Bump version to 0.0.48

Cargo.lock

@@ -382,26 +382,24 @@ checksum = "fff857943da45f546682664a79488be82e69e43c1a7a2307679ab9afb3a66d2e"
 
 [[package]]
 name = "clap"
-version = "3.2.16"
+version = "4.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a3dbbb6653e7c55cc8595ad3e1f7be8f32aba4eb7ff7f0fd1163d4f3d137c0a9"
+checksum = "dd03107d0f87139c1774a15f3db2165b0652b5460c58c27e561f89c20c599eaf"
 dependencies = [
  "atty",
  "bitflags",
  "clap_derive",
  "clap_lex",
- "indexmap",
  "once_cell",
  "strsim",
  "termcolor",
- "textwrap",
 ]
 
 [[package]]
 name = "clap_derive"
-version = "3.2.15"
+version = "4.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9ba52acd3b0a5c33aeada5cdaa3267cdc7c594a98731d4268cdc1532f4264cb4"
+checksum = "ca689d7434ce44517a12a89456b2be4d1ea1cafcd8f581978c03d45f5a5c12a7"
 dependencies = [
  "heck",
  "proc-macro-error",
@@ -412,9 +410,9 @@ dependencies = [
 
 [[package]]
 name = "clap_lex"
-version = "0.2.4"
+version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2850f2f5a82cbf437dd5af4d49848fbdfc27c157c3d010345776f952765261c5"
+checksum = "0d4198f73e42b4936b35b5bb248d81d2b595ecb170da0bac7655c54eedfa8da8"
 dependencies = [
  "os_str_bytes",
 ]
@@ -1801,7 +1799,7 @@ dependencies = [
 
 [[package]]
 name = "ruff"
-version = "0.0.45"
+version = "0.0.48"
 dependencies = [
  "anyhow",
  "bincode",
@@ -2187,12 +2185,6 @@ dependencies = [
  "phf_codegen 0.8.0",
 ]
 
-[[package]]
-name = "textwrap"
-version = "0.15.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b1141d4d61095b28419e22cb0bbf02755f5e54e0526f97f1e3d1d160e60885fb"
-
 [[package]]
 name = "thiserror"
 version = "1.0.32"

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ruff"
-version = "0.0.45"
+version = "0.0.48"
 edition = "2021"
 
 [lib]
@@ -11,7 +11,7 @@ anyhow = { version = "1.0.60" }
 bincode = { version = "1.3.3" }
 cacache = { version = "10.0.1" }
 chrono = { version = "0.4.21" }
-clap = { version = "3.2.16", features = ["derive"] }
+clap = { version = "4.0.1", features = ["derive"] }
 clearscreen = { version = "1.0.10" }
 colored = { version = "2.0.0" }
 common-path = { version = "1.0.0" }

README.md

@@ -20,7 +20,7 @@ An extremely fast Python linter, written in Rust.
 - 🤝 Python 3.10 compatibility
 - 🛠️ `pyproject.toml` support
 - 📦 [ESLint](https://eslint.org/docs/latest/user-guide/command-line-interface#caching)-inspired cache support
-- 🔧 [ESLint](https://eslint.org/docs/latest/user-guide/command-line-interface#caching)-inspired `--fix` support
+- 🔧 [ESLint](https://eslint.org/docs/latest/user-guide/command-line-interface#--fix)-inspired `--fix` support
 - 👀 [TypeScript](https://www.typescriptlang.org/docs/handbook/configuring-watch.html)-inspired `--watch` support
 - ⚖️ [Near-complete parity](#Parity-with-Flake8) with the built-in Flake8 rule set
 
@@ -80,59 +80,60 @@ select = [
 Alternatively, on the command-line:
 
 ```shell
-ruff path/to/code/ --select F401 F403
+ruff path/to/code/ --select F401 --select F403
 ```
 
