Bump Ruff version to 0.0.122

.github/workflows/ci.yaml

@@ -6,6 +6,11 @@ on:
   pull_request:
     branches: [main]
 
+env:
+  CARGO_INCREMENTAL: 0
+  CARGO_NET_RETRY: 10
+  RUSTUP_MAX_RETRIES: 10
+
 jobs:
   cargo_build:
     name: "cargo build"

.github/workflows/flake8-to-ruff.yaml

@@ -10,6 +10,9 @@ env:
   PACKAGE_NAME: flake8-to-ruff
   CRATE_NAME: flake8_to_ruff
   PYTHON_VERSION: "3.7" # to build abi3 wheels
+  CARGO_INCREMENTAL: 0
+  CARGO_NET_RETRY: 10
+  RUSTUP_MAX_RETRIES: 10
 
 jobs:
   macos-x86_64:

.github/workflows/ruff.yaml

@@ -12,6 +12,9 @@ concurrency:
 env:
   PACKAGE_NAME: ruff
   PYTHON_VERSION: "3.7" # to build abi3 wheels
+  CARGO_INCREMENTAL: 0
+  CARGO_NET_RETRY: 10
+  RUSTUP_MAX_RETRIES: 10
 
 jobs:
   macos-x86_64:

.pre-commit-config.yaml

@@ -1,6 +1,6 @@
 repos:
   - repo: https://github.com/charliermarsh/ruff-pre-commit
-    rev: v0.0.119
+    rev: v0.0.122
     hooks:
       - id: ruff
 

Cargo.lock

@@ -930,7 +930,7 @@ checksum = "0ce7134b9999ecaf8bcd65542e436736ef32ddca1b3e06094cb6ec5755203b80"
 
 [[package]]
 name = "flake8-to-ruff"
-version = "0.0.119-dev.0"
+version = "0.0.122-dev.0"
 dependencies = [
  "anyhow",
  "clap 4.0.22",
@@ -2238,10 +2238,11 @@ dependencies = [
 
 [[package]]
 name = "ruff"
-version = "0.0.119"
+version = "0.0.122"
 dependencies = [
  "anyhow",
  "assert_cmd",
+ "atty",
  "bincode",
  "bitflags",
  "cacache",
@@ -2286,7 +2287,7 @@ dependencies = [
 
 [[package]]
 name = "ruff_dev"
-version = "0.0.119"
+version = "0.0.122"
 dependencies = [
  "anyhow",
  "clap 4.0.22",

Cargo.toml

@@ -6,7 +6,7 @@ members = [
 
 [package]
 name = "ruff"
-version = "0.0.119"
+version = "0.0.122"
 edition = "2021"
 
 [lib]
@@ -14,6 +14,7 @@ name = "ruff"
 
 [dependencies]
 anyhow = { version = "1.0.66" }
+atty = { version = "0.2.14" }
 bincode = { version = "1.3.3" }
 bitflags = { version = "1.3.2" }
 chrono = { version = "0.4.21", default-features = false, features = ["clock"] }

README.md

@@ -52,15 +52,16 @@ Read the [launch blog post](https://notes.crmarsh.com/python-tooling-could-be-mu
    4. [pydocstyle](#pydocstyle)
    5. [pyupgrade](#pyupgrade)
    6. [pep8-naming](#pep8-naming)
-   7. [flake8-comprehensions](#flake8-comprehensions)
-   8. [flake8-bugbear](#flake8-bugbear)
-   9. [flake8-builtins](#flake8-builtins)
-   10. [flake8-print](#flake8-print)
-   11. [flake8-quotes](#flake8-quotes)
-   12. [flake8-annotations](#flake8-annotations)
-   13. [flake8-2020](#flake8-2020)
-   14. [Ruff-specific rules](#ruff-specific-rules)
-   15. [Meta rules](#meta-rules)
+   7. [flake8-bandit](#flake8-bandit)
+   8. [flake8-comprehensions](#flake8-comprehensions)
+   9. [flake8-bugbear](#flake8-bugbear)
+   10. [flake8-builtins](#flake8-builtins)
+   11. [flake8-print](#flake8-print)
+   12. [flake8-quotes](#flake8-quotes)
+   13. [flake8-annotations](#flake8-annotations)
+   14. [flake8-2020](#flake8-2020)
+   15. [Ruff-specific rules](#ruff-specific-rules)
+   16. [Meta rules](#meta-rules)
 5. [Editor Integrations](#editor-integrations)
 6. [FAQ](#faq)
 7. [Development](#development)
@@ -236,6 +237,8 @@ Options:
           Regular expression matching the name of dummy variables
       --target-version <TARGET_VERSION>
           The minimum Python version that should be supported
+      --line-length <LINE_LENGTH>
+          Set the line-length for length-associated checks and automatic formatting
       --stdin-filename <STDIN_FILENAME>
           The name of the file when passing it through stdin
   -h, --help
@@ -528,6 +531,7 @@ For more, see [flake8-bugbear](https://pypi.org/project/flake8-bugbear/22.10.27/
 | B017 | NoAssertRaisesException | `assertRaises(Exception)` should be considered evil |  |
 | B018 | UselessExpression | Found useless expression. Either assign it to a variable or remove it. |  |
 | B019 | CachedInstanceMethod | Use of `functools.lru_cache` or `functools.cache` on methods can lead to memory leaks |  |
+| B020 | LoopVariableOverridesIterator | Loop control variable `...` overrides iterable it iterates |  |
 | B021 | FStringDocstring | f-string used as docstring. This will be interpreted by python as a joined string rather than a docstring. |  |
 | B022 | UselessContextlibSuppress | No arguments passed to `contextlib.suppress`. No exceptions will be suppressed and therefore this context manager is redundant |  |
 | B024 | AbstractBaseClassWithoutAbstractMethod | `...` is an abstract base class, but it has no abstract methods |  |
@@ -731,7 +735,7 @@ Today, Ruff can be used to replace Flake8 when used with any of the following pl
 - [`flake8-annotations`](https://pypi.org/project/flake8-annotations/)
 - [`flake8-bandit`](https://pypi.org/project/flake8-bandit/) (6/40)
 - [`flake8-comprehensions`](https://pypi.org/project/flake8-comprehensions/)
-- [`flake8-bugbear`](https://pypi.org/project/flake8-bugbear/) (25/32)
+- [`flake8-bugbear`](https://pypi.org/project/flake8-bugbear/) (26/32)
 - [`flake8-2020`](https://pypi.org/project/flake8-2020/)
 
 Ruff can also replace [`isort`](https://pypi.org/project/isort/), [`yesqa`](https://github.com/asottile/yesqa),

flake8_to_ruff/Cargo.lock

@@ -771,7 +771,7 @@ checksum = "0ce7134b9999ecaf8bcd65542e436736ef32ddca1b3e06094cb6ec5755203b80"
 
 [[package]]
 name = "flake8_to_ruff"
-version = "0.0.119"
+version = "0.0.122"
 dependencies = [
  "anyhow",
  "clap",
@@ -1975,7 +1975,7 @@ dependencies = [
 
 [[package]]
 name = "ruff"
-version = "0.0.119"
+version = "0.0.122"
 dependencies = [
  "anyhow",
  "bincode",

flake8_to_ruff/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "flake8-to-ruff"
-version = "0.0.119-dev.0"
+version = "0.0.122-dev.0"
 edition = "2021"
 
 [lib]

resources/test/fixtures/B020.py

@@ -0,0 +1,40 @@
+"""
+Should emit:
+B020 - on lines 8, 21, and 36
+"""
+
+items = [1, 2, 3]
+
+for items in items:
+    print(items)
+
+items = [1, 2, 3]
+
+for item in items:
+    print(item)
+
+values = {"secret": 123}
+
+for key, value in values.items():
+    print(f"{key}, {value}")
+
+for key, values in values.items():
+    print(f"{key}, {values}")
+
+# Variables defined in a comprehension are local in scope
+# to that comprehension and are therefore allowed.
+for var in [var for var in range(10)]:
+    print(var)
+
+for var in (var for var in range(10)):
+    print(var)
+
+for k, v in {k: v for k, v in zip(range(10), range(10, 20))}.items():
+    print(k, v)
+
+# However we still call out reassigning the iterable in the comprehension.
+for vars in [i for i in vars]:
+    print(vars)
+
+for var in sorted(range(10), key=lambda var: var.real):
+    print(var)

resources/test/fixtures/F821_5.py

@@ -0,0 +1,14 @@
+"""Test: inner class annotation."""
+
+
+class RandomClass:
+    def random_func(self) -> "InnerClass":
+        pass
+
+
+class OuterClass:
+    class InnerClass:
+        pass
+
+    def failing_func(self) -> "InnerClass":
+        return self.InnerClass()

resources/test/fixtures/isort/add_newline_before_comments.py

@@ -0,0 +1,7 @@
+import os
+# This is a comment in the same section, so we need to add one newline.
+import sys
+import numpy as np
+# This is a comment, but it starts a new section, so we don't need to add a newline
+# before it.
+import leading_prefix

resources/test/fixtures/isort/comments.py

@@ -0,0 +1,25 @@
+# Comment 1
+# Comment 2
+import D
+
+# Comment 3a
+import C
+
+# Comment 3b
+import C
+
+import B  # Comment 4
+
+# Comment 5
+
+# Comment 6
+from A import (
+    a,  # Comment 7
+    b,
+    c,  # Comment 8
+)
+from A import (
+    a,  # Comment 9
+    b,  # Comment 10
+    c,  # Comment 11
+)

resources/test/fixtures/isort/fit_line_length_comment.py

@@ -0,0 +1,4 @@
+import a
+# Don't take this comment into account when determining whether the next import can fit on one line.
+from b import c
+from d import e  # Do take this comment into account when determining whether the next import can fit on one line.

