Bump version to 0.0.71

Cargo.lock

@@ -64,6 +64,20 @@ dependencies = [
  "term",
 ]
 
+[[package]]
+name = "assert_cmd"
+version = "2.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93ae1ddd39efd67689deb1979d80bad3bf7f2b09c6e6117c8d1f2443b5e2f83e"
+dependencies = [
+ "bstr",
+ "doc-comment",
+ "predicates",
+ "predicates-core",
+ "predicates-tree",
+ "wait-timeout",
+]
+
 [[package]]
 name = "async-channel"
 version = "1.7.1"
@@ -580,6 +594,12 @@ version = "0.1.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "56254986775e3233ffa9c4d7d3faaf6d36a2c09d30b20687e9f88bc8bafc16c8"
 
+[[package]]
+name = "difflib"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6184e33543162437515c2e2b48714794e37845ec9851711914eec9d308f6ebe8"
+
 [[package]]
 name = "digest"
 version = "0.8.1"
@@ -658,6 +678,12 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
+[[package]]
+name = "doc-comment"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fea41bba32d969b513997752735605054bc0dfa92b4c56bf1189f2e174be7a10"
+
 [[package]]
 name = "either"
 version = "1.8.0"
@@ -1089,6 +1115,12 @@ version = "1.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6c8af84674fe1f223a982c933a0ee1086ac4d4052aa0fb8060c12c6ad838e754"
 
+[[package]]
+name = "joinery"
+version = "2.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72167d68f5fce3b8655487b8038691a3c9984ee769590f93f2a631f4ad64e4f5"
+
 [[package]]
 name = "js-sys"
 version = "0.3.60"
@@ -1685,6 +1717,33 @@ version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "925383efa346730478fb4838dbe9137d2a47675ad789c546d150a6e1dd4ab31c"
 
+[[package]]
+name = "predicates"
+version = "2.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a5aab5be6e4732b473071984b3164dbbfb7a3674d30ea5ff44410b6bcd960c3c"
+dependencies = [
+ "difflib",
+ "itertools",
+ "predicates-core",
+]
+
+[[package]]
+name = "predicates-core"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "da1c2388b1513e1b605fcec39a95e0a9e8ef088f71443ef37099fa9ae6673fcb"
+
+[[package]]
+name = "predicates-tree"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4d86de6de25020a36c6d3643a86d9a6a9f552107c0559c60ea03551b5e16c032"
+dependencies = [
+ "predicates-core",
+ "termtree",
+]
+
 [[package]]
 name = "proc-macro-error"
 version = "1.0.4"
@@ -1907,9 +1966,10 @@ dependencies = [
 
 [[package]]
 name = "ruff"
-version = "0.0.65"
+version = "0.0.71"
 dependencies = [
  "anyhow",
+ "assert_cmd",
  "bincode",
  "cacache",
  "chrono",
@@ -1938,6 +1998,7 @@ dependencies = [
  "serde_json",
  "strum",
  "strum_macros",
+ "titlecase",
  "toml",
  "update-informer",
  "walkdir",
@@ -2345,6 +2406,12 @@ dependencies = [
  "phf_codegen 0.8.0",
 ]
 
+[[package]]
+name = "termtree"
+version = "0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "507e9898683b6c43a9aa55b64259b721b52ba226e0f3779137e50ad114a4c90b"
+
 [[package]]
 name = "thiserror"
 version = "1.0.37"
@@ -2400,6 +2467,17 @@ version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cda74da7e1a664f795bb1f8a87ec406fb89a02522cf6e50620d016add6dbbf5c"
 
+[[package]]
+name = "titlecase"
+version = "2.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "38397a8cdb017cfeb48bf6c154d6de975ac69ffeed35980fde199d2ee0842042"
+dependencies = [
+ "joinery",
+ "lazy_static",
+ "regex",
+]
+
 [[package]]
 name = "toml"
 version = "0.5.9"
@@ -2593,6 +2671,15 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f8e76fae08f03f96e166d2dfda232190638c10e0383841252416f9cfe2ae60e6"
 
+[[package]]
+name = "wait-timeout"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9f200f5b12eb75f8c1ed65abd4b2db8a6e1b138a20de009dacee265a2498f3f6"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "waker-fn"
 version = "1.1.0"

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ruff"
-version = "0.0.65"
+version = "0.0.71"
 edition = "2021"
 
 [lib]
@@ -38,8 +38,10 @@ walkdir = { version = "2.3.2" }
 strum = { version = "0.24.1", features = ["strum_macros"] }
 strum_macros = "0.24.3"
 num-bigint = "0.4.3"
+titlecase = "2.2.1"
 
 [dev-dependencies]
+assert_cmd = "2.0.4"
 insta = { version = "1.19.1", features = ["yaml"] }
 
 [features]

README.md

@@ -57,7 +57,7 @@ ruff also works with [pre-commit](https://pre-commit.com):
 ```yaml
 repos:
   - repo: https://github.com/charliermarsh/ruff-pre-commit
-    rev: v0.0.48
+    rev: v0.0.71
     hooks:
       - id: lint
 ```
@@ -215,8 +215,10 @@ ruff also implements some of the most popular Flake8 plugins natively, including
 - [`flake8-builtins`](https://pypi.org/project/flake8-builtins/)
 - [`flake8-super`](https://pypi.org/project/flake8-super/)
 - [`flake8-print`](https://pypi.org/project/flake8-print/)
-- [`flake8-comprehensions`](https://pypi.org/project/flake8-comprehensions/) (partial)
-- [`pyupgrade`](https://pypi.org/project/pyupgrade/) (partial)
+- [`flake8-comprehensions`](https://pypi.org/project/flake8-comprehensions/) (12/16)
+- [`flake8-bugbear`](https://pypi.org/project/flake8-bugbear/) (3/32)
+- [`flake8-docstrings`](https://pypi.org/project/flake8-docstrings/) (37/48)
+- [`pyupgrade`](https://pypi.org/project/pyupgrade/) (8/34)
 
 Beyond rule-set parity, ruff suffers from the following limitations vis-à-vis Flake8:
 
@@ -278,6 +280,9 @@ The 🛠 emoji indicates that a rule is automatically fixable by the `--fix` com
 | A001 | BuiltinVariableShadowing | Variable `...` is shadowing a python builtin |  |  |
 | A002 | BuiltinArgumentShadowing | Argument `...` is shadowing a python builtin |  |  |
 | A003 | BuiltinAttributeShadowing | Class attribute `...` is shadowing a python builtin |  |  |
+| B011 | DoNotAssertFalse | Do not `assert False` (`python -O` removes these calls), raise `AssertionError()` |  | 🛠 |
+| B014 | DuplicateHandlerException | Exception handler with duplicate exception: `ValueError` |  | 🛠 |
+| B025 | DuplicateTryBlockException | try-except block with duplicate exception `Exception` |  |  |
 | C400 | UnnecessaryGeneratorList | Unnecessary generator - rewrite as a list comprehension |  |  |
 | C401 | UnnecessaryGeneratorSet | Unnecessary generator - rewrite as a set comprehension |  |  |
 | C402 | UnnecessaryGeneratorDict | Unnecessary generator - rewrite as a dict comprehension |  |  |
@@ -286,6 +291,9 @@ The 🛠 emoji indicates that a rule is automatically fixable by the `--fix` com
 | C405 | UnnecessaryLiteralSet | Unnecessary <list/tuple> literal - rewrite as a set literal |  |  |
 | C406 | UnnecessaryLiteralDict | Unnecessary <list/tuple> literal - rewrite as a dict literal |  |  |
 | C408 | UnnecessaryCollectionCall | Unnecessary <dict/list/tuple> call - rewrite as a literal |  |  |
+| C409 | UnnecessaryLiteralWithinTupleCall | Unnecessary <list/tuple> literal passed to tuple() - remove the outer call to tuple() |  |  |
+| C410 | UnnecessaryLiteralWithinListCall | Unnecessary <list/tuple> literal passed to list() - rewrite as a list literal |  |  |
+| C414 | UnnecessaryDoubleCastOrProcess | Unnecessary <list/reversed/set/sorted/tuple> call within <list/set/sorted/tuple>(). |  |  |
 | C415 | UnnecessarySubscriptReversal | Unnecessary subscript reversal of iterable within <reversed/set/sorted>() |  |  |
 | T201 | PrintFound | `print` found |  | 🛠 |
 | T203 | PPrintFound | `pprint` found |  | 🛠 |
@@ -293,10 +301,47 @@ The 🛠 emoji indicates that a rule is automatically fixable by the `--fix` com
 | U002 | UnnecessaryAbspath | `abspath(__file__)` is unnecessary in Python 3.9 and later |  | 🛠 |
 | U003 | TypeOfPrimitive | Use `str` instead of `type(...)` |  | 🛠 |
 | U004 | UselessObjectInheritance | Class `...` inherits from object |  | 🛠 |
-| U005 | NoAssertEquals | `assertEquals` is deprecated, use `assertEqual` instead |  | 🛠 |
+| U005 | DeprecatedUnittestAlias | `assertEquals` is deprecated, use `assertEqual` instead |  | 🛠 |
 | U006 | UsePEP585Annotation | Use `list` instead of `List` for type annotations |  | 🛠 |
 | U007 | UsePEP604Annotation | Use `X \| Y` for type annotations |  | 🛠 |
 | U008 | SuperCallWithParameters | Use `super()` instead of `super(__class__, self)` |  | 🛠 |
+| D100 | PublicModule | Missing docstring in public module |  |  |
+| D101 | PublicClass | Missing docstring in public class |  |  |
+| D102 | PublicMethod | Missing docstring in public method |  |  |
+| D103 | PublicFunction | Missing docstring in public function |  |  |
+| D104 | PublicPackage | Missing docstring in public package |  |  |
+| D105 | MagicMethod | Missing docstring in magic method |  |  |
+| D106 | PublicNestedClass | Missing docstring in public nested class |  |  |
+| D107 | PublicInit | Missing docstring in __init__ |  |  |
+| D200 | FitsOnOneLine | One-line docstring should fit on one line |  |  |
+| D205 | NoBlankLineAfterSummary | 1 blank line required between summary line and description |  |  |
+| D209 | NewLineAfterLastParagraph | Multi-line docstring closing quotes should be on a separate line |  |  |
+| D210 | NoSurroundingWhitespace | No whitespaces allowed surrounding docstring text |  |  |
+| D212 | MultiLineSummaryFirstLine | Multi-line docstring summary should start at the first line |  |  |
+| D213 | MultiLineSummarySecondLine | Multi-line docstring summary should start at the second line |  |  |
+| D300 | UsesTripleQuotes | Use """triple double quotes""" |  |  |
+| D400 | EndsInPeriod | First line should end with a period |  |  |
+| D402 | NoSignature | First line should not be the function's 'signature' |  |  |
+| D403 | FirstLineCapitalized | First word of the first line should be properly capitalized |  |  |
+| D404 | NoThisPrefix | First word of the docstring should not be `This` |  |  |
+| D415 | EndsInPunctuation | First line should end with a period, question mark, or exclamation point |  |  |
+| D418 | SkipDocstring | Function decorated with @overload shouldn't contain a docstring |  |  |
+| D419 | NonEmpty | Docstring is empty |  |  |
+| D201 | NoBlankLineBeforeFunction | No blank lines allowed before function docstring (found 1) |  |  |
+| D202 | NoBlankLineAfterFunction | No blank lines allowed after function docstring (found 1) |  |  |
+| D211 | NoBlankLineBeforeClass | No blank lines allowed before class docstring |  |  |
+| D203 | OneBlankLineBeforeClass | 1 blank line required before class docstring |  |  |
+| D204 | OneBlankLineAfterClass | 1 blank line required after class docstring |  |  |
+| D405 | CapitalizeSectionName | Section name should be properly capitalized ("returns") |  |  |
+| D413 | BlankLineAfterLastSection | Missing blank line after last section ("Returns") |  |  |
+| D410 | BlankLineAfterSection | Missing blank line after section ("Returns") |  |  |
+| D411 | BlankLineBeforeSection | Missing blank line before section ("Returns") |  |  |
+| D406 | NewLineAfterSectionName | Section name should end with a newline ("Returns") |  |  |
+| D407 | DashedUnderlineAfterSection | Missing dashed underline after section ("Returns") |  |  |
+| D408 | SectionUnderlineAfterName | Section underline should be in the line following the section's name ("Returns") |  |  |
+| D409 | SectionUnderlineMatchesSectionLength | Section underline should match the length of its name ("Returns") |  |  |
+| D412 | NoBlankLinesBetweenHeaderAndContent | No blank lines allowed between a section header and its content ("Returns") |  |  |
+| D414 | NonEmptySection | Section has no content ("Returns") |  |  |
 | M001 | UnusedNOQA | Unused `noqa` directive |  | 🛠 |
 
 ## Integrations

resources/test/fixtures/B011.py

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

resources/test/fixtures/B014.py

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

resources/test/fixtures/B025.py

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

resources/test/fixtures/C409.py

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

resources/test/fixtures/C410.py

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

resources/test/fixtures/C414.py

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

resources/test/fixtures/D.py

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

resources/test/fixtures/F404.py

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

resources/test/fixtures/F821.py

@@ -122,3 +122,12 @@ class PEP593Test:
         dict["foo", "bar"],  # Expected to fail as undefined.
         123,
     ]
+
+
+def in_ipython_notebook() -> bool:
+    try:
+        # autoimported by notebooks
+        get_ipython()  # type: ignore[name-defined]
+    except NameError:
+        return False  # not in notebook
+    return True

resources/test/fixtures/M001.py

@@ -15,6 +15,9 @@ def f() -> None:
     # Invalid
     d = 1  # noqa: F841, E501
 
+    # Invalid (and unimplemented)
+    d = 1  # noqa: F841, W191
+
 
 # Valid
 _ = """Lorem ipsum dolor sit amet.

resources/test/fixtures/sections.py

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

setup.py

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

src/ast.rs

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

src/ast/checkers.rs

@@ -9,6 +9,7 @@ use rustpython_parser::ast::{
 };
 use serde::{Deserialize, Serialize};
 
+use crate::ast::helpers;
 use crate::ast::types::{
     Binding, BindingKind, CheckLocator, FunctionScope, Range, Scope, ScopeKind,
 };
@@ -16,7 +17,7 @@ use crate::checks::{Check, CheckKind, RejectedCmpop};
 use crate::python::builtins::BUILTINS;
 
 /// Check IfTuple compliance.
-pub fn check_if_tuple(test: &Expr, location: Range) -> Option<Check> {
+pub fn if_tuple(test: &Expr, location: Range) -> Option<Check> {
     if let ExprKind::Tuple { elts, .. } = &test.node {
         if !elts.is_empty() {
             return Some(Check::new(CheckKind::IfTuple, location));
@@ -26,7 +27,7 @@ pub fn check_if_tuple(test: &Expr, location: Range) -> Option<Check> {
 }
 
 /// Check AssertTuple compliance.
-pub fn check_assert_tuple(test: &Expr, location: Range) -> Option<Check> {
+pub fn assert_tuple(test: &Expr, location: Range) -> Option<Check> {
     if let ExprKind::Tuple { elts, .. } = &test.node {
         if !elts.is_empty() {
             return Some(Check::new(CheckKind::AssertTuple, location));
@@ -36,7 +37,7 @@ pub fn check_assert_tuple(test: &Expr, location: Range) -> Option<Check> {
 }
 
 /// Check NotInTest and NotIsTest compliance.
-pub fn check_not_tests(
+pub fn not_tests(
     op: &Unaryop,
     operand: &Expr,
     check_not_in: bool,
@@ -75,7 +76,7 @@ pub fn check_not_tests(
 }
 
 /// Check UnusedVariable compliance.
-pub fn check_unused_variables(
+pub fn unused_variables(
     scope: &Scope,
     locator: &dyn CheckLocator,
     dummy_variable_rgx: &Regex,
@@ -108,7 +109,7 @@ pub fn check_unused_variables(
 }
 
 /// Check DoNotAssignLambda compliance.
-pub fn check_do_not_assign_lambda(value: &Expr, location: Range) -> Option<Check> {
+pub fn do_not_assign_lambda(value: &Expr, location: Range) -> Option<Check> {
     if let ExprKind::Lambda { .. } = &value.node {
         Some(Check::new(CheckKind::DoNotAssignLambda, location))
     } else {
@@ -117,11 +118,7 @@ pub fn check_do_not_assign_lambda(value: &Expr, location: Range) -> Option<Check
 }
 
 /// Check UselessMetaclassType compliance.
-pub fn check_useless_metaclass_type(
-    targets: &Vec<Expr>,
-    value: &Expr,
-    location: Range,
-) -> Option<Check> {
+pub fn useless_metaclass_type(targets: &Vec<Expr>, value: &Expr, location: Range) -> Option<Check> {
     if targets.len() == 1 {
         if let ExprKind::Name { id, .. } = targets.first().map(|expr| &expr.node).unwrap() {
             if id == "__metaclass__" {
@@ -137,7 +134,7 @@ pub fn check_useless_metaclass_type(
 }
 
 /// Check UnnecessaryAbspath compliance.
-pub fn check_unnecessary_abspath(func: &Expr, args: &Vec<Expr>, location: Range) -> Option<Check> {
+pub fn unnecessary_abspath(func: &Expr, args: &Vec<Expr>, location: Range) -> Option<Check> {
     // Validate the arguments.
     if args.len() == 1 {
         if let ExprKind::Name { id, .. } = &args[0].node {
@@ -193,7 +190,7 @@ impl Primitive {
 }
 
 /// Check TypeOfPrimitive compliance.
-pub fn check_type_of_primitive(func: &Expr, args: &Vec<Expr>, location: Range) -> Option<Check> {
+pub fn type_of_primitive(func: &Expr, args: &Vec<Expr>, location: Range) -> Option<Check> {
     // Validate the arguments.
     if args.len() == 1 {
         match &func.node {
@@ -221,7 +218,7 @@ fn is_ambiguous_name(name: &str) -> bool {
 }
 
 /// Check AmbiguousVariableName compliance.
-pub fn check_ambiguous_variable_name(name: &str, location: Range) -> Option<Check> {
+pub fn ambiguous_variable_name(name: &str, location: Range) -> Option<Check> {
     if is_ambiguous_name(name) {
         Some(Check::new(
             CheckKind::AmbiguousVariableName(name.to_string()),
@@ -233,7 +230,7 @@ pub fn check_ambiguous_variable_name(name: &str, location: Range) -> Option<Chec
 }
 
 /// Check AmbiguousClassName compliance.
-pub fn check_ambiguous_class_name(name: &str, location: Range) -> Option<Check> {
+pub fn ambiguous_class_name(name: &str, location: Range) -> Option<Check> {
     if is_ambiguous_name(name) {
         Some(Check::new(
             CheckKind::AmbiguousClassName(name.to_string()),
@@ -245,7 +242,7 @@ pub fn check_ambiguous_class_name(name: &str, location: Range) -> Option<Check>
 }
 
 /// Check AmbiguousFunctionName compliance.
-pub fn check_ambiguous_function_name(name: &str, location: Range) -> Option<Check> {
+pub fn ambiguous_function_name(name: &str, location: Range) -> Option<Check> {
     if is_ambiguous_name(name) {
         Some(Check::new(
             CheckKind::AmbiguousFunctionName(name.to_string()),
@@ -257,11 +254,7 @@ pub fn check_ambiguous_function_name(name: &str, location: Range) -> Option<Chec
 }
 
 /// Check UselessObjectInheritance compliance.
-pub fn check_useless_object_inheritance(
-    name: &str,
-    bases: &[Expr],
-    scope: &Scope,
-) -> Option<Check> {
+pub fn useless_object_inheritance(name: &str, bases: &[Expr], scope: &Scope) -> Option<Check> {
     for expr in bases {
         if let ExprKind::Name { id, .. } = &expr.node {
             if id == "object" {
@@ -286,7 +279,7 @@ pub fn check_useless_object_inheritance(
 }
 
 /// Check DefaultExceptNotLast compliance.
-pub fn check_default_except_not_last(handlers: &Vec<Excepthandler>) -> Option<Check> {
+pub fn default_except_not_last(handlers: &Vec<Excepthandler>) -> Option<Check> {
     for (idx, handler) in handlers.iter().enumerate() {
         let ExcepthandlerKind::ExceptHandler { type_, .. } = &handler.node;
         if type_.is_none() && idx < handlers.len() - 1 {
@@ -301,7 +294,7 @@ pub fn check_default_except_not_last(handlers: &Vec<Excepthandler>) -> Option<Ch
 }
 
 /// Check RaiseNotImplemented compliance.
-pub fn check_raise_not_implemented(expr: &Expr) -> Option<Check> {
+pub fn raise_not_implemented(expr: &Expr) -> Option<Check> {
     match &expr.node {
         ExprKind::Call { func, .. } => {
             if let ExprKind::Name { id, .. } = &func.node {
@@ -328,7 +321,7 @@ pub fn check_raise_not_implemented(expr: &Expr) -> Option<Check> {
 }
 
 /// Check DuplicateArgumentName compliance.
-pub fn check_duplicate_arguments(arguments: &Arguments) -> Vec<Check> {
+pub fn duplicate_arguments(arguments: &Arguments) -> Vec<Check> {
     let mut checks: Vec<Check> = vec![];
 
     // Collect all the arguments into a single vector.
@@ -376,7 +369,7 @@ fn convert_to_value(expr: &Expr) -> Option<DictionaryKey> {
 }
 
 /// Check MultiValueRepeatedKeyLiteral and MultiValueRepeatedKeyVariable compliance.
-pub fn check_repeated_keys(
+pub fn repeated_keys(
     keys: &Vec<Expr>,
     check_repeated_literals: bool,
     check_repeated_variables: bool,
@@ -416,7 +409,7 @@ pub fn check_repeated_keys(
 }
 
 /// Check TrueFalseComparison and NoneComparison compliance.
-pub fn check_literal_comparisons(
+pub fn literal_comparisons(
     left: &Expr,
     ops: &Vec<Cmpop>,
     comparators: &Vec<Expr>,
@@ -547,7 +540,7 @@ fn is_constant_non_singleton(expr: &Expr) -> bool {
 }
 