 See `ruff --help` for more:
 
 ```shell
-ruff (v0.0.45) 0.0.45
-An extremely fast Python linter.
+ruff: An extremely fast Python linter.
 
-USAGE:
-    ruff [OPTIONS] <FILES>...
+Usage: ruff [OPTIONS] <FILES>...
 
-ARGS:
-    <FILES>...
+Arguments:
+  <FILES>...
 
-OPTIONS:
-        --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>
-            Output serialization format for error messages [default: text] [possible values: text,
-            json]
-    -h, --help
-            Print help information
-    -n, --no-cache
-            Disable cache reads
-    -q, --quiet
-            Disable all logging (but still exit with status code "1" upon detecting errors)
-        --add-noqa
-            Enable automatic additions of noqa directives to failing lines
-        --show-files
-            See the files ruff will be run against with the current settings
-        --show-settings
-            See ruff's settings
-    -v, --verbose
-            Enable verbose logging
-    -V, --version
-            Print version information
-    -w, --watch
-            Run in watch mode by re-running whenever files change
+Options:
+  -v, --verbose
+          Enable verbose logging
+  -q, --quiet
+          Disable all logging (but still exit with status code "1" upon detecting errors)
+  -e, --exit-zero
+          Exit with status code "0", even upon detecting errors
+  -w, --watch
+          Run in watch mode by re-running whenever files change
+  -f, --fix
+          Attempt to automatically fix lint errors
+  -n, --no-cache
+          Disable cache reads
+      --select <SELECT>
+          List of error codes to enable
+      --extend-select <EXTEND_SELECT>
+          Like --select, but adds additional error codes on top of the selected ones
+      --ignore <IGNORE>
+          List of error codes to ignore
+      --extend-ignore <EXTEND_IGNORE>
+          Like --ignore, but adds additional error codes on top of the ignored ones
+      --exclude <EXCLUDE>
+          List of paths, used to exclude files and/or directories from checks
+      --extend-exclude <EXTEND_EXCLUDE>
+          Like --exclude, but adds additional files and directories on top of the excluded ones
+      --per-file-ignores <PER_FILE_IGNORES>
+          List of mappings from file pattern to code to exclude
+      --format <FORMAT>
+          Output serialization format for error messages [default: text] [possible values: text, json]
+      --show-files
+          See the files ruff will be run against with the current settings
+      --show-settings
+          See ruff's settings
+      --add-noqa
+          Enable automatic additions of noqa directives to failing lines
+      --dummy-variable-rgx <DUMMY_VARIABLE_RGX>
+          Regular expression matching the name of dummy variables
+  -h, --help
+          Print help information
+  -V, --version
+          Print version information
 ```
 
 ### Excluding files
@@ -210,8 +211,8 @@ 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 a few Python 3.9 and 3.10 language features, including structural
+   pattern matching and parenthesized context managers.
 
 ## Rules
 

examples/print_ast.rs

@@ -2,14 +2,14 @@
 use std::path::PathBuf;
 
 use anyhow::Result;
-use clap::{Parser, ValueHint};
+use clap::Parser;
 use rustpython_parser::parser;
 
 use ruff::fs;
 
 #[derive(Debug, Parser)]
 struct Cli {
-    #[clap(parse(from_os_str), value_hint = ValueHint::FilePath, required = true)]
+    #[arg(required = true)]
     file: PathBuf,
 }
 

examples/print_tokens.rs

@@ -2,14 +2,14 @@
 use std::path::PathBuf;
 
 use anyhow::Result;
-use clap::{Parser, ValueHint};
+use clap::Parser;
 use rustpython_parser::lexer;
 
 use ruff::fs;
 
 #[derive(Debug, Parser)]
 struct Cli {
-    #[clap(parse(from_os_str), value_hint = ValueHint::FilePath, required = true)]
+    #[arg(required = true)]
     file: PathBuf,
 }
 

pyproject.toml

@@ -8,7 +8,6 @@ classifiers = [
     "License :: OSI Approved :: MIT License",
     "Operating System :: OS Independent",
     "Programming Language :: Python",
-    "Programming Language :: Python :: 3.6",
     "Programming Language :: Python :: 3.7",
     "Programming Language :: Python :: 3.8",
     "Programming Language :: Python :: 3.9",

resources/test/fixtures/A001.py

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

resources/test/fixtures/A002.py

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

resources/test/fixtures/A003.py

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

resources/test/fixtures/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,
@@ -10,6 +11,7 @@ use crate::ast::operations::SourceCodeLocator;
 use crate::ast::types::{Binding, BindingKind, CheckLocator, FunctionScope, Scope, ScopeKind};
 use crate::autofix::{fixer, fixes};
 use crate::checks::{Check, CheckKind, Fix, RejectedCmpop};
+use crate::python::builtins::BUILTINS;
 