resources/test/fixtures/isort/preserve_comment_order.py

@@ -0,0 +1,11 @@
+import io
+# Old MacDonald had a farm,
+# EIEIO
+# And on his farm he had a cow,
+# EIEIO
+# With a moo-moo here and a moo-moo there
+# Here a moo, there a moo, everywhere moo-moo
+# Old MacDonald had a farm,
+# EIEIO
+from errno import EIO
+import abc

resources/test/fixtures/isort/type_comments.py

@@ -0,0 +1,2 @@
+import A  # type: ignore
+from B import C  # type: ignore

ruff_dev/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ruff_dev"
-version = "0.0.119"
+version = "0.0.122"
 edition = "2021"
 
 [dependencies]

src/cache.rs

@@ -23,7 +23,7 @@ use crate::autofix::fixer;
 use crate::message::Message;
 use crate::settings::Settings;
 
-const VERSION: &str = env!("CARGO_PKG_VERSION");
+const CARGO_PKG_VERSION: &str = env!("CARGO_PKG_VERSION");
 
 #[derive(Serialize, Deserialize)]
 struct CacheMetadata {
@@ -89,7 +89,7 @@ fn cache_key(path: &Path, settings: &Settings, autofix: &fixer::Mode) -> String
     format!(
         "{}@{}@{}",
         path.absolutize().unwrap().to_string_lossy(),
-        VERSION,
+        CARGO_PKG_VERSION,
         hasher.finish()
     )
 }

src/check_ast.rs

@@ -65,7 +65,7 @@ pub struct Checker<'a> {
     scopes: Vec<Scope<'a>>,
     scope_stack: Vec<usize>,
     dead_scopes: Vec<usize>,
-    deferred_string_annotations: Vec<(Range, &'a str)>,
+    deferred_string_annotations: Vec<(Range, &'a str, Vec<usize>, Vec<usize>)>,
     deferred_annotations: Vec<(&'a Expr, Vec<usize>, Vec<usize>)>,
     deferred_functions: Vec<(&'a Stmt, Vec<usize>, Vec<usize>, VisibleScope)>,
     deferred_lambdas: Vec<(&'a Expr, Vec<usize>, Vec<usize>)>,
@@ -159,7 +159,13 @@ impl<'a> Checker<'a> {
     }
 
     /// Return `true` if the `Expr` is a reference to `typing.${target}`.
-    pub fn match_typing_module(&self, call_path: &[&str], target: &str) -> bool {
+    pub fn match_typing_expr(&self, expr: &Expr, target: &str) -> bool {
+        let call_path = dealias_call_path(collect_call_paths(expr), &self.import_aliases);
+        self.match_typing_call_path(&call_path, target)
+    }
+
+    /// Return `true` if the call path is a reference to `typing.${target}`.
+    pub fn match_typing_call_path(&self, call_path: &[&str], target: &str) -> bool {
         match_call_path(call_path, "typing", target, &self.from_imports)
             || (typing::in_extensions(target)
                 && match_call_path(call_path, "typing_extensions", target, &self.from_imports))
@@ -867,10 +873,15 @@ where
                     flake8_bugbear::plugins::assert_raises_exception(self, stmt, items);
                 }
             }
-            StmtKind::For { target, body, .. } => {
+            StmtKind::For {
+                target, body, iter, ..
+            } => {
                 if self.settings.enabled.contains(&CheckCode::B007) {
                     flake8_bugbear::plugins::unused_loop_control_variable(self, target, body);
                 }
+                if self.settings.enabled.contains(&CheckCode::B020) {
+                    flake8_bugbear::plugins::loop_variable_overrides_iterator(self, target, iter);
+                }
             }
             StmtKind::Try { handlers, .. } => {
                 if self.settings.enabled.contains(&CheckCode::F707) {
@@ -1036,8 +1047,12 @@ where
                 ..
             } = &expr.node
             {
-                self.deferred_string_annotations
-                    .push((Range::from_located(expr), value));
+                self.deferred_string_annotations.push((
+                    Range::from_located(expr),
+                    value,
+                    self.scope_stack.clone(),
+                    self.parent_stack.clone(),
+                ));
             } else {
                 self.deferred_annotations.push((
                     expr,
@@ -1053,12 +1068,12 @@ where
             ExprKind::Subscript { value, slice, .. } => {
                 // Ex) typing.List[...]
                 if self.settings.enabled.contains(&CheckCode::U007)
-                    && self.settings.target_version >= PythonVersion::Py39
+                    && self.settings.target_version >= PythonVersion::Py310
                 {
                     pyupgrade::plugins::use_pep604_annotation(self, expr, value, slice);
                 }
 
-                if self.match_typing_module(&collect_call_paths(value), "Literal") {
+                if self.match_typing_expr(value, "Literal") {
                     self.in_literal = true;
                 }
 
@@ -1563,8 +1578,12 @@ where
                 ..
             } => {
                 if self.in_annotation && !self.in_literal {
-                    self.deferred_string_annotations
-                        .push((Range::from_located(expr), value));
+                    self.deferred_string_annotations.push((
+                        Range::from_located(expr),
+                        value,
+                        self.scope_stack.clone(),
+                        self.parent_stack.clone(),
+                    ));
                 }
                 if self.settings.enabled.contains(&CheckCode::S104) {
                     if let Some(check) = flake8_bandit::plugins::hardcoded_bind_all_interfaces(
@@ -1646,12 +1665,12 @@ where
                 keywords,
             } => {
                 let call_path = dealias_call_path(collect_call_paths(func), &self.import_aliases);
-                if self.match_typing_module(&call_path, "ForwardRef") {
+                if self.match_typing_call_path(&call_path, "ForwardRef") {
                     self.visit_expr(func);
                     for expr in args {
                         self.visit_annotation(expr);
                     }
-                } else if self.match_typing_module(&call_path, "cast") {
+                } else if self.match_typing_call_path(&call_path, "cast") {
                     self.visit_expr(func);
                     if !args.is_empty() {
                         self.visit_annotation(&args[0]);
@@ -1659,12 +1678,12 @@ where
                     for expr in args.iter().skip(1) {
                         self.visit_expr(expr);
                     }
-                } else if self.match_typing_module(&call_path, "NewType") {
+                } else if self.match_typing_call_path(&call_path, "NewType") {
                     self.visit_expr(func);
                     for expr in args.iter().skip(1) {
                         self.visit_annotation(expr);
                     }
-                } else if self.match_typing_module(&call_path, "TypeVar") {
+                } else if self.match_typing_call_path(&call_path, "TypeVar") {
                     self.visit_expr(func);
                     for expr in args.iter().skip(1) {
                         self.visit_annotation(expr);
@@ -1681,7 +1700,7 @@ where
                             }
                         }
                     }
-                } else if self.match_typing_module(&call_path, "NamedTuple") {
+                } else if self.match_typing_call_path(&call_path, "NamedTuple") {
                     self.visit_expr(func);
 
                     // Ex) NamedTuple("a", [("a", int)])
@@ -1713,7 +1732,7 @@ where
                         let KeywordData { value, .. } = &keyword.node;
                         self.visit_annotation(value);
                     }
-                } else if self.match_typing_module(&call_path, "TypedDict") {
+                } else if self.match_typing_call_path(&call_path, "TypedDict") {
                     self.visit_expr(func);
 
