored.sort();
     for index in ignored.iter().rev() {
         checks.swap_remove(*index);
@@ -56,25 +180,28 @@ 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/checks.rs

@@ -1,12 +1,10 @@
 use std::str::FromStr;
 
 use anyhow::Result;
-use once_cell::sync::Lazy;
-use regex::Regex;
 use rustpython_parser::ast::Location;
 use serde::{Deserialize, Serialize};
 
-pub const ALL_CHECK_CODES: [CheckCode; 44] = [
+pub const DEFAULT_CHECK_CODES: [CheckCode; 42] = [
     CheckCode::E402,
     CheckCode::E501,
     CheckCode::E711,
@@ -49,6 +47,52 @@ pub const ALL_CHECK_CODES: [CheckCode; 44] = [
     CheckCode::F831,
     CheckCode::F841,
     CheckCode::F901,
+];
+
+pub const ALL_CHECK_CODES: [CheckCode; 45] = [
+    CheckCode::E402,
+    CheckCode::E501,
+    CheckCode::E711,
+    CheckCode::E712,
+    CheckCode::E713,
+    CheckCode::E714,
+    CheckCode::E721,
+    CheckCode::E722,
+    CheckCode::E731,
+    CheckCode::E741,
+    CheckCode::E742,
+    CheckCode::E743,
+    CheckCode::E902,
+    CheckCode::E999,
+    CheckCode::F401,
+    CheckCode::F402,
+    CheckCode::F403,
+    CheckCode::F404,
+    CheckCode::F405,
+    CheckCode::F406,
+    CheckCode::F407,
+    CheckCode::F541,
+    CheckCode::F601,
+    CheckCode::F602,
+    CheckCode::F621,
+    CheckCode::F622,
+    CheckCode::F631,
+    CheckCode::F632,
+    CheckCode::F633,
+    CheckCode::F634,
+    CheckCode::F701,
+    CheckCode::F702,
+    CheckCode::F704,
+    CheckCode::F706,
+    CheckCode::F707,
+    CheckCode::F722,
+    CheckCode::F821,
+    CheckCode::F822,
+    CheckCode::F823,
+    CheckCode::F831,
+    CheckCode::F841,
+    CheckCode::F901,
+    CheckCode::M001,
     CheckCode::R001,
     CheckCode::R002,
 ];
@@ -99,6 +143,7 @@ pub enum CheckCode {
     F901,
     R001,
     R002,
+    M001,
 }
 
 impl FromStr for CheckCode {
@@ -150,6 +195,7 @@ impl FromStr for CheckCode {
             "F901" => Ok(CheckCode::F901),
             "R001" => Ok(CheckCode::R001),
             "R002" => Ok(CheckCode::R002),
+            "M001" => Ok(CheckCode::M001),
             _ => Err(anyhow::anyhow!("Unknown check code: {s}")),
         }
     }
@@ -202,13 +248,14 @@ impl CheckCode {
             CheckCode::F901 => "F901",
             CheckCode::R001 => "R001",
             CheckCode::R002 => "R002",
+            CheckCode::M001 => "M001",
         }
     }
 
     /// The source for the check (either the AST, the filesystem, or the physical lines).
     pub fn lint_source(&self) -> &'static LintSource {
         match self {
-            CheckCode::E501 => &LintSource::Lines,
+            CheckCode::E501 | CheckCode::M001 => &LintSource::Lines,
             CheckCode::E902 | CheckCode::E999 => &LintSource::FileSystem,
             _ => &LintSource::AST,
         }
@@ -259,6 +306,7 @@ impl CheckCode {
             CheckCode::F831 => CheckKind::DuplicateArgumentName,
             CheckCode::F841 => CheckKind::UnusedVariable("...".to_string()),
             CheckCode::F901 => CheckKind::RaiseNotImplemented,
+            CheckCode::M001 => CheckKind::UnusedNOQA(None),
             CheckCode::R001 => CheckKind::UselessObjectInheritance("...".to_string()),
             CheckCode::R002 => CheckKind::NoAssertEquals,
         }
@@ -280,6 +328,7 @@ pub enum RejectedCmpop {
 
 #[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]
 pub enum CheckKind {
+    UnusedNOQA(Option<String>),
     AmbiguousClassName(String),
     AmbiguousFunctionName(String),
     AmbiguousVariableName(String),
@@ -376,6 +425,7 @@ impl CheckKind {
             CheckKind::UnusedVariable(_) => "UnusedVariable",
             CheckKind::UselessObjectInheritance(_) => "UselessObjectInheritance",
             CheckKind::YieldOutsideFunction => "YieldOutsideFunction",
+            CheckKind::UnusedNOQA(_) => "UnusedNOQA",
         }
     }
 
@@ -399,8 +449,8 @@ impl CheckKind {
             CheckKind::IfTuple => &CheckCode::F634,
             CheckKind::ImportShadowedByLoopVar(_, _) => &CheckCode::F402,
             CheckKind::ImportStarNotPermitted(_) => &CheckCode::F406,
-            CheckKind::ImportStarUsed(_) => &CheckCode::F403,
             CheckKind::ImportStarUsage(_, _) => &CheckCode::F405,
+            CheckKind::ImportStarUsed(_) => &CheckCode::F403,
             CheckKind::InvalidPrintSyntax => &CheckCode::F633,
             CheckKind::IsLiteral => &CheckCode::F632,
             CheckKind::LateFutureImport => &CheckCode::F404,
@@ -423,6 +473,7 @@ impl CheckKind {
             CheckKind::UndefinedLocal(_) => &CheckCode::F823,
             CheckKind::UndefinedName(_) => &CheckCode::F821,
             CheckKind::UnusedImport(_) => &CheckCode::F401,
+            CheckKind::UnusedNOQA(_) => &CheckCode::M001,
             CheckKind::UnusedVariable(_) => &CheckCode::F841,
             CheckKind::UselessObjectInheritance(_) => &CheckCode::R001,
             CheckKind::YieldOutsideFunction => &CheckCode::F704,
@@ -556,6 +607,10 @@ impl CheckKind {
             CheckKind::YieldOutsideFunction => {
                 "a `yield` or `yield from` statement outside of a function/method".to_string()
             }
+            CheckKind::UnusedNOQA(code) => match code {
+                None => "Unused `noqa` directive".to_string(),
+                Some(code) => format!("Unused `noqa` directive for: {code}"),
+            },
         }
     }
 