 /// Check IsLiteral compliance.
-pub fn check_is_literal(
+pub fn is_literal(
     left: &Expr,
     ops: &Vec<Cmpop>,
     comparators: &Vec<Expr>,
@@ -569,11 +562,7 @@ pub fn check_is_literal(
 }
 
 /// Check TypeComparison compliance.
-pub fn check_type_comparison(
-    ops: &Vec<Cmpop>,
-    comparators: &Vec<Expr>,
-    location: Range,
-) -> Vec<Check> {
+pub fn type_comparison(ops: &Vec<Cmpop>, comparators: &Vec<Expr>, location: Range) -> Vec<Check> {
     let mut checks: Vec<Check> = vec![];
 
     for (op, right) in izip!(ops, comparators) {
@@ -609,7 +598,7 @@ pub fn check_type_comparison(
 }
 
 /// Check TwoStarredExpressions and TooManyExpressionsInStarredAssignment compliance.
-pub fn check_starred_expressions(
+pub fn starred_expressions(
     elts: &[Expr],
     check_too_many_expressions: bool,
     check_two_starred_expressions: bool,
@@ -639,7 +628,7 @@ pub fn check_starred_expressions(
 }
 
 /// Check BreakOutsideLoop compliance.
-pub fn check_break_outside_loop(
+pub fn break_outside_loop(
     stmt: &Stmt,
     parents: &[&Stmt],
     parent_stack: &[usize],
@@ -680,7 +669,7 @@ pub fn check_break_outside_loop(
 }
 
 /// Check ContinueOutsideLoop compliance.
-pub fn check_continue_outside_loop(
+pub fn continue_outside_loop(
     stmt: &Stmt,
     parents: &[&Stmt],
     parent_stack: &[usize],
@@ -728,11 +717,7 @@ pub enum ShadowingType {
 }
 
 /// Check builtin name shadowing
-pub fn check_builtin_shadowing(
-    name: &str,
-    location: Range,
-    node_type: ShadowingType,
-) -> Option<Check> {
+pub fn builtin_shadowing(name: &str, location: Range, node_type: ShadowingType) -> Option<Check> {
     if BUILTINS.contains(&name) {
         Some(Check::new(
             match node_type {
@@ -747,17 +732,7 @@ pub fn check_builtin_shadowing(
     }
 }
 
-/// Returns `true` if a call is an argumented `super` invocation.
-pub fn is_super_call_with_arguments(func: &Expr, args: &Vec<Expr>) -> bool {
-    // Check: is this a `super` call?
-    if let ExprKind::Name { id, .. } = &func.node {
-        id == "super" && !args.is_empty()
-    } else {
-        false
-    }
-}
-
-// flakes8-comprehensions
+// flake8-comprehensions
 /// Check `list(generator)` compliance.
 pub fn unnecessary_generator_list(expr: &Expr, func: &Expr, args: &Vec<Expr>) -> Option<Check> {
     if args.len() == 1 {
@@ -969,6 +944,128 @@ pub fn unnecessary_collection_call(
     None
 }
 
+pub fn unnecessary_literal_within_tuple_call(
+    expr: &Expr,
+    func: &Expr,
+    args: &[Expr],
+) -> Option<Check> {
+    if let ExprKind::Name { id, .. } = &func.node {
+        if id == "tuple" {
+            if let Some(arg) = args.first() {
+                match &arg.node {
+                    ExprKind::Tuple { .. } => {
+                        return Some(Check::new(
+                            CheckKind::UnnecessaryLiteralWithinTupleCall("tuple".to_string()),
+                            Range::from_located(expr),
+                        ));
+                    }
+                    ExprKind::List { .. } => {
+                        return Some(Check::new(
+                            CheckKind::UnnecessaryLiteralWithinTupleCall("list".to_string()),
+                            Range::from_located(expr),
+                        ));
+                    }
+                    _ => {}
+                }
+            }
+        }
+    }
+
+    None
+}
+
+pub fn unnecessary_literal_within_list_call(
+    expr: &Expr,
+    func: &Expr,
+    args: &[Expr],
+) -> Option<Check> {
+    if let ExprKind::Name { id, .. } = &func.node {
+        if id == "list" {
+            if let Some(arg) = args.first() {
+                match &arg.node {
+                    ExprKind::Tuple { .. } => {
+                        return Some(Check::new(
+                            CheckKind::UnnecessaryLiteralWithinListCall("tuple".to_string()),
+                            Range::from_located(expr),
+                        ));
+                    }
+                    ExprKind::List { .. } => {
+                        return Some(Check::new(
+                            CheckKind::UnnecessaryLiteralWithinListCall("list".to_string()),
+                            Range::from_located(expr),
+                        ));
+                    }
+                    _ => {}
+                }
+            }
+        }
+    }
+
+    None
+}
+
+pub fn unnecessary_double_cast_or_process(
+    expr: &Expr,
+    func: &Expr,
+    args: &[Expr],
+) -> Option<Check> {
+    if let ExprKind::Name { id: outer, .. } = &func.node {
+        if outer == "list"
+            || outer == "tuple"
+            || outer == "set"
+            || outer == "reversed"
+            || outer == "sorted"
+        {
+            if let Some(arg) = args.first() {
+                if let ExprKind::Call { func, .. } = &arg.node {
+                    if let ExprKind::Name { id: inner, .. } = &func.node {
+                        // Ex) set(tuple(...))
+                        if (outer == "set" || outer == "sorted")
+                            && (inner == "list"
+                                || inner == "tuple"
+                                || inner == "reversed"
+                                || inner == "sorted")
+                        {
+                            return Some(Check::new(
+                                CheckKind::UnnecessaryDoubleCastOrProcess(
+                                    inner.to_string(),
+                                    outer.to_string(),
+                                ),
+                                Range::from_located(expr),
+                            ));
+                        }
+
+                        // Ex) list(tuple(...))
+                        if (outer == "list" || outer == "tuple")
+                            && (inner == "list" || inner == "tuple")
+                        {
+                            return Some(Check::new(
+                                CheckKind::UnnecessaryDoubleCastOrProcess(
+                                    inner.to_string(),
+                                    outer.to_string(),
+                                ),
+                                Range::from_located(expr),
+                            ));
+                        }
+
+                        // Ex) set(set(...))
+                        if outer == "set" && inner == "set" {
+                            return Some(Check::new(
+                                CheckKind::UnnecessaryDoubleCastOrProcess(
+                                    inner.to_string(),
+                                    outer.to_string(),
+                                ),
+                                Range::from_located(expr),
+                            ));
+                        }
+                    }
+                }
+            }
+        }
+    }
+    None
+}
+
 pub fn unnecessary_subscript_reversal(expr: &Expr, func: &Expr, args: &[Expr]) -> Option<Check> {
     if let Some(first_arg) = args.first() {
         if let ExprKind::Name { id, .. } = &func.node {
@@ -1009,14 +1106,14 @@ pub fn unnecessary_subscript_reversal(expr: &Expr, func: &Expr, args: &[Expr]) -
 
 // flake8-super
 /// Check that `super()` has no args
-pub fn check_super_args(
+pub fn super_args(
     scope: &Scope,
     parents: &[&Stmt],
     expr: &Expr,
     func: &Expr,
     args: &Vec<Expr>,
 ) -> Option<Check> {
-    if !is_super_call_with_arguments(func, args) {
+    if !helpers::is_super_call_with_arguments(func, args) {
         return None;
     }
 
@@ -1075,7 +1172,7 @@ pub fn check_super_args(
 
 // flake8-print
 /// Check whether a function call is a `print` or `pprint` invocation
-pub fn check_print_call(
+pub fn print_call(
     expr: &Expr,
     func: &Expr,
     check_print: bool,

src/ast/helpers.rs

@@ -1,10 +1,42 @@
 use once_cell::sync::Lazy;
 use regex::Regex;
-use rustpython_ast::{Expr, ExprKind, StmtKind};
+use rustpython_ast::{Excepthandler, ExcepthandlerKind, Expr, ExprKind, StmtKind};
 
 use crate::python::typing;
 
-static DUNDER_REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"__[^\s]+__").unwrap());
+fn compose_call_path_inner<'a>(expr: &'a Expr, parts: &mut Vec<&'a str>) {
+    match &expr.node {
+        ExprKind::Call { func, .. } => {
+            compose_call_path_inner(func, parts);
+        }
+        ExprKind::Attribute { value, attr, .. } => {
+            compose_call_path_inner(value, parts);
+            parts.push(attr);
+        }
+        ExprKind::Name { id, .. } => {
+            parts.push(id);
+        }
+        _ => {}
+    }
+}
+
+pub fn compose_call_path(expr: &Expr) -> Option<String> {
+    let mut segments = vec![];
+    compose_call_path_inner(expr, &mut segments);
+    if segments.is_empty() {
+        None
+    } else {
+        Some(segments.join("."))
+    }
+}
+
+pub fn match_name_or_attr(expr: &Expr, target: &str) -> bool {
+    match &expr.node {
+        ExprKind::Attribute { attr, .. } => target == attr,
+        ExprKind::Name { id, .. } => target == id,
+        _ => false,
+    }
+}
 
 pub enum SubscriptKind {
     AnnotatedSubscript,
@@ -35,6 +67,8 @@ pub fn match_annotated_subscript(expr: &Expr) -> Option<SubscriptKind> {
     }
 }
 
+static DUNDER_REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"__[^\s]+__").unwrap());
+
 pub fn is_assignment_to_a_dunder(node: &StmtKind) -> bool {
     // Check whether it's an assignment to a dunder, with or without a type annotation.
     // This is what pycodestyle (as of 2.9.1) does.
@@ -65,10 +99,35 @@ pub fn is_assignment_to_a_dunder(node: &StmtKind) -> bool {
     }
 }
 
-pub fn match_name_or_attr(expr: &Expr, target: &str) -> bool {
-    match &expr.node {
-        ExprKind::Attribute { attr, .. } => target == attr,
-        ExprKind::Name { id, .. } => target == id,
-        _ => false,
+/// Extract the names of all handled exceptions.
+pub fn extract_handler_names(handlers: &[Excepthandler]) -> Vec<String> {
+    let mut handler_names = vec![];
+    for handler in handlers {
+        match &handler.node {
+            ExcepthandlerKind::ExceptHandler { type_, .. } => {
+                if let Some(type_) = type_ {
+                    if let ExprKind::Tuple { elts, .. } = &type_.node {
+                        for type_ in elts {
+                            if let Some(name) = compose_call_path(type_) {
+                                handler_names.push(name);
+                            }
+                        }
+                    } else if let Some(name) = compose_call_path(type_) {
+                        handler_names.push(name);
+                    }
+                }
+            }
+        }
+    }
+    handler_names
+}
+
+/// Returns `true` if a call is an argumented `super` invocation.
+pub fn is_super_call_with_arguments(func: &Expr, args: &Vec<Expr>) -> bool {
+    // Check: is this a `super` call?
+    if let ExprKind::Name { id, .. } = &func.node {
+        id == "super" && !args.is_empty()
+    } else {
+        false
     }
 }

src/ast/operations.rs

@@ -134,7 +134,7 @@ impl<'a> SourceCodeLocator<'a> {
         }
     }
 
-    pub fn slice_source_code_at(&mut self, location: &Location) -> &'a str {
+    fn init(&mut self) {
         if !self.initialized {
             let mut offset = 0;
             for i in self.content.lines() {
@@ -142,24 +142,40 @@ impl<'a> SourceCodeLocator<'a> {
                 offset += i.len();
                 offset += 1;
             }
+            self.offsets.push(offset);
             self.initialized = true;
         }
+    }
+
+    pub fn slice_source_code_at(&mut self, location: &Location) -> &'a str {
+        self.init();
         let offset = self.offsets[location.row() - 1] + location.column() - 1;
         &self.content[offset..]
     }
 
     pub fn slice_source_code_range(&mut self, range: &Range) -> &'a str {
-        if !self.initialized {
-            let mut offset = 0;
-            for i in self.content.lines() {
-                self.offsets.push(offset);
-                offset += i.len();
-                offset += 1;
-            }
-            self.initialized = true;
-        }
+        self.init();
         let start = self.offsets[range.location.row() - 1] + range.location.column() - 1;
         let end = self.offsets[range.end_location.row() - 1] + range.end_location.column() - 1;
         &self.content[start..end]
     }
+
+    pub fn partition_source_code_at(
+        &mut self,
+        outer: &Range,
+        inner: &Range,
+    ) -> (&'a str, &'a str, &'a str) {
+        self.init();
+        let outer_start = self.offsets[outer.location.row() - 1] + outer.location.column() - 1;
+        let outer_end =
+            self.offsets[outer.end_location.row() - 1] + outer.end_location.column() - 1;
+        let inner_start = self.offsets[inner.location.row() - 1] + inner.location.column() - 1;
+        let inner_end =
+            self.offsets[inner.end_location.row() - 1] + inner.end_location.column() - 1;
+        (
+            &self.content[outer_start..inner_start],
+            &self.content[inner_start..inner_end],
+            &self.content[inner_end..outer_end],
+        )
+    }
 }

src/ast/visitor.rs

@@ -1,10 +1,11 @@
-use crate::ast::helpers::match_name_or_attr;
 use rustpython_parser::ast::{
     Alias, Arg, Arguments, Boolop, Cmpop, Comprehension, Constant, Excepthandler,
     ExcepthandlerKind, Expr, ExprContext, ExprKind, Keyword, MatchCase, Operator, Pattern,
     PatternKind, Stmt, StmtKind, Unaryop, Withitem,
 };
 
+use crate::ast::helpers::match_name_or_attr;
+
 pub trait Visitor<'a> {
     fn visit_stmt(&mut self, stmt: &'a Stmt) {
         walk_stmt(self, stmt);

src/check_ast.rs

@@ -10,7 +10,7 @@ use rustpython_parser::ast::{
 };
 use rustpython_parser::parser;
 
-use crate::ast::helpers::{match_name_or_attr, SubscriptKind};
+use crate::ast::helpers::{extract_handler_names, match_name_or_attr, SubscriptKind};
 use crate::ast::operations::{extract_all_names, SourceCodeLocator};
 use crate::ast::relocate::relocate_expr;
 use crate::ast::types::{
@@ -18,25 +18,30 @@ use crate::ast::types::{
     ScopeKind,
 };
 use crate::ast::visitor::{walk_excepthandler, Visitor};
-use crate::ast::{checks, helpers, operations, visitor};
+use crate::ast::{checkers, helpers, operations, visitor};
 use crate::autofix::{fixer, fixes};
 use crate::checks::{Check, CheckCode, CheckKind};
+use crate::docstrings::docstring_checks;
+use crate::docstrings::types::{Definition, DefinitionKind, Documentable};
 use crate::plugins;
 use crate::python::builtins::{BUILTINS, MAGIC_GLOBALS};
 use crate::python::future::ALL_FEATURE_NAMES;
 use crate::settings::{PythonVersion, Settings};
+use crate::visibility::{module_visibility, transition_scope, Modifier, Visibility, VisibleScope};
 
 pub const GLOBAL_SCOPE_INDEX: usize = 0;
 
 pub struct Checker<'a> {
     // Input data.
-    path: &'a Path,
+    pub(crate) path: &'a Path,
     // TODO(charlie): Separate immutable from mutable state. (None of these should ever change.)
     pub(crate) locator: SourceCodeLocator<'a>,
     pub(crate) settings: &'a Settings,
     pub(crate) autofix: &'a fixer::Mode,
     // Computed checks.
     checks: Vec<Check>,
+    // Docstring tracking.
+    docstrings: Vec<(Definition<'a>, Visibility)>,
     // Edit tracking.
     // TODO(charlie): Instead of exposing deletions, wrap in a public API.
     pub(crate) deletions: BTreeSet<usize>,
@@ -49,17 +54,18 @@ pub struct Checker<'a> {
     dead_scopes: Vec<usize>,
     deferred_string_annotations: Vec<(Range, &'a str)>,
     deferred_annotations: Vec<(&'a Expr, Vec<usize>, Vec<usize>)>,
-    deferred_functions: Vec<(&'a Stmt, Vec<usize>, Vec<usize>)>,
+    deferred_functions: Vec<(&'a Stmt, Vec<usize>, Vec<usize>, VisibleScope)>,
     deferred_lambdas: Vec<(&'a Expr, Vec<usize>, Vec<usize>)>,
     deferred_assignments: Vec<usize>,
     // Internal, derivative state.
+    visible_scope: VisibleScope,
     in_f_string: Option<Range>,
     in_annotation: bool,
     in_literal: bool,
-    seen_non_import: bool,
-    seen_docstring: bool,
+    seen_import_boundary: bool,
     futures_allowed: bool,
     annotations_future_enabled: bool,
+    except_handlers: Vec<Vec<String>>,
 }
 
 impl<'a> Checker<'a> {
@@ -74,25 +80,30 @@ impl<'a> Checker<'a> {
             autofix,
             path,
             locator: SourceCodeLocator::new(content),
-            checks: vec![],
-            parents: vec![],
-            parent_stack: vec![],
-            scopes: vec![],
-            scope_stack: vec![],
-            dead_scopes: vec![],
-            deferred_string_annotations: vec![],
-            deferred_annotations: vec![],
-            deferred_functions: vec![],
-            deferred_lambdas: vec![],
-            deferred_assignments: vec![],
-            in_f_string: None,
-            in_annotation: false,
-            in_literal: false,
-            seen_non_import: false,
-            seen_docstring: false,
-            futures_allowed: true,
-            annotations_future_enabled: false,
+            checks: Default::default(),
+            docstrings: Default::default(),
             deletions: Default::default(),
+            parents: Default::default(),
+            parent_stack: Default::default(),
+            scopes: Default::default(),
+            scope_stack: Default::default(),
+            dead_scopes: Default::default(),
+            deferred_string_annotations: Default::default(),
+            deferred_annotations: Default::default(),
+            deferred_functions: Default::default(),
+            deferred_lambdas: Default::default(),
+            deferred_assignments: Default::default(),
+            visible_scope: VisibleScope {
+                modifier: Modifier::Module,
+                visibility: module_visibility(path),
+            },
+            in_f_string: None,
+            in_annotation: Default::default(),
+            in_literal: Default::default(),
+            seen_import_boundary: Default::default(),
+            futures_allowed: true,
+            annotations_future_enabled: Default::default(),
+            except_handlers: Default::default(),
         }
     }
 }
@@ -119,48 +130,13 @@ where
             StmtKind::Import { .. } => {
                 self.futures_allowed = false;
             }
-            StmtKind::Expr { value } => {
-                if self.seen_docstring
-                    && !self.seen_non_import
-                    && !operations::in_nested_block(&self.parent_stack, &self.parents)
-                {
-                    self.seen_non_import = true;
-                }
-
-                if !self.seen_docstring
-                    && !operations::in_nested_block(&self.parent_stack, &self.parents)
-                    && matches!(
-                        &value.node,
-                        ExprKind::Constant {
-                            value: Constant::Str(_),
-                            ..
-                        },
-                    )
-                {
-                    self.seen_docstring = true;
-                }
-
-                // Allow docstrings to interrupt __future__ imports.
-                if self.futures_allowed
-                    && !matches!(
-                        &value.node,
-                        ExprKind::Constant {
-                            value: Constant::Str(_),
-                            ..
-                        },
-                    )
-                {
-                    self.futures_allowed = false;
-                }
-            }
             node => {
                 self.futures_allowed = false;
-
-                if !self.seen_non_import
+                if !self.seen_import_boundary
                     && !helpers::is_assignment_to_a_dunder(node)
                     && !operations::in_nested_block(&self.parent_stack, &self.parents)
                 {
-                    self.seen_non_import = true;
+                    self.seen_import_boundary = true;
                 }
             }
         }
@@ -190,27 +166,24 @@ where
                 if self.settings.enabled.contains(&CheckCode::E741) {
                     let location = self.locate_check(Range::from_located(stmt));
                     self.checks.extend(
-                        names.iter().filter_map(|name| {
-                            checks::check_ambiguous_variable_name(name, location)
-                        }),
+                        names
+                            .iter()
+                            .filter_map(|name| checkers::ambiguous_variable_name(name, location)),
                     );
                 }
             }
             StmtKind::Break => {
                 if self.settings.enabled.contains(&CheckCode::F701) {
-                    if let Some(check) = checks::check_break_outside_loop(
-                        stmt,
-                        &self.parents,
-                        &self.parent_stack,
-                        self,
-                    ) {
+                    if let Some(check) =
+                        checkers::break_outside_loop(stmt, &self.parents, &self.parent_stack, self)
+                    {
                         self.checks.push(check);
                     }
                 }
             }
             StmtKind::Continue => {
                 if self.settings.enabled.contains(&CheckCode::F702) {
-                    if let Some(check) = checks::check_continue_outside_loop(
+                    if let Some(check) = checkers::continue_outside_loop(
                         stmt,
                         &self.parents,
                         &self.parent_stack,
@@ -235,7 +208,7 @@ where
                 ..
             } => {
                 if self.settings.enabled.contains(&CheckCode::E743) {
-                    if let Some(check) = checks::check_ambiguous_function_name(
+                    if let Some(check) = checkers::ambiguous_function_name(
                         name,
                         self.locate_check(Range::from_located(stmt)),
                     ) {
@@ -323,7 +296,7 @@ where
                 }
 
                 if self.settings.enabled.contains(&CheckCode::E742) {
-                    if let Some(check) = checks::check_ambiguous_class_name(
+                    if let Some(check) = checkers::ambiguous_class_name(
                         name,
                         self.locate_check(Range::from_located(stmt)),
                     ) {
@@ -353,7 +326,7 @@ where
                     .settings
                     .enabled
                     .contains(CheckKind::ModuleImportNotAtTopOfFile.code())
-                    && self.seen_non_import
+                    && self.seen_import_boundary
                     && stmt.location.column() == 1
                 {
                     self.checks.push(Check::new(
@@ -414,7 +387,7 @@ where
                     .settings
                     .enabled
                     .contains(CheckKind::ModuleImportNotAtTopOfFile.code())
-                    && self.seen_non_import
+                    && self.seen_import_boundary
                     && stmt.location.column() == 1
                 {
                     self.checks.push(Check::new(
@@ -532,7 +505,7 @@ where
             StmtKind::Raise { exc, .. } => {
                 if self.settings.enabled.contains(&CheckCode::F901) {
                     if let Some(expr) = exc {
-                        if let Some(check) = checks::check_raise_not_implemented(expr) {
+                        if let Some(check) = checkers::raise_not_implemented(expr) {
                             self.checks.push(check);
                         }
                     }
@@ -546,21 +519,29 @@ where
                     plugins::if_tuple(self, stmt, test);
                 }
             }
-            StmtKind::Assert { test, .. } => {
+            StmtKind::Assert { test, msg } => {
                 if self.settings.enabled.contains(&CheckCode::F631) {
                     plugins::assert_tuple(self, stmt, test);
                 }
+                if self.settings.enabled.contains(&CheckCode::B011) {
+                    plugins::assert_false(self, stmt, test, msg);
+                }
             }
             StmtKind::Try { handlers, .. } => {
                 if self.settings.enabled.contains(&CheckCode::F707) {
-                    if let Some(check) = checks::check_default_except_not_last(handlers) {
+                    if let Some(check) = checkers::default_except_not_last(handlers) {
                         self.checks.push(check);
                     }
                 }
+                if self.settings.enabled.contains(&CheckCode::B014)
+                    || self.settings.enabled.contains(&CheckCode::B025)
+                {
+                    plugins::duplicate_exceptions(self, stmt, handlers);
+                }
             }
             StmtKind::Assign { targets, value, .. } => {
                 if self.settings.enabled.contains(&CheckCode::E731) {
-                    if let Some(check) = checks::check_do_not_assign_lambda(
+                    if let Some(check) = checkers::do_not_assign_lambda(
                         value,
                         self.locate_check(Range::from_located(stmt)),
                     ) {
@@ -574,7 +555,7 @@ where
             StmtKind::AnnAssign { value, .. } => {
                 if self.settings.enabled.contains(&CheckCode::E731) {
                     if let Some(value) = value {
-                        if let Some(check) = checks::check_do_not_assign_lambda(
+                        if let Some(check) = checkers::do_not_assign_lambda(
                             value,
                             self.locate_check(Range::from_located(stmt)),
                         ) {
@@ -588,21 +569,65 @@ where
         }
 