                     // Ex) TypedDict("a", {"a": int})
@@ -2122,6 +2141,7 @@ impl<'a> Checker<'a> {
             let mut import_starred = false;
             for scope_index in self.scope_stack.iter().rev() {
                 let scope = &mut self.scopes[*scope_index];
+
                 if matches!(scope.kind, ScopeKind::Class(_)) {
                     if id == "__class__" {
                         return;
@@ -2338,8 +2358,8 @@ impl<'a> Checker<'a> {
 
     fn check_deferred_annotations(&mut self) {
         while let Some((expr, scopes, parents)) = self.deferred_annotations.pop() {
-            self.parent_stack = parents;
             self.scope_stack = scopes;
+            self.parent_stack = parents;
             self.visit_expr(expr);
         }
     }
@@ -2348,10 +2368,14 @@ impl<'a> Checker<'a> {
     where
         'b: 'a,
     {
-        while let Some((range, expression)) = self.deferred_string_annotations.pop() {
+        let mut stacks = vec![];
+        while let Some((range, expression, scopes, parents)) =
+            self.deferred_string_annotations.pop()
+        {
             if let Ok(mut expr) = parser::parse_expression(expression, "<filename>") {
                 relocate_expr(&mut expr, range);
                 allocator.push(expr);
+                stacks.push((scopes, parents));
             } else {
                 if self.settings.enabled.contains(&CheckCode::F722) {
                     self.add_check(Check::new(
@@ -2361,7 +2385,9 @@ impl<'a> Checker<'a> {
                 }
             }
         }
-        for expr in allocator {
+        for (expr, (scopes, parents)) in allocator.iter().zip(stacks) {
+            self.scope_stack = scopes;
+            self.parent_stack = parents;
             self.visit_expr(expr);
         }
     }

src/checks.rs

@@ -95,6 +95,7 @@ pub enum CheckCode {
     B017,
     B018,
     B019,
+    B020,
     B021,
     B022,
     B024,
@@ -399,6 +400,7 @@ pub enum CheckKind {
     NoAssertRaisesException,
     UselessExpression,
     CachedInstanceMethod,
+    LoopVariableOverridesIterator(String),
     FStringDocstring,
     UselessContextlibSuppress,
     AbstractBaseClassWithoutAbstractMethod(String),
@@ -645,6 +647,7 @@ impl CheckCode {
             CheckCode::B017 => CheckKind::NoAssertRaisesException,
             CheckCode::B018 => CheckKind::UselessExpression,
             CheckCode::B019 => CheckKind::CachedInstanceMethod,
+            CheckCode::B020 => CheckKind::LoopVariableOverridesIterator("...".to_string()),
             CheckCode::B021 => CheckKind::FStringDocstring,
             CheckCode::B022 => CheckKind::UselessContextlibSuppress,
             CheckCode::B024 => CheckKind::AbstractBaseClassWithoutAbstractMethod("...".to_string()),
@@ -890,6 +893,7 @@ impl CheckCode {
             CheckCode::B017 => CheckCategory::Flake8Bugbear,
             CheckCode::B018 => CheckCategory::Flake8Bugbear,
             CheckCode::B019 => CheckCategory::Flake8Bugbear,
+            CheckCode::B020 => CheckCategory::Flake8Bugbear,
             CheckCode::B021 => CheckCategory::Flake8Bugbear,
             CheckCode::B022 => CheckCategory::Flake8Bugbear,
             CheckCode::B024 => CheckCategory::Flake8Bugbear,
@@ -1098,6 +1102,7 @@ impl CheckKind {
             CheckKind::NoAssertRaisesException => &CheckCode::B017,
             CheckKind::UselessExpression => &CheckCode::B018,
             CheckKind::CachedInstanceMethod => &CheckCode::B019,
+            CheckKind::LoopVariableOverridesIterator(_) => &CheckCode::B020,
             CheckKind::FStringDocstring => &CheckCode::B021,
             CheckKind::UselessContextlibSuppress => &CheckCode::B022,
             CheckKind::AbstractBaseClassWithoutAbstractMethod(_) => &CheckCode::B024,
@@ -1472,6 +1477,9 @@ impl CheckKind {
             CheckKind::CachedInstanceMethod => "Use of `functools.lru_cache` or `functools.cache` \
                                                 on methods can lead to memory leaks"
                 .to_string(),
+            CheckKind::LoopVariableOverridesIterator(name) => {
+                format!("Loop control variable `{name}` overrides iterable it iterates")
+            }
             CheckKind::FStringDocstring => "f-string used as docstring. This will be interpreted \
                                             by python as a joined string rather than a docstring."
                 .to_string(),

src/checks_gen.rs

@@ -56,6 +56,7 @@ pub enum CheckCodePrefix {
     B018,
     B019,
     B02,
+    B020,
     B021,
     B022,
     B024,
@@ -386,6 +387,7 @@ impl CheckCodePrefix {
                 CheckCode::B017,
                 CheckCode::B018,
                 CheckCode::B019,
+                CheckCode::B020,
                 CheckCode::B021,
                 CheckCode::B022,
                 CheckCode::B024,
@@ -412,6 +414,7 @@ impl CheckCodePrefix {
                 CheckCode::B017,
                 CheckCode::B018,
                 CheckCode::B019,
+                CheckCode::B020,
                 CheckCode::B021,
                 CheckCode::B022,
                 CheckCode::B024,
@@ -460,6 +463,7 @@ impl CheckCodePrefix {
             CheckCodePrefix::B018 => vec![CheckCode::B018],
             CheckCodePrefix::B019 => vec![CheckCode::B019],
             CheckCodePrefix::B02 => vec![
+                CheckCode::B020,
                 CheckCode::B021,
                 CheckCode::B022,
                 CheckCode::B024,
@@ -467,6 +471,7 @@ impl CheckCodePrefix {
                 CheckCode::B026,
                 CheckCode::B027,
             ],
+            CheckCodePrefix::B020 => vec![CheckCode::B020],
             CheckCodePrefix::B021 => vec![CheckCode::B021],
             CheckCodePrefix::B022 => vec![CheckCode::B022],
             CheckCodePrefix::B024 => vec![CheckCode::B024],
@@ -1213,6 +1218,7 @@ impl CheckCodePrefix {
             CheckCodePrefix::B018 => PrefixSpecificity::Explicit,
             CheckCodePrefix::B019 => PrefixSpecificity::Explicit,
             CheckCodePrefix::B02 => PrefixSpecificity::Tens,
+            CheckCodePrefix::B020 => PrefixSpecificity::Explicit,
             CheckCodePrefix::B021 => PrefixSpecificity::Explicit,
             CheckCodePrefix::B022 => PrefixSpecificity::Explicit,
             CheckCodePrefix::B024 => PrefixSpecificity::Explicit,

src/cli.rs

@@ -87,6 +87,10 @@ pub struct Cli {
     /// The minimum Python version that should be supported.
     #[arg(long)]
     pub target_version: Option<PythonVersion>,
+    /// Set the line-length for length-associated checks and automatic
+    /// formatting.
+    #[arg(long)]
+    pub line_length: Option<usize>,
     /// Round-trip auto-formatting.
     // TODO(charlie): This should be a sub-command.
     #[arg(long, hide = true)]
@@ -120,6 +124,8 @@ pub fn extract_log_level(cli: &Cli) -> LogLevel {
         LogLevel::Quiet
     } else if cli.verbose {
         LogLevel::Verbose
+    } else if matches!(cli.format, SerializationFormat::Json) {
+        LogLevel::Quiet
     } else {
         LogLevel::Default
     }

src/flake8_annotations/plugins.rs

@@ -1,6 +1,5 @@
 use rustpython_ast::{Arguments, Constant, Expr, ExprKind, Stmt, StmtKind};
 