@@ -563,7 +618,9 @@ impl CheckKind {
     pub fn fixable(&self) -> bool {
         matches!(
             self,
-            CheckKind::NoAssertEquals | CheckKind::UselessObjectInheritance(_)
+            CheckKind::NoAssertEquals
+                | CheckKind::UselessObjectInheritance(_)
+                | CheckKind::UnusedNOQA(_)
         )
     }
 }
@@ -583,11 +640,6 @@ pub struct Check {
     pub fix: Option<Fix>,
 }
 
-static NO_QA_REGEX: Lazy<Regex> = Lazy::new(|| {
-    Regex::new(r"(?i)# noqa(?::\s?(?P<codes>([A-Z]+[0-9]+(?:[,\s]+)?)+))?").expect("Invalid regex")
-});
-static SPLIT_COMMA_REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"[,\s]").expect("Invalid regex"));
-
 impl Check {
     pub fn new(kind: CheckKind, location: Location) -> Self {
         Self {
@@ -600,25 +652,4 @@ impl Check {
     pub fn amend(&mut self, fix: Fix) {
         self.fix = Some(fix);
     }
-
-    pub fn is_inline_ignored(&self, line: &str) -> bool {
-        match NO_QA_REGEX.captures(line) {
-            Some(caps) => match caps.name("codes") {
-                Some(codes) => {
-                    for code in SPLIT_COMMA_REGEX
-                        .split(codes.as_str())
-                        .map(|code| code.trim())
-                        .filter(|code| !code.is_empty())
-                    {
-                        if code == self.kind.code().as_str() {
-                            return true;
-                        }
-                    }
-                    false
-                }
-                None => true,
-            },
-            None => false,
-        }
-    }
 }

src/fs.rs

@@ -1,4 +1,5 @@
 use std::borrow::Cow;
+use std::collections::BTreeSet;
 use std::fs::File;
 use std::io::{BufReader, Read};
 use std::ops::Deref;
@@ -10,7 +11,8 @@ use path_absolutize::path_dedot;
 use path_absolutize::Absolutize;
 use walkdir::{DirEntry, WalkDir};
 
-use crate::settings::FilePattern;
+use crate::checks::CheckCode;
+use crate::settings::{FilePattern, PerFileIgnore};
 
 /// Extract the absolute path and basename (as strings) from a Path.
 fn extract_path_names(path: &Path) -> Result<(&str, &str)> {
@@ -25,9 +27,12 @@ fn extract_path_names(path: &Path) -> Result<(&str, &str)> {
     Ok((file_path, file_basename))
 }
 
-fn is_excluded(file_path: &str, file_basename: &str, exclude: &[FilePattern]) -> bool {
+fn is_excluded<'a, T>(file_path: &str, file_basename: &str, exclude: T) -> bool
+where
+    T: Iterator<Item = &'a FilePattern>,
+{
     for pattern in exclude {
-        match &pattern {
+        match pattern {
             FilePattern::Simple(basename) => {
                 if *basename == file_basename {
                     return true;
@@ -45,7 +50,7 @@ fn is_excluded(file_path: &str, file_basename: &str, exclude: &[FilePattern]) ->
                     return true;
                 }
             }
-        }
+        };
     }
     false
 }
@@ -85,13 +90,13 @@ pub fn iter_python_files<'a>(
 
                     if has_exclude
                         && (!exclude_simple || file_type.is_dir())
-                        && is_excluded(file_path, file_basename, exclude)
+                        && is_excluded(file_path, file_basename, exclude.iter())
                     {
                         debug!("Ignored path via `exclude`: {:?}", path);
                         false
                     } else if has_extend_exclude
                         && (!extend_exclude_simple || file_type.is_dir())
-                        && is_excluded(file_path, file_basename, extend_exclude)
+                        && is_excluded(file_path, file_basename, extend_exclude.iter())
                     {
                         debug!("Ignored path via `extend-exclude`: {:?}", path);
                         false
@@ -112,6 +117,25 @@ pub fn iter_python_files<'a>(
         })
 }
 
+/// Create tree set with codes matching the pattern/code pairs.
+pub fn ignores_from_path<'a>(
+    path: &Path,
+    pattern_code_pairs: &'a [PerFileIgnore],
+) -> Result<BTreeSet<&'a CheckCode>> {
+    let (file_path, file_basename) = extract_path_names(path)?;
+    Ok(pattern_code_pairs
+        .iter()
+        .filter(|pattern_code_pair| {
+            is_excluded(
+                file_path,
+                file_basename,
+                [&pattern_code_pair.pattern].into_iter(),
+            )
+        })
+        .map(|pattern_code_pair| &pattern_code_pair.code)
+        .collect())
+}
+
 /// Convert any path to an absolute path (based on the current working directory).
 pub fn normalize_path(path: &Path) -> PathBuf {
     if let Ok(path) = path.absolutize() {
@@ -180,7 +204,7 @@ mod tests {
             &Some(project_root.to_path_buf()),
         )];
         let (file_path, file_basename) = extract_path_names(&path)?;
-        assert!(is_excluded(file_path, file_basename, &exclude));
+        assert!(is_excluded(file_path, file_basename, exclude.iter()));
 
         let path = Path::new("foo/bar").absolutize_from(project_root).unwrap();
         let exclude = vec![FilePattern::from_user(
@@ -188,7 +212,7 @@ mod tests {
             &Some(project_root.to_path_buf()),
         )];
         let (file_path, file_basename) = extract_path_names(&path)?;
-        assert!(is_excluded(file_path, file_basename, &exclude));
+        assert!(is_excluded(file_path, file_basename, exclude.iter()));
 
         let path = Path::new("foo/bar/baz.py")
             .absolutize_from(project_root)
@@ -198,7 +222,7 @@ mod tests {
             &Some(project_root.to_path_buf()),
         )];
         let (file_path, file_basename) = extract_path_names(&path)?;
-        assert!(is_excluded(file_path, file_basename, &exclude));
+        assert!(is_excluded(file_path, file_basename, exclude.iter()));
 
         let path = Path::new("foo/bar").absolutize_from(project_root).unwrap();
         let exclude = vec![FilePattern::from_user(
@@ -206,7 +230,7 @@ mod tests {
             &Some(project_root.to_path_buf()),
         )];
         let (file_path, file_basename) = extract_path_names(&path)?;
-        assert!(is_excluded(file_path, file_basename, &exclude));
+        assert!(is_excluded(file_path, file_basename, exclude.iter()));
 
