Bump version to 0.0.46

Cargo.lock

@@ -1801,7 +1801,7 @@ dependencies = [
 
 [[package]]
 name = "ruff"
-version = "0.0.45"
+version = "0.0.46"
 dependencies = [
  "anyhow",
  "bincode",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ruff"
-version = "0.0.45"
+version = "0.0.46"
 edition = "2021"
 
 [lib]

README.md

@@ -86,7 +86,7 @@ ruff path/to/code/ --select F401 F403
 See `ruff --help` for more:
 
 ```shell
-ruff (v0.0.45) 0.0.45
+ruff (v0.0.46)
 An extremely fast Python linter.
 
 USAGE:
@@ -119,6 +119,8 @@ OPTIONS:
             Print help information
     -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)
         --add-noqa
@@ -210,8 +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
 

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/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

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

@@ -180,10 +180,11 @@ pub fn check_lines(
 
 #[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() {
@@ -191,19 +192,14 @@ mod tests {
         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,
                 &noqa_line_for,
-                &settings,
+                &settings::Settings {
+                    line_length,
+                    ..settings::Settings::for_rule(CheckCode::E501)
+                },
                 &fixer::Mode::Generate,
             );
             return checks;

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/linter.rs

@@ -21,7 +21,7 @@ fn check_path(
     tokens: Vec<LexResult>,
     settings: &Settings,
     autofix: &fixer::Mode,
-) -> Vec<Check> {
+) -> Result<Vec<Check>> {
     // Aggregate all checks.
     let mut checks: Vec<Check> = vec![];
 
@@ -52,7 +52,18 @@ fn check_path(
     // Run the lines-based checks.
     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(
@@ -76,7 +87,7 @@ pub fn lint_path(
     let tokens: Vec<LexResult> = lexer::make_tokenizer(&contents).collect();
 
     // Generate checks.
-    let mut checks = check_path(path, &contents, tokens, settings, autofix);
+    let mut checks = check_path(path, &contents, tokens, settings, autofix)?;
 
     // Apply autofix.
     if matches!(autofix, fixer::Mode::Apply) {
@@ -109,7 +120,7 @@ pub fn add_noqa_to_path(path: &Path, settings: &Settings) -> Result<usize> {
     let noqa_line_for = noqa::extract_noqa_line_for(&tokens);
 
     // Generate checks.
-    let checks = check_path(path, &contents, tokens, settings, &fixer::Mode::None);
+    let checks = check_path(path, &contents, tokens, settings, &fixer::Mode::None)?;
 
     add_noqa(&checks, &contents, &noqa_line_for, path)
 }
@@ -119,6 +130,7 @@ mod tests {
     use std::path::Path;
 
     use anyhow::Result;
+    use regex::Regex;
     use rustpython_parser::lexer;
     use rustpython_parser::lexer::LexResult;
 
@@ -135,9 +147,7 @@ mod tests {
     ) -> Result<Vec<Check>> {
         let contents = fs::read_file(path)?;
         let tokens: Vec<LexResult> = lexer::make_tokenizer(&contents).collect();
-        Ok(linter::check_path(
-            path, &contents, tokens, settings, autofix,
-        ))
+        linter::check_path(path, &contents, tokens, settings, autofix)
     }
 
     #[test]
@@ -596,6 +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(

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;
@@ -18,14 +19,14 @@ 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;
-use ruff::linter::add_noqa_to_path;
 
 const CARGO_PKG_NAME: &str = env!("CARGO_PKG_NAME");
 const CARGO_PKG_VERSION: &str = env!("CARGO_PKG_VERSION");
@@ -73,6 +74,9 @@ struct Cli {
     /// 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,
@@ -85,6 +89,9 @@ struct Cli {
     /// 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")]
@@ -244,14 +251,22 @@ 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);
@@ -265,9 +280,12 @@ fn inner_main() -> Result<ExitCode> {
     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 {
@@ -284,15 +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 {
-            println!("Warning: --no-qa is not enabled in watch mode.");
+            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.
@@ -354,6 +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/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, 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
@@ -129,13 +161,27 @@ impl Settings {
             } else {
                 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,
         };
         if let Some(ignore) = &config.ignore {
             settings.ignore(ignore);
         }
-        settings
+        Ok(settings)
     }
 
     pub fn clear(&mut self) {

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: ~
+