 /// Check IfTuple compliance.
 pub fn check_if_tuple(test: &Expr, location: Location) -> Option<Check> {
@@ -71,7 +73,11 @@ 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 +88,12 @@ 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()),
@@ -648,3 +653,30 @@ pub fn check_continue_outside_loop(
         None
     }
 }
+
+// flake8-builtins
+pub enum ShadowingType {
+    Variable,
+    Argument,
+    Attribute,
+}
+
+/// Check builtin name shadowing
+pub fn check_builtin_shadowing(
+    name: &str,
+    location: Location,
+    node_type: ShadowingType,
+) -> Option<Check> {
+    if BUILTINS.contains(&name) {
+        Some(Check::new(
+            match node_type {
+                ShadowingType::Variable => CheckKind::BuiltinVariableShadowing(name.to_string()),
+                ShadowingType::Argument => CheckKind::BuiltinArgumentShadowing(name.to_string()),
+                ShadowingType::Attribute => CheckKind::BuiltinAttributeShadowing(name.to_string()),
+            },
+            location,
+        ))
+    } else {
+        None
+    }
+}

src/check_ast.rs

@@ -246,6 +246,9 @@ where
                         self.checks.push(check);
                     }
                 }
+
+                self.check_builtin_shadowing(name, stmt.location, true);
+
                 for expr in decorator_list {
                     self.visit_expr(expr);
                 }
@@ -342,6 +345,8 @@ where
                     }
                 }
 
+                self.check_builtin_shadowing(name, self.locate_check(stmt.location), false);
+
                 for expr in bases {
                     self.visit_expr(expr)
                 }
@@ -382,6 +387,10 @@ where
                             },
                         )
                     } else {
+                        if let Some(asname) = &alias.node.asname {
+                            self.check_builtin_shadowing(asname, stmt.location, false);
+                        }
+
                         self.add_binding(
                             alias
                                 .node
@@ -504,6 +513,10 @@ where
                             .expect("No current scope found."))];
                         scope.import_starred = true;
                     } else {
+                        if let Some(asname) = &alias.node.asname {
+                            self.check_builtin_shadowing(asname, stmt.location, false);
+                        }
+
                         let binding = Binding {
                             kind: BindingKind::Importation(match module {
                                 None => name.clone(),
@@ -667,6 +680,9 @@ where
                             self.checks.push(check);
                         }
                     }
+
+                    self.check_builtin_shadowing(id, expr.location, true);
+
                     let parent =
                         self.parents[*(self.parent_stack.last().expect("No parent found."))];
                     self.handle_node_store(expr, parent);
@@ -977,6 +993,9 @@ where
                                 self.checks.push(check);
                             }
                         }
+
+                        self.check_builtin_shadowing(name, excepthandler.location, false);
+
                         let scope = &self.scopes
                             [*(self.scope_stack.last().expect("No current scope found."))];
                         if scope.values.contains_key(name) {
@@ -1080,6 +1099,8 @@ where
                 self.checks.push(check);
             }
         }
+
+        self.check_builtin_arg_shadowing(&arg.node.arg, arg.location);
     }
 }
 
@@ -1415,8 +1436,11 @@ 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,
+                ));
             }
         }
     }
@@ -1502,6 +1526,44 @@ impl<'a> Checker<'a> {
             }
         }
     }
+
+    fn check_builtin_shadowing(&mut self, name: &str, location: Location, is_attribute: bool) {
+        let scope = &self.scopes[*(self.scope_stack.last().expect("No current scope found."))];
+
+        // flake8-builtins
+        if is_attribute
+            && matches!(scope.kind, ScopeKind::Class)
+            && self.settings.select.contains(&CheckCode::A003)
+        {
+            if let Some(check) = checks::check_builtin_shadowing(
+                name,
+                self.locate_check(location),
+                checks::ShadowingType::Attribute,
+            ) {
+                self.checks.push(check);
+            }
+        } else if self.settings.select.contains(&CheckCode::A001) {
+            if let Some(check) = checks::check_builtin_shadowing(
+                name,
+                self.locate_check(location),
+                checks::ShadowingType::Variable,
+            ) {
+                self.checks.push(check);
+            }
+        }
+    }
+
+    fn check_builtin_arg_shadowing(&mut self, name: &str, location: Location) {
+        if self.settings.select.contains(&CheckCode::A002) {
+            if let Some(check) = checks::check_builtin_shadowing(
+                name,
+                self.locate_check(location),
+                checks::ShadowingType::Argument,
+            ) {
+                self.checks.push(check);
+            }
+        }
+    }
 }
 
 pub fn check_ast(

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/checks.rs

@@ -4,7 +4,7 @@ use anyhow::Result;
 use rustpython_parser::ast::Location;
 use serde::{Deserialize, Serialize};
 
-pub const DEFAULT_CHECK_CODES: [CheckCode; 42] = [
+pub const DEFAULT_CHECK_CODES: [CheckCode; 45] = [
     CheckCode::E402,
     CheckCode::E501,
     CheckCode::E711,
@@ -47,9 +47,13 @@ pub const DEFAULT_CHECK_CODES: [CheckCode; 42] = [
     CheckCode::F831,
     CheckCode::F841,
     CheckCode::F901,
+    // flake8-builtins
+    CheckCode::A001,
+    CheckCode::A002,
+    CheckCode::A003,
 ];
 