         let path = Path::new("foo/bar/baz.py")
             .absolutize_from(project_root)
@@ -216,7 +240,7 @@ mod tests {
             &Some(project_root.to_path_buf()),
         )];
         let (file_path, file_basename) = extract_path_names(&path)?;
-        assert!(is_excluded(file_path, file_basename, &exclude));
+        assert!(is_excluded(file_path, file_basename, exclude.iter()));
 
         let path = Path::new("foo/bar/baz.py")
             .absolutize_from(project_root)
@@ -226,7 +250,7 @@ mod tests {
             &Some(project_root.to_path_buf()),
         )];
         let (file_path, file_basename) = extract_path_names(&path)?;
-        assert!(is_excluded(file_path, file_basename, &exclude));
+        assert!(is_excluded(file_path, file_basename, exclude.iter()));
 
         let path = Path::new("foo/bar/baz.py")
             .absolutize_from(project_root)
@@ -236,7 +260,7 @@ mod tests {
             &Some(project_root.to_path_buf()),
         )];
         let (file_path, file_basename) = extract_path_names(&path)?;
-        assert!(!is_excluded(file_path, file_basename, &exclude));
+        assert!(!is_excluded(file_path, file_basename, exclude.iter()));
 
         Ok(())
     }

src/lib.rs

@@ -10,6 +10,7 @@ pub mod fs;
 pub mod linter;
 pub mod logging;
 pub mod message;
+mod noqa;
 pub mod printer;
 pub mod pyproject;
 mod python;

src/linter.rs

@@ -2,7 +2,8 @@ use std::path::Path;
 
 use anyhow::Result;
 use log::debug;
-use rustpython_parser::parser;
+use rustpython_parser::lexer::LexResult;
+use rustpython_parser::{lexer, parser};
 
 use crate::autofix::fixer;
 use crate::autofix::fixer::fix_file;
@@ -10,25 +11,30 @@ use crate::check_ast::check_ast;
 use crate::check_lines::check_lines;
 use crate::checks::{Check, CheckCode, CheckKind, LintSource};
 use crate::message::Message;
+use crate::noqa::add_noqa;
 use crate::settings::Settings;
-use crate::{cache, fs};
+use crate::{cache, fs, noqa};
 
 fn check_path(
     path: &Path,
     contents: &str,
+    tokens: Vec<LexResult>,
     settings: &Settings,
     autofix: &fixer::Mode,
-) -> Vec<Check> {
+) -> Result<Vec<Check>> {
     // Aggregate all checks.
     let mut checks: Vec<Check> = vec![];
 
+    // Determine the noqa line for every line in the source.
+    let noqa_line_for = noqa::extract_noqa_line_for(&tokens);
+
     // Run the AST-based checks.
     if settings
         .select
         .iter()
         .any(|check_code| matches!(check_code.lint_source(), LintSource::AST))
     {
-        match parser::parse_program(contents, "<filename>") {
+        match parser::parse_program_tokens(tokens, "<filename>") {
             Ok(python_ast) => {
                 checks.extend(check_ast(&python_ast, contents, settings, autofix, path))
             }
@@ -44,9 +50,20 @@ fn check_path(
     }
 
     // Run the lines-based checks.
-    check_lines(&mut checks, contents, settings);
+    check_lines(&mut checks, contents, &noqa_line_for, settings, autofix);
 
-    checks
+    // Create path ignores.
+    if !checks.is_empty() && !settings.per_file_ignores.is_empty() {
+        let ignores = fs::ignores_from_path(path, &settings.per_file_ignores)?;
+        if !ignores.is_empty() {
+            return Ok(checks
+                .into_iter()
+                .filter(|check| !ignores.contains(check.kind.code()))
+                .collect());
+        }
+    }
+
+    Ok(checks)
 }
 
 pub fn lint_path(
@@ -66,8 +83,11 @@ pub fn lint_path(
     // Read the file from disk.
     let contents = fs::read_file(path)?;
 
+    // Tokenize once.
+    let tokens: Vec<LexResult> = lexer::make_tokenizer(&contents).collect();
+
     // Generate checks.
-    let mut checks = check_path(path, &contents, settings, autofix);
+    let mut checks = check_path(path, &contents, tokens, settings, autofix)?;
 
     // Apply autofix.
     if matches!(autofix, fixer::Mode::Apply) {
@@ -89,11 +109,30 @@ pub fn lint_path(
     Ok(messages)
 }
 
+pub fn add_noqa_to_path(path: &Path, settings: &Settings) -> Result<usize> {
+    // Read the file from disk.
+    let contents = fs::read_file(path)?;
+
+    // Tokenize once.
+    let tokens: Vec<LexResult> = lexer::make_tokenizer(&contents).collect();
+
+    // Determine the noqa line for every line in the source.
+    let noqa_line_for = noqa::extract_noqa_line_for(&tokens);
+
+    // Generate checks.
+    let checks = check_path(path, &contents, tokens, settings, &fixer::Mode::None)?;
+
+    add_noqa(&checks, &contents, &noqa_line_for, path)
+}
+
 #[cfg(test)]
 mod tests {
     use std::path::Path;
 
     use anyhow::Result;
+    use regex::Regex;
+    use rustpython_parser::lexer;
+    use rustpython_parser::lexer::LexResult;
 
     use crate::autofix::fixer;
     use crate::checks::{Check, CheckCode};
@@ -107,7 +146,8 @@ mod tests {
         autofix: &fixer::Mode,
     ) -> Result<Vec<Check>> {
         let contents = fs::read_file(path)?;
-        Ok(linter::check_path(path, &contents, settings, autofix))
+        let tokens: Vec<LexResult> = lexer::make_tokenizer(&contents).collect();
+        linter::check_path(path, &contents, tokens, settings, autofix)
     }
 
     #[test]
@@ -566,6 +606,21 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn f841_dummy_variable_rgx() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/F841.py"),
+            &settings::Settings {
+                dummy_variable_rgx: Regex::new(r"^z$").unwrap(),
+                ..settings::Settings::for_rule(CheckCode::F841)
+            },
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
     #[test]
     fn f901() -> Result<()> {
         let mut checks = check_path(
@@ -578,6 +633,18 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn m001() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/M001.py"),
+            &settings::Settings::for_rules(vec![CheckCode::M001, CheckCode::E501, CheckCode::F841]),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
     #[test]
     fn r001() -> Result<()> {
         let mut checks = check_path(

src/main.rs

@@ -1,5 +1,6 @@
 extern crate core;
 