         // Recurse.
+        let prev_visibile_scope = self.visible_scope.clone();
         match &stmt.node {
-            StmtKind::FunctionDef { .. } | StmtKind::AsyncFunctionDef { .. } => {
+            StmtKind::FunctionDef { body, .. } | StmtKind::AsyncFunctionDef { body, .. } => {
+                let definition = docstring_checks::extract(
+                    &self.visible_scope,
+                    stmt,
+                    body,
+                    &Documentable::Function,
+                );
+                let scope = transition_scope(&self.visible_scope, stmt, &Documentable::Function);
+                self.docstrings.push((definition, scope.visibility.clone()));
+                self.visible_scope = scope;
+
                 self.deferred_functions.push((
                     stmt,
                     self.scope_stack.clone(),
                     self.parent_stack.clone(),
+                    self.visible_scope.clone(),
                 ));
             }
             StmtKind::ClassDef { body, .. } => {
+                let definition = docstring_checks::extract(
+                    &self.visible_scope,
+                    stmt,
+                    body,
+                    &Documentable::Class,
+                );
+                let scope = transition_scope(&self.visible_scope, stmt, &Documentable::Class);
+                self.docstrings.push((definition, scope.visibility.clone()));
+                self.visible_scope = scope;
+
                 for stmt in body {
                     self.visit_stmt(stmt);
                 }
             }
+            StmtKind::Try {
+                body,
+                handlers,
+                orelse,
+                finalbody,
+            } => {
+                self.except_handlers.push(extract_handler_names(handlers));
+                for stmt in body {
+                    self.visit_stmt(stmt);
+                }
+                self.except_handlers.pop();
+                for excepthandler in handlers {
+                    self.visit_excepthandler(excepthandler)
+                }
+                for stmt in orelse {
+                    self.visit_stmt(stmt);
+                }
+                for stmt in finalbody {
+                    self.visit_stmt(stmt);
+                }
+            }
             _ => visitor::walk_stmt(self, stmt),
         };
+        self.visible_scope = prev_visibile_scope;
 
         // Post-visit.
         if let StmtKind::ClassDef { name, .. } = &stmt.node {
@@ -670,7 +695,7 @@ where
                         self.settings.enabled.contains(&CheckCode::F621);
                     let check_two_starred_expressions =
                         self.settings.enabled.contains(&CheckCode::F622);
-                    if let Some(check) = checks::check_starred_expressions(
+                    if let Some(check) = checkers::starred_expressions(
                         elts,
                         check_too_many_expressions,
                         check_two_starred_expressions,
@@ -693,7 +718,7 @@ where
                 }
                 ExprContext::Store => {
                     if self.settings.enabled.contains(&CheckCode::E741) {
-                        if let Some(check) = checks::check_ambiguous_variable_name(
+                        if let Some(check) = checkers::ambiguous_variable_name(
                             id,
                             self.locate_check(Range::from_located(expr)),
                         ) {
@@ -743,26 +768,26 @@ where
 
                 // flake8-comprehensions
                 if self.settings.enabled.contains(&CheckCode::C400) {
-                    if let Some(check) = checks::unnecessary_generator_list(expr, func, args) {
+                    if let Some(check) = checkers::unnecessary_generator_list(expr, func, args) {
                         self.checks.push(check);
                     };
                 }
 
                 if self.settings.enabled.contains(&CheckCode::C401) {
-                    if let Some(check) = checks::unnecessary_generator_set(expr, func, args) {
+                    if let Some(check) = checkers::unnecessary_generator_set(expr, func, args) {
                         self.checks.push(check);
                     };
                 }
 
                 if self.settings.enabled.contains(&CheckCode::C402) {
-                    if let Some(check) = checks::unnecessary_generator_dict(expr, func, args) {
+                    if let Some(check) = checkers::unnecessary_generator_dict(expr, func, args) {
                         self.checks.push(check);
                     };
                 }
 
                 if self.settings.enabled.contains(&CheckCode::C403) {
                     if let Some(check) =
-                        checks::unnecessary_list_comprehension_set(expr, func, args)
+                        checkers::unnecessary_list_comprehension_set(expr, func, args)
                     {
                         self.checks.push(check);
                     };
@@ -770,34 +795,59 @@ where
 
                 if self.settings.enabled.contains(&CheckCode::C404) {
                     if let Some(check) =
-                        checks::unnecessary_list_comprehension_dict(expr, func, args)
+                        checkers::unnecessary_list_comprehension_dict(expr, func, args)
                     {
                         self.checks.push(check);
                     };
                 }
 
                 if self.settings.enabled.contains(&CheckCode::C405) {
-                    if let Some(check) = checks::unnecessary_literal_set(expr, func, args) {
+                    if let Some(check) = checkers::unnecessary_literal_set(expr, func, args) {
                         self.checks.push(check);
                     };
                 }
 
                 if self.settings.enabled.contains(&CheckCode::C406) {
-                    if let Some(check) = checks::unnecessary_literal_dict(expr, func, args) {
+                    if let Some(check) = checkers::unnecessary_literal_dict(expr, func, args) {
                         self.checks.push(check);
                     };
                 }
 
                 if self.settings.enabled.contains(&CheckCode::C408) {
                     if let Some(check) =
-                        checks::unnecessary_collection_call(expr, func, args, keywords)
+                        checkers::unnecessary_collection_call(expr, func, args, keywords)
+                    {
+                        self.checks.push(check);
+                    };
+                }
+
+                if self.settings.enabled.contains(&CheckCode::C409) {
+                    if let Some(check) =
+                        checkers::unnecessary_literal_within_tuple_call(expr, func, args)
+                    {
+                        self.checks.push(check);
+                    };
+                }
+
+                if self.settings.enabled.contains(&CheckCode::C410) {
+                    if let Some(check) =
+                        checkers::unnecessary_literal_within_list_call(expr, func, args)
+                    {
+                        self.checks.push(check);
+                    };
+                }
+
+                if self.settings.enabled.contains(&CheckCode::C414) {
+                    if let Some(check) =
+                        checkers::unnecessary_double_cast_or_process(expr, func, args)
                     {
                         self.checks.push(check);
                     };
                 }
 
                 if self.settings.enabled.contains(&CheckCode::C415) {
-                    if let Some(check) = checks::unnecessary_subscript_reversal(expr, func, args) {
+                    if let Some(check) = checkers::unnecessary_subscript_reversal(expr, func, args)
+                    {
                         self.checks.push(check);
                     };
                 }
@@ -832,7 +882,7 @@ where
                 let check_repeated_literals = self.settings.enabled.contains(&CheckCode::F601);
                 let check_repeated_variables = self.settings.enabled.contains(&CheckCode::F602);
                 if check_repeated_literals || check_repeated_variables {
-                    self.checks.extend(checks::check_repeated_keys(
+                    self.checks.extend(checkers::repeated_keys(
                         keys,
                         check_repeated_literals,
                         check_repeated_variables,
@@ -884,7 +934,7 @@ where
                 let check_not_in = self.settings.enabled.contains(&CheckCode::E713);
                 let check_not_is = self.settings.enabled.contains(&CheckCode::E714);
                 if check_not_in || check_not_is {
-                    self.checks.extend(checks::check_not_tests(
+                    self.checks.extend(checkers::not_tests(
                         op,
                         operand,
                         check_not_in,
@@ -901,7 +951,7 @@ where
                 let check_none_comparisons = self.settings.enabled.contains(&CheckCode::E711);
                 let check_true_false_comparisons = self.settings.enabled.contains(&CheckCode::E712);
                 if check_none_comparisons || check_true_false_comparisons {
-                    self.checks.extend(checks::check_literal_comparisons(
+                    self.checks.extend(checkers::literal_comparisons(
                         left,
                         ops,
                         comparators,
@@ -912,7 +962,7 @@ where
                 }
 
                 if self.settings.enabled.contains(&CheckCode::F632) {
-                    self.checks.extend(checks::check_is_literal(
+                    self.checks.extend(checkers::is_literal(
                         left,
                         ops,
                         comparators,
@@ -921,7 +971,7 @@ where
                 }
 
                 if self.settings.enabled.contains(&CheckCode::E721) {
-                    self.checks.extend(checks::check_type_comparison(
+                    self.checks.extend(checkers::type_comparison(
                         ops,
                         comparators,
                         self.locate_check(Range::from_located(expr)),
@@ -1148,7 +1198,7 @@ where
                 match name {
                     Some(name) => {
                         if self.settings.enabled.contains(&CheckCode::E741) {
-                            if let Some(check) = checks::check_ambiguous_variable_name(
+                            if let Some(check) = checkers::ambiguous_variable_name(
                                 name,
                                 self.locate_check(Range::from_located(excepthandler)),
                             ) {
@@ -1216,8 +1266,7 @@ where
 
     fn visit_arguments(&mut self, arguments: &'b Arguments) {
         if self.settings.enabled.contains(&CheckCode::F831) {
-            self.checks
-                .extend(checks::check_duplicate_arguments(arguments));
+            self.checks.extend(checkers::duplicate_arguments(arguments));
         }
 
         // Bind, but intentionally avoid walking default expressions, as we handle them upstream.
@@ -1250,7 +1299,7 @@ where
         );
 
         if self.settings.enabled.contains(&CheckCode::E741) {
-            if let Some(check) = checks::check_ambiguous_variable_name(
+            if let Some(check) = checkers::ambiguous_variable_name(
                 &arg.node.arg,
                 self.locate_check(Range::from_located(arg)),
             ) {
@@ -1471,6 +1520,14 @@ impl<'a> Checker<'a> {
                 if self.path.ends_with("__init__.py") && id == "__path__" {
                     return;
                 }
+
+                // Avoid flagging if NameError is handled.
+                if let Some(handler_names) = self.except_handlers.last() {
+                    if handler_names.contains(&"NameError".to_string()) {
+                        return;
+                    }
+                }
+
                 self.checks.push(Check::new(
                     CheckKind::UndefinedName(id.clone()),
                     self.locate_check(Range::from_located(expr)),
@@ -1594,6 +1651,25 @@ impl<'a> Checker<'a> {
         }
     }
 
+    fn visit_docstring<'b>(&mut self, python_ast: &'b Suite) -> bool
+    where
+        'b: 'a,
+    {
+        let docstring = docstring_checks::docstring_from(python_ast);
+        self.docstrings.push((
+            Definition {
+                kind: if self.path.ends_with("__init__.py") {
+                    DefinitionKind::Package
+                } else {
+                    DefinitionKind::Module
+                },
+                docstring,
+            },
+            self.visible_scope.visibility.clone(),
+        ));
+        docstring.is_some()
+    }
+
     fn check_deferred_annotations(&mut self) {
         while let Some((expr, scopes, parents)) = self.deferred_annotations.pop() {
             self.parent_stack = parents;
@@ -1646,9 +1722,10 @@ impl<'a> Checker<'a> {
     }
 
     fn check_deferred_functions(&mut self) {
-        while let Some((stmt, scopes, parents)) = self.deferred_functions.pop() {
+        while let Some((stmt, scopes, parents, visibility)) = self.deferred_functions.pop() {
             self.parent_stack = parents;
             self.scope_stack = scopes;
+            self.visible_scope = visibility;
             self.push_scope(Scope::new(ScopeKind::Function(Default::default())));
 
             match &stmt.node {
@@ -1690,7 +1767,7 @@ impl<'a> Checker<'a> {
     fn check_deferred_assignments(&mut self) {
         if self.settings.enabled.contains(&CheckCode::F841) {
             while let Some(index) = self.deferred_assignments.pop() {
-                self.checks.extend(checks::check_unused_variables(
+                self.checks.extend(checkers::unused_variables(
                     &self.scopes[index],
                     self,
                     &self.settings.dummy_variable_rgx,
@@ -1839,25 +1916,102 @@ impl<'a> Checker<'a> {
         }
     }
 
+    fn check_docstrings(&mut self) {
+        while let Some((docstring, visibility)) = self.docstrings.pop() {
+            if !docstring_checks::not_empty(self, &docstring) {
+                continue;
+            }
+            if !docstring_checks::not_missing(self, &docstring, &visibility) {
+                continue;
+            }
+            if self.settings.enabled.contains(&CheckCode::D200) {
+                docstring_checks::one_liner(self, &docstring);
+            }
+            if self.settings.enabled.contains(&CheckCode::D201)
+                || self.settings.enabled.contains(&CheckCode::D202)
+            {
+                docstring_checks::blank_before_after_function(self, &docstring);
+            }
+            if self.settings.enabled.contains(&CheckCode::D203)
+                || self.settings.enabled.contains(&CheckCode::D204)
+                || self.settings.enabled.contains(&CheckCode::D211)
+            {
+                docstring_checks::blank_before_after_class(self, &docstring);
+            }
+            if self.settings.enabled.contains(&CheckCode::D205) {
+                docstring_checks::blank_after_summary(self, &docstring);
+            }
+            if self.settings.enabled.contains(&CheckCode::D209) {
+                docstring_checks::newline_after_last_paragraph(self, &docstring);
+            }
+            if self.settings.enabled.contains(&CheckCode::D210) {
+                docstring_checks::no_surrounding_whitespace(self, &docstring);
+            }
+            if self.settings.enabled.contains(&CheckCode::D212)
+                || self.settings.enabled.contains(&CheckCode::D213)
+            {
+                docstring_checks::multi_line_summary_start(self, &docstring);
+            }
+            if self.settings.enabled.contains(&CheckCode::D300) {
+                docstring_checks::triple_quotes(self, &docstring);
+            }
+            if self.settings.enabled.contains(&CheckCode::D400) {
+                docstring_checks::ends_with_period(self, &docstring);
+            }
+            if self.settings.enabled.contains(&CheckCode::D402) {
+                docstring_checks::no_signature(self, &docstring);
+            }
+            if self.settings.enabled.contains(&CheckCode::D403) {
+                docstring_checks::capitalized(self, &docstring);
+            }
+            if self.settings.enabled.contains(&CheckCode::D404) {
+                docstring_checks::starts_with_this(self, &docstring);
+            }
+            if self.settings.enabled.contains(&CheckCode::D415) {
+                docstring_checks::ends_with_punctuation(self, &docstring);
+            }
+            if self.settings.enabled.contains(&CheckCode::D418) {
+                docstring_checks::if_needed(self, &docstring);
+            }
+            if self.settings.enabled.contains(&CheckCode::D407)
+                || self.settings.enabled.contains(&CheckCode::D414)
+                || self.settings.enabled.contains(&CheckCode::D407)
+                || self.settings.enabled.contains(&CheckCode::D212)
+                || self.settings.enabled.contains(&CheckCode::D408)
+                || self.settings.enabled.contains(&CheckCode::D409)
+                || self.settings.enabled.contains(&CheckCode::D414)
+                || self.settings.enabled.contains(&CheckCode::D412)
+                || self.settings.enabled.contains(&CheckCode::D414)
+                || self.settings.enabled.contains(&CheckCode::D405)
+                || self.settings.enabled.contains(&CheckCode::D413)
+                || self.settings.enabled.contains(&CheckCode::D410)
+                || self.settings.enabled.contains(&CheckCode::D411)
+                || self.settings.enabled.contains(&CheckCode::D406)
+            {
+                docstring_checks::check_sections(self, &docstring);
+            }
+        }
+    }
+
     fn check_builtin_shadowing(&mut self, name: &str, location: Range, is_attribute: bool) {
         let scope = self.current_scope();
 
         // flake8-builtins
         if is_attribute && matches!(scope.kind, ScopeKind::Class) {
             if self.settings.enabled.contains(&CheckCode::A003) {
-                if let Some(check) = checks::check_builtin_shadowing(
+                if let Some(check) = checkers::builtin_shadowing(
                     name,
                     self.locate_check(location),
-                    checks::ShadowingType::Attribute,
+                    checkers::ShadowingType::Attribute,
                 ) {
                     self.checks.push(check);
                 }
             }
         } else if self.settings.enabled.contains(&CheckCode::A001) {
-            if let Some(check) = checks::check_builtin_shadowing(
+            if let Some(check) = checkers::builtin_shadowing(
                 name,
                 self.locate_check(location),
-                checks::ShadowingType::Variable,
+                checkers::ShadowingType::Variable,
             ) {
                 self.checks.push(check);
             }
@@ -1866,10 +2020,10 @@ impl<'a> Checker<'a> {
 
     fn check_builtin_arg_shadowing(&mut self, name: &str, location: Range) {
         if self.settings.enabled.contains(&CheckCode::A002) {
-            if let Some(check) = checks::check_builtin_shadowing(
+            if let Some(check) = checkers::builtin_shadowing(
                 name,
                 self.locate_check(location),
-                checks::ShadowingType::Argument,
+                checkers::ShadowingType::Argument,
             ) {
                 self.checks.push(check);
             }
@@ -1888,6 +2042,13 @@ pub fn check_ast(
     checker.push_scope(Scope::new(ScopeKind::Module));
     checker.bind_builtins();
 
+    // Check for module docstring.
+    let python_ast = if checker.visit_docstring(python_ast) {
+        &python_ast[1..]
+    } else {
+        python_ast
+    };
+
     // Iterate over the AST.
     for stmt in python_ast {
         checker.visit_stmt(stmt);
@@ -1906,5 +2067,8 @@ pub fn check_ast(
     checker.pop_scope();
     checker.check_dead_scopes();
 
+    // Check docstrings.
+    checker.check_docstrings();
+
     checker.checks
 }

src/check_lines.rs

@@ -184,15 +184,15 @@ pub fn check_lines(
                     let mut valid_codes = vec![];
                     for code in codes {
                         if !matches.contains(&code) {
-                            invalid_codes.push(code);
+                            invalid_codes.push(code.to_string());
                         } else {
-                            valid_codes.push(code);
+                            valid_codes.push(code.to_string());
                         }
                     }
 
                     if !invalid_codes.is_empty() {
                         let mut check = Check::new(
-                            CheckKind::UnusedNOQA(Some(invalid_codes.join(", "))),
+                            CheckKind::UnusedNOQA(Some(invalid_codes)),
                             Range {
                                 location: Location::new(row + 1, start + 1),
                                 end_location: Location::new(row + 1, end + 1),

src/checks.rs

@@ -1,9 +1,11 @@
+use std::str::FromStr;
+
 use itertools::Itertools;
 use rustpython_parser::ast::Location;
 use serde::{Deserialize, Serialize};
 use strum_macros::{AsRefStr, EnumIter, EnumString};
 
