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# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
# For details: https://github.com/PyCQA/pylint/blob/main/LICENSE
# Copyright (c) https://github.com/PyCQA/pylint/blob/main/CONTRIBUTORS.txt
"""Basic checker for Python code."""
from __future__ import annotations
import collections
import itertools
import sys
from collections.abc import Iterator
from typing import TYPE_CHECKING, cast
import astroid
from astroid import nodes, objects, util
from pylint import utils as lint_utils
from pylint.checkers import BaseChecker, utils
from pylint.interfaces import HIGH, INFERENCE, Confidence
from pylint.reporters.ureports import nodes as reporter_nodes
from pylint.utils import LinterStats
if TYPE_CHECKING:
from pylint.lint.pylinter import PyLinter
if sys.version_info >= (3, 8):
from typing import Literal
else:
from typing_extensions import Literal
class _BasicChecker(BaseChecker):
"""Permits separating multiple checks with the same checker name into
classes/file.
"""
name = "basic"
REVERSED_PROTOCOL_METHOD = "__reversed__"
SEQUENCE_PROTOCOL_METHODS = ("__getitem__", "__len__")
REVERSED_METHODS = (SEQUENCE_PROTOCOL_METHODS, (REVERSED_PROTOCOL_METHOD,))
# A mapping from qname -> symbol, to be used when generating messages
# about dangerous default values as arguments
DEFAULT_ARGUMENT_SYMBOLS = dict(
zip(
[".".join(["builtins", x]) for x in ("set", "dict", "list")],
["set()", "{}", "[]"],
),
**{
x: f"{x}()"
for x in (
"collections.deque",
"collections.ChainMap",
"collections.Counter",
"collections.OrderedDict",
"collections.defaultdict",
"collections.UserDict",
"collections.UserList",
)
},
)
def report_by_type_stats(
sect: reporter_nodes.Section,
stats: LinterStats,
old_stats: LinterStats | None,
) -> None:
"""Make a report of.
* percentage of different types documented
* percentage of different types with a bad name
"""
# percentage of different types documented and/or with a bad name
nice_stats: dict[str, dict[str, str]] = {}
for node_type in ("module", "class", "method", "function"):
node_type = cast(Literal["function", "class", "method", "module"], node_type)
total = stats.get_node_count(node_type)
nice_stats[node_type] = {}
if total != 0:
undocumented_node = stats.get_undocumented(node_type)
documented = total - undocumented_node
percent = (documented * 100.0) / total
nice_stats[node_type]["percent_documented"] = f"{percent:.2f}"
badname_node = stats.get_bad_names(node_type)
percent = (badname_node * 100.0) / total
nice_stats[node_type]["percent_badname"] = f"{percent:.2f}"
lines = ["type", "number", "old number", "difference", "%documented", "%badname"]
for node_type in ("module", "class", "method", "function"):
node_type = cast(Literal["function", "class", "method", "module"], node_type)
new = stats.get_node_count(node_type)
old = old_stats.get_node_count(node_type) if old_stats else None
diff_str = lint_utils.diff_string(old, new) if old else None
lines += [
node_type,
str(new),
str(old) if old else "NC",
diff_str if diff_str else "NC",
nice_stats[node_type].get("percent_documented", "0"),
nice_stats[node_type].get("percent_badname", "0"),
]
sect.append(reporter_nodes.Table(children=lines, cols=6, rheaders=1))
# pylint: disable-next = too-many-public-methods
class BasicChecker(_BasicChecker):
"""Basic checker.