+use regex::Regex;
 use std::io;
 use std::path::{Path, PathBuf};
 use std::process::ExitCode;
@@ -18,12 +19,13 @@ use ::ruff::cache;
 use ::ruff::checks::CheckCode;
 use ::ruff::checks::CheckKind;
 use ::ruff::fs::iter_python_files;
+use ::ruff::linter::add_noqa_to_path;
 use ::ruff::linter::lint_path;
 use ::ruff::logging::set_up_logging;
 use ::ruff::message::Message;
 use ::ruff::printer::{Printer, SerializationFormat};
-use ::ruff::pyproject;
-use ::ruff::settings::{FilePattern, Settings};
+use ::ruff::pyproject::{self, StrCheckCodePair};
+use ::ruff::settings::{FilePattern, PerFileIgnore, Settings};
 use ::ruff::tell_user;
 
 const CARGO_PKG_NAME: &str = env!("CARGO_PKG_NAME");
@@ -57,15 +59,24 @@ struct Cli {
     /// List of error codes to enable.
     #[clap(long, multiple = true)]
     select: Vec<CheckCode>,
+    /// Like --select, but adds additional error codes on top of the selected ones.
+    #[clap(long, multiple = true)]
+    extend_select: Vec<CheckCode>,
     /// List of error codes to ignore.
     #[clap(long, multiple = true)]
     ignore: Vec<CheckCode>,
+    /// Like --ignore, but adds additional error codes on top of the ignored ones.
+    #[clap(long, multiple = true)]
+    extend_ignore: Vec<CheckCode>,
     /// List of paths, used to exclude files and/or directories from checks.
     #[clap(long, multiple = true)]
     exclude: Vec<String>,
     /// Like --exclude, but adds additional files and directories on top of the excluded ones.
     #[clap(long, multiple = true)]
     extend_exclude: Vec<String>,
+    /// List of mappings from file pattern to code to exclude
+    #[clap(long, multiple = true)]
+    per_file_ignores: Vec<StrCheckCodePair>,
     /// Output serialization format for error messages.
     #[clap(long, arg_enum, default_value_t=SerializationFormat::Text)]
     format: SerializationFormat,
@@ -75,6 +86,12 @@ struct Cli {
     /// See ruff's settings.
     #[clap(long, action)]
     show_settings: bool,
+    /// Enable automatic additions of noqa directives to failing lines.
+    #[clap(long, action)]
+    add_noqa: bool,
+    /// Regular expression matching the name of dummy variables.
+    #[clap(long)]
+    dummy_variable_rgx: Option<Regex>,
 }
 
 #[cfg(feature = "update-informer")]
@@ -177,6 +194,35 @@ fn run_once(
     Ok(messages)
 }
 
+fn add_noqa(files: &[PathBuf], settings: &Settings) -> Result<usize> {
+    // Collect all the files to check.
+    let start = Instant::now();
+    let paths: Vec<Result<DirEntry, walkdir::Error>> = files
+        .iter()
+        .flat_map(|path| iter_python_files(path, &settings.exclude, &settings.extend_exclude))
+        .collect();
+    let duration = start.elapsed();
+    debug!("Identified files to lint in: {:?}", duration);
+
+    let start = Instant::now();
+    let modifications: usize = paths
+        .par_iter()
+        .map(|entry| match entry {
+            Ok(entry) => {
+                let path = entry.path();
+                add_noqa_to_path(path, settings)
+            }
+            Err(_) => Ok(0),
+        })
+        .flatten()
+        .sum();
+
+    let duration = start.elapsed();
+    debug!("Added noqa to files in: {:?}", duration);
+
+    Ok(modifications)
+}
+
 fn inner_main() -> Result<ExitCode> {
     let cli = Cli::parse();
 
@@ -205,23 +251,41 @@ fn inner_main() -> Result<ExitCode> {
         .iter()
         .map(|path| FilePattern::from_user(path, &project_root))
         .collect();
+    let per_file_ignores: Vec<PerFileIgnore> = cli
+        .per_file_ignores
+        .into_iter()
+        .map(|pair| PerFileIgnore::new(pair, &project_root))
+        .collect();
 
-    let mut settings = Settings::from_pyproject(pyproject, project_root);
+    let mut settings = Settings::from_pyproject(pyproject, project_root)?;
     if !exclude.is_empty() {
         settings.exclude = exclude;
     }
     if !extend_exclude.is_empty() {
         settings.extend_exclude = extend_exclude;
     }
+    if !per_file_ignores.is_empty() {
+        settings.per_file_ignores = per_file_ignores;
+    }
     if !cli.select.is_empty() {
+        settings.clear();
         settings.select(cli.select);
     }
+    if !cli.extend_select.is_empty() {
+        settings.select(cli.extend_select);
+    }
     if !cli.ignore.is_empty() {
         settings.ignore(&cli.ignore);
     }
+    if !cli.extend_ignore.is_empty() {
+        settings.ignore(&cli.extend_ignore);
+    }
+    if let Some(dummy_variable_rgx) = cli.dummy_variable_rgx {
+        settings.dummy_variable_rgx = dummy_variable_rgx;
+    }
 
     if cli.show_settings && cli.show_files {
-        println!("Error: specify --show-settings or show-files (not both).");
+        eprintln!("Error: specify --show-settings or show-files (not both).");
         return Ok(ExitCode::FAILURE);
     }
     if cli.show_settings {
@@ -238,11 +302,15 @@ fn inner_main() -> Result<ExitCode> {
     let mut printer = Printer::new(cli.format, cli.verbose);
     if cli.watch {
         if cli.fix {
-            println!("Warning: --fix is not enabled in watch mode.");
+            eprintln!("Warning: --fix is not enabled in watch mode.");
+        }
+
+        if cli.add_noqa {
+            eprintln!("Warning: --no-qa is not enabled in watch mode.");
         }
 
         if cli.format != SerializationFormat::Text {
-            println!("Warning: --format 'text' is used in watch mode.");
+            eprintln!("Warning: --format 'text' is used in watch mode.");
         }
 