-use crate::ast::checks::Primitive;
+use crate::ast::checkers::Primitive;
 use crate::ast::types::Range;
 
 pub const DEFAULT_CHECK_CODES: [CheckCode; 43] = [
@@ -120,6 +122,10 @@ pub enum CheckCode {
     A001,
     A002,
     A003,
+    // flake8-bugbear
+    B011,
+    B014,
+    B025,
     // flake8-comprehensions
     C400,
     C401,
@@ -129,6 +135,9 @@ pub enum CheckCode {
     C405,
     C406,
     C408,
+    C409,
+    C410,
+    C414,
     C415,
     // flake8-print
     T201,
@@ -142,6 +151,44 @@ pub enum CheckCode {
     U006,
     U007,
     U008,
+    // pydocstyle
+    D100,
+    D101,
+    D102,
+    D103,
+    D104,
+    D105,
+    D106,
+    D107,
+    D200,
+    D201,
+    D202,
+    D203,
+    D204,
+    D205,
+    D209,
+    D210,
+    D211,
+    D212,
+    D213,
+    D300,
+    D400,
+    D402,
+    D403,
+    D404,
+    D405,
+    D406,
+    D407,
+    D408,
+    D409,
+    D410,
+    D411,
+    D412,
+    D413,
+    D414,
+    D415,
+    D418,
+    D419,
     // Meta
     M001,
 }
@@ -210,7 +257,11 @@ pub enum CheckKind {
     BuiltinVariableShadowing(String),
     BuiltinArgumentShadowing(String),
     BuiltinAttributeShadowing(String),
-    // flakes8-comprehensions
+    // flake8-bugbear
+    DoNotAssertFalse,
+    DuplicateHandlerException(Vec<String>),
+    DuplicateTryBlockException(String),
+    // flake8-comprehensions
     UnnecessaryGeneratorList,
     UnnecessaryGeneratorSet,
     UnnecessaryGeneratorDict,
@@ -219,6 +270,9 @@ pub enum CheckKind {
     UnnecessaryLiteralSet(String),
     UnnecessaryLiteralDict(String),
     UnnecessaryCollectionCall(String),
+    UnnecessaryLiteralWithinTupleCall(String),
+    UnnecessaryLiteralWithinListCall(String),
+    UnnecessaryDoubleCastOrProcess(String, String),
     UnnecessarySubscriptReversal(String),
     // flake8-print
     PrintFound,
@@ -232,8 +286,46 @@ pub enum CheckKind {
     UsePEP585Annotation(String),
     UsePEP604Annotation,
     SuperCallWithParameters,
+    // pydocstyle
+    BlankLineAfterLastSection(String),
+    BlankLineAfterSection(String),
+    BlankLineBeforeSection(String),
+    CapitalizeSectionName(String),
+    DashedUnderlineAfterSection(String),
+    EndsInPeriod,
+    EndsInPunctuation,
+    FirstLineCapitalized,
+    FitsOnOneLine,
+    MagicMethod,
+    MultiLineSummaryFirstLine,
+    MultiLineSummarySecondLine,
+    NewLineAfterLastParagraph,
+    NewLineAfterSectionName(String),
+    NoBlankLineAfterFunction(usize),
+    NoBlankLineAfterSummary,
+    NoBlankLineBeforeClass(usize),
+    NoBlankLineBeforeFunction(usize),
+    NoBlankLinesBetweenHeaderAndContent(String),
+    NoSignature,
+    NoSurroundingWhitespace,
+    NoThisPrefix,
+    NonEmpty,
+    NonEmptySection(String),
+    OneBlankLineAfterClass(usize),
+    OneBlankLineBeforeClass(usize),
+    PublicClass,
+    PublicFunction,
+    PublicInit,
+    PublicMethod,
+    PublicModule,
+    PublicNestedClass,
+    PublicPackage,
+    SectionUnderlineAfterName(String),
+    SectionUnderlineMatchesSectionLength(String),
+    SkipDocstring,
+    UsesTripleQuotes,
     // Meta
-    UnusedNOQA(Option<String>),
+    UnusedNOQA(Option<Vec<String>>),
 }
 
 impl CheckCode {
@@ -301,6 +393,10 @@ impl CheckCode {
             CheckCode::A001 => CheckKind::BuiltinVariableShadowing("...".to_string()),
             CheckCode::A002 => CheckKind::BuiltinArgumentShadowing("...".to_string()),
             CheckCode::A003 => CheckKind::BuiltinAttributeShadowing("...".to_string()),
+            // flake8-bugbear
+            CheckCode::B011 => CheckKind::DoNotAssertFalse,
+            CheckCode::B014 => CheckKind::DuplicateHandlerException(vec!["ValueError".to_string()]),
+            CheckCode::B025 => CheckKind::DuplicateTryBlockException("Exception".to_string()),
             // flake8-comprehensions
             CheckCode::C400 => CheckKind::UnnecessaryGeneratorList,
             CheckCode::C401 => CheckKind::UnnecessaryGeneratorSet,
@@ -312,6 +408,16 @@ impl CheckCode {
             CheckCode::C408 => {
                 CheckKind::UnnecessaryCollectionCall("<dict/list/tuple>".to_string())
             }
+            CheckCode::C409 => {
+                CheckKind::UnnecessaryLiteralWithinTupleCall("<list/tuple>".to_string())
+            }
+            CheckCode::C410 => {
+                CheckKind::UnnecessaryLiteralWithinListCall("<list/tuple>".to_string())
+            }
+            CheckCode::C414 => CheckKind::UnnecessaryDoubleCastOrProcess(
+                "<list/reversed/set/sorted/tuple>".to_string(),
+                "<list/set/sorted/tuple>".to_string(),
+            ),
             CheckCode::C415 => {
                 CheckKind::UnnecessarySubscriptReversal("<reversed/set/sorted>".to_string())
             }
@@ -330,6 +436,48 @@ impl CheckCode {
             CheckCode::U006 => CheckKind::UsePEP585Annotation("List".to_string()),
             CheckCode::U007 => CheckKind::UsePEP604Annotation,
             CheckCode::U008 => CheckKind::SuperCallWithParameters,
+            // pydocstyle
+            CheckCode::D100 => CheckKind::PublicModule,
+            CheckCode::D101 => CheckKind::PublicClass,
+            CheckCode::D102 => CheckKind::PublicMethod,
+            CheckCode::D103 => CheckKind::PublicFunction,
+            CheckCode::D104 => CheckKind::PublicPackage,
+            CheckCode::D105 => CheckKind::MagicMethod,
+            CheckCode::D106 => CheckKind::PublicNestedClass,
+            CheckCode::D107 => CheckKind::PublicInit,
+            CheckCode::D200 => CheckKind::FitsOnOneLine,
+            CheckCode::D201 => CheckKind::NoBlankLineBeforeFunction(1),
+            CheckCode::D202 => CheckKind::NoBlankLineAfterFunction(1),
+            CheckCode::D203 => CheckKind::OneBlankLineBeforeClass(0),
+            CheckCode::D204 => CheckKind::OneBlankLineAfterClass(0),
+            CheckCode::D205 => CheckKind::NoBlankLineAfterSummary,
+            CheckCode::D209 => CheckKind::NewLineAfterLastParagraph,
+            CheckCode::D210 => CheckKind::NoSurroundingWhitespace,
+            CheckCode::D211 => CheckKind::NoBlankLineBeforeClass(1),
+            CheckCode::D212 => CheckKind::MultiLineSummaryFirstLine,
+            CheckCode::D213 => CheckKind::MultiLineSummarySecondLine,
+            CheckCode::D300 => CheckKind::UsesTripleQuotes,
+            CheckCode::D400 => CheckKind::EndsInPeriod,
+            CheckCode::D402 => CheckKind::NoSignature,
+            CheckCode::D403 => CheckKind::FirstLineCapitalized,
+            CheckCode::D404 => CheckKind::NoThisPrefix,
+            CheckCode::D405 => CheckKind::CapitalizeSectionName("returns".to_string()),
+            CheckCode::D406 => CheckKind::NewLineAfterSectionName("Returns".to_string()),
+            CheckCode::D407 => CheckKind::DashedUnderlineAfterSection("Returns".to_string()),
+            CheckCode::D408 => CheckKind::SectionUnderlineAfterName("Returns".to_string()),
+            CheckCode::D409 => {
+                CheckKind::SectionUnderlineMatchesSectionLength("Returns".to_string())
+            }
+            CheckCode::D410 => CheckKind::BlankLineAfterSection("Returns".to_string()),
+            CheckCode::D411 => CheckKind::BlankLineBeforeSection("Returns".to_string()),
+            CheckCode::D412 => {
+                CheckKind::NoBlankLinesBetweenHeaderAndContent("Returns".to_string())
+            }
+            CheckCode::D413 => CheckKind::BlankLineAfterLastSection("Returns".to_string()),
+            CheckCode::D414 => CheckKind::NonEmptySection("Returns".to_string()),
+            CheckCode::D415 => CheckKind::EndsInPunctuation,
+            CheckCode::D418 => CheckKind::SkipDocstring,
+            CheckCode::D419 => CheckKind::NonEmpty,
             // Meta
             CheckCode::M001 => CheckKind::UnusedNOQA(None),
         }
@@ -389,6 +537,10 @@ impl CheckKind {
             CheckKind::BuiltinVariableShadowing(_) => &CheckCode::A001,
             CheckKind::BuiltinArgumentShadowing(_) => &CheckCode::A002,
             CheckKind::BuiltinAttributeShadowing(_) => &CheckCode::A003,
+            // flake8-bugbear
+            CheckKind::DoNotAssertFalse => &CheckCode::B011,
+            CheckKind::DuplicateHandlerException(_) => &CheckCode::B014,
+            CheckKind::DuplicateTryBlockException(_) => &CheckCode::B025,
             // flake8-comprehensions
             CheckKind::UnnecessaryGeneratorList => &CheckCode::C400,
             CheckKind::UnnecessaryGeneratorSet => &CheckCode::C401,
@@ -398,6 +550,9 @@ impl CheckKind {
             CheckKind::UnnecessaryLiteralSet(_) => &CheckCode::C405,
             CheckKind::UnnecessaryLiteralDict(_) => &CheckCode::C406,
             CheckKind::UnnecessaryCollectionCall(_) => &CheckCode::C408,
+            CheckKind::UnnecessaryLiteralWithinTupleCall(..) => &CheckCode::C409,
+            CheckKind::UnnecessaryLiteralWithinListCall(..) => &CheckCode::C410,
+            CheckKind::UnnecessaryDoubleCastOrProcess(..) => &CheckCode::C414,
             CheckKind::UnnecessarySubscriptReversal(_) => &CheckCode::C415,
             // flake8-print
             CheckKind::PrintFound => &CheckCode::T201,
@@ -411,6 +566,44 @@ impl CheckKind {
             CheckKind::UsePEP604Annotation => &CheckCode::U007,
             CheckKind::UselessObjectInheritance(_) => &CheckCode::U004,
             CheckKind::SuperCallWithParameters => &CheckCode::U008,
+            // pydocstyle
+            CheckKind::BlankLineAfterLastSection(_) => &CheckCode::D413,
+            CheckKind::BlankLineAfterSection(_) => &CheckCode::D410,
+            CheckKind::BlankLineBeforeSection(_) => &CheckCode::D411,
+            CheckKind::CapitalizeSectionName(_) => &CheckCode::D405,
+            CheckKind::DashedUnderlineAfterSection(_) => &CheckCode::D407,
+            CheckKind::EndsInPeriod => &CheckCode::D400,
+            CheckKind::EndsInPunctuation => &CheckCode::D415,
+            CheckKind::FirstLineCapitalized => &CheckCode::D403,
+            CheckKind::FitsOnOneLine => &CheckCode::D200,
+            CheckKind::MagicMethod => &CheckCode::D105,
+            CheckKind::MultiLineSummaryFirstLine => &CheckCode::D212,
+            CheckKind::MultiLineSummarySecondLine => &CheckCode::D213,
+            CheckKind::NewLineAfterLastParagraph => &CheckCode::D209,
+            CheckKind::NewLineAfterSectionName(_) => &CheckCode::D406,
+            CheckKind::NoBlankLineAfterFunction(_) => &CheckCode::D202,
+            CheckKind::NoBlankLineAfterSummary => &CheckCode::D205,
+            CheckKind::NoBlankLineBeforeClass(_) => &CheckCode::D211,
+            CheckKind::NoBlankLineBeforeFunction(_) => &CheckCode::D201,
+            CheckKind::NoBlankLinesBetweenHeaderAndContent(_) => &CheckCode::D412,
+            CheckKind::NoSignature => &CheckCode::D402,
+            CheckKind::NoSurroundingWhitespace => &CheckCode::D210,
+            CheckKind::NoThisPrefix => &CheckCode::D404,
+            CheckKind::NonEmpty => &CheckCode::D419,
+            CheckKind::NonEmptySection(_) => &CheckCode::D414,
+            CheckKind::OneBlankLineAfterClass(_) => &CheckCode::D204,
+            CheckKind::OneBlankLineBeforeClass(_) => &CheckCode::D203,
+            CheckKind::PublicClass => &CheckCode::D101,
+            CheckKind::PublicFunction => &CheckCode::D103,
+            CheckKind::PublicInit => &CheckCode::D107,
+            CheckKind::PublicMethod => &CheckCode::D102,
+            CheckKind::PublicModule => &CheckCode::D100,
+            CheckKind::PublicNestedClass => &CheckCode::D106,
+            CheckKind::PublicPackage => &CheckCode::D104,
+            CheckKind::SectionUnderlineAfterName(_) => &CheckCode::D408,
+            CheckKind::SectionUnderlineMatchesSectionLength(_) => &CheckCode::D409,
+            CheckKind::SkipDocstring => &CheckCode::D418,
+            CheckKind::UsesTripleQuotes => &CheckCode::D300,
             // Meta
             CheckKind::UnusedNOQA(_) => &CheckCode::M001,
         }
@@ -559,6 +752,23 @@ impl CheckKind {
             CheckKind::BuiltinAttributeShadowing(name) => {
                 format!("Class attribute `{name}` is shadowing a python builtin")
             }
+            // flake8-bugbear
+            CheckKind::DoNotAssertFalse => {
+                "Do not `assert False` (`python -O` removes these calls), raise `AssertionError()`"
+                    .to_string()
+            }
+            CheckKind::DuplicateHandlerException(names) => {
+                if names.len() == 1 {
+                    let name = &names[0];
+                    format!("Exception handler with duplicate exception: `{name}`")
+                } else {
+                    let names = names.iter().map(|name| format!("`{name}`")).join(", ");
+                    format!("Exception handler with duplicate exceptions: {names}")
+                }
+            }
+            CheckKind::DuplicateTryBlockException(name) => {
+                format!("try-except block with duplicate exception `{name}`")
+            }
             // flake8-comprehensions
             CheckKind::UnnecessaryGeneratorList => {
                 "Unnecessary generator - rewrite as a list comprehension".to_string()
@@ -584,6 +794,31 @@ impl CheckKind {
             CheckKind::UnnecessaryCollectionCall(obj_type) => {
                 format!("Unnecessary {obj_type} call - rewrite as a literal")
             }
+            CheckKind::UnnecessaryLiteralWithinTupleCall(literal) => {
+                if literal == "list" {
+                    format!(
+                        "Unnecessary {literal} literal passed to tuple() - rewrite as a tuple literal"
+                    )
+                } else {
+                    format!(
+                        "Unnecessary {literal} literal passed to tuple() - remove the outer call to tuple()"
+                    )
+                }
+            }
+            CheckKind::UnnecessaryLiteralWithinListCall(literal) => {
+                if literal == "list" {
+                    format!(
+                        "Unnecessary {literal} literal passed to list() - remove the outer call to list()"
+                    )
+                } else {
+                    format!(
+                        "Unnecessary {literal} literal passed to list() - rewrite as a list literal"
+                    )
+                }
+            }
+            CheckKind::UnnecessaryDoubleCastOrProcess(inner, outer) => {
+                format!("Unnecessary {inner} call within {outer}().")
+            }
             CheckKind::UnnecessarySubscriptReversal(func) => {
                 format!("Unnecessary subscript reversal of iterable within {func}()")
             }
@@ -615,10 +850,111 @@ impl CheckKind {
             CheckKind::SuperCallWithParameters => {
                 "Use `super()` instead of `super(__class__, self)`".to_string()
             }
+            // pydocstyle
+            CheckKind::FitsOnOneLine => "One-line docstring should fit on one line".to_string(),
+            CheckKind::NoBlankLineAfterSummary => {
+                "1 blank line required between summary line and description".to_string()
+            }
+            CheckKind::NewLineAfterLastParagraph => {
+                "Multi-line docstring closing quotes should be on a separate line".to_string()
+            }
+            CheckKind::NoSurroundingWhitespace => {
+                "No whitespaces allowed surrounding docstring text".to_string()
+            }
+            CheckKind::EndsInPeriod => "First line should end with a period".to_string(),
+            CheckKind::NonEmpty => "Docstring is empty".to_string(),
+            CheckKind::EndsInPunctuation => {
+                "First line should end with a period, question mark, or exclamation point"
+                    .to_string()
+            }
+            CheckKind::FirstLineCapitalized => {
+                "First word of the first line should be properly capitalized".to_string()
+            }
+            CheckKind::UsesTripleQuotes => r#"Use """triple double quotes""""#.to_string(),
+            CheckKind::MultiLineSummaryFirstLine => {
+                "Multi-line docstring summary should start at the first line".to_string()
+            }
+            CheckKind::MultiLineSummarySecondLine => {
+                "Multi-line docstring summary should start at the second line".to_string()
+            }
+            CheckKind::NoSignature => {
+                "First line should not be the function's 'signature'".to_string()
+            }
+            CheckKind::NoBlankLineBeforeFunction(num_lines) => {
+                format!("No blank lines allowed before function docstring (found {num_lines})")
+            }
+            CheckKind::NoBlankLineAfterFunction(num_lines) => {
+                format!("No blank lines allowed after function docstring (found {num_lines})")
+            }
+            CheckKind::NoBlankLineBeforeClass(_) => {
+                "No blank lines allowed before class docstring".to_string()
+            }
+            CheckKind::OneBlankLineBeforeClass(_) => {
+                "1 blank line required before class docstring".to_string()
+            }
+            CheckKind::OneBlankLineAfterClass(_) => {
+                "1 blank line required after class docstring".to_string()
+            }
+            CheckKind::PublicModule => "Missing docstring in public module".to_string(),
+            CheckKind::PublicClass => "Missing docstring in public class".to_string(),
+            CheckKind::PublicMethod => "Missing docstring in public method".to_string(),
+            CheckKind::PublicFunction => "Missing docstring in public function".to_string(),
+            CheckKind::PublicPackage => "Missing docstring in public package".to_string(),
+            CheckKind::MagicMethod => "Missing docstring in magic method".to_string(),
+            CheckKind::PublicNestedClass => "Missing docstring in public nested class".to_string(),
+            CheckKind::PublicInit => "Missing docstring in __init__".to_string(),
+            CheckKind::NoThisPrefix => {
+                "First word of the docstring should not be `This`".to_string()
+            }
+            CheckKind::SkipDocstring => {
+                "Function decorated with @overload shouldn't contain a docstring".to_string()
+            }
+            CheckKind::CapitalizeSectionName(name) => {
+                format!("Section name should be properly capitalized (\"{name}\")")
+            }
+            CheckKind::BlankLineAfterLastSection(name) => {
+                format!("Missing blank line after last section (\"{name}\")")
+            }
+            CheckKind::BlankLineAfterSection(name) => {
+                format!("Missing blank line after section (\"{name}\")")
+            }
+            CheckKind::BlankLineBeforeSection(name) => {
+                format!("Missing blank line before section (\"{name}\")")
+            }
+            CheckKind::NewLineAfterSectionName(name) => {
+                format!("Section name should end with a newline (\"{name}\")")
+            }
+            CheckKind::DashedUnderlineAfterSection(name) => {
+                format!("Missing dashed underline after section (\"{name}\")")
+            }
+            CheckKind::SectionUnderlineAfterName(name) => {
+                format!("Section underline should be in the line following the section's name (\"{name}\")")
+            }
+            CheckKind::SectionUnderlineMatchesSectionLength(name) => {
+                format!("Section underline should match the length of its name (\"{name}\")")
+            }
+            CheckKind::NoBlankLinesBetweenHeaderAndContent(name) => {
+                format!(
+                    "No blank lines allowed between a section header and its content (\"{name}\")"
+                )
+            }
+            CheckKind::NonEmptySection(name) => format!("Section has no content (\"{name}\")"),
             // Meta
-            CheckKind::UnusedNOQA(code) => match code {
+            CheckKind::UnusedNOQA(codes) => match codes {
                 None => "Unused `noqa` directive".to_string(),
-                Some(code) => format!("Unused `noqa` directive for: {code}"),
+                Some(codes) => {
+                    let codes = codes
+                        .iter()
+                        .map(|code| {
+                            if CheckCode::from_str(code).is_ok() {
+                                code.to_string()
+                            } else {
+                                format!("{code} (not implemented)")
+                            }
+                        })
+                        .join(", ");
+                    format!("Unused `noqa` directive for: {codes}")
+                }
             },
         }
     }
@@ -628,6 +964,8 @@ impl CheckKind {
         matches!(
             self,
             CheckKind::DeprecatedUnittestAlias(_, _)
+                | CheckKind::DoNotAssertFalse
+                | CheckKind::DuplicateHandlerException(_)
                 | CheckKind::PPrintFound
                 | CheckKind::PrintFound
                 | CheckKind::SuperCallWithParameters

src/cli.rs

@@ -78,6 +78,9 @@ pub struct Cli {
     // TODO(charlie): This should be a sub-command.
     #[arg(long, hide = true)]
     pub autoformat: bool,
+    /// The name of the file when passing it through stdin.
+    #[arg(long)]
+    pub stdin_filename: Option<String>,
 }
 
 pub enum Warnable {

src/code_gen.rs

@@ -115,7 +115,7 @@ impl SourceGenerator {
         Ok(())
     }
 
-    fn unparse_stmt<U>(&mut self, ast: &Stmt<U>) -> fmt::Result {
+    pub fn unparse_stmt<U>(&mut self, ast: &Stmt<U>) -> fmt::Result {
         macro_rules! statement {
             ($body:block) => {{
                 self.newline()?;

src/docstrings.rs

@@ -0,0 +1,3 @@
+pub mod docstring_checks;
+pub mod sections;
+pub mod types;