Checks for :
* doc strings
* number of arguments, local variables, branches, returns and statements in
functions, methods
* required module attributes
* dangerous default values as arguments
* redefinition of function / method / class
* uses of the global statement
"""
name = "basic"
msgs = {
"W0101": (
"Unreachable code",
"unreachable",
'Used when there is some code behind a "return" or "raise" '
"statement, which will never be accessed.",
),
"W0102": (
"Dangerous default value %s as argument",
"dangerous-default-value",
"Used when a mutable value as list or dictionary is detected in "
"a default value for an argument.",
),
"W0104": (
"Statement seems to have no effect",
"pointless-statement",
"Used when a statement doesn't have (or at least seems to) any effect.",
),
"W0105": (
"String statement has no effect",
"pointless-string-statement",
"Used when a string is used as a statement (which of course "
"has no effect). This is a particular case of W0104 with its "
"own message so you can easily disable it if you're using "
"those strings as documentation, instead of comments.",
),
"W0106": (
'Expression "%s" is assigned to nothing',
"expression-not-assigned",
"Used when an expression that is not a function call is assigned "
"to nothing. Probably something else was intended.",
),
"W0108": (
"Lambda may not be necessary",
"unnecessary-lambda",
"Used when the body of a lambda expression is a function call "
"on the same argument list as the lambda itself; such lambda "
"expressions are in all but a few cases replaceable with the "
"function being called in the body of the lambda.",
),
"W0109": (
"Duplicate key %r in dictionary",
"duplicate-key",
"Used when a dictionary expression binds the same key multiple times.",
),
"W0122": (
"Use of exec",
"exec-used",
"Raised when the 'exec' statement is used. It's dangerous to use this "
"function for a user input, and it's also slower than actual code in "
"general. This doesn't mean you should never use it, but you should "
"consider alternatives first and restrict the functions available.",
),
"W0123": (
"Use of eval",
"eval-used",
'Used when you use the "eval" function, to discourage its '
"usage. Consider using `ast.literal_eval` for safely evaluating "
"strings containing Python expressions "
"from untrusted sources.",
),
"W0150": (
"%s statement in finally block may swallow exception",
"lost-exception",
"Used when a break or a return statement is found inside the "
"finally clause of a try...finally block: the exceptions raised "
"in the try clause will be silently swallowed instead of being "
"re-raised.",
),
"W0199": (
"Assert called on a populated tuple. Did you mean 'assert x,y'?",
"assert-on-tuple",
"A call of assert on a tuple will always evaluate to true if "
"the tuple is not empty, and will always evaluate to false if "
"it is.",
),
"W0124": (
'Following "as" with another context manager looks like a tuple.',
"confusing-with-statement",
"Emitted when a `with` statement component returns multiple values "
"and uses name binding with `as` only for a part of those values, "
"as in with ctx() as a, b. This can be misleading, since it's not "
"clear if the context manager returns a tuple or if the node without "
"a name binding is another context manager.",
),
"W0125": (
"Using a conditional statement with a constant value",
"using-constant-test",
"Emitted when a conditional statement (If or ternary if) "
"uses a constant value for its test. This might not be what "
"the user intended to do.",
),
"W0126": (
"Using a conditional statement with potentially wrong function or method call due to "
"missing parentheses",
"missing-parentheses-for-call-in-test",
"Emitted when a conditional statement (If or ternary if) "
"seems to wrongly call a function due to missing parentheses",
),
"W0127": (
"Assigning the same variable %r to itself",
"self-assigning-variable",
"Emitted when we detect that a variable is assigned to itself",
),
"W0128": (
"Redeclared variable %r in assignment",
"redeclared-assigned-name",
"Emitted when we detect that a variable was redeclared in the same assignment.",
),
"E0111": (
"The first reversed() argument is not a sequence",
"bad-reversed-sequence",
"Used when the first argument to reversed() builtin "
"isn't a sequence (does not implement __reversed__, "
"nor __getitem__ and __len__",
),
"E0119": (
"format function is not called on str",
"misplaced-format-function",
"Emitted when format function is not called on str object. "
'e.g doing print("value: {}").format(123) instead of '
'print("value: {}".format(123)). This might not be what the user '
"intended to do.",
),
"W0129": (
"Assert statement has a string literal as its first argument. The assert will %s fail.",
"assert-on-string-literal",
"Used when an assert statement has a string literal as its first argument, which will "
"cause the assert to always pass.",
),
"W0130": (
"Duplicate value %r in set",
"duplicate-value",
"This message is emitted when a set contains the same value two or more times.",
),
"W0131": (
"Named expression used without context",
"named-expr-without-context",
"Emitted if named expression is used to do a regular assignment "
"outside a context like if, for, while, or a comprehension.",
),
"W0133": (
"Exception statement has no effect",
"pointless-exception-statement",
"Used when an exception is created without being assigned, raised or returned "
"for subsequent use elsewhere.",
),
}
reports = (("RP0101", "Statistics by type", report_by_type_stats),)
def __init__(self, linter: PyLinter) -> None:
super().__init__(linter)
self._tryfinallys: list[nodes.TryFinally] | None = None
def open(self) -> None:
"""Initialize visit variables and statistics."""
