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Use match statement in checkers (2) #10528

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6373074
Use match statement in checkers (2)
cdce8p Aug 29, 2025
dd1dea3
Add test case for skipped multi-assignments [unnecessary-lambda-assig…
cdce8p Aug 29, 2025
18cc751
Fix regression in unnecessary-lambda-assignment check
cdce8p Aug 30, 2025
933a16c
Raise AssertionError for uncovered fallback case
cdce8p Aug 30, 2025
c738ed9
Cleanup
cdce8p Aug 31, 2025
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65 changes: 32 additions & 33 deletions pylint/checkers/async_checker.py
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@
from typing import TYPE_CHECKING

import astroid
from astroid import nodes, util
from astroid import nodes

from pylint import checkers
from pylint.checkers import utils as checker_utils
Expand Down Expand Up @@ -54,39 +54,38 @@ def visit_asyncfunctiondef(self, node: nodes.AsyncFunctionDef) -> None:
@checker_utils.only_required_for_messages("not-async-context-manager")
def visit_asyncwith(self, node: nodes.AsyncWith) -> None:
for ctx_mgr, _ in node.items:
inferred = checker_utils.safe_infer(ctx_mgr)
if inferred is None or isinstance(inferred, util.UninferableBase):
continue

if isinstance(inferred, nodes.AsyncFunctionDef):
# Check if we are dealing with a function decorated
# with contextlib.asynccontextmanager.
if decorated_with(inferred, self._async_generators):
continue
elif isinstance(inferred, astroid.bases.AsyncGenerator):
# Check if we are dealing with a function decorated
# with contextlib.asynccontextmanager.
if decorated_with(inferred.parent, self._async_generators):
continue
else:
try:
inferred.getattr("__aenter__")
inferred.getattr("__aexit__")
except astroid.exceptions.NotFoundError:
if isinstance(inferred, astroid.Instance):
# If we do not know the bases of this class,
# just skip it.
if not checker_utils.has_known_bases(inferred):
continue
# Ignore mixin classes if they match the rgx option.
if (
"not-async-context-manager"
in self.linter.config.ignored_checks_for_mixins
and self._mixin_class_rgx.match(inferred.name)
):
continue
else:
match inferred := checker_utils.safe_infer(ctx_mgr):
case _ if not inferred:
continue
case nodes.AsyncFunctionDef():
# Check if we are dealing with a function decorated
# with contextlib.asynccontextmanager.
if decorated_with(inferred, self._async_generators):
continue
case astroid.bases.AsyncGenerator():
# Check if we are dealing with a function decorated
# with contextlib.asynccontextmanager.
if decorated_with(inferred.parent, self._async_generators):
continue
case _:
try:
inferred.getattr("__aenter__")
inferred.getattr("__aexit__")
except astroid.exceptions.NotFoundError:
if isinstance(inferred, astroid.Instance):
# If we do not know the bases of this class,
# just skip it.
if not checker_utils.has_known_bases(inferred):
continue
# Ignore mixin classes if they match the rgx option.
if (
"not-async-context-manager"
in self.linter.config.ignored_checks_for_mixins
and self._mixin_class_rgx.match(inferred.name)
):
continue
else:
continue
self.add_message(
"not-async-context-manager", node=node, args=(inferred.name,)
)
Expand Down
30 changes: 16 additions & 14 deletions pylint/checkers/exceptions.py
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Original file line number Diff line number Diff line change
Expand Up @@ -447,25 +447,27 @@ def _check_catching_non_exception(
# Don't emit the warning if the inferred stmt
# is None, but the exception handler is something else,
# maybe it was redefined.
if isinstance(exc, nodes.Const) and exc.value is None:
if (
isinstance(handler.type, nodes.Const) and handler.type.value is None
) or handler.type.parent_of(exc):
# If the exception handler catches None or
# the exception component, which is None, is
# defined by the entire exception handler, then
# emit a warning.
match exc:
case nodes.Const(value=None):
if (
isinstance(handler.type, nodes.Const)
and handler.type.value is None
) or handler.type.parent_of(exc):
# If the exception handler catches None or
# the exception component, which is None, is
# defined by the entire exception handler, then
# emit a warning.
self.add_message(
"catching-non-exception",
node=handler.type,
args=(part.as_string(),),
)
case _:
self.add_message(
"catching-non-exception",
node=handler.type,
args=(part.as_string(),),
)
else:
self.add_message(
"catching-non-exception",
node=handler.type,
args=(part.as_string(),),
)
return

if (
Expand Down
162 changes: 81 additions & 81 deletions pylint/checkers/format.py
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Original file line number Diff line number Diff line change
Expand Up @@ -268,7 +268,7 @@ def new_line(self, tokens: TokenWrapper, line_end: int, line_start: int) -> None
def process_module(self, node: nodes.Module) -> None:
pass

# pylint: disable-next = too-many-return-statements, too-many-branches
# pylint: disable-next = too-many-return-statements
def _check_keyword_parentheses(
self, tokens: list[tokenize.TokenInfo], start: int
) -> None:
Expand Down Expand Up @@ -347,30 +347,31 @@ def _check_keyword_parentheses(
)
return
elif depth == 1:
# This is a tuple, which is always acceptable.
if token[1] == ",":
return
# 'and' and 'or' are the only boolean operators with lower precedence
# than 'not', so parens are only required when they are found.
if token[1] in {"and", "or"}:
found_and_or = True
# A yield inside an expression must always be in parentheses,
# quit early without error.
elif token[1] == "yield":
return
# A generator expression always has a 'for' token in it, and
# the 'for' token is only legal inside parens when it is in a
# generator expression. The parens are necessary here, so bail
# without an error.
elif token[1] == "for":
return
# A generator expression can have an 'else' token in it.
# We check the rest of the tokens to see if any problems occur after
# the 'else'.
elif token[1] == "else":
if "(" in (i.string for i in tokens[i:]):
self._check_keyword_parentheses(tokens[i:], 0)
return
match token[1]:
case ",":
# This is a tuple, which is always acceptable.
return
case "and" | "or":
# 'and' and 'or' are the only boolean operators with lower precedence
# than 'not', so parens are only required when they are found.
found_and_or = True
case "yield":
# A yield inside an expression must always be in parentheses,
# quit early without error.
return
case "for":
# A generator expression always has a 'for' token in it, and
# the 'for' token is only legal inside parens when it is in a
# generator expression. The parens are necessary here, so bail
# without an error.
return
case "else":
# A generator expression can have an 'else' token in it.
# We check the rest of the tokens to see if any problems occur after
# the 'else'.
if "(" in (i.string for i in tokens[i:]):
self._check_keyword_parentheses(tokens[i:], 0)
return