src/docstrings/docstring_checks.rs

@@ -0,0 +1,676 @@
+//! Abstractions for tracking and validating docstrings in Python code.
+
+use once_cell::sync::Lazy;
+use regex::Regex;
+use rustpython_ast::{Constant, Expr, ExprKind, Location, Stmt, StmtKind};
+
+use crate::ast::types::Range;
+use crate::check_ast::Checker;
+use crate::checks::{Check, CheckCode, CheckKind};
+use crate::docstrings::sections::{check_numpy_section, section_contexts};
+use crate::docstrings::types::{Definition, DefinitionKind, Documentable};
+use crate::visibility::{is_init, is_magic, is_overload, Modifier, Visibility, VisibleScope};
+
+/// Extract a docstring from a function or class body.
+pub fn docstring_from(suite: &[Stmt]) -> Option<&Expr> {
+    if let Some(stmt) = suite.first() {
+        if let StmtKind::Expr { value } = &stmt.node {
+            if matches!(
+                &value.node,
+                ExprKind::Constant {
+                    value: Constant::Str(_),
+                    ..
+                }
+            ) {
+                return Some(value);
+            }
+        }
+    }
+    None
+}
+
+/// Extract a `Definition` from the AST node defined by a `Stmt`.
+pub fn extract<'a>(
+    scope: &VisibleScope,
+    stmt: &'a Stmt,
+    body: &'a [Stmt],
+    kind: &Documentable,
+) -> Definition<'a> {
+    let expr = docstring_from(body);
+    match kind {
+        Documentable::Function => match scope {
+            VisibleScope {
+                modifier: Modifier::Module,
+                ..
+            } => Definition {
+                kind: DefinitionKind::Function(stmt),
+                docstring: expr,
+            },
+            VisibleScope {
+                modifier: Modifier::Class,
+                ..
+            } => Definition {
+                kind: DefinitionKind::Method(stmt),
+                docstring: expr,
+            },
+            VisibleScope {
+                modifier: Modifier::Function,
+                ..
+            } => Definition {
+                kind: DefinitionKind::NestedFunction(stmt),
+                docstring: expr,
+            },
+        },
+        Documentable::Class => match scope {
+            VisibleScope {
+                modifier: Modifier::Module,
+                ..
+            } => Definition {
+                kind: DefinitionKind::Class(stmt),
+                docstring: expr,
+            },
+            VisibleScope {
+                modifier: Modifier::Class,
+                ..
+            } => Definition {
+                kind: DefinitionKind::NestedClass(stmt),
+                docstring: expr,
+            },
+            VisibleScope {
+                modifier: Modifier::Function,
+                ..
+            } => Definition {
+                kind: DefinitionKind::NestedClass(stmt),
+                docstring: expr,
+            },
+        },
+    }
+}
+
+/// Extract the source code range for a docstring.
+pub fn range_for(docstring: &Expr) -> Range {
+    // RustPython currently omits the first quotation mark in a string, so offset the location.
+    Range {
+        location: Location::new(docstring.location.row(), docstring.location.column() - 1),
+        end_location: docstring.end_location,
+    }
+}
+
+/// D100, D101, D102, D103, D104, D105, D106, D107
+pub fn not_missing(
+    checker: &mut Checker,
+    definition: &Definition,
+    visibility: &Visibility,
+) -> bool {
+    if matches!(visibility, Visibility::Private) {
+        return true;
+    }
+
+    if definition.docstring.is_some() {
+        return true;
+    }
+
+    match definition.kind {
+        DefinitionKind::Module => {
+            if checker.settings.enabled.contains(&CheckCode::D100) {
+                checker.add_check(Check::new(
+                    CheckKind::PublicModule,
+                    Range {
+                        location: Location::new(1, 1),
+                        end_location: Location::new(1, 1),
+                    },
+                ));
+            }
+            false
+        }
+        DefinitionKind::Package => {
+            if checker.settings.enabled.contains(&CheckCode::D104) {
+                checker.add_check(Check::new(
+                    CheckKind::PublicPackage,
+                    Range {
+                        location: Location::new(1, 1),
+                        end_location: Location::new(1, 1),
+                    },
+                ));
+            }
+            false
+        }
+        DefinitionKind::Class(stmt) => {
+            if checker.settings.enabled.contains(&CheckCode::D101) {
+                checker.add_check(Check::new(
+                    CheckKind::PublicClass,
+                    Range::from_located(stmt),
+                ));
+            }
+            false
+        }
+        DefinitionKind::NestedClass(stmt) => {
+            if checker.settings.enabled.contains(&CheckCode::D106) {
+                checker.add_check(Check::new(
+                    CheckKind::PublicNestedClass,
+                    Range::from_located(stmt),
+                ));
+            }
+            false
+        }
+        DefinitionKind::Function(stmt) | DefinitionKind::NestedFunction(stmt) => {
+            if is_overload(stmt) {
+                true
+            } else {
+                if checker.settings.enabled.contains(&CheckCode::D103) {
+                    checker.add_check(Check::new(
+                        CheckKind::PublicFunction,
+                        Range::from_located(stmt),
+                    ));
+                }
+                false
+            }
+        }
+        DefinitionKind::Method(stmt) => {
+            if is_overload(stmt) {
+                true
+            } else if is_magic(stmt) {
+                if checker.settings.enabled.contains(&CheckCode::D105) {
+                    checker.add_check(Check::new(
+                        CheckKind::MagicMethod,
+                        Range::from_located(stmt),
+                    ));
+                }
+                true
+            } else if is_init(stmt) {
+                if checker.settings.enabled.contains(&CheckCode::D107) {
+                    checker.add_check(Check::new(CheckKind::PublicInit, Range::from_located(stmt)));
+                }
+                true
+            } else {
+                if checker.settings.enabled.contains(&CheckCode::D102) {
+                    checker.add_check(Check::new(
+                        CheckKind::PublicMethod,
+                        Range::from_located(stmt),
+                    ));
+                }
+                true
+            }
+        }
+    }
+}
+
+/// D200
+pub fn one_liner(checker: &mut Checker, definition: &Definition) {
+    if let Some(docstring) = &definition.docstring {
+        if let ExprKind::Constant {
+            value: Constant::Str(string),
+            ..
+        } = &docstring.node
+        {
+            let mut line_count = 0;
+            let mut non_empty_line_count = 0;
+            for line in string.lines() {
+                line_count += 1;
+                if !line.trim().is_empty() {
+                    non_empty_line_count += 1;
+                }
+                if non_empty_line_count > 1 {
+                    break;
+                }
+            }
+
+            if non_empty_line_count == 1 && line_count > 1 {
+                checker.add_check(Check::new(CheckKind::FitsOnOneLine, range_for(docstring)));
+            }
+        }
+    }
+}
+
+static COMMENT_REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"^\s*#").unwrap());
+
+static INNER_FUNCTION_OR_CLASS_REGEX: Lazy<Regex> =
+    Lazy::new(|| Regex::new(r"^\s+(?:(?:class|def|async def)\s|@)").unwrap());
+
+/// D201, D202
+pub fn blank_before_after_function(checker: &mut Checker, definition: &Definition) {
+    if let Some(docstring) = definition.docstring {
+        if let DefinitionKind::Function(parent)
+        | DefinitionKind::NestedFunction(parent)
+        | DefinitionKind::Method(parent) = &definition.kind
+        {
+            if let ExprKind::Constant {
+                value: Constant::Str(_),
+                ..
+            } = &docstring.node
+            {
+                let (before, _, after) = checker
+                    .locator
+                    .partition_source_code_at(&Range::from_located(parent), &range_for(docstring));
+
+                if checker.settings.enabled.contains(&CheckCode::D201) {
+                    let blank_lines_before = before
+                        .lines()
+                        .rev()
+                        .skip(1)
+                        .take_while(|line| line.trim().is_empty())
+                        .count();
+                    if blank_lines_before != 0 {
+                        checker.add_check(Check::new(
+                            CheckKind::NoBlankLineBeforeFunction(blank_lines_before),
+                            range_for(docstring),
+                        ));
+                    }
+                }
+
+                if checker.settings.enabled.contains(&CheckCode::D202) {
+                    let blank_lines_after = after
+                        .lines()
+                        .skip(1)
+                        .take_while(|line| line.trim().is_empty())
+                        .count();
+                    let all_blank_after = after
+                        .lines()
+                        .skip(1)
+                        .all(|line| line.trim().is_empty() || COMMENT_REGEX.is_match(line));
+                    // Report a D202 violation if the docstring is followed by a blank line
+                    // and the blank line is not itself followed by an inner function or
+                    // class.
+                    if !all_blank_after
+                        && blank_lines_after != 0
+                        && !(blank_lines_after == 1
+                            && INNER_FUNCTION_OR_CLASS_REGEX.is_match(after))
+                    {
+                        checker.add_check(Check::new(
+                            CheckKind::NoBlankLineAfterFunction(blank_lines_after),
+                            range_for(docstring),
+                        ));
+                    }
+                }
+            }
+        }
+    }
+}
+
+/// D203, D204, D211
+pub fn blank_before_after_class(checker: &mut Checker, definition: &Definition) {
+    if let Some(docstring) = &definition.docstring {
+        if let DefinitionKind::Class(parent) | DefinitionKind::NestedClass(parent) =
+            &definition.kind
+        {
+            if let ExprKind::Constant {
+                value: Constant::Str(_),
+                ..
+            } = &docstring.node
+            {
+                let (before, _, after) = checker
+                    .locator
+                    .partition_source_code_at(&Range::from_located(parent), &range_for(docstring));
+
+                if checker.settings.enabled.contains(&CheckCode::D203)
+                    || checker.settings.enabled.contains(&CheckCode::D211)
+                {
+                    let blank_lines_before = before
+                        .lines()
+                        .rev()
+                        .skip(1)
+                        .take_while(|line| line.trim().is_empty())
+                        .count();
+                    if blank_lines_before != 0
+                        && checker.settings.enabled.contains(&CheckCode::D211)
+                    {
+                        checker.add_check(Check::new(
+                            CheckKind::NoBlankLineBeforeClass(blank_lines_before),
+                            range_for(docstring),
+                        ));
+                    }
+                    if blank_lines_before != 1
+                        && checker.settings.enabled.contains(&CheckCode::D203)
+                    {
+                        checker.add_check(Check::new(
+                            CheckKind::OneBlankLineBeforeClass(blank_lines_before),
+                            range_for(docstring),
+                        ));
+                    }
+                }
+
+                if checker.settings.enabled.contains(&CheckCode::D204) {
+                    let blank_lines_after = after
+                        .lines()
+                        .skip(1)
+                        .take_while(|line| line.trim().is_empty())
+                        .count();
+                    let all_blank_after = after
+                        .lines()
+                        .skip(1)
+                        .all(|line| line.trim().is_empty() || COMMENT_REGEX.is_match(line));
+                    if !all_blank_after && blank_lines_after != 1 {
+                        checker.add_check(Check::new(
+                            CheckKind::OneBlankLineAfterClass(blank_lines_after),
+                            range_for(docstring),
+                        ));
+                    }
+                }
+            }
+        }
+    }
+}
+
+/// D205
+pub fn blank_after_summary(checker: &mut Checker, definition: &Definition) {
+    if let Some(docstring) = definition.docstring {
+        if let ExprKind::Constant {
+            value: Constant::Str(string),
+            ..
+        } = &docstring.node
+        {
+            let mut lines_count = 1;
+            let mut blanks_count = 0;
+            for line in string.trim().lines().skip(1) {
+                lines_count += 1;
+                if line.trim().is_empty() {
+                    blanks_count += 1;
+                } else {
+                    break;
+                }
+            }
+            if lines_count > 1 && blanks_count != 1 {
+                checker.add_check(Check::new(
+                    CheckKind::NoBlankLineAfterSummary,
+                    range_for(docstring),
+                ));
+            }
+        }
+    }
+}
+
+/// D209
+pub fn newline_after_last_paragraph(checker: &mut Checker, definition: &Definition) {
+    if let Some(docstring) = definition.docstring {
+        if let ExprKind::Constant {
+            value: Constant::Str(string),
+            ..
+        } = &docstring.node
+        {
+            let mut line_count = 0;
+            for line in string.lines() {
+                if !line.trim().is_empty() {
+                    line_count += 1;
+                }
+                if line_count > 1 {
+                    let content = checker
+                        .locator
+                        .slice_source_code_range(&range_for(docstring));
+                    if let Some(line) = content.lines().last() {
+                        let line = line.trim();
+                        if line != "\"\"\"" && line != "'''" {
+                            checker.add_check(Check::new(
+                                CheckKind::NewLineAfterLastParagraph,
+                                range_for(docstring),
+                            ));
+                        }
+                    }
+                    return;
+                }
+            }
+        }
+    }
+}
+
+/// D210
+pub fn no_surrounding_whitespace(checker: &mut Checker, definition: &Definition) {
+    if let Some(docstring) = definition.docstring {
+        if let ExprKind::Constant {
+            value: Constant::Str(string),
+            ..
+        } = &docstring.node
+        {
+            let mut lines = string.lines();
+            if let Some(line) = lines.next() {
+                if line.trim().is_empty() {
+                    return;
+                }
+                if line.starts_with(' ') || (matches!(lines.next(), None) && line.ends_with(' ')) {
+                    checker.add_check(Check::new(
+                        CheckKind::NoSurroundingWhitespace,
+                        range_for(docstring),
+                    ));
+                }
+            }
+        }
+    }
+}
+
+/// D212, D213
+pub fn multi_line_summary_start(checker: &mut Checker, definition: &Definition) {
+    if let Some(docstring) = definition.docstring {
+        if let ExprKind::Constant {
+            value: Constant::Str(string),
+            ..
+        } = &docstring.node
+        {
+            if string.lines().nth(1).is_some() {
+                let content = checker
+                    .locator
+                    .slice_source_code_range(&range_for(docstring));
+                if let Some(first_line) = content.lines().next() {
+                    let first_line = first_line.trim();
+                    if first_line == "\"\"\"" || first_line == "'''" {
+                        if checker.settings.enabled.contains(&CheckCode::D212) {
+                            checker.add_check(Check::new(
+                                CheckKind::MultiLineSummaryFirstLine,
+                                range_for(docstring),
+                            ));
+                        }
+                    } else if checker.settings.enabled.contains(&CheckCode::D213) {
+                        checker.add_check(Check::new(
+                            CheckKind::MultiLineSummarySecondLine,
+                            range_for(docstring),
+                        ));
+                    }
+                }
+            }
+        }
+    }
+}
+
+/// D300
+pub fn triple_quotes(checker: &mut Checker, definition: &Definition) {
+    if let Some(docstring) = definition.docstring {
+        if let ExprKind::Constant {
+            value: Constant::Str(string),
+            ..
+        } = &docstring.node
+        {
+            let content = checker
+                .locator
+                .slice_source_code_range(&range_for(docstring));
+            if string.contains("\"\"\"") {
+                if !content.starts_with("'''") {
+                    checker.add_check(Check::new(
+                        CheckKind::UsesTripleQuotes,
+                        range_for(docstring),
+                    ));
+                }
+            } else if !content.starts_with("\"\"\"") {
+                checker.add_check(Check::new(
+                    CheckKind::UsesTripleQuotes,
+                    range_for(docstring),
+                ));
+            }
+        }
+    }
+}
+
+/// D400
+pub fn ends_with_period(checker: &mut Checker, definition: &Definition) {
+    if let Some(docstring) = definition.docstring {
+        if let ExprKind::Constant {
+            value: Constant::Str(string),
+            ..
+        } = &docstring.node
+        {
+            if let Some(string) = string.lines().next() {
+                if !string.ends_with('.') {
+                    checker.add_check(Check::new(CheckKind::EndsInPeriod, range_for(docstring)));
+                }
+            }
+        }
+    }
+}
+
+/// D402
+pub fn no_signature(checker: &mut Checker, definition: &Definition) {
+    if let Some(docstring) = definition.docstring {
+        if let DefinitionKind::Function(parent)
+        | DefinitionKind::NestedFunction(parent)
+        | DefinitionKind::Method(parent) = definition.kind
+        {
+            if let StmtKind::FunctionDef { name, .. } = &parent.node {
+                if let ExprKind::Constant {
+                    value: Constant::Str(string),
+                    ..
+                } = &docstring.node
+                {
+                    if let Some(first_line) = string.lines().next() {
+                        if first_line.contains(&format!("{name}(")) {
+                            checker.add_check(Check::new(
+                                CheckKind::NoSignature,
+                                range_for(docstring),
+                            ));
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+/// D403
+pub fn capitalized(checker: &mut Checker, definition: &Definition) {
+    if !matches!(definition.kind, DefinitionKind::Function(_)) {
+        return;
+    }
+
+    if let Some(docstring) = definition.docstring {
+        if let ExprKind::Constant {
+            value: Constant::Str(string),
+            ..
+        } = &docstring.node
+        {
+            if let Some(first_word) = string.split(' ').next() {
+                if first_word == first_word.to_uppercase() {
+                    return;
+                }
+                for char in first_word.chars() {
+                    if !char.is_ascii_alphabetic() && char != '\'' {
+                        return;
+                    }
+                }
+                if let Some(first_char) = first_word.chars().next() {
+                    if !first_char.is_uppercase() {
+                        checker.add_check(Check::new(
+                            CheckKind::FirstLineCapitalized,
+                            range_for(docstring),
+                        ));
+                    }
+                }
+            }
+        }
+    }
+}
+
+/// D404
+pub fn starts_with_this(checker: &mut Checker, definition: &Definition) {
+    if let Some(docstring) = definition.docstring {
+        if let ExprKind::Constant {
+            value: Constant::Str(string),
+            ..
+        } = &docstring.node
+        {
+            let trimmed = string.trim();
+            if trimmed.is_empty() {
+                return;
+            }
+
+            if let Some(first_word) = string.split(' ').next() {
+                if first_word
+                    .replace(|c: char| !c.is_alphanumeric(), "")
+                    .to_lowercase()
+                    == "this"
+                {
+                    checker.add_check(Check::new(CheckKind::NoThisPrefix, range_for(docstring)));
+                }
+            }
+        }
+    }
+}
+
+/// D415
+pub fn ends_with_punctuation(checker: &mut Checker, definition: &Definition) {
+    if let Some(docstring) = definition.docstring {
+        if let ExprKind::Constant {
+            value: Constant::Str(string),
+            ..
+        } = &docstring.node
+        {
+            if let Some(string) = string.lines().next() {
+                if !(string.ends_with('.') || string.ends_with('!') || string.ends_with('?')) {
+                    checker.add_check(Check::new(
+                        CheckKind::EndsInPunctuation,
+                        range_for(docstring),
+                    ));
+                }
+            }
+        }
+    }
+}
+
+/// D418
+pub fn if_needed(checker: &mut Checker, definition: &Definition) {
+    if definition.docstring.is_some() {
+        if let DefinitionKind::Function(stmt)
+        | DefinitionKind::NestedFunction(stmt)
+        | DefinitionKind::Method(stmt) = definition.kind
+        {
+            if is_overload(stmt) {
+                checker.add_check(Check::new(
+                    CheckKind::SkipDocstring,
+                    Range::from_located(stmt),
+                ));
+            }
+        }
+    }
+}
+
+/// D419
+pub fn not_empty(checker: &mut Checker, definition: &Definition) -> bool {
+    if let Some(docstring) = definition.docstring {
+        if let ExprKind::Constant {
+            value: Constant::Str(string),
+            ..
+        } = &docstring.node
+        {
+            if string.trim().is_empty() {
+                if checker.settings.enabled.contains(&CheckCode::D419) {
+                    checker.add_check(Check::new(CheckKind::NonEmpty, range_for(docstring)));
+                }
+                return false;
+            }
+        }
+    }
+    true
+}
+
+pub fn check_sections(checker: &mut Checker, definition: &Definition) {
+    if let Some(docstring) = definition.docstring {
+        if let ExprKind::Constant {
+            value: Constant::Str(string),
+            ..
+        } = &docstring.node
+        {
+            let lines: Vec<&str> = string.lines().collect();
+            if lines.len() < 2 {
+                return;
+            }
+            for context in &section_contexts(&lines) {
+                check_numpy_section(checker, definition, context);
+            }
+        }
+    }
+}