py_version = self.linter.config.py_version
self._py38_plus = py_version >= (3, 8)
self._tryfinallys = []
self.linter.stats.reset_node_count()
@utils.only_required_for_messages(
"using-constant-test", "missing-parentheses-for-call-in-test"
)
def visit_if(self, node: nodes.If) -> None:
self._check_using_constant_test(node, node.test)
@utils.only_required_for_messages(
"using-constant-test", "missing-parentheses-for-call-in-test"
)
def visit_ifexp(self, node: nodes.IfExp) -> None:
self._check_using_constant_test(node, node.test)
@utils.only_required_for_messages(
"using-constant-test", "missing-parentheses-for-call-in-test"
)
def visit_comprehension(self, node: nodes.Comprehension) -> None:
if node.ifs:
for if_test in node.ifs:
self._check_using_constant_test(node, if_test)
def _check_using_constant_test(
self,
node: nodes.If | nodes.IfExp | nodes.Comprehension,
test: nodes.NodeNG | None,
) -> None:
const_nodes = (
nodes.Module,
nodes.GeneratorExp,
nodes.Lambda,
nodes.FunctionDef,
nodes.ClassDef,
astroid.bases.Generator,
astroid.UnboundMethod,
astroid.BoundMethod,
nodes.Module,
)
structs = (nodes.Dict, nodes.Tuple, nodes.Set, nodes.List)
# These nodes are excepted, since they are not constant
# values, requiring a computation to happen.
except_nodes = (
nodes.Call,
nodes.BinOp,
nodes.BoolOp,
nodes.UnaryOp,
nodes.Subscript,
)
inferred = None
emit = isinstance(test, (nodes.Const,) + structs + const_nodes)
maybe_generator_call = None
if not isinstance(test, except_nodes):
inferred = utils.safe_infer(test)
if isinstance(inferred, util.UninferableBase) and isinstance(
test, nodes.Name
):
emit, maybe_generator_call = BasicChecker._name_holds_generator(test)
# Emit if calling a function that only returns GeneratorExp (always tests True)
elif isinstance(test, nodes.Call):
maybe_generator_call = test
if maybe_generator_call:
inferred_call = utils.safe_infer(maybe_generator_call.func)
if isinstance(inferred_call, nodes.FunctionDef):
# Can't use all(x) or not any(not x) for this condition, because it
# will return True for empty generators, which is not what we want.
all_returns_were_generator = None
for return_node in inferred_call._get_return_nodes_skip_functions():
if not isinstance(return_node.value, nodes.GeneratorExp):
all_returns_were_generator = False
break
all_returns_were_generator = True
if all_returns_were_generator:
self.add_message(
"using-constant-test", node=node, confidence=INFERENCE
)
return
if emit:
self.add_message("using-constant-test", node=test, confidence=INFERENCE)
elif isinstance(inferred, const_nodes):
# If the constant node is a FunctionDef or Lambda then
# it may be an illicit function call due to missing parentheses
call_inferred = None
try:
# Just forcing the generator to infer all elements.
# astroid.exceptions.InferenceError are false positives
# see https://github.com/PyCQA/pylint/pull/8185
if isinstance(inferred, nodes.FunctionDef):
call_inferred = list(inferred.infer_call_result())
elif isinstance(inferred, nodes.Lambda):
call_inferred = list(inferred.infer_call_result(node))
except astroid.InferenceError:
call_inferred = None
if call_inferred:
self.add_message(
"missing-parentheses-for-call-in-test",
node=test,
confidence=INFERENCE,
)
self.add_message("using-constant-test", node=test, confidence=INFERENCE)
@staticmethod
def _name_holds_generator(test: nodes.Name) -> tuple[bool, nodes.Call | None]:
"""Return whether `test` tests a name certain to hold a generator, or optionally
a call that should be then tested to see if *it* returns only generators.