-use crate::ast::helpers::collect_call_paths;
 use crate::ast::types::Range;
 use crate::ast::visitor;
 use crate::ast::visitor::Visitor;
@@ -54,7 +53,7 @@ fn check_dynamically_typed<F>(checker: &mut Checker, annotation: &Expr, func: F)
 where
     F: FnOnce() -> String,
 {
-    if checker.match_typing_module(&collect_call_paths(annotation), "Any") {
+    if checker.match_typing_expr(annotation, "Any") {
         checker.add_check(Check::new(
             CheckKind::DynamicallyTypedExpression(func()),
             Range::from_located(annotation),

src/flake8_bugbear/plugins/loop_variable_overrides_iterator.rs

@@ -0,0 +1,64 @@
+use fnv::FnvHashMap;
+use rustpython_ast::{Expr, ExprKind};
+
+use crate::ast::types::Range;
+use crate::ast::visitor;
+use crate::ast::visitor::Visitor;
+use crate::check_ast::Checker;
+use crate::checks::{Check, CheckKind};
+
+#[derive(Default)]
+struct NameFinder<'a> {
+    names: FnvHashMap<&'a str, &'a Expr>,
+}
+
+impl<'a, 'b> Visitor<'b> for NameFinder<'a>
+where
+    'b: 'a,
+{
+    fn visit_expr(&mut self, expr: &'b Expr) {
+        match &expr.node {
+            ExprKind::Name { id, .. } => {
+                self.names.insert(id, expr);
+            }
+            ExprKind::ListComp { generators, .. }
+            | ExprKind::DictComp { generators, .. }
+            | ExprKind::SetComp { generators, .. }
+            | ExprKind::GeneratorExp { generators, .. } => {
+                for comp in generators {
+                    self.visit_expr(&comp.iter);
+                }
+            }
+            ExprKind::Lambda { args, body } => {
+                visitor::walk_expr(self, body);
+                for arg in args.args.iter() {
+                    self.names.remove(arg.node.arg.as_str());
+                }
+            }
+            _ => visitor::walk_expr(self, expr),
+        }
+    }
+}
+
+/// B020
+pub fn loop_variable_overrides_iterator(checker: &mut Checker, target: &Expr, iter: &Expr) {
+    let target_names = {
+        let mut target_finder = NameFinder::default();
+        target_finder.visit_expr(target);
+        target_finder.names
+    };
+    let iter_names = {
+        let mut iter_finder = NameFinder::default();
+        iter_finder.visit_expr(iter);
+        iter_finder.names
+    };
+
+    for (name, expr) in target_names {
+        if iter_names.contains_key(name) {
+            checker.add_check(Check::new(
+                CheckKind::LoopVariableOverridesIterator(name.to_string()),
+                Range::from_located(expr),
+            ));
+        }
+    }
+}

src/flake8_bugbear/plugins/mod.rs

@@ -9,6 +9,7 @@ pub use f_string_docstring::f_string_docstring;
 pub use function_call_argument_default::function_call_argument_default;
 pub use getattr_with_constant::getattr_with_constant;
 pub use jump_statement_in_finally::jump_statement_in_finally;
+pub use loop_variable_overrides_iterator::loop_variable_overrides_iterator;
 pub use mutable_argument_default::mutable_argument_default;
 pub use redundant_tuple_in_exception_handler::redundant_tuple_in_exception_handler;
 pub use setattr_with_constant::setattr_with_constant;
@@ -32,6 +33,7 @@ mod f_string_docstring;
 mod function_call_argument_default;
 mod getattr_with_constant;
 mod jump_statement_in_finally;
+mod loop_variable_overrides_iterator;
 mod mutable_argument_default;
 mod redundant_tuple_in_exception_handler;
 mod setattr_with_constant;

src/isort/comments.rs

@@ -0,0 +1,40 @@
+use std::borrow::Cow;
+
+use rustpython_ast::Location;
+use rustpython_parser::lexer;
+use rustpython_parser::lexer::Tok;
+
+use crate::ast::helpers;
+use crate::ast::types::Range;
+use crate::SourceCodeLocator;
+
+#[derive(Debug)]
+pub struct Comment<'a> {
+    pub value: Cow<'a, str>,
+    pub location: Location,
+    pub end_location: Location,
+}
+
+/// Collect all comments in an import block.
+pub fn collect_comments<'a>(range: &Range, locator: &'a SourceCodeLocator) -> Vec<Comment<'a>> {
+    let contents = locator.slice_source_code_range(range);
+    lexer::make_tokenizer(&contents)
+        .flatten()
+        .filter_map(|(start, tok, end)| {
+            if matches!(tok, Tok::Comment) {
+                let start = helpers::to_absolute(&start, &range.location);
+                let end = helpers::to_absolute(&end, &range.location);
+                Some(Comment {
+                    value: locator.slice_source_code_range(&Range {
+                        location: start,
+                        end_location: end,
+                    }),
+                    location: start,
+                    end_location: end,
+                })
+            } else {
+                None
+            }
+        })
+        .collect()
+}

src/isort/format.rs

@@ -0,0 +1,182 @@
+use crate::isort::types::{AliasData, CommentSet, ImportFromData, Importable};
+
+// Hard-code four-space indentation for the imports themselves, to match Black.
+const INDENT: &str = "    ";
+
+// Guess a capacity to use for string allocation.
+const CAPACITY: usize = 200;
+
+/// Add a plain import statement to the `RopeBuilder`.
+pub fn format_import(alias: &AliasData, comments: &CommentSet, is_first: bool) -> String {
+    let mut output = String::with_capacity(CAPACITY);
+    if !is_first && !comments.atop.is_empty() {
+        output.push('\n');
+    }
+    for comment in &comments.atop {
+        output.push_str(comment);
+        output.push('\n');
+    }
+    if let Some(asname) = alias.asname {
+        output.push_str("import ");
+        output.push_str(alias.name);
+        output.push_str(" as ");
+        output.push_str(asname);
+    } else {
+        output.push_str("import ");
+        output.push_str(alias.name);
+    }
+    for comment in &comments.inline {
+        output.push_str("  ");
+        output.push_str(comment);
+    }
+    output.push('\n');
+    output
+}
+
+/// Add an import-from statement to the `RopeBuilder`.
+pub fn format_import_from(
+    import_from: &ImportFromData,
+    comments: &CommentSet,
+    aliases: &[(AliasData, CommentSet)],
+    line_length: &usize,
+    is_first: bool,
+) -> String {
+    // We can only inline if: (1) none of the aliases have atop comments, and (3)
+    // only the last alias (if any) has inline comments.
+    if aliases
+        .iter()
+        .all(|(_, CommentSet { atop, .. })| atop.is_empty())
+        && aliases
+            .iter()
+            .rev()
+            .skip(1)
+            .all(|(_, CommentSet { inline, .. })| inline.is_empty())
+    {
+        let (single_line, import_length) =
+            format_single_line(import_from, comments, aliases, is_first);
+        if import_length <= *line_length {
+            return single_line;
+        }
+    }
+
+    format_multi_line(import_from, comments, aliases, is_first)
+}
+
+/// Format an import-from statement in single-line format.
+///
+/// This method assumes that the output source code is syntactically valid.
+fn format_single_line(
+    import_from: &ImportFromData,
+    comments: &CommentSet,
+    aliases: &[(AliasData, CommentSet)],
+    is_first: bool,
+) -> (String, usize) {
+    let mut output = String::with_capacity(CAPACITY);
+    let mut line_length = 0;
+
+    if !is_first && !comments.atop.is_empty() {
+        output.push('\n');
+    }
+    for comment in &comments.atop {
+        output.push_str(comment);
+        output.push('\n');
+    }
+
+    let module_name = import_from.module_name();
+    output.push_str("from ");
+    output.push_str(&module_name);
+    output.push_str(" import ");
+    line_length += 5 + module_name.len() + 8;
+
+    for (index, (AliasData { name, asname }, comments)) in aliases.iter().enumerate() {
+        if let Some(asname) = asname {
+            output.push_str(name);
+            output.push_str(" as ");
+            output.push_str(asname);
+            line_length += name.len() + 4 + asname.len();
+        } else {
+            output.push_str(name);
+            line_length += name.len();
+        }
+        if index < aliases.len() - 1 {
+            output.push_str(", ");
+            line_length += 2;
+        }
+
+        for comment in &comments.inline {
+            output.push(' ');
+            output.push(' ');
+            output.push_str(comment);
+            line_length += 2 + comment.len();
+        }
+    }
+
+    for comment in &comments.inline {
+        output.push(' ');
+        output.push(' ');
+        output.push_str(comment);
+        line_length += 2 + comment.len();
+    }
+
+    output.push('\n');
+
+    (output, line_length)
+}
+
+/// Format an import-from statement in multi-line format.
+fn format_multi_line(
+    import_from: &ImportFromData,
+    comments: &CommentSet,
+    aliases: &[(AliasData, CommentSet)],
+    is_first: bool,
+) -> String {
+    let mut output = String::with_capacity(CAPACITY);
+
+    if !is_first && !comments.atop.is_empty() {
+        output.push('\n');
+    }
+    for comment in &comments.atop {
+        output.push_str(comment);
+        output.push('\n');
+    }
+
+    output.push_str("from ");
+    output.push_str(&import_from.module_name());
+    output.push_str(" import ");
+    output.push('(');
+    for comment in &comments.inline {
+        output.push(' ');
+        output.push(' ');
+        output.push_str(comment);
+    }
+    output.push('\n');
+
+    for (AliasData { name, asname }, comments) in aliases {
+        for comment in &comments.atop {
+            output.push_str(INDENT);
+            output.push_str(comment);
+            output.push('\n');
+        }
+        output.push_str(INDENT);
+        if let Some(asname) = asname {
+            output.push_str(name);
+            output.push_str(" as ");
+            output.push_str(asname);
+        } else {
+            output.push_str(name);
+        }
+        output.push(',');
+
+        for comment in &comments.inline {
+            output.push(' ');
+            output.push(' ');
+            output.push_str(comment);
+        }
+        output.push('\n');
+    }
+
+    output.push(')');
+    output.push('\n');
+
+    output
+}

src/isort/mod.rs

@@ -1,64 +1,266 @@
 use std::collections::{BTreeMap, BTreeSet};
 use std::path::PathBuf;
 