def process_tokens(self, tokens: list[tokenize.TokenInfo]) -> None:
"""Process tokens and search for:
Expand All @@ -397,39 +398,42 @@ def process_tokens(self, tokens: list[tokenize.TokenInfo]) -> None:
else:
self.new_line(TokenWrapper(tokens), idx - 1, idx)

if tok_type == tokenize.NEWLINE:
# a program statement, or ENDMARKER, will eventually follow,
# after some (possibly empty) run of tokens of the form
# (NL | COMMENT)* (INDENT | DEDENT+)?
# If an INDENT appears, setting check_equal is wrong, and will
# be undone when we see the INDENT.
check_equal = True
self._check_line_ending(string, line_num)
elif tok_type == tokenize.INDENT:
check_equal = False
self.check_indent_level(string, indents[-1] + 1, line_num)
indents.append(indents[-1] + 1)
elif tok_type == tokenize.DEDENT:
# there's nothing we need to check here! what's important is
# that when the run of DEDENTs ends, the indentation of the
# program statement (or ENDMARKER) that triggered the run is
# equal to what's left at the top of the indents stack
check_equal = True
if len(indents) > 1:
del indents[-1]
elif tok_type == tokenize.NL:
if not line.strip("\r\n"):
last_blank_line_num = line_num
elif tok_type not in (tokenize.COMMENT, tokenize.ENCODING):
# This is the first concrete token following a NEWLINE, so it
# must be the first token of the next program statement, or an
# ENDMARKER; the "line" argument exposes the leading white-space
# for this statement; in the case of ENDMARKER, line is an empty
# string, so will properly match the empty string with which the
# "indents" stack was seeded
if check_equal:
match tok_type:
case tokenize.NEWLINE:
# a program statement, or ENDMARKER, will eventually follow,
# after some (possibly empty) run of tokens of the form
# (NL | COMMENT)* (INDENT | DEDENT+)?
# If an INDENT appears, setting check_equal is wrong, and will
# be undone when we see the INDENT.
check_equal = True
self._check_line_ending(string, line_num)
case tokenize.INDENT:
check_equal = False
self.check_indent_level(line, indents[-1], line_num)
self.check_indent_level(string, indents[-1] + 1, line_num)
indents.append(indents[-1] + 1)
case tokenize.DEDENT:
# there's nothing we need to check here! what's important is
# that when the run of DEDENTs ends, the indentation of the
# program statement (or ENDMARKER) that triggered the run is
# equal to what's left at the top of the indents stack
check_equal = True
if len(indents) > 1:
del indents[-1]
case tokenize.NL:
if not line.strip("\r\n"):
last_blank_line_num = line_num
case tokenize.COMMENT | tokenize.ENCODING:
pass
case _:
# This is the first concrete token following a NEWLINE, so it
# must be the first token of the next program statement, or an
# ENDMARKER; the "line" argument exposes the leading white-space
# for this statement; in the case of ENDMARKER, line is an empty
# string, so will properly match the empty string with which the
# "indents" stack was seeded
if check_equal:
check_equal = False
self.check_indent_level(line, indents[-1], line_num)

if tok_type == tokenize.NUMBER and string.endswith("l"):
self.add_message("lowercase-l-suffix", line=line_num)
Expand Down Expand Up @@ -546,30 +550,26 @@ def _infer_else_finally_line_number(

def _check_multi_statement_line(self, node: nodes.NodeNG, line: int) -> None:
"""Check for lines containing multiple statements."""
if isinstance(node, nodes.With):
# Do not warn about multiple nested context managers in with statements.
return
if (
isinstance(node.parent, nodes.If)
and not node.parent.orelse
and self.linter.config.single_line_if_stmt
):
return
if (
isinstance(node.parent, nodes.ClassDef)
and len(node.parent.body) == 1
and self.linter.config.single_line_class_stmt
):
return

# Functions stubs and class with ``Ellipsis`` as body are exempted.
if (
isinstance(node, nodes.Expr)
and isinstance(node.parent, (nodes.FunctionDef, nodes.ClassDef))
and isinstance(node.value, nodes.Const)
and node.value.value is Ellipsis
):
return
match node:
case nodes.With():
# Do not warn about multiple nested context managers in with statements.
return
case nodes.NodeNG(
parent=nodes.If(orelse=[])
) if self.linter.config.single_line_if_stmt:
return
case nodes.NodeNG(
parent=nodes.ClassDef(body=[_])
) if self.linter.config.single_line_class_stmt:
return
case nodes.Expr(
parent=nodes.FunctionDef() | nodes.ClassDef(),
value=nodes.Const(value=value),
) if (
value is Ellipsis
):
# Functions stubs and class with ``Ellipsis`` as body are exempted.
return

self.add_message("multiple-statements", node=node, confidence=HIGH)
self._visited_lines[line] = 2
Expand Down
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