src/docstrings/sections.rs

@@ -0,0 +1,384 @@
+use std::collections::BTreeSet;
+
+use once_cell::sync::Lazy;
+use titlecase::titlecase;
+
+use crate::check_ast::Checker;
+use crate::checks::{Check, CheckCode, CheckKind};
+use crate::docstrings::docstring_checks::range_for;
+use crate::docstrings::types::Definition;
+
+static NUMPY_SECTION_NAMES: Lazy<BTreeSet<&'static str>> = Lazy::new(|| {
+    BTreeSet::from([
+        "Short Summary",
+        "Extended Summary",
+        "Parameters",
+        "Returns",
+        "Yields",
+        "Other Parameters",
+        "Raises",
+        "See Also",
+        "Notes",
+        "References",
+        "Examples",
+        "Attributes",
+        "Methods",
+    ])
+});
+
+static NUMPY_SECTION_NAMES_LOWERCASE: Lazy<BTreeSet<&'static str>> = Lazy::new(|| {
+    BTreeSet::from([
+        "short summary",
+        "extended summary",
+        "parameters",
+        "returns",
+        "yields",
+        "other parameters",
+        "raises",
+        "see also",
+        "notes",
+        "references",
+        "examples",
+        "attributes",
+        "methods",
+    ])
+});
+
+// TODO(charlie): Include Google section names.
+// static GOOGLE_SECTION_NAMES: Lazy<BTreeSet<&'static str>> = Lazy::new(|| {
+//     BTreeSet::from([
+//         "Args",
+//         "Arguments",
+//         "Attention",
+//         "Attributes",
+//         "Caution",
+//         "Danger",
+//         "Error",
+//         "Example",
+//         "Examples",
+//         "Hint",
+//         "Important",
+//         "Keyword Args",
+//         "Keyword Arguments",
+//         "Methods",
+//         "Note",
+//         "Notes",
+//         "Return",
+//         "Returns",
+//         "Raises",
+//         "References",
+//         "See Also",
+//         "Tip",
+//         "Todo",
+//         "Warning",
+//         "Warnings",
+//         "Warns",
+//         "Yield",
+//         "Yields",
+//     ])
+// });
+
+fn get_leading_words(line: &str) -> String {
+    line.trim()
+        .chars()
+        .take_while(|char| char.is_alphanumeric() || char.is_whitespace())
+        .collect()
+}
+
+fn suspected_as_section(line: &str) -> bool {
+    NUMPY_SECTION_NAMES_LOWERCASE.contains(&get_leading_words(line).to_lowercase().as_str())
+}
+
+#[derive(Debug)]
+pub struct SectionContext<'a> {
+    section_name: String,
+    previous_line: &'a str,
+    line: &'a str,
+    following_lines: &'a [&'a str],
+    original_index: usize,
+    is_last_section: bool,
+}
+
+/// Check if the suspected context is really a section header.
+fn is_docstring_section(context: &SectionContext) -> bool {
+    let section_name_suffix = context
+        .line
+        .trim()
+        .strip_prefix(&context.section_name)
+        .unwrap()
+        .trim();
+    let this_looks_like_a_section_name =
+        section_name_suffix == ":" || section_name_suffix.is_empty();
+    if !this_looks_like_a_section_name {
+        return false;
+    }
+
+    let prev_line = context.previous_line.trim();
+    let prev_line_ends_with_punctuation = [',', ';', '.', '-', '\\', '/', ']', '}', ')']
+        .into_iter()
+        .any(|char| prev_line.ends_with(char));
+    let prev_line_looks_like_end_of_paragraph =
+        prev_line_ends_with_punctuation || prev_line.is_empty();
+    if !prev_line_looks_like_end_of_paragraph {
+        return false;
+    }
+
+    true
+}
+
+/// Extract all `SectionContext` values from a docstring.
+pub fn section_contexts<'a>(lines: &'a [&'a str]) -> Vec<SectionContext<'a>> {
+    let suspected_section_indices: Vec<usize> = lines
+        .iter()
+        .enumerate()
+        .filter_map(|(lineno, line)| {
+            if lineno > 0 && suspected_as_section(line) {
+                Some(lineno)
+            } else {
+                None
+            }
+        })
+        .collect();
+
+    let mut contexts = vec![];
+    for lineno in suspected_section_indices {
+        let context = SectionContext {
+            section_name: get_leading_words(lines[lineno]),
+            previous_line: lines[lineno - 1],
+            line: lines[lineno],
+            following_lines: &lines[lineno + 1..],
+            original_index: lineno,
+            is_last_section: false,
+        };
+        if is_docstring_section(&context) {
+            contexts.push(context);
+        }
+    }
+
+    let mut truncated_contexts = vec![];
+    let mut end: Option<usize> = None;
+    for context in contexts.into_iter().rev() {
+        let next_end = context.original_index;
+        truncated_contexts.push(SectionContext {
+            section_name: context.section_name,
+            previous_line: context.previous_line,
+            line: context.line,
+            following_lines: if let Some(end) = end {
+                &lines[context.original_index + 1..end]
+            } else {
+                context.following_lines
+            },
+            original_index: context.original_index,
+            is_last_section: end.is_none(),
+        });
+        end = Some(next_end);
+    }
+    truncated_contexts.reverse();
+    truncated_contexts
+}
+
+fn check_blanks_and_section_underline(
+    checker: &mut Checker,
+    definition: &Definition,
+    context: &SectionContext,
+) {
+    let docstring = definition
+        .docstring
+        .expect("Sections are only available for docstrings.");
+
+    let mut blank_lines_after_header = 0;
+    for line in context.following_lines {
+        if !line.trim().is_empty() {
+            break;
+        }
+        blank_lines_after_header += 1;
+    }
+
+    // Nothing but blank lines after the section header.
+    if blank_lines_after_header == context.following_lines.len() {
+        // D407
+        if checker.settings.enabled.contains(&CheckCode::D407) {
+            checker.add_check(Check::new(
+                CheckKind::DashedUnderlineAfterSection(context.section_name.to_string()),
+                range_for(docstring),
+            ));
+        }
+        // D414
+        if checker.settings.enabled.contains(&CheckCode::D414) {
+            checker.add_check(Check::new(
+                CheckKind::NonEmptySection(context.section_name.to_string()),
+                range_for(docstring),
+            ));
+        }
+        return;
+    }
+
+    let non_empty_line = context.following_lines[blank_lines_after_header];
+    let dash_line_found = non_empty_line
+        .chars()
+        .all(|char| char.is_whitespace() || char == '-');
+
+    if !dash_line_found {
+        // D407
+        if checker.settings.enabled.contains(&CheckCode::D407) {
+            checker.add_check(Check::new(
+                CheckKind::DashedUnderlineAfterSection(context.section_name.to_string()),
+                range_for(docstring),
+            ));
+        }
+        if blank_lines_after_header > 0 {
+            // D212
+            if checker.settings.enabled.contains(&CheckCode::D212) {
+                checker.add_check(Check::new(
+                    CheckKind::NoBlankLinesBetweenHeaderAndContent(
+                        context.section_name.to_string(),
+                    ),
+                    range_for(docstring),
+                ));
+            }
+        }
+    } else {
+        if blank_lines_after_header > 0 {
+            // D408
+            if checker.settings.enabled.contains(&CheckCode::D408) {
+                checker.add_check(Check::new(
+                    CheckKind::SectionUnderlineAfterName(context.section_name.to_string()),
+                    range_for(docstring),
+                ));
+            }
+        }
+
+        if non_empty_line
+            .trim()
+            .chars()
+            .filter(|char| *char == '-')
+            .count()
+            != context.section_name.len()
+        {
+            // D409
+            if checker.settings.enabled.contains(&CheckCode::D409) {
+                checker.add_check(Check::new(
+                    CheckKind::SectionUnderlineMatchesSectionLength(
+                        context.section_name.to_string(),
+                    ),
+                    range_for(docstring),
+                ));
+            }
+        }
+
+        // TODO(charlie): Implement D215, which requires indentation and leading space tracking.
+        let line_after_dashes_index = blank_lines_after_header + 1;
+
+        if line_after_dashes_index < context.following_lines.len() {
+            let line_after_dashes = context.following_lines[line_after_dashes_index];
+
+            if line_after_dashes.trim().is_empty() {
+                let rest_of_lines = &context.following_lines[line_after_dashes_index..];
+                if rest_of_lines.iter().all(|line| line.trim().is_empty()) {
+                    // D414
+                    if checker.settings.enabled.contains(&CheckCode::D414) {
+                        checker.add_check(Check::new(
+                            CheckKind::NonEmptySection(context.section_name.to_string()),
+                            range_for(docstring),
+                        ));
+                    }
+                } else {
+                    // 412
+                    if checker.settings.enabled.contains(&CheckCode::D412) {
+                        checker.add_check(Check::new(
+                            CheckKind::NoBlankLinesBetweenHeaderAndContent(
+                                context.section_name.to_string(),
+                            ),
+                            range_for(docstring),
+                        ));
+                    }
+                }
+            }
+        } else {
+            // D414
+            if checker.settings.enabled.contains(&CheckCode::D414) {
+                checker.add_check(Check::new(
+                    CheckKind::NonEmptySection(context.section_name.to_string()),
+                    range_for(docstring),
+                ));
+            }
+        }
+    }
+}
+
+fn check_common_section(checker: &mut Checker, definition: &Definition, context: &SectionContext) {
+    // TODO(charlie): Implement D214, which requires indentation and leading space tracking.
+    let docstring = definition
+        .docstring
+        .expect("Sections are only available for docstrings.");
+
+    if checker.settings.enabled.contains(&CheckCode::D405) {
+        if !NUMPY_SECTION_NAMES.contains(&context.section_name.as_str())
+            && NUMPY_SECTION_NAMES.contains(titlecase(&context.section_name).as_str())
+        {
+            checker.add_check(Check::new(
+                CheckKind::CapitalizeSectionName(context.section_name.to_string()),
+                range_for(docstring),
+            ))
+        }
+    }
+
+    if context
+        .following_lines
+        .last()
+        .map(|line| !line.trim().is_empty())
+        .unwrap_or(true)
+    {
+        if context.is_last_section {
+            if checker.settings.enabled.contains(&CheckCode::D413) {
+                checker.add_check(Check::new(
+                    CheckKind::BlankLineAfterLastSection(context.section_name.to_string()),
+                    range_for(docstring),
+                ))
+            }
+        } else {
+            if checker.settings.enabled.contains(&CheckCode::D410) {
+                checker.add_check(Check::new(
+                    CheckKind::BlankLineAfterSection(context.section_name.to_string()),
+                    range_for(docstring),
+                ))
+            }
+        }
+    }
+
+    if checker.settings.enabled.contains(&CheckCode::D411) {
+        if !context.previous_line.is_empty() {
+            checker.add_check(Check::new(
+                CheckKind::BlankLineBeforeSection(context.section_name.to_string()),
+                range_for(docstring),
+            ))
+        }
+    }
+}
+
+pub fn check_numpy_section(
+    checker: &mut Checker,
+    definition: &Definition,
+    context: &SectionContext,
+) {
+    // TODO(charlie): Implement `_check_parameters_section`.
+    check_common_section(checker, definition, context);
+    check_blanks_and_section_underline(checker, definition, context);
+
+    if checker.settings.enabled.contains(&CheckCode::D406) {
+        let suffix = context
+            .line
+            .trim()
+            .strip_prefix(&context.section_name)
+            .unwrap();
+        if !suffix.is_empty() {
+            let docstring = definition
+                .docstring
+                .expect("Sections are only available for docstrings.");
+            checker.add_check(Check::new(
+                CheckKind::NewLineAfterSectionName(context.section_name.to_string()),
+                range_for(docstring),
+            ))
+        }
+    }
+}

src/docstrings/types.rs

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

src/lib.rs

@@ -1,3 +1,4 @@
+#![allow(clippy::collapsible_if, clippy::collapsible_else_if)]
 use std::path::Path;
 
 use anyhow::Result;
@@ -17,6 +18,7 @@ mod check_lines;
 pub mod checks;
 pub mod cli;
 pub mod code_gen;
+mod docstrings;
 pub mod fs;
 pub mod linter;
 pub mod logging;
@@ -27,6 +29,7 @@ pub mod printer;
 pub mod pyproject;
 mod python;
 pub mod settings;
+pub mod visibility;
 
 /// Run ruff over Python source code directly.
 pub fn check(path: &Path, contents: &str) -> Result<Vec<Message>> {

src/linter.rs

@@ -83,6 +83,36 @@ pub(crate) fn check_path(
     Ok(checks)
 }
 
+pub fn lint_stdin(path: &Path, stdin: &str, settings: &Settings) -> Result<Vec<Message>> {
+    // Tokenize once.
+    let tokens: Vec<LexResult> = tokenize(stdin);
+
+    // 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,
+        stdin,
+        tokens,
+        &noqa_line_for,
+        settings,
+        &fixer::Mode::None,
+    )?;
+
+    // Convert to messages.
+    Ok(checks
+        .into_iter()
+        .map(|check| Message {
+            kind: check.kind,
+            fixed: check.fix.map(|fix| fix.applied).unwrap_or_default(),
+            location: check.location,
+            end_location: check.end_location,
+            filename: path.to_string_lossy().to_string(),
+        })
+        .collect())
+}
+
 pub fn lint_path(
     path: &Path,
     settings: &Settings,
@@ -762,42 +792,6 @@ mod tests {
         Ok(())
     }
 
-    #[test]
-    fn m001() -> Result<()> {
-        let mut checks = check_path(
-            Path::new("./resources/test/fixtures/M001.py"),
-            &settings::Settings::for_rules(vec![CheckCode::M001, CheckCode::E501, CheckCode::F841]),
-            &fixer::Mode::Generate,
-        )?;
-        checks.sort_by_key(|check| check.location);
-        insta::assert_yaml_snapshot!(checks);
-        Ok(())
-    }
-
-    #[test]
-    fn init() -> Result<()> {
-        let mut checks = check_path(
-            Path::new("./resources/test/fixtures/__init__.py"),
-            &settings::Settings::for_rules(vec![CheckCode::F821, CheckCode::F822]),
-            &fixer::Mode::Generate,
-        )?;
-        checks.sort_by_key(|check| check.location);
-        insta::assert_yaml_snapshot!(checks);
-        Ok(())
-    }
-
-    #[test]
-    fn future_annotations() -> Result<()> {
-        let mut checks = check_path(
-            Path::new("./resources/test/fixtures/future_annotations.py"),
-            &settings::Settings::for_rules(vec![CheckCode::F401, CheckCode::F821]),
-            &fixer::Mode::Generate,
-        )?;
-        checks.sort_by_key(|check| check.location);
-        insta::assert_yaml_snapshot!(checks);
-        Ok(())
-    }
-
     #[test]
     fn e999() -> Result<()> {
         let mut checks = check_path(
@@ -846,6 +840,42 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn b011() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/B011.py"),
+            &settings::Settings::for_rule(CheckCode::B011),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn b014() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/B014.py"),
+            &settings::Settings::for_rule(CheckCode::B014),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn b025() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/B025.py"),
+            &settings::Settings::for_rule(CheckCode::B025),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
     #[test]
     fn c400() -> Result<()> {
         let mut checks = check_path(
@@ -942,6 +972,42 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn c409() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/C409.py"),
+            &settings::Settings::for_rule(CheckCode::C409),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn c410() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/C410.py"),
+            &settings::Settings::for_rule(CheckCode::C410),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn c414() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/C414.py"),
+            &settings::Settings::for_rule(CheckCode::C414),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
     #[test]
     fn c415() -> Result<()> {
         let mut checks = check_path(
@@ -955,10 +1021,430 @@ mod tests {
     }
 
     #[test]
-    fn u008() -> Result<()> {
+    fn d100() -> Result<()> {
         let mut checks = check_path(
-            Path::new("./resources/test/fixtures/U008.py"),
-            &settings::Settings::for_rule(CheckCode::U008),
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D100),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d101() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D101),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d102() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D102),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d103() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D103),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d104() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D104),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d105() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D105),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d106() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D106),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d107() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D107),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d201() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D201),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d202() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D202),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d203() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D203),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d204() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D204),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d205() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D205),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d209() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D209),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d210() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D210),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d211() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D211),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d212() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D212),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d213() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D213),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d300() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D300),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d400() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D400),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d402() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D402),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d403() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D403),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d404() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D404),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d405() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/sections.py"),
+            &settings::Settings::for_rule(CheckCode::D405),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d406() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/sections.py"),
+            &settings::Settings::for_rule(CheckCode::D406),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d407() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/sections.py"),
+            &settings::Settings::for_rule(CheckCode::D407),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d408() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/sections.py"),
+            &settings::Settings::for_rule(CheckCode::D408),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d409() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/sections.py"),
+            &settings::Settings::for_rule(CheckCode::D409),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d410() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/sections.py"),
+            &settings::Settings::for_rule(CheckCode::D410),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d411() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/sections.py"),
+            &settings::Settings::for_rule(CheckCode::D411),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d412() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/sections.py"),
+            &settings::Settings::for_rule(CheckCode::D412),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d413() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/sections.py"),
+            &settings::Settings::for_rule(CheckCode::D413),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d414() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/sections.py"),
+            &settings::Settings::for_rule(CheckCode::D414),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d415() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D415),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d418() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D418),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn d419() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/D.py"),
+            &settings::Settings::for_rule(CheckCode::D419),
             &fixer::Mode::Generate,
         )?;
         checks.sort_by_key(|check| check.location);
@@ -1073,4 +1559,52 @@ mod tests {
         insta::assert_yaml_snapshot!(checks);
         Ok(())
     }
+
+    #[test]
+    fn u008() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/U008.py"),
+            &settings::Settings::for_rule(CheckCode::U008),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn m001() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/M001.py"),
+            &settings::Settings::for_rules(vec![CheckCode::M001, CheckCode::E501, CheckCode::F841]),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn init() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/__init__.py"),
+            &settings::Settings::for_rules(vec![CheckCode::F821, CheckCode::F822]),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
+
+    #[test]
+    fn future_annotations() -> Result<()> {
+        let mut checks = check_path(
+            Path::new("./resources/test/fixtures/future_annotations.py"),
+            &settings::Settings::for_rules(vec![CheckCode::F401, CheckCode::F821]),
+            &fixer::Mode::Generate,
+        )?;
+        checks.sort_by_key(|check| check.location);
+        insta::assert_yaml_snapshot!(checks);
+        Ok(())
+    }
 }

src/main.rs

@@ -1,4 +1,4 @@
-use std::io;
+use std::io::{self, Read};
 use std::path::{Path, PathBuf};
 use std::process::ExitCode;
 use std::sync::mpsc::channel;
@@ -19,7 +19,7 @@ use ruff::cli::{warn_on, Cli, Warnable};
 use ruff::fs::iter_python_files;
 use ruff::linter::add_noqa_to_path;
 use ruff::linter::autoformat_path;
-use ruff::linter::lint_path;
+use ruff::linter::{lint_path, lint_stdin};
 use ruff::logging::set_up_logging;
 use ruff::message::Message;
 use ruff::printer::{Printer, SerializationFormat};
@@ -75,6 +75,19 @@ fn show_files(files: &[PathBuf], settings: &Settings) {
     }
 }
 
+fn read_from_stdin() -> Result<String> {
+    let mut buffer = String::new();
+    io::stdin().lock().read_to_string(&mut buffer)?;
+    Ok(buffer)
+}
+
+fn run_once_stdin(settings: &Settings, filename: &Path) -> Result<Vec<Message>> {
+    let stdin = read_from_stdin()?;
+    let mut messages = lint_stdin(filename, &stdin, settings)?;
+    messages.sort_unstable();
+    Ok(messages)
+}
+
 fn run_once(
     files: &[PathBuf],
     settings: &Settings,
@@ -352,7 +365,17 @@ fn inner_main() -> Result<ExitCode> {
             println!("Formatted {modifications} files.");
         }
     } else {
-        let messages = run_once(&cli.files, &settings, !cli.no_cache, cli.fix)?;
+        let messages = if cli.files == vec![PathBuf::from("-")] {
+            if cli.fix {
+                eprintln!("Warning: --fix is not enabled when reading from stdin.");
+            }
+
+            let filename = cli.stdin_filename.unwrap_or_else(|| "-".to_string());
+            let path = Path::new(&filename);
+            run_once_stdin(&settings, path)?
+        } else {
+            run_once(&cli.files, &settings, !cli.no_cache, cli.fix)?
+        };
         if !cli.quiet {
             printer.write_once(&messages)?;
         }

src/plugins.rs

@@ -1,5 +1,7 @@
+pub use assert_false::assert_false;
 pub use assert_tuple::assert_tuple;
 pub use deprecated_unittest_alias::deprecated_unittest_alias;
+pub use duplicate_exceptions::duplicate_exceptions;
 pub use if_tuple::if_tuple;
 pub use invalid_print_syntax::invalid_print_syntax;
 pub use print_call::print_call;
@@ -11,8 +13,10 @@ pub use use_pep604_annotation::use_pep604_annotation;
 pub use useless_metaclass_type::useless_metaclass_type;
 pub use useless_object_inheritance::useless_object_inheritance;
 
+mod assert_false;
 mod assert_tuple;
 mod deprecated_unittest_alias;
+mod duplicate_exceptions;
 mod if_tuple;
 mod invalid_print_syntax;
 mod print_call;

src/plugins/assert_false.rs

@@ -0,0 +1,61 @@
+use rustpython_ast::{Constant, Expr, ExprContext, ExprKind, Stmt, StmtKind};
+
+use crate::ast::types::Range;
+use crate::autofix::fixer;
+use crate::check_ast::Checker;
+use crate::checks::{Check, CheckKind, Fix};
+use crate::code_gen::SourceGenerator;
+
+fn assertion_error(msg: &Option<Box<Expr>>) -> Stmt {
+    Stmt::new(
+        Default::default(),
+        Default::default(),
+        StmtKind::Raise {
+            exc: Some(Box::new(Expr::new(
+                Default::default(),
+                Default::default(),
+                ExprKind::Call {
+                    func: Box::new(Expr::new(
+                        Default::default(),
+                        Default::default(),
+                        ExprKind::Name {
+                            id: "AssertionError".to_string(),
+                            ctx: ExprContext::Load,
+                        },
+                    )),
+                    args: if let Some(msg) = msg {
+                        vec![*msg.clone()]
+                    } else {
+                        vec![]
+                    },
+                    keywords: vec![],
+                },
+            ))),
+            cause: None,
+        },
+    )
+}
+
+pub fn assert_false(checker: &mut Checker, stmt: &Stmt, test: &Expr, msg: &Option<Box<Expr>>) {
+    if let ExprKind::Constant {
+        value: Constant::Bool(false),
+        ..
+    } = &test.node
+    {
+        let mut check = Check::new(CheckKind::DoNotAssertFalse, Range::from_located(test));
+        if matches!(checker.autofix, fixer::Mode::Generate | fixer::Mode::Apply) {
+            let mut generator = SourceGenerator::new();
+            if let Ok(()) = generator.unparse_stmt(&assertion_error(msg)) {
+                if let Ok(content) = generator.generate() {
+                    check.amend(Fix {
+                        content,
+                        location: stmt.location,
+                        end_location: stmt.end_location,
+                        applied: false,
+                    })
+                }
+            }
+        }
+        checker.add_check(check);
+    }
+}

src/plugins/assert_tuple.rs

@@ -1,12 +1,12 @@
 use rustpython_ast::{Expr, Stmt};
 