-use fnv::FnvHashSet;
+use fnv::FnvHashMap;
 use itertools::Itertools;
 use ropey::RopeBuilder;
 use rustpython_ast::{Stmt, StmtKind};
 
 use crate::isort::categorize::{categorize, ImportType};
+use crate::isort::comments::Comment;
 use crate::isort::sorting::{member_key, module_key};
-use crate::isort::types::{AliasData, ImportBlock, ImportFromData, Importable, OrderedImportBlock};
+use crate::isort::types::{
+    AliasData, CommentSet, ImportBlock, ImportFromData, Importable, OrderedImportBlock,
+};
 
 mod categorize;
+mod comments;
+pub mod format;
 pub mod plugins;
 pub mod settings;
 mod sorting;
 pub mod track;
 mod types;
 
-// Hard-code four-space indentation for the imports themselves, to match Black.
-const INDENT: &str = "    ";
+#[derive(Debug)]
+pub struct AnnotatedAliasData<'a> {
+    pub name: &'a str,
+    pub asname: &'a Option<String>,
+    pub atop: Vec<Comment<'a>>,
+    pub inline: Vec<Comment<'a>>,
+}
+#[derive(Debug)]
+pub enum AnnotatedImport<'a> {
+    Import {
+        names: Vec<AliasData<'a>>,
+        atop: Vec<Comment<'a>>,
+        inline: Vec<Comment<'a>>,
+    },
+    ImportFrom {
+        module: &'a Option<String>,
+        names: Vec<AnnotatedAliasData<'a>>,
+        level: &'a Option<usize>,
+        atop: Vec<Comment<'a>>,
+        inline: Vec<Comment<'a>>,
+    },
+}
 
-fn normalize_imports<'a>(imports: &'a [&'a Stmt]) -> ImportBlock<'a> {
-    let mut block: ImportBlock = Default::default();
+fn annotate_imports<'a>(
+    imports: &'a [&'a Stmt],
+    comments: Vec<Comment<'a>>,
+) -> Vec<AnnotatedImport<'a>> {
+    let mut annotated = vec![];
+    let mut comments_iter = comments.into_iter().peekable();
     for import in imports {
         match &import.node {
             StmtKind::Import { names } => {
-                for name in names {
-                    block.import.insert(AliasData {
-                        name: &name.node.name,
-                        asname: &name.node.asname,
-                    });
+                // Find comments above.
+                let mut atop = vec![];
+                while let Some(comment) =
+                    comments_iter.next_if(|comment| comment.location.row() < import.location.row())
+                {
+                    atop.push(comment);
                 }
+
+                // Find comments inline.
+                let mut inline = vec![];
+                while let Some(comment) = comments_iter.next_if(|comment| {
+                    comment.end_location.row() == import.end_location.unwrap().row()
+                }) {
+                    inline.push(comment);
+                }
+
+                annotated.push(AnnotatedImport::Import {
+                    names: names
+                        .iter()
+                        .map(|alias| AliasData {
+                            name: &alias.node.name,
+                            asname: &alias.node.asname,
+                        })
+                        .collect(),
+                    atop,
+                    inline,
+                });
             }
             StmtKind::ImportFrom {
                 module,
                 names,
                 level,
             } => {
-                for name in names {
-                    if name.node.asname.is_none() {
-                        block
+                // Find comments above.
+                let mut atop = vec![];
+                while let Some(comment) =
+                    comments_iter.next_if(|comment| comment.location.row() < import.location.row())
+                {
+                    atop.push(comment);
+                }
+
+                // Find comments inline.
+                let mut inline = vec![];
+                while let Some(comment) =
+                    comments_iter.next_if(|comment| comment.location.row() == import.location.row())
+                {
+                    inline.push(comment);
+                }
+
+                // Capture names.
+                let mut aliases = vec![];
+                for alias in names {
+                    // Find comments above.
+                    let mut alias_atop = vec![];
+                    while let Some(comment) = comments_iter
+                        .next_if(|comment| comment.location.row() < alias.location.row())
+                    {
+                        alias_atop.push(comment);
+                    }
+
+                    // Find comments inline.
+                    let mut alias_inline = vec![];
+                    while let Some(comment) = comments_iter.next_if(|comment| {
+                        comment.end_location.row() == alias.end_location.unwrap().row()
+                    }) {
+                        alias_inline.push(comment);
+                    }
+
+                    aliases.push(AnnotatedAliasData {
+                        name: &alias.node.name,
+                        asname: &alias.node.asname,
+                        atop: alias_atop,
+                        inline: alias_inline,
+                    })
+                }
+
+                annotated.push(AnnotatedImport::ImportFrom {
+                    module,
+                    names: aliases,
+                    level,
+                    atop,
+                    inline,
+                });
+            }
+            _ => unreachable!("Expected StmtKind::Import | StmtKind::ImportFrom"),
+        }
+    }
+    annotated
+}
+
+fn normalize_imports(imports: Vec<AnnotatedImport>) -> ImportBlock {
+    let mut block: ImportBlock = Default::default();
+    for import in imports {
+        match import {
+            AnnotatedImport::Import {
+                names,
+                atop,
+                inline,
+            } => {
+                // Associate the comments with the first alias (best effort).
+                if let Some(name) = names.first() {
+                    let entry = block
+                        .import
+                        .entry(AliasData {
+                            name: name.name,
+                            asname: name.asname,
+                        })
+                        .or_default();
+                    for comment in atop {
+                        entry.atop.push(comment.value);
+                    }
+                    for comment in inline {
+                        entry.inline.push(comment.value);
+                    }
+                }
+
+                // Create an entry for every alias.
+                for name in &names {
+                    block
+                        .import
+                        .entry(AliasData {
+                            name: name.name,
+                            asname: name.asname,
+                        })
+                        .or_default();
+                }
+            }
+            AnnotatedImport::ImportFrom {
+                module,
+                names,
+                level,
+                atop,
+                inline,
+            } => {
+                // Associate the comments with the first alias (best effort).
+                if let Some(alias) = names.first() {
+                    if alias.asname.is_none() {
+                        let entry = &mut block
                             .import_from
                             .entry(ImportFromData { module, level })
                             .or_default()
-                            .insert(AliasData {
-                                name: &name.node.name,
-                                asname: &name.node.asname,
-                            });
+                            .0;
+                        for comment in atop {
+                            entry.atop.push(comment.value);
+                        }
+                        for comment in inline {
+                            entry.inline.push(comment.value);
+                        }
                     } else {
-                        block.import_from_as.insert((
-                            ImportFromData { module, level },
-                            AliasData {
-                                name: &name.node.name,
-                                asname: &name.node.asname,
-                            },
-                        ));
+                        let entry = &mut block
+                            .import_from_as
+                            .entry((
+                                ImportFromData { module, level },
+                                AliasData {
+                                    name: alias.name,
+                                    asname: alias.asname,
+                                },
+                            ))
+                            .or_default();
+                        for comment in atop {
+                            entry.atop.push(comment.value);
+                        }
+                        for comment in inline {
+                            entry.inline.push(comment.value);
+                        }
+                    }
+                }
+
+                // Create an entry for every alias.
+                for alias in names {
+                    if alias.asname.is_none() {
+                        let entry = block
+                            .import_from
+                            .entry(ImportFromData { module, level })
+                            .or_default()
+                            .1
+                            .entry(AliasData {
+                                name: alias.name,
+                                asname: alias.asname,
+                            })
+                            .or_default();
+                        for comment in alias.atop {
+                            entry.atop.push(comment.value);
+                        }
+                        for comment in alias.inline {
+                            entry.inline.push(comment.value);
+                        }
+                    } else {
+                        let entry = block
+                            .import_from_as
+                            .entry((
+                                ImportFromData { module, level },
+                                AliasData {
+                                    name: alias.name,
+                                    asname: alias.asname,
+                                },
+                            ))
+                            .or_default();
+                        entry
+                            .atop
+                            .extend(alias.atop.into_iter().map(|comment| comment.value));
+                        for comment in alias.inline {
+                            entry.inline.push(comment.value);
+                        }
                     }
                 }
             }
-            _ => unreachable!("Expected StmtKind::Import | StmtKind::ImportFrom"),
         }
     }
     block
@@ -73,7 +275,7 @@ fn categorize_imports<'a>(
 ) -> BTreeMap<ImportType, ImportBlock<'a>> {
     let mut block_by_type: BTreeMap<ImportType, ImportBlock> = Default::default();
     // Categorize `StmtKind::Import`.
-    for alias in block.import {
+    for (alias, comments) in block.import {
         let import_type = categorize(
             &alias.module_base(),
             &None,
@@ -86,7 +288,7 @@ fn categorize_imports<'a>(
             .entry(import_type)
             .or_default()
             .import
-            .insert(alias);
+            .insert(alias, comments);
     }
     // Categorize `StmtKind::ImportFrom` (without re-export).
     for (import_from, aliases) in block.import_from {
@@ -105,7 +307,7 @@ fn categorize_imports<'a>(
             .insert(import_from, aliases);
     }
     // Categorize `StmtKind::ImportFrom` (with re-export).
-    for (import_from, alias) in block.import_from_as {
+    for ((import_from, alias), comments) in block.import_from_as {
         let classification = categorize(
             &import_from.module_base(),
             import_from.level,
@@ -118,7 +320,7 @@ fn categorize_imports<'a>(
             .entry(classification)
             .or_default()
             .import_from_as
-            .insert((import_from, alias));
+            .insert((import_from, alias), comments);
     }
     block_by_type
 }
@@ -131,7 +333,7 @@ fn sort_imports(block: ImportBlock) -> OrderedImportBlock {
         block
             .import
             .into_iter()
-            .sorted_by_cached_key(|alias| module_key(alias.name, alias.asname)),
+            .sorted_by_cached_key(|(alias, _)| module_key(alias.name, alias.asname)),
     );
 