         // Perform an initial run instantly.
@@ -279,6 +347,11 @@ fn inner_main() -> Result<ExitCode> {
                 Err(e) => return Err(e.into()),
             }
         }
+    } else if cli.add_noqa {
+        let modifications = add_noqa(&cli.files, &settings)?;
+        if modifications > 0 {
+            println!("Added {modifications} noqa directives.");
+        }
     } else {
         let messages = run_once(&cli.files, &settings, !cli.no_cache, cli.fix)?;
         if !cli.quiet {
@@ -299,6 +372,9 @@ fn inner_main() -> Result<ExitCode> {
 fn main() -> ExitCode {
     match inner_main() {
         Ok(code) => code,
-        Err(_) => ExitCode::FAILURE,
+        Err(err) => {
+            eprintln!("{} {:?}", "error".red().bold(), err);
+            ExitCode::FAILURE
+        }
     }
 }

src/noqa.rs

@@ -0,0 +1,280 @@
+use std::cmp::{max, min};
+
+use crate::checks::{Check, CheckCode};
+use anyhow::Result;
+use once_cell::sync::Lazy;
+use regex::Regex;
+use rustpython_parser::lexer::{LexResult, Tok};
+use std::collections::{BTreeMap, BTreeSet};
+use std::fs;
+use std::path::Path;
+
+static NO_QA_REGEX: Lazy<Regex> = Lazy::new(|| {
+    Regex::new(r"(?i)(?P<noqa>\s*# noqa(?::\s?(?P<codes>([A-Z]+[0-9]+(?:[,\s]+)?)+))?)")
+        .expect("Invalid regex")
+});
+static SPLIT_COMMA_REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"[,\s]").expect("Invalid regex"));
+
+#[derive(Debug)]
+pub enum Directive<'a> {
+    None,
+    All(usize),
+    Codes(usize, Vec<&'a str>),
+}
+
+pub fn extract_noqa_directive(line: &str) -> Directive {
+    match NO_QA_REGEX.captures(line) {
+        Some(caps) => match caps.name("noqa") {
+            Some(noqa) => match caps.name("codes") {
+                Some(codes) => Directive::Codes(
+                    noqa.start(),
+                    SPLIT_COMMA_REGEX
+                        .split(codes.as_str())
+                        .map(|code| code.trim())
+                        .filter(|code| !code.is_empty())
+                        .collect(),
+                ),
+                None => Directive::All(noqa.start()),
+            },
+            None => Directive::None,
+        },
+        None => Directive::None,
+    }
+}
+
+pub fn extract_noqa_line_for(lxr: &[LexResult]) -> Vec<usize> {
+    let mut noqa_line_for: Vec<usize> = vec![];
+
+    let mut last_is_string = false;
+    let mut last_seen = usize::MIN;
+    let mut min_line = usize::MAX;
+    let mut max_line = usize::MIN;
+
+    for (start, tok, end) in lxr.iter().flatten() {
+        if matches!(tok, Tok::EndOfFile) {
+            break;
+        }
+
+        if matches!(tok, Tok::Newline) {
+            min_line = min(min_line, start.row());
+            max_line = max(max_line, start.row());
+
+            // For now, we only care about preserving noqa directives across multi-line strings.
+            if last_is_string {
+                noqa_line_for.extend(vec![max_line; (max_line + 1) - min_line]);
+            } else {
+                for i in (min_line - 1)..(max_line) {
+                    noqa_line_for.push(i + 1);
+                }
+            }
+
+            min_line = usize::MAX;
+            max_line = usize::MIN;
+        } else {
+            // Handle empty lines.
+            if start.row() > last_seen {
+                for i in last_seen..(start.row() - 1) {
+                    noqa_line_for.push(i + 1);
+                }
+            }
+
+            min_line = min(min_line, start.row());
+            max_line = max(max_line, end.row());
+        }
+        last_seen = start.row();
+        last_is_string = matches!(tok, Tok::String { .. });
+    }
+
+    noqa_line_for
+}
+
+fn add_noqa_inner(
+    checks: &Vec<Check>,
+    contents: &str,
+    noqa_line_for: &[usize],
+) -> Result<(usize, String)> {
+    let lines: Vec<&str> = contents.lines().collect();
+    let mut matches_by_line: BTreeMap<usize, BTreeSet<&CheckCode>> = BTreeMap::new();
+    for lineno in 0..lines.len() {
+        let mut codes: BTreeSet<&CheckCode> = BTreeSet::new();
+        for check in checks {
+            if check.location.row() == lineno + 1 {
+                codes.insert(check.kind.code());
+            }
+        }
+
+        // Grab the noqa (logical) line number for the current (physical) line.
+        // If there are newlines at the end of the file, they won't be represented in
+        // `noqa_line_for`, so fallback to the current line.
+        let noqa_lineno = noqa_line_for
+            .get(lineno)
+            .map(|lineno| lineno - 1)
+            .unwrap_or(lineno);
+
+        if !codes.is_empty() {
+            let matches = matches_by_line
+                .entry(noqa_lineno)
+                .or_insert_with(BTreeSet::new);
+            matches.append(&mut codes);
+        }
+    }
+
+    let mut count: usize = 0;
+    let mut output = "".to_string();
+    for (lineno, line) in lines.iter().enumerate() {
+        match matches_by_line.get(&lineno) {
+            None => {
+                output.push_str(line);
+                output.push('\n');
+            }
+            Some(codes) => {
+                match extract_noqa_directive(line) {
+                    Directive::None => {
+                        output.push_str(line);
+                    }
+                    Directive::All(start) => output.push_str(&line[..start]),
+                    Directive::Codes(start, _) => output.push_str(&line[..start]),
+                };
+                let codes: Vec<&str> = codes.iter().map(|code| code.as_str()).collect();
+                output.push_str("  # noqa: ");
+                output.push_str(&codes.join(", "));
+                output.push('\n');
+                count += 1;
+            }
+        }
+    }
+
+    Ok((count, output))
+}
+
+pub fn add_noqa(
+    checks: &Vec<Check>,
+    contents: &str,
+    noqa_line_for: &[usize],
+    path: &Path,
+) -> Result<usize> {
+    let (count, output) = add_noqa_inner(checks, contents, noqa_line_for)?;
+    fs::write(path, output)?;
+    Ok(count)
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::checks::{Check, CheckKind};
+    use anyhow::Result;
+    use rustpython_parser::ast::Location;
+    use rustpython_parser::lexer;
+    use rustpython_parser::lexer::LexResult;
+
+    use crate::noqa::{add_noqa_inner, extract_noqa_line_for};
+
+    #[test]
+    fn extraction() -> Result<()> {
+        let lxr: Vec<LexResult> = lexer::make_tokenizer(
+            "x = 1
+y = 2
+z = x + 1",
+        )
+        .collect();
+        println!("{:?}", extract_noqa_line_for(&lxr));
+        assert_eq!(extract_noqa_line_for(&lxr), vec![1, 2, 3]);
+
+        let lxr: Vec<LexResult> = lexer::make_tokenizer(
+            "
+x = 1
+y = 2
+z = x + 1",
+        )
+        .collect();
+        println!("{:?}", extract_noqa_line_for(&lxr));
+        assert_eq!(extract_noqa_line_for(&lxr), vec![1, 2, 3, 4]);
+
+        let lxr: Vec<LexResult> = lexer::make_tokenizer(
+            "x = 1
+y = 2
+z = x + 1
+        ",
+        )
+        .collect();
+        println!("{:?}", extract_noqa_line_for(&lxr));
+        assert_eq!(extract_noqa_line_for(&lxr), vec![1, 2, 3]);
+
+        let lxr: Vec<LexResult> = lexer::make_tokenizer(
+            "x = 1
+
+y = 2
+z = x + 1
+        ",
+        )
+        .collect();
+        println!("{:?}", extract_noqa_line_for(&lxr));
+        assert_eq!(extract_noqa_line_for(&lxr), vec![1, 2, 3, 4]);
+
+        let lxr: Vec<LexResult> = lexer::make_tokenizer(
+            "x = '''abc
+def
+ghi
+'''
+y = 2
+z = x + 1",
+        )
+        .collect();
+        assert_eq!(extract_noqa_line_for(&lxr), vec![4, 4, 4, 4, 5, 6]);
+
+        Ok(())
+    }
+
+    #[test]
+    fn modification() -> Result<()> {
+        let checks = vec![];
+        let contents = "x = 1";
+        let noqa_line_for = vec![1];
+        let (count, output) = add_noqa_inner(&checks, contents, &noqa_line_for)?;
+        assert_eq!(count, 0);
+        assert_eq!(output.trim(), contents.trim());
+
+        let checks = vec![Check::new(
+            CheckKind::UnusedVariable("x".to_string()),
+            Location::new(1, 1),
+        )];
+        let contents = "x = 1";
+        let noqa_line_for = vec![1];
+        let (count, output) = add_noqa_inner(&checks, contents, &noqa_line_for)?;
+        assert_eq!(count, 1);
+        assert_eq!(output.trim(), "x = 1  # noqa: F841".trim());
+
+        let checks = vec![
+            Check::new(
+                CheckKind::AmbiguousVariableName("x".to_string()),
+                Location::new(1, 1),
+            ),
+            Check::new(
+                CheckKind::UnusedVariable("x".to_string()),
+                Location::new(1, 1),
+            ),
+        ];
+        let contents = "x = 1  # noqa: E741";
+        let noqa_line_for = vec![1];
+        let (count, output) = add_noqa_inner(&checks, contents, &noqa_line_for)?;
+        assert_eq!(count, 1);
+        assert_eq!(output.trim(), "x = 1  # noqa: E741, F841".trim());
+
+        let checks = vec![
+            Check::new(
+                CheckKind::AmbiguousVariableName("x".to_string()),
+                Location::new(1, 1),
+            ),
+            Check::new(
+                CheckKind::UnusedVariable("x".to_string()),
+                Location::new(1, 1),
+            ),
+        ];
+        let contents = "x = 1  # noqa";
+        let noqa_line_for = vec![1];
+        let (count, output) = add_noqa_inner(&checks, contents, &noqa_line_for)?;
+        assert_eq!(count, 1);
+        assert_eq!(output.trim(), "x = 1  # noqa: E741, F841".trim());
+
+        Ok(())
+    }
+}