-use crate::ast::checks;
+use crate::ast::checkers;
 use crate::ast::types::{CheckLocator, Range};
 use crate::check_ast::Checker;
 
 pub fn assert_tuple(checker: &mut Checker, stmt: &Stmt, test: &Expr) {
     if let Some(check) =
-        checks::check_assert_tuple(test, checker.locate_check(Range::from_located(stmt)))
+        checkers::assert_tuple(test, checker.locate_check(Range::from_located(stmt)))
     {
         checker.add_check(check);
     }

src/plugins/duplicate_exceptions.rs

@@ -0,0 +1,114 @@
+use std::collections::BTreeSet;
+
+use itertools::Itertools;
+use rustpython_ast::{Excepthandler, ExcepthandlerKind, Expr, ExprContext, ExprKind, Stmt};
+
+use crate::ast::helpers;
+use crate::ast::types::{CheckLocator, Range};
+use crate::autofix::fixer;
+use crate::check_ast::Checker;
+use crate::checks::{Check, CheckCode, CheckKind, Fix};
+use crate::code_gen::SourceGenerator;
+
+fn type_pattern(elts: Vec<&Expr>) -> Expr {
+    Expr::new(
+        Default::default(),
+        Default::default(),
+        ExprKind::Tuple {
+            elts: elts.into_iter().cloned().collect(),
+            ctx: ExprContext::Load,
+        },
+    )
+}
+
+pub fn duplicate_handler_exceptions(
+    checker: &mut Checker,
+    expr: &Expr,
+    elts: &Vec<Expr>,
+) -> BTreeSet<String> {
+    let mut seen: BTreeSet<String> = Default::default();
+    let mut duplicates: BTreeSet<String> = Default::default();
+    let mut unique_elts: Vec<&Expr> = Default::default();
+    for type_ in elts {
+        if let Some(name) = helpers::compose_call_path(type_) {
+            if seen.contains(&name) {
+                duplicates.insert(name);
+            } else {
+                seen.insert(name);
+                unique_elts.push(type_);
+            }
+        }
+    }
+
+    if checker.settings.enabled.contains(&CheckCode::B014) {
+        // TODO(charlie): Handle "BaseException" and redundant exception aliases.
+        if !duplicates.is_empty() {
+            let mut check = Check::new(
+                CheckKind::DuplicateHandlerException(
+                    duplicates.into_iter().sorted().collect::<Vec<String>>(),
+                ),
+                checker.locate_check(Range::from_located(expr)),
+            );
+            if matches!(checker.autofix, fixer::Mode::Generate | fixer::Mode::Apply) {
+                // TODO(charlie): If we have a single element, remove the tuple.
+                let mut generator = SourceGenerator::new();
+                if let Ok(()) = generator.unparse_expr(&type_pattern(unique_elts), 0) {
+                    if let Ok(content) = generator.generate() {
+                        check.amend(Fix {
+                            content,
+                            location: expr.location,
+                            end_location: expr.end_location,
+                            applied: false,
+                        })
+                    }
+                }
+            }
+            checker.add_check(check);
+        }
+    }
+
+    seen
+}
+
+pub fn duplicate_exceptions(checker: &mut Checker, stmt: &Stmt, handlers: &[Excepthandler]) {
+    let mut seen: BTreeSet<String> = Default::default();
+    let mut duplicates: BTreeSet<String> = Default::default();
+    for handler in handlers {
+        match &handler.node {
+            ExcepthandlerKind::ExceptHandler { type_, .. } => {
+                if let Some(type_) = type_ {
+                    match &type_.node {
+                        ExprKind::Attribute { .. } | ExprKind::Name { .. } => {
+                            if let Some(name) = helpers::compose_call_path(type_) {
+                                if seen.contains(&name) {
+                                    duplicates.insert(name);
+                                } else {
+                                    seen.insert(name);
+                                }
+                            }
+                        }
+                        ExprKind::Tuple { elts, .. } => {
+                            for name in duplicate_handler_exceptions(checker, type_, elts) {
+                                if seen.contains(&name) {
+                                    duplicates.insert(name);
+                                } else {
+                                    seen.insert(name);
+                                }
+                            }
+                        }
+                        _ => {}
+                    }
+                }
+            }
+        }
+    }
+
+    if checker.settings.enabled.contains(&CheckCode::B025) {
+        for duplicate in duplicates.into_iter().sorted() {
+            checker.add_check(Check::new(
+                CheckKind::DuplicateTryBlockException(duplicate),
+                checker.locate_check(Range::from_located(stmt)),
+            ));
+        }
+    }
+}

src/plugins/if_tuple.rs

@@ -1,13 +1,11 @@
 use rustpython_ast::{Expr, Stmt};
 
-use crate::ast::checks;
+use crate::ast::checkers;
 use crate::ast::types::{CheckLocator, Range};
 use crate::check_ast::Checker;
 
 pub fn if_tuple(checker: &mut Checker, stmt: &Stmt, test: &Expr) {
-    if let Some(check) =
-        checks::check_if_tuple(test, checker.locate_check(Range::from_located(stmt)))
-    {
+    if let Some(check) = checkers::if_tuple(test, checker.locate_check(Range::from_located(stmt))) {
         checker.add_check(check);
     }
 }

src/plugins/print_call.rs

@@ -1,13 +1,13 @@
 use log::error;
 use rustpython_ast::{Expr, Stmt, StmtKind};
 
-use crate::ast::checks;
+use crate::ast::checkers;
 use crate::autofix::{fixer, fixes};
 use crate::check_ast::Checker;
 use crate::checks::CheckCode;
 
 pub fn print_call(checker: &mut Checker, expr: &Expr, func: &Expr) {
-    if let Some(mut check) = checks::check_print_call(
+    if let Some(mut check) = checkers::print_call(
         expr,
         func,
         checker.settings.enabled.contains(&CheckCode::T201),

src/plugins/super_call_with_parameters.rs

@@ -1,6 +1,6 @@
 use rustpython_ast::{Expr, Stmt};
 
-use crate::ast::checks;
+use crate::ast::{checkers, helpers};
 use crate::autofix::{fixer, fixes};
 use crate::check_ast::Checker;
 
@@ -12,14 +12,14 @@ pub fn super_call_with_parameters(
 ) {
     // Only bother going through the super check at all if we're in a `super` call.
     // (We check this in `check_super_args` too, so this is just an optimization.)
-    if checks::is_super_call_with_arguments(func, args) {
+    if helpers::is_super_call_with_arguments(func, args) {
         let scope = checker.current_scope();
         let parents: Vec<&Stmt> = checker
             .parent_stack
             .iter()
             .map(|index| checker.parents[*index])
             .collect();
-        if let Some(mut check) = checks::check_super_args(scope, &parents, expr, func, args) {
+        if let Some(mut check) = checkers::super_args(scope, &parents, expr, func, args) {
             if matches!(checker.autofix, fixer::Mode::Generate | fixer::Mode::Apply) {
                 if let Some(fix) = fixes::remove_super_arguments(&mut checker.locator, expr) {
                     check.amend(fix);

src/plugins/type_of_primitive.rs

@@ -1,6 +1,6 @@
 use rustpython_ast::Expr;
 
-use crate::ast::checks;
+use crate::ast::checkers;
 use crate::ast::types::{CheckLocator, Range};
 use crate::autofix::fixer;
 use crate::check_ast::Checker;
@@ -8,7 +8,7 @@ use crate::checks::{CheckKind, Fix};
 
 pub fn type_of_primitive(checker: &mut Checker, expr: &Expr, func: &Expr, args: &Vec<Expr>) {
     if let Some(mut check) =
-        checks::check_type_of_primitive(func, args, checker.locate_check(Range::from_located(expr)))
+        checkers::type_of_primitive(func, args, checker.locate_check(Range::from_located(expr)))
     {
         if matches!(checker.autofix, fixer::Mode::Generate | fixer::Mode::Apply) {
             if let CheckKind::TypeOfPrimitive(primitive) = &check.kind {

src/plugins/unnecessary_abspath.rs

@@ -1,17 +1,15 @@
 use rustpython_ast::Expr;
 
-use crate::ast::checks;
+use crate::ast::checkers;
 use crate::ast::types::{CheckLocator, Range};
 use crate::autofix::fixer;
 use crate::check_ast::Checker;
 use crate::checks::Fix;
 
 pub fn unnecessary_abspath(checker: &mut Checker, expr: &Expr, func: &Expr, args: &Vec<Expr>) {
-    if let Some(mut check) = checks::check_unnecessary_abspath(
-        func,
-        args,
-        checker.locate_check(Range::from_located(expr)),
-    ) {
+    if let Some(mut check) =
+        checkers::unnecessary_abspath(func, args, checker.locate_check(Range::from_located(expr)))
+    {
         if matches!(checker.autofix, fixer::Mode::Generate | fixer::Mode::Apply) {
             check.amend(Fix {
                 content: "__file__".to_string(),

src/plugins/useless_metaclass_type.rs

@@ -1,7 +1,7 @@
 use log::error;
 use rustpython_ast::{Expr, Stmt};
 
-use crate::ast::checks;
+use crate::ast::checkers;
 use crate::ast::types::{CheckLocator, Range};
 use crate::autofix::{fixer, fixes};
 use crate::check_ast::Checker;
@@ -12,7 +12,7 @@ pub fn useless_metaclass_type(
     value: &Expr,
     targets: &Vec<Expr>,
 ) {
-    if let Some(mut check) = checks::check_useless_metaclass_type(
+    if let Some(mut check) = checkers::useless_metaclass_type(
         targets,
         value,
         checker.locate_check(Range::from_located(stmt)),

src/plugins/useless_object_inheritance.rs

@@ -1,6 +1,6 @@
 use rustpython_ast::{Expr, Keyword, Stmt};
 
-use crate::ast::checks;
+use crate::ast::checkers;
 use crate::autofix::{fixer, fixes};
 use crate::check_ast::Checker;
 
@@ -12,7 +12,7 @@ pub fn useless_object_inheritance(
     keywords: &[Keyword],
 ) {
     let scope = checker.current_scope();
-    if let Some(mut check) = checks::check_useless_object_inheritance(name, bases, scope) {
+    if let Some(mut check) = checkers::useless_object_inheritance(name, bases, scope) {
         if matches!(checker.autofix, fixer::Mode::Generate | fixer::Mode::Apply) {
             if let Some(fix) = fixes::remove_class_def_base(
                 &mut checker.locator,

src/snapshots/ruff__linter__tests__b011.snap

@@ -0,0 +1,37 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: DoNotAssertFalse
+  location:
+    row: 8
+    column: 8
+  end_location:
+    row: 8
+    column: 13
+  fix:
+    content: raise AssertionError()
+    location:
+      row: 8
+      column: 1
+    end_location:
+      row: 8
+      column: 13
+    applied: false
+- kind: DoNotAssertFalse
+  location:
+    row: 10
+    column: 8
+  end_location:
+    row: 10
+    column: 13
+  fix:
+    content: "raise AssertionError(\"message\")"
+    location:
+      row: 10
+      column: 1
+    end_location:
+      row: 10
+      column: 24
+    applied: false
+

src/snapshots/ruff__linter__tests__b014.snap

@@ -0,0 +1,59 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    DuplicateHandlerException:
+      - OSError
+  location:
+    row: 17
+    column: 9
+  end_location:
+    row: 17
+    column: 25
+  fix:
+    content: "OSError,"
+    location:
+      row: 17
+      column: 9
+    end_location:
+      row: 17
+      column: 25
+    applied: false
+- kind:
+    DuplicateHandlerException:
+      - MyError
+  location:
+    row: 28
+    column: 9
+  end_location:
+    row: 28
+    column: 25
+  fix:
+    content: "MyError,"
+    location:
+      row: 28
+      column: 9
+    end_location:
+      row: 28
+      column: 25
+    applied: false
+- kind:
+    DuplicateHandlerException:
+      - re.error
+  location:
+    row: 49
+    column: 9
+  end_location:
+    row: 49
+    column: 27
+  fix:
+    content: "re.error,"
+    location:
+      row: 49
+      column: 9
+    end_location:
+      row: 49
+      column: 27
+    applied: false
+

src/snapshots/ruff__linter__tests__b025.snap

@@ -0,0 +1,41 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    DuplicateTryBlockException: ValueError
+  location:
+    row: 15
+    column: 1
+  end_location:
+    row: 22
+    column: 1
+  fix: ~
+- kind:
+    DuplicateTryBlockException: pickle.PickleError
+  location:
+    row: 22
+    column: 1
+  end_location:
+    row: 31
+    column: 1
+  fix: ~
+- kind:
+    DuplicateTryBlockException: TypeError
+  location:
+    row: 31
+    column: 1
+  end_location:
+    row: 39
+    column: 1
+  fix: ~
+- kind:
+    DuplicateTryBlockException: ValueError
+  location:
+    row: 31
+    column: 1
+  end_location:
+    row: 39
+    column: 1
+  fix: ~
+

src/snapshots/ruff__linter__tests__c409.snap

@@ -0,0 +1,32 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    UnnecessaryLiteralWithinTupleCall: list
+  location:
+    row: 1
+    column: 6
+  end_location:
+    row: 1
+    column: 19
+  fix: ~
+- kind:
+    UnnecessaryLiteralWithinTupleCall: tuple
+  location:
+    row: 2
+    column: 6
+  end_location:
+    row: 2
+    column: 19
+  fix: ~
+- kind:
+    UnnecessaryLiteralWithinTupleCall: list
+  location:
+    row: 3
+    column: 6
+  end_location:
+    row: 3
+    column: 15
+  fix: ~
+

src/snapshots/ruff__linter__tests__c410.snap

@@ -0,0 +1,41 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    UnnecessaryLiteralWithinListCall: list
+  location:
+    row: 1
+    column: 6
+  end_location:
+    row: 1
+    column: 18
+  fix: ~
+- kind:
+    UnnecessaryLiteralWithinListCall: tuple
+  location:
+    row: 2
+    column: 6
+  end_location:
+    row: 2
+    column: 18
+  fix: ~
+- kind:
+    UnnecessaryLiteralWithinListCall: list
+  location:
+    row: 3
+    column: 6
+  end_location:
+    row: 3
+    column: 14
+  fix: ~
+- kind:
+    UnnecessaryLiteralWithinListCall: tuple
+  location:
+    row: 4
+    column: 6
+  end_location:
+    row: 4
+    column: 14
+  fix: ~
+

src/snapshots/ruff__linter__tests__c414.snap

@@ -0,0 +1,148 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    UnnecessaryDoubleCastOrProcess:
+      - list
+      - list
+  location:
+    row: 2
+    column: 1
+  end_location:
+    row: 2
+    column: 14
+  fix: ~
+- kind:
+    UnnecessaryDoubleCastOrProcess:
+      - tuple
+      - list
+  location:
+    row: 3
+    column: 1
+  end_location:
+    row: 3
+    column: 15
+  fix: ~
+- kind:
+    UnnecessaryDoubleCastOrProcess:
+      - list
+      - tuple
+  location:
+    row: 4
+    column: 1
+  end_location:
+    row: 4
+    column: 15
+  fix: ~
+- kind:
+    UnnecessaryDoubleCastOrProcess:
+      - tuple
+      - tuple
+  location:
+    row: 5
+    column: 1
+  end_location:
+    row: 5
+    column: 16
+  fix: ~
+- kind:
+    UnnecessaryDoubleCastOrProcess:
+      - set
+      - set
+  location:
+    row: 6
+    column: 1
+  end_location:
+    row: 6
+    column: 12
+  fix: ~
+- kind:
+    UnnecessaryDoubleCastOrProcess:
+      - list
+      - set
+  location:
+    row: 7
+    column: 1
+  end_location:
+    row: 7
+    column: 13
+  fix: ~
+- kind:
+    UnnecessaryDoubleCastOrProcess:
+      - tuple
+      - set
+  location:
+    row: 8
+    column: 1
+  end_location:
+    row: 8
+    column: 14
+  fix: ~
+- kind:
+    UnnecessaryDoubleCastOrProcess:
+      - sorted
+      - set
+  location:
+    row: 9
+    column: 1
+  end_location:
+    row: 9
+    column: 15
+  fix: ~
+- kind:
+    UnnecessaryDoubleCastOrProcess:
+      - reversed
+      - set
+  location:
+    row: 10
+    column: 1
+  end_location:
+    row: 10
+    column: 17
+  fix: ~
+- kind:
+    UnnecessaryDoubleCastOrProcess:
+      - list
+      - sorted
+  location:
+    row: 11
+    column: 1
+  end_location:
+    row: 11
+    column: 16
+  fix: ~
+- kind:
+    UnnecessaryDoubleCastOrProcess:
+      - tuple
+      - sorted
+  location:
+    row: 12
+    column: 1
+  end_location:
+    row: 12
+    column: 17
+  fix: ~
+- kind:
+    UnnecessaryDoubleCastOrProcess:
+      - sorted
+      - sorted
+  location:
+    row: 13
+    column: 1
+  end_location:
+    row: 13
+    column: 18
+  fix: ~
+- kind:
+    UnnecessaryDoubleCastOrProcess:
+      - reversed
+      - sorted
+  location:
+    row: 14
+    column: 1
+  end_location:
+    row: 14
+    column: 20
+  fix: ~
+

src/snapshots/ruff__linter__tests__d100.snap

@@ -0,0 +1,13 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: PublicModule
+  location:
+    row: 1
+    column: 1
+  end_location:
+    row: 1
+    column: 1
+  fix: ~
+

src/snapshots/ruff__linter__tests__d101.snap

@@ -0,0 +1,13 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: PublicClass
+  location:
+    row: 14
+    column: 1
+  end_location:
+    row: 67
+    column: 1
+  fix: ~
+

src/snapshots/ruff__linter__tests__d102.snap

@@ -0,0 +1,29 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: PublicMethod
+  location:
+    row: 22
+    column: 5
+  end_location:
+    row: 25
+    column: 5
+  fix: ~
+- kind: PublicMethod
+  location:
+    row: 51
+    column: 5
+  end_location:
+    row: 54
+    column: 5
+  fix: ~
+- kind: PublicMethod
+  location:
+    row: 63
+    column: 5
+  end_location:
+    row: 67
+    column: 1
+  fix: ~
+

src/snapshots/ruff__linter__tests__d103.snap

@@ -0,0 +1,13 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: PublicFunction
+  location:
+    row: 395
+    column: 1
+  end_location:
+    row: 396
+    column: 1
+  fix: ~
+

src/snapshots/ruff__linter__tests__d104.snap

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

src/snapshots/ruff__linter__tests__d105.snap

@@ -0,0 +1,13 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: MagicMethod
+  location:
+    row: 59
+    column: 5
+  end_location:
+    row: 62
+    column: 5
+  fix: ~
+

src/snapshots/ruff__linter__tests__d106.snap

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

src/snapshots/ruff__linter__tests__d107.snap

@@ -0,0 +1,21 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: PublicInit
+  location:
+    row: 55
+    column: 5
+  end_location:
+    row: 58
+    column: 5
+  fix: ~
+- kind: PublicInit
+  location:
+    row: 529
+    column: 5
+  end_location:
+    row: 533
+    column: 1
+  fix: ~
+

src/snapshots/ruff__linter__tests__d200.snap

@@ -0,0 +1,13 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: FitsOnOneLine
+  location:
+    row: 124
+    column: 5
+  end_location:
+    row: 126
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__d201.snap

@@ -0,0 +1,23 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    NoBlankLineBeforeFunction: 1
+  location:
+    row: 132
+    column: 5
+  end_location:
+    row: 132
+    column: 25
+  fix: ~
+- kind:
+    NoBlankLineBeforeFunction: 1
+  location:
+    row: 146
+    column: 5
+  end_location:
+    row: 146
+    column: 38
+  fix: ~
+

src/snapshots/ruff__linter__tests__d202.snap

@@ -0,0 +1,23 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    NoBlankLineAfterFunction: 1
+  location:
+    row: 137
+    column: 5
+  end_location:
+    row: 137
+    column: 25
+  fix: ~
+- kind:
+    NoBlankLineAfterFunction: 1
+  location:
+    row: 146
+    column: 5
+  end_location:
+    row: 146
+    column: 38
+  fix: ~
+

src/snapshots/ruff__linter__tests__d203.snap

@@ -0,0 +1,32 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    OneBlankLineBeforeClass: 0
+  location:
+    row: 156
+    column: 5
+  end_location:
+    row: 156
+    column: 33
+  fix: ~
+- kind:
+    OneBlankLineBeforeClass: 0
+  location:
+    row: 187
+    column: 5
+  end_location:
+    row: 187
+    column: 46
+  fix: ~
+- kind:
+    OneBlankLineBeforeClass: 0
+  location:
+    row: 521
+    column: 5
+  end_location:
+    row: 527
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__d204.snap

@@ -0,0 +1,23 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    OneBlankLineAfterClass: 0
+  location:
+    row: 176
+    column: 5
+  end_location:
+    row: 176
+    column: 25
+  fix: ~
+- kind:
+    OneBlankLineAfterClass: 0
+  location:
+    row: 187
+    column: 5
+  end_location:
+    row: 187
+    column: 46
+  fix: ~
+

src/snapshots/ruff__linter__tests__d205.snap

@@ -0,0 +1,21 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: NoBlankLineAfterSummary
+  location:
+    row: 195
+    column: 5
+  end_location:
+    row: 198
+    column: 8
+  fix: ~
+- kind: NoBlankLineAfterSummary
+  location:
+    row: 205
+    column: 5
+  end_location:
+    row: 210
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__d209.snap

@@ -0,0 +1,13 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: NewLineAfterLastParagraph
+  location:
+    row: 276
+    column: 5
+  end_location:
+    row: 278
+    column: 20
+  fix: ~
+

src/snapshots/ruff__linter__tests__d210.snap

@@ -0,0 +1,29 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: NoSurroundingWhitespace
+  location:
+    row: 283
+    column: 5
+  end_location:
+    row: 283
+    column: 34
+  fix: ~
+- kind: NoSurroundingWhitespace
+  location:
+    row: 288
+    column: 5
+  end_location:
+    row: 288
+    column: 38
+  fix: ~
+- kind: NoSurroundingWhitespace
+  location:
+    row: 294
+    column: 5
+  end_location:
+    row: 297
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__d211.snap

@@ -0,0 +1,23 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    NoBlankLineBeforeClass: 1
+  location:
+    row: 165
+    column: 5
+  end_location:
+    row: 165
+    column: 30
+  fix: ~
+- kind:
+    NoBlankLineBeforeClass: 1
+  location:
+    row: 176
+    column: 5
+  end_location:
+    row: 176
+    column: 25
+  fix: ~
+

src/snapshots/ruff__linter__tests__d212.snap

@@ -0,0 +1,13 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: MultiLineSummaryFirstLine
+  location:
+    row: 124
+    column: 5
+  end_location:
+    row: 126
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__d213.snap