     // Sort `StmtKind::ImportFrom`.
@@ -145,19 +347,37 @@ fn sort_imports(block: ImportBlock) -> OrderedImportBlock {
                 block
                     .import_from_as
                     .into_iter()
-                    .map(|(import_from, alias)| (import_from, FnvHashSet::from_iter([alias]))),
+                    .map(|((import_from, alias), comments)| {
+                        (
+                            import_from,
+                            (
+                                CommentSet {
+                                    atop: comments.atop,
+                                    inline: Default::default(),
+                                },
+                                FnvHashMap::from_iter([(
+                                    alias,
+                                    CommentSet {
+                                        atop: Default::default(),
+                                        inline: comments.inline,
+                                    },
+                                )]),
+                            ),
+                        )
+                    }),
             )
-            .map(|(import_from, aliases)| {
+            .map(|(import_from, (comments, aliases))| {
                 // Within each `StmtKind::ImportFrom`, sort the members.
                 (
                     import_from,
+                    comments,
                     aliases
                         .into_iter()
-                        .sorted_by_cached_key(|alias| member_key(alias.name, alias.asname))
-                        .collect::<Vec<AliasData>>(),
+                        .sorted_by_cached_key(|(alias, _)| member_key(alias.name, alias.asname))
+                        .collect::<Vec<(AliasData, CommentSet)>>(),
                 )
             })
-            .sorted_by_cached_key(|(import_from, aliases)| {
+            .sorted_by_cached_key(|(import_from, _, aliases)| {
                 // Sort each `StmtKind::ImportFrom` by module key, breaking ties based on
                 // members.
                 (
@@ -167,7 +387,7 @@ fn sort_imports(block: ImportBlock) -> OrderedImportBlock {
                         .map(|module| module_key(module, &None)),
                     aliases
                         .first()
-                        .map(|alias| member_key(alias.name, alias.asname)),
+                        .map(|(alias, _)| member_key(alias.name, alias.asname)),
                 )
             }),
     );
@@ -176,15 +396,18 @@ fn sort_imports(block: ImportBlock) -> OrderedImportBlock {
 }
 
 pub fn format_imports(
-    block: Vec<&Stmt>,
+    block: &[&Stmt],
+    comments: Vec<Comment>,
     line_length: &usize,
     src: &[PathBuf],
     known_first_party: &BTreeSet<String>,
     known_third_party: &BTreeSet<String>,
     extra_standard_library: &BTreeSet<String>,
 ) -> String {
+    let block = annotate_imports(block, comments);
+
     // Normalize imports (i.e., deduplicate, aggregate `from` imports).
-    let block = normalize_imports(&block);
+    let block = normalize_imports(block);
 
     // Categorize by type (e.g., first-party vs. third-party).
     let block_by_type = categorize_imports(
@@ -195,81 +418,38 @@ pub fn format_imports(
         extra_standard_library,
     );
 
-    // Generate replacement source code.
     let mut output = RopeBuilder::new();
-    let mut first_block = true;
+
+    // Generate replacement source code.
+    let mut is_first_block = true;
     for import_block in block_by_type.into_values() {
         let import_block = sort_imports(import_block);
 
         // Add a blank line between every section.
-        if !first_block {
+        if !is_first_block {
             output.append("\n");
         } else {
-            first_block = false;
+            is_first_block = false;
         }
 
+        let mut is_first_statement = true;
+
         // Format `StmtKind::Import` statements.
-        for AliasData { name, asname } in import_block.import.iter() {
-            if let Some(asname) = asname {
-                output.append(&format!("import {} as {}\n", name, asname));
-            } else {
-                output.append(&format!("import {}\n", name));
-            }
+        for (alias, comments) in import_block.import.iter() {
+            output.append(&format::format_import(alias, comments, is_first_statement));
+            is_first_statement = false;
         }
 
         // Format `StmtKind::ImportFrom` statements.
-        for (import_from, aliases) in import_block.import_from.iter() {
-            let prelude: String = format!("from {} import ", import_from.module_name());
-            let members: Vec<String> = aliases
-                .iter()
-                .map(|AliasData { name, asname }| {
-                    if let Some(asname) = asname {
-                        format!("{} as {}", name, asname)
-                    } else {
-                        name.to_string()
-                    }
-                })
-                .collect();
-
-            // Can we fit the import on a single line?
-            let expected_len: usize =
-                    // `from base import `
-                    prelude.len()
-                        // `member( as alias)?`
-                        + members.iter().map(|part| part.len()).sum::<usize>()
-                        // `, `
-                        + 2 * (members.len() - 1);
-
-            if expected_len <= *line_length {
-                // `from base import `
-                output.append(&prelude);
-                // `member( as alias)?(, )?`
-                for (index, part) in members.into_iter().enumerate() {
-                    if index > 0 {
-                        output.append(", ");
-                    }
-                    output.append(&part);
-                }
-                // `\n`
-                output.append("\n");
-            } else {
-                // `from base import (\n`
-                output.append(&prelude);
-                output.append("(");
-                output.append("\n");
-
-                // `    member( as alias)?,\n`
-                for part in members {
-                    output.append(INDENT);
-                    output.append(&part);
-                    output.append(",");
-                    output.append("\n");
-                }
-
-                // `)\n`
-                output.append(")");
-                output.append("\n");
-            }
+        for (import_from, comments, aliases) in import_block.import_from.iter() {
+            output.append(&format::format_import_from(
+                import_from,
+                comments,
+                aliases,
+                line_length,
+                is_first_statement,
+            ));
+            is_first_statement = false;
         }
     }
     output.finish().to_string()
@@ -287,13 +467,17 @@ mod tests {
     use crate::linter::test_path;
     use crate::Settings;
 