-pub const ALL_CHECK_CODES: [CheckCode; 45] = [
+pub const ALL_CHECK_CODES: [CheckCode; 48] = [
     CheckCode::E402,
     CheckCode::E501,
     CheckCode::E711,
@@ -95,6 +99,10 @@ pub const ALL_CHECK_CODES: [CheckCode; 45] = [
     CheckCode::M001,
     CheckCode::R001,
     CheckCode::R002,
+    // flake8-builtins
+    CheckCode::A001,
+    CheckCode::A002,
+    CheckCode::A003,
 ];
 
 #[derive(Debug, PartialEq, Eq, Clone, Serialize, Deserialize, Hash, PartialOrd, Ord)]
@@ -144,6 +152,10 @@ pub enum CheckCode {
     R001,
     R002,
     M001,
+    // flake8-builtins
+    A001,
+    A002,
+    A003,
 }
 
 impl FromStr for CheckCode {
@@ -196,6 +208,10 @@ impl FromStr for CheckCode {
             "R001" => Ok(CheckCode::R001),
             "R002" => Ok(CheckCode::R002),
             "M001" => Ok(CheckCode::M001),
+            // flake8-builtins
+            "A001" => Ok(CheckCode::A001),
+            "A002" => Ok(CheckCode::A002),
+            "A003" => Ok(CheckCode::A003),
             _ => Err(anyhow::anyhow!("Unknown check code: {s}")),
         }
     }
@@ -249,6 +265,10 @@ impl CheckCode {
             CheckCode::R001 => "R001",
             CheckCode::R002 => "R002",
             CheckCode::M001 => "M001",
+            // flake8-builtins
+            CheckCode::A001 => "A001",
+            CheckCode::A002 => "A002",
+            CheckCode::A003 => "A003",
         }
     }
 
@@ -256,7 +276,7 @@ impl CheckCode {
     pub fn lint_source(&self) -> &'static LintSource {
         match self {
             CheckCode::E501 | CheckCode::M001 => &LintSource::Lines,
-            CheckCode::E902 | CheckCode::E999 => &LintSource::FileSystem,
+            CheckCode::E902 => &LintSource::FileSystem,
             _ => &LintSource::AST,
         }
     }
@@ -309,6 +329,10 @@ impl CheckCode {
             CheckCode::M001 => CheckKind::UnusedNOQA(None),
             CheckCode::R001 => CheckKind::UselessObjectInheritance("...".to_string()),
             CheckCode::R002 => CheckKind::NoAssertEquals,
+            // flake8-builtins
+            CheckCode::A001 => CheckKind::BuiltinVariableShadowing("...".to_string()),
+            CheckCode::A002 => CheckKind::BuiltinArgumentShadowing("...".to_string()),
+            CheckCode::A003 => CheckKind::BuiltinAttributeShadowing("...".to_string()),
         }
     }
 }
@@ -373,6 +397,10 @@ pub enum CheckKind {
     UnusedVariable(String),
     UselessObjectInheritance(String),
     YieldOutsideFunction,
+    // flake8-builtin
+    BuiltinVariableShadowing(String),
+    BuiltinArgumentShadowing(String),
+    BuiltinAttributeShadowing(String),
 }
 
 impl CheckKind {
@@ -426,6 +454,10 @@ impl CheckKind {
             CheckKind::UselessObjectInheritance(_) => "UselessObjectInheritance",
             CheckKind::YieldOutsideFunction => "YieldOutsideFunction",
             CheckKind::UnusedNOQA(_) => "UnusedNOQA",
+            // flake8-builtins
+            CheckKind::BuiltinVariableShadowing(_) => "BuiltinVariableShadowing",
+            CheckKind::BuiltinArgumentShadowing(_) => "BuiltinArgumentShadowing",
+            CheckKind::BuiltinAttributeShadowing(_) => "BuiltinAttributeShadowing",
         }
     }
 
@@ -477,6 +509,10 @@ impl CheckKind {
             CheckKind::UnusedVariable(_) => &CheckCode::F841,
             CheckKind::UselessObjectInheritance(_) => &CheckCode::R001,
             CheckKind::YieldOutsideFunction => &CheckCode::F704,
+            // flake8-builtins
+            CheckKind::BuiltinVariableShadowing(_) => &CheckCode::A001,
+            CheckKind::BuiltinArgumentShadowing(_) => &CheckCode::A002,
+            CheckKind::BuiltinAttributeShadowing(_) => &CheckCode::A003,
         }
     }
 