"""
assert isinstance(test, nodes.Name)
emit = False
maybe_generator_call = None
lookup_result = test.frame(future=True).lookup(test.name)
if not lookup_result:
return emit, maybe_generator_call
maybe_generator_assigned = (
isinstance(assign_name.parent.value, nodes.GeneratorExp)
for assign_name in lookup_result[1]
if isinstance(assign_name.parent, nodes.Assign)
)
first_item = next(maybe_generator_assigned, None)
if first_item is not None:
# Emit if this variable is certain to hold a generator
if all(itertools.chain((first_item,), maybe_generator_assigned)):
emit = True
# If this variable holds the result of a call, save it for next test
elif (
len(lookup_result[1]) == 1
and isinstance(lookup_result[1][0].parent, nodes.Assign)
and isinstance(lookup_result[1][0].parent.value, nodes.Call)
):
maybe_generator_call = lookup_result[1][0].parent.value
return emit, maybe_generator_call
def visit_module(self, _: nodes.Module) -> None:
"""Check module name, docstring and required arguments."""
self.linter.stats.node_count["module"] += 1
def visit_classdef(self, _: nodes.ClassDef) -> None:
"""Check module name, docstring and redefinition
increment branch counter.
"""
self.linter.stats.node_count["klass"] += 1
@utils.only_required_for_messages(
"pointless-statement",
"pointless-exception-statement",
"pointless-string-statement",
"expression-not-assigned",
"named-expr-without-context",
)
def visit_expr(self, node: nodes.Expr) -> None:
"""Check for various kind of statements without effect."""
expr = node.value
if isinstance(expr, nodes.Const) and isinstance(expr.value, str):
# treat string statement in a separated message
# Handle PEP-257 attribute docstrings.
# An attribute docstring is defined as being a string right after
# an assignment at the module level, class level or __init__ level.
scope = expr.scope()
if isinstance(scope, (nodes.ClassDef, nodes.Module, nodes.FunctionDef)):
if isinstance(scope, nodes.FunctionDef) and scope.name != "__init__":
pass
else:
sibling = expr.previous_sibling()
if (
sibling is not None
and sibling.scope() is scope
and isinstance(sibling, (nodes.Assign, nodes.AnnAssign))
):
return
self.add_message("pointless-string-statement", node=node)
return
# Warn W0133 for exceptions that are used as statements
if isinstance(expr, nodes.Call):
name = ""
if isinstance(expr.func, nodes.Name):
name = expr.func.name
elif isinstance(expr.func, nodes.Attribute):
name = expr.func.attrname
# Heuristic: only run inference for names that begin with an uppercase char
# This reduces W0133's coverage, but retains acceptable runtime performance
# For more details, see: https://github.com/PyCQA/pylint/issues/8073
inferred = utils.safe_infer(expr) if name[:1].isupper() else None
if isinstance(inferred, objects.ExceptionInstance):
self.add_message(
"pointless-exception-statement", node=node, confidence=INFERENCE
)
return
# Ignore if this is :
# * the unique child of a try/except body
# * a yield statement
# * an ellipsis (which can be used on Python 3 instead of pass)
# warn W0106 if we have any underlying function call (we can't predict
# side effects), else pointless-statement
if (
isinstance(expr, (nodes.Yield, nodes.Await))
or (isinstance(node.parent, nodes.TryExcept) and node.parent.body == [node])
or (isinstance(expr, nodes.Const) and expr.value is Ellipsis)
):
return
if isinstance(expr, nodes.NamedExpr):
self.add_message("named-expr-without-context", node=node, confidence=HIGH)
elif any(expr.nodes_of_class(nodes.Call)):
self.add_message(
"expression-not-assigned", node=node, args=expr.as_string()
)
else:
self.add_message("pointless-statement", node=node)
@staticmethod
def _filter_vararg(
node: nodes.Lambda, call_args: list[nodes.NodeNG]
) -> Iterator[nodes.NodeNG]:
# Return the arguments for the given call which are
# not passed as vararg.
for arg in call_args:
if isinstance(arg, nodes.Starred):
if (
isinstance(arg.value, nodes.Name)
and arg.value.name != node.args.vararg
):
yield arg
else:
yield arg
@staticmethod
def _has_variadic_argument(
args: list[nodes.Starred | nodes.Keyword], variadic_name: str
) -> bool:
return not args or any(
isinstance(a.value, nodes.Name)
and a.value.name != variadic_name
or not isinstance(a.value, nodes.Name)
for a in args
)
@utils.only_required_for_messages("unnecessary-lambda")
# pylint: disable-next=too-many-return-statements
def visit_lambda(self, node: nodes.Lambda) -> None:
"""Check whether the lambda is suspicious."""