+    #[test_case(Path::new("add_newline_before_comments.py"))]
     #[test_case(Path::new("combine_import_froms.py"))]
+    #[test_case(Path::new("comments.py"))]
     #[test_case(Path::new("deduplicate_imports.py"))]
     #[test_case(Path::new("fit_line_length.py"))]
+    #[test_case(Path::new("fit_line_length_comment.py"))]
     #[test_case(Path::new("import_from_after_import.py"))]
     #[test_case(Path::new("leading_prefix.py"))]
     #[test_case(Path::new("no_reorder_within_section.py"))]
     #[test_case(Path::new("order_by_type.py"))]
+    #[test_case(Path::new("preserve_comment_order.py"))]
     #[test_case(Path::new("preserve_indentation.py"))]
     #[test_case(Path::new("reorder_within_section.py"))]
     #[test_case(Path::new("separate_first_party_imports.py"))]
@@ -303,6 +487,7 @@ mod tests {
     #[test_case(Path::new("skip.py"))]
     #[test_case(Path::new("sort_similar_imports.py"))]
     #[test_case(Path::new("trailing_suffix.py"))]
+    #[test_case(Path::new("type_comments.py"))]
     fn isort(path: &Path) -> Result<()> {
         let snapshot = format!("{}", path.to_string_lossy());
         let mut checks = test_path(

src/isort/plugins.rs

@@ -5,7 +5,7 @@ use crate::ast::types::Range;
 use crate::autofix::{fixer, Fix};
 use crate::checks::CheckKind;
 use crate::docstrings::helpers::leading_space;
-use crate::isort::format_imports;
+use crate::isort::{comments, format_imports};
 use crate::{Check, Settings, SourceCodeLocator};
 
 fn extract_range(body: &[&Stmt]) -> Range {
@@ -44,7 +44,15 @@ fn match_trailing_content(body: &[&Stmt], locator: &SourceCodeLocator) -> bool {
         end_location: Location::new(end_location.row() + 1, 0),
     };
     let suffix = locator.slice_source_code_range(&range);
-    suffix.chars().any(|char| !char.is_whitespace())
+    for char in suffix.chars() {
+        if char == '#' {
+            return false;
+        }
+        if !char.is_whitespace() {
+            return true;
+        }
+    }
+    false
 }
 
 /// I001
@@ -57,13 +65,23 @@ pub fn check_imports(
     let range = extract_range(&body);
     let indentation = extract_indentation(&body, locator);
 
+    // Extract comments. Take care to grab any inline comments from the last line.
+    let comments = comments::collect_comments(
+        &Range {
+            location: range.location,
+            end_location: Location::new(range.end_location.row() + 1, 0),
+        },
+        locator,
+    );
+
     // Special-cases: there's leading or trailing content in the import block.
     let has_leading_content = match_leading_content(&body, locator);
     let has_trailing_content = match_trailing_content(&body, locator);
 
     // Generate the sorted import block.
     let expected = format_imports(
-        body,
+        &body,
+        comments,
         &(settings.line_length - indentation.len()),
         &settings.src,
         &settings.isort.known_first_party,

src/isort/snapshots/ruff__isort__tests__add_newline_before_comments.py.snap

@@ -0,0 +1,22 @@
+---
+source: src/isort/mod.rs
+expression: checks
+---
+- kind: UnsortedImports
+  location:
+    row: 1
+    column: 0
+  end_location:
+    row: 8
+    column: 0
+  fix:
+    patch:
+      content: "import os\n\n# This is a comment in the same section, so we need to add one newline.\nimport sys\n\nimport numpy as np\n\n# This is a comment, but it starts a new section, so we don't need to add a newline\n# before it.\nimport leading_prefix\n"
+      location:
+        row: 1
+        column: 0
+      end_location:
+        row: 8
+        column: 0
+    applied: false
+

src/isort/snapshots/ruff__isort__tests__comments.py.snap

@@ -0,0 +1,22 @@
+---
+source: src/isort/mod.rs
+expression: checks
+---
+- kind: UnsortedImports
+  location:
+    row: 3
+    column: 0
+  end_location:
+    row: 26
+    column: 0
+  fix:
+    patch:
+      content: "import B  # Comment 4\n\n# Comment 3a\n# Comment 3b\nimport C\nimport D\n\n# Comment 5\n# Comment 6\nfrom A import (\n    a,  # Comment 7  # Comment 9\n    b,  # Comment 10\n    c,  # Comment 8  # Comment 11\n)\n"
+      location:
+        row: 3
+        column: 0
+      end_location:
+        row: 26
+        column: 0
+    applied: false
+

src/isort/snapshots/ruff__isort__tests__fit_line_length_comment.py.snap

@@ -0,0 +1,22 @@
+---
+source: src/isort/mod.rs
+expression: checks
+---
+- kind: UnsortedImports
+  location:
+    row: 1
+    column: 0
+  end_location:
+    row: 5
+    column: 0
+  fix:
+    patch:
+      content: "import a\n\n# Don't take this comment into account when determining whether the next import can fit on one line.\nfrom b import c\nfrom d import (  # Do take this comment into account when determining whether the next import can fit on one line.\n    e,\n)\n"
+      location:
+        row: 1
+        column: 0
+      end_location:
+        row: 5
+        column: 0
+    applied: false
+

src/isort/snapshots/ruff__isort__tests__preserve_comment_order.py.snap

@@ -0,0 +1,22 @@
+---
+source: src/isort/mod.rs
+expression: checks
+---
+- kind: UnsortedImports
+  location:
+    row: 1
+    column: 0
+  end_location:
+    row: 12
+    column: 0
+  fix:
+    patch:
+      content: "import abc\nimport io\n\n# Old MacDonald had a farm,\n# EIEIO\n# And on his farm he had a cow,\n# EIEIO\n# With a moo-moo here and a moo-moo there\n# Here a moo, there a moo, everywhere moo-moo\n# Old MacDonald had a farm,\n# EIEIO\nfrom errno import EIO\n"
+      location:
+        row: 1
+        column: 0
+      end_location:
+        row: 12
+        column: 0
+    applied: false
+

src/isort/snapshots/ruff__isort__tests__type_comments.py.snap

@@ -0,0 +1,6 @@
+---
+source: src/isort/mod.rs
+expression: checks
+---
+[]
+

src/isort/types.rs

@@ -1,4 +1,6 @@
-use fnv::{FnvHashMap, FnvHashSet};
+use std::borrow::Cow;
+
+use fnv::FnvHashMap;
 
 #[derive(Debug, Hash, Ord, PartialOrd, Eq, PartialEq)]
 pub struct ImportFromData<'a> {
@@ -12,6 +14,12 @@ pub struct AliasData<'a> {
     pub asname: &'a Option<String>,
 }
 
+#[derive(Debug, Default)]
+pub struct CommentSet<'a> {
+    pub atop: Vec<Cow<'a, str>>,
+    pub inline: Vec<Cow<'a, str>>,
+}
+
 pub trait Importable {
     fn module_name(&self) -> String;
     fn module_base(&self) -> String;
@@ -50,17 +58,24 @@ impl Importable for ImportFromData<'_> {
 pub struct ImportBlock<'a> {
     // Set of (name, asname), used to track regular imports.
     // Ex) `import module`
-    pub import: FnvHashSet<AliasData<'a>>,
+    pub import: FnvHashMap<AliasData<'a>, CommentSet<'a>>,
     // Map from (module, level) to `AliasData`, used to track 'from' imports.
     // Ex) `from module import member`
-    pub import_from: FnvHashMap<ImportFromData<'a>, FnvHashSet<AliasData<'a>>>,
+    pub import_from:
+        FnvHashMap<ImportFromData<'a>, (CommentSet<'a>, FnvHashMap<AliasData<'a>, CommentSet<'a>>)>,
     // Set of (module, level, name, asname), used to track re-exported 'from' imports.
     // Ex) `from module import member as member`
-    pub import_from_as: FnvHashSet<(ImportFromData<'a>, AliasData<'a>)>,
+    pub import_from_as: FnvHashMap<(ImportFromData<'a>, AliasData<'a>), CommentSet<'a>>,
 }
 
+type AliasDataWithComments<'a> = (AliasData<'a>, CommentSet<'a>);
+
 #[derive(Debug, Default)]
 pub struct OrderedImportBlock<'a> {
-    pub import: Vec<AliasData<'a>>,
-    pub import_from: Vec<(ImportFromData<'a>, Vec<AliasData<'a>>)>,
+    pub import: Vec<AliasDataWithComments<'a>>,
+    pub import_from: Vec<(
+        ImportFromData<'a>,
+        CommentSet<'a>,
+        Vec<AliasDataWithComments<'a>>,
+    )>,
 }

src/lib.rs

@@ -52,6 +52,8 @@ mod pyupgrade;
 mod rules;
 pub mod settings;
 pub mod source_code_locator;
+#[cfg(feature = "update-informer")]
+pub mod updates;
 pub mod visibility;
 
 /// Run Ruff over Python source code directly.