src/printer.rs

@@ -1,7 +1,10 @@
 use anyhow::Result;
 use clap::ValueEnum;
 use colored::Colorize;
+use rustpython_parser::ast::Location;
+use serde::Serialize;
 
+use crate::checks::{CheckCode, CheckKind};
 use crate::message::Message;
 use crate::tell_user;
 
@@ -11,6 +14,16 @@ pub enum SerializationFormat {
     Json,
 }
 
+#[derive(Serialize)]
+struct ExpandedMessage<'a> {
+    kind: &'a CheckKind,
+    code: &'a CheckCode,
+    message: String,
+    fixed: bool,
+    location: Location,
+    filename: &'a String,
+}
+
 pub struct Printer {
     format: SerializationFormat,
     verbose: bool,
@@ -31,7 +44,22 @@ impl Printer {
 
         match self.format {
             SerializationFormat::Json => {
-                println!("{}", serde_json::to_string_pretty(&messages)?)
+                println!(
+                    "{}",
+                    serde_json::to_string_pretty(
+                        &messages
+                            .iter()
+                            .map(|m| ExpandedMessage {
+                                kind: &m.kind,
+                                code: m.kind.code(),
+                                message: m.kind.body(),
+                                fixed: m.fixed,
+                                location: m.location,
+                                filename: &m.filename,
+                            })
+                            .collect::<Vec<_>>()
+                    )?
+                )
             }
             SerializationFormat::Text => {
                 if !fixed.is_empty() {

src/pyproject.rs

@@ -1,30 +1,25 @@
 use std::path::{Path, PathBuf};
+use std::str::FromStr;
 
-use anyhow::Result;
+use anyhow::{anyhow, Result};
 use common_path::common_path_all;
 use path_absolutize::Absolutize;
-use serde::Deserialize;
+use serde::de;
+use serde::{Deserialize, Deserializer};
 
 use crate::checks::CheckCode;
 use crate::fs;
 