@@ -611,6 +647,16 @@ impl CheckKind {
                 None => "Unused `noqa` directive".to_string(),
                 Some(code) => format!("Unused `noqa` directive for: {code}"),
             },
+            // flake8-builtins
+            CheckKind::BuiltinVariableShadowing(name) => {
+                format!("Variable `{name}` is shadowing a python builtin")
+            }
+            CheckKind::BuiltinArgumentShadowing(name) => {
+                format!("Argument `{name}` is shadowing a python builtin")
+            }
+            CheckKind::BuiltinAttributeShadowing(name) => {
+                format!("class attribute `{name}` is shadowing a python builtin")
+            }
         }
     }
 

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
 }
@@ -71,7 +76,6 @@ pub fn iter_python_files<'a>(
         .all(|pattern| matches!(pattern, FilePattern::Simple(_)));
 
     WalkDir::new(normalize_path(path))
-        .follow_links(true)
         .into_iter()
         .filter_entry(move |entry| {
             if !has_exclude && !has_extend_exclude {
@@ -85,13 +89,13 @@ 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
@@ -107,11 +111,32 @@ pub fn iter_python_files<'a>(
         })
         .filter(|entry| {
             entry.as_ref().map_or(true, |entry| {
-                (entry.depth() == 0 && !entry.file_type().is_dir()) || is_included(entry.path())
+                (entry.depth() == 0 || is_included(entry.path()))
+                    && !entry.file_type().is_dir()
+                    && !(entry.file_type().is_symlink() && entry.path().is_dir())
             })
         })
 }
 
+/// 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 +205,7 @@ 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 +213,7 @@ 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 +223,7 @@ 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 +231,7 @@ 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 +241,7 @@ 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 +251,7 @@ 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 +261,7 @@ 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

@@ -15,19 +15,30 @@ use crate::noqa::add_noqa;
 use crate::settings::Settings;
 use crate::{cache, fs, noqa};
 
+/// Collect tokens up to and including the first error.
+fn tokenize(contents: &str) -> Vec<LexResult> {
+    let mut tokens: Vec<LexResult> = vec![];
+    for tok in lexer::make_tokenizer(contents) {
+        let is_err = tok.is_err();
+        tokens.push(tok);
+        if is_err {
+            break;
+        }
+    }
+    tokens
+}
+
 fn check_path(
     path: &Path,
     contents: &str,
     tokens: Vec<LexResult>,
+    noqa_line_for: &[usize],
     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
@@ -50,9 +61,20 @@ fn check_path(
     }
 
     // Run the lines-based checks.
-    check_lines(&mut checks, contents, &noqa_line_for, settings, autofix);
+    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(
@@ -73,10 +95,13 @@ pub fn lint_path(
     let contents = fs::read_file(path)?;
 
     // Tokenize once.
-    let tokens: Vec<LexResult> = lexer::make_tokenizer(&contents).collect();
+    let tokens: Vec<LexResult> = tokenize(&contents);
+
+    // Determine the noqa line for every line in the source.
+    let noqa_line_for = noqa::extract_noqa_line_for(&tokens);
 
     // Generate checks.
-    let mut checks = check_path(path, &contents, tokens, settings, autofix);
+    let mut checks = check_path(path, &contents, tokens, &noqa_line_for, settings, autofix)?;
 
     // Apply autofix.
     if matches!(autofix, fixer::Mode::Apply) {
@@ -103,13 +128,20 @@ pub fn add_noqa_to_path(path: &Path, settings: &Settings) -> Result<usize> {
     let contents = fs::read_file(path)?;
 
     // Tokenize once.
-    let tokens: Vec<LexResult> = lexer::make_tokenizer(&contents).collect();
+    let tokens: Vec<LexResult> = tokenize(&contents);
 
     // Determine the noqa line for every line in the source.
     let noqa_line_for = noqa::extract_noqa_line_for(&tokens);
 