src/linter.rs

@@ -344,6 +344,7 @@ mod tests {
     #[test_case(CheckCode::B017, Path::new("B017.py"); "B017")]
     #[test_case(CheckCode::B018, Path::new("B018.py"); "B018")]
     #[test_case(CheckCode::B019, Path::new("B019.py"); "B019")]
+    #[test_case(CheckCode::B020, Path::new("B020.py"); "B020")]
     #[test_case(CheckCode::B021, Path::new("B021.py"); "B021")]
     #[test_case(CheckCode::B022, Path::new("B022.py"); "B022")]
     #[test_case(CheckCode::B024, Path::new("B024.py"); "B024")]
@@ -456,6 +457,7 @@ mod tests {
     #[test_case(CheckCode::F821, Path::new("F821_2.py"); "F821_2")]
     #[test_case(CheckCode::F821, Path::new("F821_3.py"); "F821_3")]
     #[test_case(CheckCode::F821, Path::new("F821_4.py"); "F821_4")]
+    #[test_case(CheckCode::F821, Path::new("F821_5.py"); "F821_5")]
     #[test_case(CheckCode::F822, Path::new("F822.py"); "F822")]
     #[test_case(CheckCode::F823, Path::new("F823.py"); "F823")]
     #[test_case(CheckCode::F831, Path::new("F831.py"); "F831")]

src/main.rs

@@ -17,6 +17,8 @@ use ::ruff::settings::configuration::Configuration;
 use ::ruff::settings::types::FilePattern;
 use ::ruff::settings::user::UserConfiguration;
 use ::ruff::settings::{pyproject, Settings};
+#[cfg(feature = "update-informer")]
+use ::ruff::updates;
 use anyhow::Result;
 use clap::Parser;
 use colored::Colorize;
@@ -26,11 +28,6 @@ use notify::{raw_watcher, RecursiveMode, Watcher};
 use rayon::prelude::*;
 use walkdir::DirEntry;
 
-#[cfg(feature = "update-informer")]
-const CARGO_PKG_NAME: &str = env!("CARGO_PKG_NAME");
-#[cfg(feature = "update-informer")]
-const CARGO_PKG_VERSION: &str = env!("CARGO_PKG_VERSION");
-
 /// Shim that calls par_iter except for wasm because there's no wasm support in
 /// rayon yet (there is a shim to be used for the web, but it requires js
 /// cooperation) Unfortunately, ParallelIterator does not implement Iterator so
@@ -45,30 +42,6 @@ fn par_iter<T: Sync>(iterable: &Vec<T>) -> impl Iterator<Item = &T> {
     iterable.iter()
 }
 
-#[cfg(feature = "update-informer")]
-fn check_for_updates() {
-    use update_informer::{registry, Check};
-
-    let informer = update_informer::new(registry::PyPI, CARGO_PKG_NAME, CARGO_PKG_VERSION);
-
-    if let Some(new_version) = informer.check_version().ok().flatten() {
-        let msg = format!(
-            "A new version of {pkg_name} is available: v{pkg_version} -> {new_version}",
-            pkg_name = CARGO_PKG_NAME.italic().cyan(),
-            pkg_version = CARGO_PKG_VERSION,
-            new_version = new_version.to_string().green()
-        );
-
-        let cmd = format!(
-            "Run to update: {cmd} {pkg_name}",
-            cmd = "pip3 install --upgrade".green(),
-            pkg_name = CARGO_PKG_NAME.green()
-        );
-
-        println!("\n{msg}\n{cmd}");
-    }
-}
-
 fn show_settings(
     configuration: Configuration,
     project_root: Option<PathBuf>,
@@ -292,6 +265,9 @@ fn inner_main() -> Result<ExitCode> {
     if !cli.extend_ignore.is_empty() {
         configuration.extend_ignore = cli.extend_ignore;
     }
+    if let Some(line_length) = cli.line_length {
+        configuration.line_length = line_length;
+    }
     if let Some(target_version) = cli.target_version {
         configuration.target_version = target_version;
     }
@@ -402,8 +378,8 @@ fn inner_main() -> Result<ExitCode> {
 
         // Check for updates if we're in a non-silent log level.
         #[cfg(feature = "update-informer")]
-        if !is_stdin && log_level >= LogLevel::Default {
-            check_for_updates();
+        if !is_stdin && log_level >= LogLevel::Default && atty::is(atty::Stream::Stdout) {
+            let _ = updates::check_for_updates();
         }
 
         if messages.iter().any(|message| !message.fixed) && !cli.exit_zero {

src/pyupgrade/plugins/use_pep604_annotation.rs

@@ -1,6 +1,6 @@
 use rustpython_ast::{Constant, Expr, ExprKind, Operator};
 
-use crate::ast::helpers::collect_call_paths;
+use crate::ast::helpers::{collect_call_paths, dealias_call_path};
 use crate::ast::types::Range;
 use crate::autofix::Fix;
 use crate::check_ast::Checker;
@@ -44,8 +44,8 @@ fn union(elts: &[Expr]) -> Expr {
 
 /// U007
 pub fn use_pep604_annotation(checker: &mut Checker, expr: &Expr, value: &Expr, slice: &Expr) {
-    let call_path = collect_call_paths(value);
-    if checker.match_typing_module(&call_path, "Optional") {
+    let call_path = dealias_call_path(collect_call_paths(value), &checker.import_aliases);
+    if checker.match_typing_call_path(&call_path, "Optional") {
         let mut check = Check::new(CheckKind::UsePEP604Annotation, Range::from_located(expr));
         if checker.patch() {
             let mut generator = SourceGenerator::new();
@@ -60,7 +60,7 @@ pub fn use_pep604_annotation(checker: &mut Checker, expr: &Expr, value: &Expr, s
             }
         }
         checker.add_check(check);
-    } else if checker.match_typing_module(&call_path, "Union") {
+    } else if checker.match_typing_call_path(&call_path, "Union") {
         let mut check = Check::new(CheckKind::UsePEP604Annotation, Range::from_located(expr));
         if checker.patch() {
             match &slice.node {

src/snapshots/ruff__linter__tests__B020_B020.py.snap

@@ -0,0 +1,32 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    LoopVariableOverridesIterator: items
+  location:
+    row: 8
+    column: 4
+  end_location:
+    row: 8
+    column: 9
+  fix: ~
+- kind:
+    LoopVariableOverridesIterator: values
+  location:
+    row: 21
+    column: 9
+  end_location:
+    row: 21
+    column: 15
+  fix: ~
+- kind:
+    LoopVariableOverridesIterator: vars
+  location:
+    row: 36
+    column: 4
+  end_location:
+    row: 36
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__F821_F821_5.py.snap

@@ -0,0 +1,14 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    UndefinedName: InnerClass
+  location:
+    row: 5
+    column: 29
+  end_location:
+    row: 5
+    column: 41
+  fix: ~
+

src/updates.rs

@@ -0,0 +1,75 @@
+use std::fs::{create_dir_all, read_to_string, File};
+use std::io::Write;
+use std::path::{Path, PathBuf};
+
+use anyhow::Result;
+use colored::Colorize;
+
+const CARGO_PKG_NAME: &str = env!("CARGO_PKG_NAME");
+const CARGO_PKG_VERSION: &str = env!("CARGO_PKG_VERSION");
+
+fn cache_dir() -> &'static str {
+    "./.ruff_cache"
+}
+
+fn file_path() -> PathBuf {
+    Path::new(cache_dir()).join(".update-informer")
+}
+
+/// Get the "latest" version for which the user has been informed.
+fn get_latest() -> Result<Option<String>> {
+    let path = file_path();
+    if path.exists() {
+        Ok(Some(read_to_string(path)?.trim().to_string()))
+    } else {
+        Ok(None)
+    }
+}
+
+/// Set the "latest" version for which the user has been informed.
+fn set_latest(version: &str) -> Result<()> {
+    create_dir_all(cache_dir())?;
+    let path = file_path();
+    let mut file = File::create(path)?;
+    file.write_all(version.trim().as_bytes())
+        .map_err(|e| e.into())
+}
+
+/// Update the user if a newer version is available.
+pub fn check_for_updates() -> Result<()> {
+    use update_informer::{registry, Check};
+
+    let informer = update_informer::new(registry::PyPI, CARGO_PKG_NAME, CARGO_PKG_VERSION);
+
+    if let Some(new_version) = informer
+        .check_version()
+        .ok()
+        .flatten()
+        .map(|version| version.to_string())
+    {
+        // If we've already notified the user about this version, return early.
+        if let Some(latest_version) = get_latest()? {
+            if latest_version == new_version {
+                return Ok(());
+            }
+        }
+        set_latest(&new_version)?;
+
+        let msg = format!(
+            "A new version of {pkg_name} is available: v{pkg_version} -> {new_version}",
+            pkg_name = CARGO_PKG_NAME.italic().cyan(),
+            pkg_version = CARGO_PKG_VERSION,
+            new_version = new_version.green()
+        );
+
+        let cmd = format!(
+            "Run to update: {cmd} {pkg_name}",
+            cmd = "pip3 install --upgrade".green(),
+            pkg_name = CARGO_PKG_NAME.green()
+        );
+
+        println!("\n{msg}\n{cmd}");
+    }
+
+    Ok(())
+}