-pub fn load_config(pyproject: &Option<PathBuf>) -> Config {
+pub fn load_config(pyproject: &Option<PathBuf>) -> Result<Config> {
     match pyproject {
-        Some(pyproject) => match parse_pyproject_toml(pyproject) {
-            Ok(pyproject) => pyproject
-                .tool
-                .and_then(|tool| tool.ruff)
-                .unwrap_or_default(),
-            Err(e) => {
-                println!("Failed to load pyproject.toml: {:?}", e);
-                println!("Falling back to default configuration...");
-                Default::default()
-            }
-        },
+        Some(pyproject) => Ok(parse_pyproject_toml(pyproject)?
+            .tool
+            .and_then(|tool| tool.ruff)
+            .unwrap_or_default()),
         None => {
-            println!("No pyproject.toml found.");
-            println!("Falling back to default configuration...");
-            Default::default()
+            eprintln!("No pyproject.toml found.");
+            eprintln!("Falling back to default configuration...");
+            Ok(Default::default())
         }
     }
 }
@@ -37,6 +32,50 @@ pub struct Config {
     pub extend_exclude: Option<Vec<String>>,
     pub select: Option<Vec<CheckCode>>,
     pub ignore: Option<Vec<CheckCode>>,
+    pub per_file_ignores: Option<Vec<StrCheckCodePair>>,
+    pub dummy_variable_rgx: Option<String>,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct StrCheckCodePair {
+    pub pattern: String,
+    pub code: CheckCode,
+}
+
+impl StrCheckCodePair {
+    const EXPECTED_PATTERN: &'static str = "<FilePattern>:<CheckCode> pattern";
+}
+
+impl<'de> Deserialize<'de> for StrCheckCodePair {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let str_result = String::deserialize(deserializer)?;
+        Self::from_str(str_result.as_str()).map_err(|_| {
+            de::Error::invalid_value(
+                de::Unexpected::Str(str_result.as_str()),
+                &Self::EXPECTED_PATTERN,
+            )
+        })
+    }
+}
+
+impl FromStr for StrCheckCodePair {
+    type Err = anyhow::Error;
+
+    fn from_str(string: &str) -> Result<Self, Self::Err> {
+        let (pattern_str, code_string) = {
+            let tokens = string.split(':').collect::<Vec<_>>();
+            if tokens.len() != 2 {
+                return Err(anyhow!("Expected {}", Self::EXPECTED_PATTERN));
+            }
+            (tokens[0], tokens[1])
+        };
+        let code = CheckCode::from_str(code_string)?;
+        let pattern = pattern_str.into();
+        Ok(Self { pattern, code })
+    }
 }
 
 #[derive(Debug, PartialEq, Eq, Deserialize)]
@@ -102,9 +141,11 @@ pub fn find_project_root(sources: &[PathBuf]) -> Option<PathBuf> {
 mod tests {
     use std::env::current_dir;
     use std::path::PathBuf;
+    use std::str::FromStr;
 
     use anyhow::Result;
 
+    use super::StrCheckCodePair;
     use crate::checks::CheckCode;
     use crate::pyproject::{
         find_project_root, find_pyproject_toml, parse_pyproject_toml, Config, PyProject, Tools,
@@ -137,6 +178,8 @@ mod tests {
                     extend_exclude: None,
                     select: None,
                     ignore: None,
+                    per_file_ignores: None,
+                    dummy_variable_rgx: None,
                 })
             })
         );
@@ -157,6 +200,8 @@ line-length = 79
                     extend_exclude: None,
                     select: None,
                     ignore: None,
+                    per_file_ignores: None,
+                    dummy_variable_rgx: None,
                 })
             })
         );
@@ -177,6 +222,8 @@ exclude = ["foo.py"]
                     extend_exclude: None,
                     select: None,
                     ignore: None,
+                    per_file_ignores: None,
+                    dummy_variable_rgx: None,
                 })
             })
         );
@@ -197,6 +244,8 @@ select = ["E501"]
                     extend_exclude: None,
                     select: Some(vec![CheckCode::E501]),
                     ignore: None,
+                    per_file_ignores: None,
+                    dummy_variable_rgx: None,
                 })
             })
         );
@@ -217,6 +266,8 @@ ignore = ["E501"]
                     extend_exclude: None,
                     select: None,
                     ignore: Some(vec![CheckCode::E501]),
+                    per_file_ignores: None,
+                    dummy_variable_rgx: None,
                 })
             })
         );
@@ -281,9 +332,29 @@ other-attribute = 1
                 ]),
                 select: None,
                 ignore: None,
+                per_file_ignores: None,
+                dummy_variable_rgx: None,
             }
         );
 
         Ok(())
     }
+
+    #[test]
+    fn str_check_code_pair_strings() {
+        let result = StrCheckCodePair::from_str("foo:E501");
+        assert!(result.is_ok());
+        let result = StrCheckCodePair::from_str("E501:foo");
+        assert!(result.is_err());
+        let result = StrCheckCodePair::from_str("E501");
+        assert!(result.is_err());
+        let result = StrCheckCodePair::from_str("foo");
+        assert!(result.is_err());
+        let result = StrCheckCodePair::from_str("foo:E501:E402");
+        assert!(result.is_err());
+        let result = StrCheckCodePair::from_str("**/bar:E501");
+        assert!(result.is_ok());
+        let result = StrCheckCodePair::from_str("bar:E502");
+        assert!(result.is_err());
+    }
 }

src/settings.rs

@@ -2,14 +2,16 @@ use std::collections::BTreeSet;
 use std::hash::{Hash, Hasher};
 use std::path::{Path, PathBuf};
 
+use anyhow::{anyhow, Result};
 use glob::Pattern;
 use once_cell::sync::Lazy;
+use regex::Regex;
 
-use crate::checks::{CheckCode, ALL_CHECK_CODES};
+use crate::checks::{CheckCode, DEFAULT_CHECK_CODES};
 use crate::fs;
-use crate::pyproject::load_config;
+use crate::pyproject::{load_config, StrCheckCodePair};
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Hash)]
 pub enum FilePattern {
     Simple(&'static str),
     Complex(Pattern, Option<Pattern>),
@@ -34,6 +36,20 @@ impl FilePattern {
     }
 }
 