     // Generate checks.
-    let checks = check_path(path, &contents, tokens, settings, &fixer::Mode::None);
+    let checks = check_path(
+        path,
+        &contents,
+        tokens,
+        &noqa_line_for,
+        settings,
+        &fixer::Mode::None,
+    )?;
 
     add_noqa(&checks, &contents, &noqa_line_for, path)
 }
@@ -119,14 +151,15 @@ mod tests {
     use std::path::Path;
 
     use anyhow::Result;
-    use rustpython_parser::lexer;
+    use regex::Regex;
     use rustpython_parser::lexer::LexResult;
 
     use crate::autofix::fixer;
     use crate::checks::{Check, CheckCode};
-    use crate::fs;
     use crate::linter;
+    use crate::linter::tokenize;
     use crate::settings;
+    use crate::{fs, noqa};
 
     fn check_path(
         path: &Path,
@@ -134,10 +167,9 @@ mod tests {
         autofix: &fixer::Mode,
     ) -> 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,
-        ))
+        let tokens: Vec<LexResult> = tokenize(&contents);
+        let noqa_line_for = noqa::extract_noqa_line_for(&tokens);
+        linter::check_path(path, &contents, tokens, &noqa_line_for, settings, autofix)
     }
 
     #[test]
@@ -596,6 +628,21 @@ 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(
@@ -667,4 +714,52 @@ mod tests {
         insta::assert_yaml_snapshot!(checks);
         Ok(())
     }
+
+    #[test]
+    fn e999() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/E999.py"),
+            &settings::Settings::for_rule(CheckCode::E999),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn a001() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/A001.py"),
+            &settings::Settings::for_rule(CheckCode::A001),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn a002() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/A002.py"),
+            &settings::Settings::for_rule(CheckCode::A002),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn a003() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/A003.py"),
+            &settings::Settings::for_rule(CheckCode::A003),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
 }

src/main.rs

@@ -7,84 +7,91 @@ use std::sync::mpsc::channel;
 use std::time::Instant;
 
 use anyhow::Result;
-use clap::{Parser, ValueHint};
+use clap::{command, Parser};
 use colored::Colorize;
 use log::{debug, error};
 use notify::{raw_watcher, RecursiveMode, Watcher};
 use rayon::prelude::*;
+use regex::Regex;
 use walkdir::DirEntry;
 
 use ::ruff::cache;
 use ::ruff::checks::CheckCode;
 use ::ruff::checks::CheckKind;
 use ::ruff::fs::iter_python_files;
+use ::ruff::linter::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;
+use ruff::settings::CurrentSettings;
 
 const CARGO_PKG_NAME: &str = env!("CARGO_PKG_NAME");
 const CARGO_PKG_VERSION: &str = env!("CARGO_PKG_VERSION");
 
 #[derive(Debug, Parser)]
-#[clap(name = format!("{CARGO_PKG_NAME} (v{CARGO_PKG_VERSION})"))]
-#[clap(about = "An extremely fast Python linter.", long_about = None)]
-#[clap(version)]
+#[command(author, about = "ruff: An extremely fast Python linter.")]
+#[command(version)]
 struct Cli {
-    #[clap(parse(from_os_str), value_hint = ValueHint::AnyPath, required = true)]
+    #[arg(required = true)]
     files: Vec<PathBuf>,
     /// Enable verbose logging.
-    #[clap(short, long, action)]
+    #[arg(short, long)]
     verbose: bool,
     /// Disable all logging (but still exit with status code "1" upon detecting errors).
-    #[clap(short, long, action)]
+    #[arg(short, long)]
     quiet: bool,
     /// Exit with status code "0", even upon detecting errors.
-    #[clap(short, long, action)]
+    #[arg(short, long)]
     exit_zero: bool,
     /// Run in watch mode by re-running whenever files change.
-    #[clap(short, long, action)]
+    #[arg(short, long)]
     watch: bool,
     /// Attempt to automatically fix lint errors.
-    #[clap(short, long, action)]
+    #[arg(short, long)]
     fix: bool,
     /// Disable cache reads.
-    #[clap(short, long, action)]
+    #[arg(short, long)]
     no_cache: bool,
     /// List of error codes to enable.
-    #[clap(long, multiple = true)]
+    #[arg(long, value_delimiter = ',')]
     select: Vec<CheckCode>,
     /// Like --select, but adds additional error codes on top of the selected ones.
-    #[clap(long, multiple = true)]
+    #[arg(long, value_delimiter = ',')]
     extend_select: Vec<CheckCode>,
     /// List of error codes to ignore.
-    #[clap(long, multiple = true)]
+    #[arg(long, value_delimiter = ',')]
     ignore: Vec<CheckCode>,
     /// Like --ignore, but adds additional error codes on top of the ignored ones.
-    #[clap(long, multiple = true)]
+    #[arg(long, value_delimiter = ',')]
     extend_ignore: Vec<CheckCode>,
     /// List of paths, used to exclude files and/or directories from checks.
-    #[clap(long, multiple = true)]
+    #[arg(long, value_delimiter = ',')]
     exclude: Vec<String>,
     /// Like --exclude, but adds additional files and directories on top of the excluded ones.
-    #[clap(long, multiple = true)]
+    #[arg(long, value_delimiter = ',')]
     extend_exclude: Vec<String>,
+    /// List of mappings from file pattern to code to exclude
+    #[arg(long, value_delimiter = ',')]
+    per_file_ignores: Vec<StrCheckCodePair>,
     /// Output serialization format for error messages.
-    #[clap(long, arg_enum, default_value_t=SerializationFormat::Text)]
+    #[arg(long, value_enum, default_value_t=SerializationFormat::Text)]
     format: SerializationFormat,
     /// See the files ruff will be run against with the current settings.
-    #[clap(long, action)]
+    #[arg(long)]
     show_files: bool,
     /// See ruff's settings.
-    #[clap(long, action)]
+    #[arg(long)]
     show_settings: bool,
     /// Enable automatic additions of noqa directives to failing lines.
-    #[clap(long, action)]
+    #[arg(long)]
     add_noqa: bool,
+    /// Regular expression matching the name of dummy variables.
+    #[arg(long)]
+    dummy_variable_rgx: Option<Regex>,
 }
 