@@ -0,0 +1,133 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 195
+    column: 5
+  end_location:
+    row: 198
+    column: 8
+  fix: ~
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 205
+    column: 5
+  end_location:
+    row: 210
+    column: 8
+  fix: ~
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 215
+    column: 5
+  end_location:
+    row: 219
+    column: 8
+  fix: ~
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 225
+    column: 5
+  end_location:
+    row: 229
+    column: 8
+  fix: ~
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 235
+    column: 5
+  end_location:
+    row: 239
+    column: 4
+  fix: ~
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 245
+    column: 5
+  end_location:
+    row: 249
+    column: 8
+  fix: ~
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 255
+    column: 5
+  end_location:
+    row: 259
+    column: 12
+  fix: ~
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 265
+    column: 5
+  end_location:
+    row: 269
+    column: 8
+  fix: ~
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 276
+    column: 5
+  end_location:
+    row: 278
+    column: 20
+  fix: ~
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 294
+    column: 5
+  end_location:
+    row: 297
+    column: 8
+  fix: ~
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 338
+    column: 5
+  end_location:
+    row: 343
+    column: 8
+  fix: ~
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 378
+    column: 5
+  end_location:
+    row: 381
+    column: 8
+  fix: ~
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 387
+    column: 5
+  end_location:
+    row: 391
+    column: 8
+  fix: ~
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 433
+    column: 37
+  end_location:
+    row: 436
+    column: 8
+  fix: ~
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 445
+    column: 5
+  end_location:
+    row: 449
+    column: 8
+  fix: ~
+- kind: MultiLineSummarySecondLine
+  location:
+    row: 521
+    column: 5
+  end_location:
+    row: 527
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__d300.snap

@@ -0,0 +1,45 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: UsesTripleQuotes
+  location:
+    row: 302
+    column: 6
+  end_location:
+    row: 302
+    column: 20
+  fix: ~
+- kind: UsesTripleQuotes
+  location:
+    row: 307
+    column: 6
+  end_location:
+    row: 307
+    column: 20
+  fix: ~
+- kind: UsesTripleQuotes
+  location:
+    row: 312
+    column: 6
+  end_location:
+    row: 312
+    column: 16
+  fix: ~
+- kind: UsesTripleQuotes
+  location:
+    row: 317
+    column: 6
+  end_location:
+    row: 317
+    column: 16
+  fix: ~
+- kind: UsesTripleQuotes
+  location:
+    row: 323
+    column: 6
+  end_location:
+    row: 323
+    column: 17
+  fix: ~
+

src/snapshots/ruff__linter__tests__d400.snap

@@ -0,0 +1,133 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: EndsInPeriod
+  location:
+    row: 124
+    column: 5
+  end_location:
+    row: 126
+    column: 8
+  fix: ~
+- kind: EndsInPeriod
+  location:
+    row: 283
+    column: 5
+  end_location:
+    row: 283
+    column: 34
+  fix: ~
+- kind: EndsInPeriod
+  location:
+    row: 288
+    column: 5
+  end_location:
+    row: 288
+    column: 38
+  fix: ~
+- kind: EndsInPeriod
+  location:
+    row: 350
+    column: 5
+  end_location:
+    row: 350
+    column: 18
+  fix: ~
+- kind: EndsInPeriod
+  location:
+    row: 401
+    column: 25
+  end_location:
+    row: 401
+    column: 40
+  fix: ~
+- kind: EndsInPeriod
+  location:
+    row: 405
+    column: 5
+  end_location:
+    row: 405
+    column: 25
+  fix: ~
+- kind: EndsInPeriod
+  location:
+    row: 411
+    column: 5
+  end_location:
+    row: 411
+    column: 25
+  fix: ~
+- kind: EndsInPeriod
+  location:
+    row: 417
+    column: 35
+  end_location:
+    row: 417
+    column: 50
+  fix: ~
+- kind: EndsInPeriod
+  location:
+    row: 424
+    column: 49
+  end_location:
+    row: 424
+    column: 64
+  fix: ~
+- kind: EndsInPeriod
+  location:
+    row: 465
+    column: 5
+  end_location:
+    row: 465
+    column: 25
+  fix: ~
+- kind: EndsInPeriod
+  location:
+    row: 470
+    column: 5
+  end_location:
+    row: 470
+    column: 25
+  fix: ~
+- kind: EndsInPeriod
+  location:
+    row: 475
+    column: 5
+  end_location:
+    row: 475
+    column: 25
+  fix: ~
+- kind: EndsInPeriod
+  location:
+    row: 482
+    column: 5
+  end_location:
+    row: 482
+    column: 25
+  fix: ~
+- kind: EndsInPeriod
+  location:
+    row: 504
+    column: 5
+  end_location:
+    row: 504
+    column: 35
+  fix: ~
+- kind: EndsInPeriod
+  location:
+    row: 509
+    column: 5
+  end_location:
+    row: 509
+    column: 34
+  fix: ~
+- kind: EndsInPeriod
+  location:
+    row: 515
+    column: 5
+  end_location:
+    row: 515
+    column: 33
+  fix: ~
+

src/snapshots/ruff__linter__tests__d402.snap

@@ -0,0 +1,13 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: NoSignature
+  location:
+    row: 373
+    column: 5
+  end_location:
+    row: 373
+    column: 31
+  fix: ~
+

src/snapshots/ruff__linter__tests__d403.snap

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

src/snapshots/ruff__linter__tests__d404.snap

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

src/snapshots/ruff__linter__tests__d405.snap

@@ -0,0 +1,23 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    CapitalizeSectionName: returns
+  location:
+    row: 17
+    column: 5
+  end_location:
+    row: 23
+    column: 8
+  fix: ~
+- kind:
+    CapitalizeSectionName: Short summary
+  location:
+    row: 207
+    column: 5
+  end_location:
+    row: 221
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__d406.snap

@@ -0,0 +1,41 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    NewLineAfterSectionName: Returns
+  location:
+    row: 30
+    column: 5
+  end_location:
+    row: 36
+    column: 8
+  fix: ~
+- kind:
+    NewLineAfterSectionName: Raises
+  location:
+    row: 207
+    column: 5
+  end_location:
+    row: 221
+    column: 8
+  fix: ~
+- kind:
+    NewLineAfterSectionName: Returns
+  location:
+    row: 252
+    column: 5
+  end_location:
+    row: 262
+    column: 8
+  fix: ~
+- kind:
+    NewLineAfterSectionName: Raises
+  location:
+    row: 252
+    column: 5
+  end_location:
+    row: 262
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__d407.snap

@@ -0,0 +1,50 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    DashedUnderlineAfterSection: Returns
+  location:
+    row: 42
+    column: 5
+  end_location:
+    row: 47
+    column: 8
+  fix: ~
+- kind:
+    DashedUnderlineAfterSection: Returns
+  location:
+    row: 54
+    column: 5
+  end_location:
+    row: 58
+    column: 8
+  fix: ~
+- kind:
+    DashedUnderlineAfterSection: Raises
+  location:
+    row: 207
+    column: 5
+  end_location:
+    row: 221
+    column: 8
+  fix: ~
+- kind:
+    DashedUnderlineAfterSection: Returns
+  location:
+    row: 252
+    column: 5
+  end_location:
+    row: 262
+    column: 8
+  fix: ~
+- kind:
+    DashedUnderlineAfterSection: Raises
+  location:
+    row: 252
+    column: 5
+  end_location:
+    row: 262
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__d408.snap

@@ -0,0 +1,14 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    SectionUnderlineAfterName: Returns
+  location:
+    row: 85
+    column: 5
+  end_location:
+    row: 92
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__d409.snap

@@ -0,0 +1,23 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    SectionUnderlineMatchesSectionLength: Returns
+  location:
+    row: 99
+    column: 5
+  end_location:
+    row: 105
+    column: 8
+  fix: ~
+- kind:
+    SectionUnderlineMatchesSectionLength: Returns
+  location:
+    row: 207
+    column: 5
+  end_location:
+    row: 221
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__d410.snap

@@ -0,0 +1,23 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    BlankLineAfterSection: Returns
+  location:
+    row: 67
+    column: 5
+  end_location:
+    row: 78
+    column: 8
+  fix: ~
+- kind:
+    BlankLineAfterSection: Returns
+  location:
+    row: 207
+    column: 5
+  end_location:
+    row: 221
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__d411.snap

@@ -0,0 +1,32 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    BlankLineBeforeSection: Yields
+  location:
+    row: 67
+    column: 5
+  end_location:
+    row: 78
+    column: 8
+  fix: ~
+- kind:
+    BlankLineBeforeSection: Returns
+  location:
+    row: 122
+    column: 5
+  end_location:
+    row: 129
+    column: 8
+  fix: ~
+- kind:
+    BlankLineBeforeSection: Raises
+  location:
+    row: 207
+    column: 5
+  end_location:
+    row: 221
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__d412.snap

@@ -0,0 +1,14 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    NoBlankLinesBetweenHeaderAndContent: Short summary
+  location:
+    row: 207
+    column: 5
+  end_location:
+    row: 221
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__d413.snap

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

src/snapshots/ruff__linter__tests__d414.snap

@@ -0,0 +1,50 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind:
+    NonEmptySection: Returns
+  location:
+    row: 54
+    column: 5
+  end_location:
+    row: 58
+    column: 8
+  fix: ~
+- kind:
+    NonEmptySection: Returns
+  location:
+    row: 67
+    column: 5
+  end_location:
+    row: 78
+    column: 8
+  fix: ~
+- kind:
+    NonEmptySection: Yields
+  location:
+    row: 67
+    column: 5
+  end_location:
+    row: 78
+    column: 8
+  fix: ~
+- kind:
+    NonEmptySection: Returns
+  location:
+    row: 161
+    column: 5
+  end_location:
+    row: 165
+    column: 8
+  fix: ~
+- kind:
+    NonEmptySection: Returns
+  location:
+    row: 252
+    column: 5
+  end_location:
+    row: 262
+    column: 8
+  fix: ~
+

src/snapshots/ruff__linter__tests__d415.snap

@@ -0,0 +1,125 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: EndsInPunctuation
+  location:
+    row: 124
+    column: 5
+  end_location:
+    row: 126
+    column: 8
+  fix: ~
+- kind: EndsInPunctuation
+  location:
+    row: 283
+    column: 5
+  end_location:
+    row: 283
+    column: 34
+  fix: ~
+- kind: EndsInPunctuation
+  location:
+    row: 288
+    column: 5
+  end_location:
+    row: 288
+    column: 38
+  fix: ~
+- kind: EndsInPunctuation
+  location:
+    row: 350
+    column: 5
+  end_location:
+    row: 350
+    column: 18
+  fix: ~
+- kind: EndsInPunctuation
+  location:
+    row: 401
+    column: 25
+  end_location:
+    row: 401
+    column: 40
+  fix: ~
+- kind: EndsInPunctuation
+  location:
+    row: 405
+    column: 5
+  end_location:
+    row: 405
+    column: 25
+  fix: ~
+- kind: EndsInPunctuation
+  location:
+    row: 411
+    column: 5
+  end_location:
+    row: 411
+    column: 25
+  fix: ~
+- kind: EndsInPunctuation
+  location:
+    row: 417
+    column: 35
+  end_location:
+    row: 417
+    column: 50
+  fix: ~
+- kind: EndsInPunctuation
+  location:
+    row: 424
+    column: 49
+  end_location:
+    row: 424
+    column: 64
+  fix: ~
+- kind: EndsInPunctuation
+  location:
+    row: 465
+    column: 5
+  end_location:
+    row: 465
+    column: 25
+  fix: ~
+- kind: EndsInPunctuation
+  location:
+    row: 470
+    column: 5
+  end_location:
+    row: 470
+    column: 25
+  fix: ~
+- kind: EndsInPunctuation
+  location:
+    row: 475
+    column: 5
+  end_location:
+    row: 475
+    column: 25
+  fix: ~
+- kind: EndsInPunctuation
+  location:
+    row: 482
+    column: 5
+  end_location:
+    row: 482
+    column: 25
+  fix: ~
+- kind: EndsInPunctuation
+  location:
+    row: 504
+    column: 5
+  end_location:
+    row: 504
+    column: 35
+  fix: ~
+- kind: EndsInPunctuation
+  location:
+    row: 515
+    column: 5
+  end_location:
+    row: 515
+    column: 33
+  fix: ~
+

src/snapshots/ruff__linter__tests__d418.snap

@@ -0,0 +1,29 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: SkipDocstring
+  location:
+    row: 33
+    column: 5
+  end_location:
+    row: 37
+    column: 5
+  fix: ~
+- kind: SkipDocstring
+  location:
+    row: 85
+    column: 5
+  end_location:
+    row: 89
+    column: 5
+  fix: ~
+- kind: SkipDocstring
+  location:
+    row: 105
+    column: 1
+  end_location:
+    row: 110
+    column: 1
+  fix: ~
+

src/snapshots/ruff__linter__tests__d419.snap

@@ -0,0 +1,29 @@
+---
+source: src/linter.rs
+expression: checks
+---
+- kind: NonEmpty
+  location:
+    row: 19
+    column: 9
+  end_location:
+    row: 19
+    column: 15
+  fix: ~
+- kind: NonEmpty
+  location:
+    row: 69
+    column: 5
+  end_location:
+    row: 69
+    column: 12
+  fix: ~
+- kind: NonEmpty
+  location:
+    row: 75
+    column: 9
+  end_location:
+    row: 75
+    column: 11
+  fix: ~
+

src/snapshots/ruff__linter__tests__f404.snap

@@ -4,10 +4,10 @@ expression: checks
 ---
 - kind: LateFutureImport
   location:
-    row: 7
+    row: 6
     column: 1
   end_location:
-    row: 7
+    row: 6
     column: 38
   fix: ~
 

src/snapshots/ruff__linter__tests__m001.snap

@@ -20,7 +20,8 @@ expression: checks
       column: 18
     applied: false
 - kind:
-    UnusedNOQA: E501
+    UnusedNOQA:
+      - E501
   location:
     row: 13
     column: 10
@@ -37,7 +38,9 @@ expression: checks
       column: 24
     applied: false
 - kind:
-    UnusedNOQA: E501
+    UnusedNOQA:
+      - F841
+      - E501
   location:
     row: 16
     column: 10
@@ -45,7 +48,7 @@ expression: checks
     row: 16
     column: 30
   fix:
-    content: "  # noqa: F841"
+    content: ""
     location:
       row: 16
       column: 10
@@ -54,54 +57,74 @@ expression: checks
       column: 30
     applied: false
 - kind:
-    UnusedNOQA: F841
+    UnusedNOQA:
+      - W191
   location:
-    row: 41
+    row: 19
+    column: 10
+  end_location:
+    row: 19
+    column: 30
+  fix:
+    content: "  # noqa: F841"
+    location:
+      row: 19
+      column: 10
+    end_location:
+      row: 19
+      column: 30
+    applied: false
+- kind:
+    UnusedNOQA:
+      - F841
+  location:
+    row: 44
     column: 4
   end_location:
-    row: 41
+    row: 44
     column: 24
   fix:
     content: "  # noqa: E501"
     location:
-      row: 41
+      row: 44
       column: 4
     end_location:
-      row: 41
+      row: 44
       column: 24
     applied: false
 - kind:
-    UnusedNOQA: E501
+    UnusedNOQA:
+      - E501
   location:
-    row: 49
+    row: 52
     column: 4
   end_location:
-    row: 49
+    row: 52
     column: 18
   fix:
     content: ""
     location:
-      row: 49
+      row: 52
       column: 4
     end_location:
-      row: 49
+      row: 52
       column: 18
     applied: false
 - kind:
     UnusedNOQA: ~
   location:
-    row: 57
+    row: 60
     column: 4
   end_location:
-    row: 57
+    row: 60
     column: 12
   fix:
     content: ""
     location:
-      row: 57
+      row: 60
       column: 4
     end_location:
-      row: 57
+      row: 60
       column: 12
     applied: false
 

src/visibility.rs

@@ -0,0 +1,158 @@
+//! Abstractions for tracking public and private visibility across modules, classes, and functions.
+
+use std::path::Path;
+
+use rustpython_ast::{Stmt, StmtKind};
+
+use crate::ast::helpers::match_name_or_attr;
+use crate::docstrings::types::Documentable;
+
+#[derive(Debug, Clone)]
+pub enum Modifier {
+    Module,
+    Class,
+    Function,
+}
+
+#[derive(Debug, Clone)]
+pub enum Visibility {
+    Public,
+    Private,
+}
+
+#[derive(Debug, Clone)]
+pub struct VisibleScope {
+    pub modifier: Modifier,
+    pub visibility: Visibility,
+}
+
+/// Returns `true` if a function definition is an `@overload`.
+pub fn is_overload(stmt: &Stmt) -> bool {
+    match &stmt.node {
+        StmtKind::FunctionDef { decorator_list, .. }
+        | StmtKind::AsyncFunctionDef { decorator_list, .. } => decorator_list
+            .iter()
+            .any(|expr| match_name_or_attr(expr, "overload")),
+        _ => panic!("Found non-FunctionDef in is_overload"),
+    }
+}
+
+/// Returns `true` if a function is a "magic method".
+pub fn is_magic(stmt: &Stmt) -> bool {
+    match &stmt.node {
+        StmtKind::FunctionDef { name, .. } | StmtKind::AsyncFunctionDef { name, .. } => {
+            name.starts_with("__")
+                && name.ends_with("__")
+                && name != "__init__"
+                && name != "__call__"
+                && name != "__new__"
+        }
+        _ => panic!("Found non-FunctionDef in is_magic"),
+    }
+}
+
+/// Returns `true` if a function is an `__init__`.
+pub fn is_init(stmt: &Stmt) -> bool {
+    match &stmt.node {
+        StmtKind::FunctionDef { name, .. } | StmtKind::AsyncFunctionDef { name, .. } => {
+            name == "__init__"
+        }
+        _ => panic!("Found non-FunctionDef in is_init"),
+    }
+}
+
+/// Returns `true` if a module name indicates private visibility.
+fn is_private_module(module_name: &str) -> bool {
+    module_name.starts_with('_') || (module_name.starts_with("__") && module_name.ends_with("__"))
+}
+
+pub fn module_visibility(path: &Path) -> Visibility {
+    for component in path.iter().rev() {
+        if is_private_module(&component.to_string_lossy()) {
+            return Visibility::Private;
+        }
+    }
+    Visibility::Public
+}
+
+fn function_visibility(stmt: &Stmt) -> Visibility {
+    match &stmt.node {
+        StmtKind::FunctionDef { name, .. } | StmtKind::AsyncFunctionDef { name, .. } => {
+            if name.starts_with('_') {
+                Visibility::Private
+            } else {
+                Visibility::Public
+            }
+        }
+        _ => panic!("Found non-FunctionDef in function_visibility"),
+    }
+}
+
+fn method_visibility(stmt: &Stmt) -> Visibility {
+    match &stmt.node {
+        StmtKind::FunctionDef { name, .. } | StmtKind::AsyncFunctionDef { name, .. } => {
+            // Is the method non-private?
+            if !name.starts_with('_') {
+                return Visibility::Public;
+            }
+
+            // Is this a magic method?
+            if name.starts_with("__") && name.ends_with("__") {
+                return Visibility::Public;
+            }
+
+            Visibility::Private
+        }
+        _ => panic!("Found non-FunctionDef in method_visibility"),
+    }
+}
+
+fn class_visibility(stmt: &Stmt) -> Visibility {
+    match &stmt.node {
+        StmtKind::ClassDef { name, .. } => {
+            if name.starts_with('_') {
+                Visibility::Private
+            } else {
+                Visibility::Public
+            }
+        }
+        _ => panic!("Found non-ClassDef in function_visibility"),
+    }
+}
+
+/// Transition a `VisibleScope` based on a new `Documentable` definition.
+///
+/// `scope` is the current `VisibleScope`, while `Documentable` and `Stmt` describe the current
+/// node used to modify visibility.
+pub fn transition_scope(scope: &VisibleScope, stmt: &Stmt, kind: &Documentable) -> VisibleScope {
+    match kind {
+        Documentable::Function => VisibleScope {
+            modifier: Modifier::Function,
+            visibility: match scope {
+                VisibleScope {
+                    modifier: Modifier::Module,
+                    visibility: Visibility::Public,
+                } => function_visibility(stmt),
+                VisibleScope {
+                    modifier: Modifier::Class,
+                    visibility: Visibility::Public,
+                } => method_visibility(stmt),
+                _ => Visibility::Private,
+            },
+        },
+        Documentable::Class => VisibleScope {
+            modifier: Modifier::Class,
+            visibility: match scope {
+                VisibleScope {
+                    modifier: Modifier::Module,
+                    visibility: Visibility::Public,
+                } => class_visibility(stmt),
+                VisibleScope {
+                    modifier: Modifier::Class,
+                    visibility: Visibility::Public,
+                } => class_visibility(stmt),
+                _ => Visibility::Private,
+            },
+        },
+    }
+}

tests/integration_test.rs

@@ -0,0 +1,47 @@
+use std::str;
+
+use anyhow::Result;
+use assert_cmd::{crate_name, Command};
+
+#[test]
+fn test_stdin_success() -> Result<()> {
+    let mut cmd = Command::cargo_bin(crate_name!())?;
+    cmd.args(&["-"]).write_stdin("").assert().success();
+    Ok(())
+}
+
+#[test]
+fn test_stdin_error() -> Result<()> {
+    let mut cmd = Command::cargo_bin(crate_name!())?;
+    let output = cmd
+        .args(&["-"])
+        .write_stdin("import os\n")
+        .assert()
+        .failure();
+    assert!(str::from_utf8(&output.get_output().stdout)?.contains("-:1:1: F401"));
+    Ok(())
+}
+
+#[test]
+fn test_stdin_filename() -> Result<()> {
+    let mut cmd = Command::cargo_bin(crate_name!())?;
+    let output = cmd
+        .args(&["-", "--stdin-filename", "F401.py"])
+        .write_stdin("import os\n")
+        .assert()
+        .failure();
+    assert!(str::from_utf8(&output.get_output().stdout)?.contains("F401.py:1:1: F401"));
+    Ok(())
+}
+
+#[test]
+fn test_stdin_autofix() -> Result<()> {
+    let mut cmd = Command::cargo_bin(crate_name!())?;
+    let output = cmd
+        .args(&["-", "--fix"])
+        .write_stdin("import os\n")
+        .assert()
+        .failure();
+    assert!(str::from_utf8(&output.get_output().stdout)?.contains("-:1:1: F401"));
+    Ok(())
+}