+#[derive(Debug, Clone, Hash)]
+pub struct PerFileIgnore {
+    pub pattern: FilePattern,
+    pub code: CheckCode,
+}
+
+impl PerFileIgnore {
+    pub fn new(user_in: StrCheckCodePair, project_root: &Option<PathBuf>) -> Self {
+        let pattern = FilePattern::from_user(user_in.pattern.as_str(), project_root);
+        let code = user_in.code;
+        Self { pattern, code }
+    }
+}
+
 #[derive(Debug)]
 pub struct Settings {
     pub pyproject: Option<PathBuf>,
@@ -42,6 +58,8 @@ pub struct Settings {
     pub exclude: Vec<FilePattern>,
     pub extend_exclude: Vec<FilePattern>,
     pub select: BTreeSet<CheckCode>,
+    pub per_file_ignores: Vec<PerFileIgnore>,
+    pub dummy_variable_rgx: Regex,
 }
 
 impl Settings {
@@ -53,6 +71,8 @@ impl Settings {
             exclude: vec![],
             extend_exclude: vec![],
             select: BTreeSet::from([check_code]),
+            per_file_ignores: vec![],
+            dummy_variable_rgx: DEFAULT_DUMMY_VARIABLE_RGX.clone(),
         }
     }
 
@@ -64,6 +84,8 @@ impl Settings {
             exclude: vec![],
             extend_exclude: vec![],
             select: BTreeSet::from_iter(check_codes),
+            per_file_ignores: vec![],
+            dummy_variable_rgx: DEFAULT_DUMMY_VARIABLE_RGX.clone(),
         }
     }
 }
@@ -71,9 +93,13 @@ impl Settings {
 impl Hash for Settings {
     fn hash<H: Hasher>(&self, state: &mut H) {
         self.line_length.hash(state);
+        self.dummy_variable_rgx.as_str().hash(state);
         for value in self.select.iter() {
             value.hash(state);
         }
+        for value in self.per_file_ignores.iter() {
+            value.hash(state);
+        }
     }
 }
 
@@ -101,9 +127,15 @@ static DEFAULT_EXCLUDE: Lazy<Vec<FilePattern>> = Lazy::new(|| {
     ]
 });
 
+static DEFAULT_DUMMY_VARIABLE_RGX: Lazy<Regex> =
+    Lazy::new(|| Regex::new("^(_+|(_+[a-zA-Z0-9_]*[a-zA-Z0-9]+?))$").unwrap());
+
 impl Settings {
-    pub fn from_pyproject(pyproject: Option<PathBuf>, project_root: Option<PathBuf>) -> Self {
-        let config = load_config(&pyproject);
+    pub fn from_pyproject(
+        pyproject: Option<PathBuf>,
+        project_root: Option<PathBuf>,
+    ) -> Result<Self> {
+        let config = load_config(&pyproject)?;
         let mut settings = Settings {
             line_length: config.line_length.unwrap_or(88),
             exclude: config
@@ -127,7 +159,21 @@ impl Settings {
             select: if let Some(select) = config.select {
                 BTreeSet::from_iter(select)
             } else {
-                BTreeSet::from_iter(ALL_CHECK_CODES)
+                BTreeSet::from_iter(DEFAULT_CHECK_CODES)
+            },
+            per_file_ignores: config
+                .per_file_ignores
+                .map(|ignore_strings| {
+                    ignore_strings
+                        .into_iter()
+                        .map(|pair| PerFileIgnore::new(pair, &project_root))
+                        .collect()
+                })
+                .unwrap_or_default(),
+            dummy_variable_rgx: match config.dummy_variable_rgx {
+                Some(pattern) => Regex::new(&pattern)
+                    .map_err(|e| anyhow!("Invalid dummy-variable-rgx value: {e}"))?,
+                None => DEFAULT_DUMMY_VARIABLE_RGX.clone(),
             },
             pyproject,
             project_root,
@@ -135,11 +181,14 @@ impl Settings {
         if let Some(ignore) = &config.ignore {
             settings.ignore(ignore);
         }
-        settings
+        Ok(settings)
+    }
+
+    pub fn clear(&mut self) {
+        self.select.clear();
     }
 
     pub fn select(&mut self, codes: Vec<CheckCode>) {
-        self.select.clear();
         for code in codes {
             self.select.insert(code);
         }

src/snapshots/ruff__linter__tests__f841_dummy_variable_rgx.snap

@@ -0,0 +1,47 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    UnusedVariable: e
+  location:
+    row: 3
+    column: 1
+  fix: ~
+- kind:
+    UnusedVariable: foo
+  location:
+    row: 20
+    column: 5
+  fix: ~
+- kind:
+    UnusedVariable: a
+  location:
+    row: 21
+    column: 6
+  fix: ~
+- kind:
+    UnusedVariable: b
+  location:
+    row: 21
+    column: 9
+  fix: ~
+- kind:
+    UnusedVariable: _
+  location:
+    row: 35
+    column: 5
+  fix: ~
+- kind:
+    UnusedVariable: __
+  location:
+    row: 36
+    column: 5
+  fix: ~
+- kind:
+    UnusedVariable: _discarded
+  location:
+    row: 37
+    column: 5
+  fix: ~
+

src/snapshots/ruff__linter__tests__m001.snap

@@ -0,0 +1,89 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    UnusedNOQA: ~
+  location:
+    row: 9
+    column: 10
+  fix:
+    content: ""
+    start:
+      row: 9
+      column: 10
+    end:
+      row: 9
+      column: 18
+    applied: false
+- kind:
+    UnusedNOQA: E501
+  location:
+    row: 13
+    column: 10
+  fix:
+    content: ""
+    start:
+      row: 13
+      column: 10
+    end:
+      row: 13
+      column: 24
+    applied: false
+- kind:
+    UnusedNOQA: E501
+  location:
+    row: 16
+    column: 10
+  fix:
+    content: "  # noqa: F841"
+    start:
+      row: 16
+      column: 10
+    end:
+      row: 16
+      column: 30
+    applied: false
+- kind:
+    UnusedNOQA: F841
+  location:
+    row: 41
+    column: 4
+  fix:
+    content: "  # noqa: E501"
+    start:
+      row: 41
+      column: 4
+    end:
+      row: 41
+      column: 24
+    applied: false
+- kind:
+    UnusedNOQA: E501
+  location:
+    row: 49
+    column: 4
+  fix:
+    content: ""
+    start:
+      row: 49
+      column: 4
+    end:
+      row: 49
+      column: 18
+    applied: false
+- kind:
+    UnusedNOQA: ~
+  location:
+    row: 57
+    column: 4
+  fix:
+    content: ""
+    start:
+      row: 57
+      column: 4
+    end:
+      row: 57
+      column: 12
+    applied: false
+