 #[cfg(feature = "update-informer")]
@@ -111,8 +118,8 @@ fn check_for_updates() {
     }
 }
 
-fn show_settings(settings: &Settings) {
-    println!("{:#?}", settings);
+fn show_settings(settings: Settings) {
+    println!("{:#?}", CurrentSettings::from_settings(settings));
 }
 
 fn show_files(files: &[PathBuf], settings: &Settings) {
@@ -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);
@@ -265,34 +280,37 @@ 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 {
-        show_settings(&settings);
-        return Ok(ExitCode::SUCCESS);
-    }
     if cli.show_files {
         show_files(&cli.files, &settings);
         return Ok(ExitCode::SUCCESS);
     }
+    if cli.show_settings {
+        show_settings(settings);
+        return Ok(ExitCode::SUCCESS);
+    }
 
     cache::init()?;
 
     let mut printer = Printer::new(cli.format, cli.verbose);
     if cli.watch {
         if cli.fix {
-            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/noqa.rs

@@ -1,13 +1,14 @@
 use std::cmp::{max, min};
+use std::collections::{BTreeMap, BTreeSet};
+use std::fs;
+use std::path::Path;
 
-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;
+
+use crate::checks::{Check, CheckCode};
 
 static NO_QA_REGEX: Lazy<Regex> = Lazy::new(|| {
     Regex::new(r"(?i)(?P<noqa>\s*# noqa(?::\s?(?P<codes>([A-Z]+[0-9]+(?:[,\s]+)?)+))?)")
@@ -160,12 +161,12 @@ pub fn add_noqa(
 
 #[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::checks::{Check, CheckKind};
     use crate::noqa::{add_noqa_inner, extract_noqa_line_for};
 
     #[test]

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(Clone, Debug, PartialEq, Eq)]
+pub struct StrCheckCodePair {
+    pub pattern: String,
+    pub code: CheckCode,
+}
+
+impl StrCheckCodePair {
+    const EXPECTED_PATTERN: &'static str = "<FilePattern>:<CheckCode> pattern";
+}
+
+impl<'de> Deserialize<'de> for StrCheckCodePair {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let str_result = String::deserialize(deserializer)?;
+        Self::from_str(str_result.as_str()).map_err(|_| {
+            de::Error::invalid_value(
+                de::Unexpected::Str(str_result.as_str()),
+                &Self::EXPECTED_PATTERN,
+            )
+        })
+    }
+}
+
+impl FromStr for StrCheckCodePair {
+    type Err = anyhow::Error;
+
+    fn from_str(string: &str) -> Result<Self, Self::Err> {
+        let (pattern_str, code_string) = {
+            let tokens = string.split(':').collect::<Vec<_>>();
+            if tokens.len() != 2 {
+                return Err(anyhow!("Expected {}", Self::EXPECTED_PATTERN));
+            }
+            (tokens[0], tokens[1])
+        };
+        let code = CheckCode::from_str(code_string)?;
+        let pattern = pattern_str.into();
+        Ok(Self { pattern, code })
+    }
 }
 
 #[derive(Debug, PartialEq, Eq, Deserialize)]
@@ -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) {
@@ -154,3 +200,62 @@ impl Settings {
         }
     }
 }
+
+/// Struct to render user-facing exclusion patterns.
+#[derive(Debug)]
+#[allow(dead_code)]
+pub struct Exclusion {
+    basename: Option<String>,
+    absolute: Option<String>,
+}
+
+impl Exclusion {
+    pub fn from_file_pattern(file_pattern: FilePattern) -> Self {
+        match file_pattern {
+            FilePattern::Simple(basename) => Exclusion {
+                basename: Some(basename.to_string()),
+                absolute: None,
+            },
+            FilePattern::Complex(absolute, basename) => Exclusion {
+                basename: basename.map(|pattern| pattern.to_string()),
+                absolute: Some(absolute.to_string()),
+            },
+        }
+    }
+}
+
+/// Struct to render user-facing Settings.
+#[derive(Debug)]
+pub struct CurrentSettings {
+    pub pyproject: Option<PathBuf>,
+    pub project_root: Option<PathBuf>,
+    pub line_length: usize,
+    pub exclude: Vec<Exclusion>,
+    pub extend_exclude: Vec<Exclusion>,
+    pub select: BTreeSet<CheckCode>,
+    pub per_file_ignores: Vec<PerFileIgnore>,
+    pub dummy_variable_rgx: Regex,
+}
+
+impl CurrentSettings {
+    pub fn from_settings(settings: Settings) -> Self {
+        Self {
+            pyproject: settings.pyproject,
+            project_root: settings.project_root,
+            line_length: settings.line_length,
+            exclude: settings
+                .exclude
+                .into_iter()
+                .map(Exclusion::from_file_pattern)
+                .collect(),
+            extend_exclude: settings
+                .extend_exclude
+                .into_iter()
+                .map(Exclusion::from_file_pattern)
+                .collect(),
+            select: settings.select,
+            per_file_ignores: settings.per_file_ignores,
+            dummy_variable_rgx: settings.dummy_variable_rgx,
+        }
+    }
+}

src/snapshots/ruff__linter__tests__a001.snap

@@ -0,0 +1,112 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    BuiltinVariableShadowing: sum
+  location:
+    row: 1
+    column: 1
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: int
+  location:
+    row: 2
+    column: 1
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: print
+  location:
+    row: 4
+    column: 1
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: copyright
+  location:
+    row: 5
+    column: 1
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: complex
+  location:
+    row: 6
+    column: 2
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: float
+  location:
+    row: 7
+    column: 1
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: object
+  location:
+    row: 7
+    column: 9
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: min
+  location:
+    row: 8
+    column: 1
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: max
+  location:
+    row: 8
+    column: 6
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: bytes
+  location:
+    row: 10
+    column: 1
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: slice
+  location:
+    row: 13
+    column: 1
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: ValueError
+  location:
+    row: 18
+    column: 1
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: memoryview
+  location:
+    row: 21
+    column: 5
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: bytearray
+  location:
+    row: 21
+    column: 18
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: str
+  location:
+    row: 24
+    column: 22
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: all
+  location:
+    row: 24
+    column: 45
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: any
+  location:
+    row: 24
+    column: 50
+  fix: ~
+- kind:
+    BuiltinVariableShadowing: sum
+  location:
+    row: 27
+    column: 8
+  fix: ~

src/snapshots/ruff__linter__tests__a002.snap

@@ -0,0 +1,46 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    BuiltinArgumentShadowing: str
+  location:
+    row: 1
+    column: 11
+  fix: ~
+- kind:
+    BuiltinArgumentShadowing: type
+  location:
+    row: 1
+    column: 19
+  fix: ~
+- kind:
+    BuiltinArgumentShadowing: complex
+  location:
+    row: 1
+    column: 26
+  fix: ~
+- kind:
+    BuiltinArgumentShadowing: Exception
+  location:
+    row: 1
+    column: 35
+  fix: ~
+- kind:
+    BuiltinArgumentShadowing: getattr
+  location:
+    row: 1
+    column: 48
+  fix: ~
+- kind:
+    BuiltinArgumentShadowing: bytes
+  location:
+    row: 5
+    column: 17
+  fix: ~
+- kind:
+    BuiltinArgumentShadowing: float
+  location:
+    row: 9
+    column: 16
+  fix: ~

src/snapshots/ruff__linter__tests__a003.snap

@@ -0,0 +1,18 @@
+---
+source: src/linter.rs
+assertion_line: 762
+expression: checks
+---
+- kind:
+    BuiltinAttributeShadowing: ImportError
+  location:
+    row: 2
+    column: 5
+  fix: ~
+- kind:
+    BuiltinAttributeShadowing: str
+  location:
+    row: 7
+    column: 5
+  fix: ~
+

src/snapshots/ruff__linter__tests__e999.snap

@@ -0,0 +1,11 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    SyntaxError: Got unexpected EOF
+  location:
+    row: 2
+    column: 1
+  fix: ~
+

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: ~
+