# if the body of the lambda is a call expression with the same
# argument list as the lambda itself, then the lambda is
# possibly unnecessary and at least suspicious.
if node.args.defaults:
# If the arguments of the lambda include defaults, then a
# judgment cannot be made because there is no way to check
# that the defaults defined by the lambda are the same as
# the defaults defined by the function called in the body
# of the lambda.
return
call = node.body
if not isinstance(call, nodes.Call):
# The body of the lambda must be a function call expression
# for the lambda to be unnecessary.
return
if isinstance(node.body.func, nodes.Attribute) and isinstance(
node.body.func.expr, nodes.Call
):
# Chained call, the intermediate call might
# return something else (but we don't check that, yet).
return
call_site = astroid.arguments.CallSite.from_call(call)
ordinary_args = list(node.args.args)
new_call_args = list(self._filter_vararg(node, call.args))
if node.args.kwarg:
if self._has_variadic_argument(call.kwargs, node.args.kwarg):
return
if node.args.vararg:
if self._has_variadic_argument(call.starargs, node.args.vararg):
return
elif call.starargs:
return
if call.keywords:
# Look for additional keyword arguments that are not part
# of the lambda's signature
lambda_kwargs = {keyword.name for keyword in node.args.defaults}
if len(lambda_kwargs) != len(call_site.keyword_arguments):
# Different lengths, so probably not identical
return
if set(call_site.keyword_arguments).difference(lambda_kwargs):
return
# The "ordinary" arguments must be in a correspondence such that:
# ordinary_args[i].name == call.args[i].name.
if len(ordinary_args) != len(new_call_args):
return
for arg, passed_arg in zip(ordinary_args, new_call_args):
if not isinstance(passed_arg, nodes.Name):
return
if arg.name != passed_arg.name:
return
# The lambda is necessary if it uses its parameter in the function it is
# calling in the lambda's body
# e.g. lambda foo: (func1 if foo else func2)(foo)
for name in call.func.nodes_of_class(nodes.Name):
if name.lookup(name.name)[0] is node:
return
self.add_message("unnecessary-lambda", line=node.fromlineno, node=node)
@utils.only_required_for_messages("dangerous-default-value")
def visit_functiondef(self, node: nodes.FunctionDef) -> None:
"""Check function name, docstring, arguments, redefinition,
variable names, max locals.
"""
if node.is_method():
self.linter.stats.node_count["method"] += 1
else:
self.linter.stats.node_count["function"] += 1
self._check_dangerous_default(node)
visit_asyncfunctiondef = visit_functiondef
def _check_dangerous_default(self, node: nodes.FunctionDef) -> None:
"""Check for dangerous default values as arguments."""
def is_iterable(internal_node: nodes.NodeNG) -> bool:
return isinstance(internal_node, (nodes.List, nodes.Set, nodes.Dict))
defaults = (node.args.defaults or []) + (node.args.kw_defaults or [])
for default in defaults:
if not default:
continue
try:
value = next(default.infer())
except astroid.InferenceError:
continue
if (
isinstance(value, astroid.Instance)
and value.qname() in DEFAULT_ARGUMENT_SYMBOLS
):
if value is default:
msg = DEFAULT_ARGUMENT_SYMBOLS[value.qname()]
elif isinstance(value, astroid.Instance) or is_iterable(value):
# We are here in the following situation(s):
# * a dict/set/list/tuple call which wasn't inferred
# to a syntax node ({}, () etc.). This can happen
# when the arguments are invalid or unknown to
# the inference.
# * a variable from somewhere else, which turns out to be a list
# or a dict.
if is_iterable(default):
msg = value.pytype()
elif isinstance(default, nodes.Call):
msg = f"{value.name}() ({value.qname()})"
else:
msg = f"{default.as_string()} ({value.qname()})"
else:
# this argument is a name
msg = f"{default.as_string()} ({DEFAULT_ARGUMENT_SYMBOLS[value.qname()]})"
self.add_message("dangerous-default-value", node=node, args=(msg,))
@utils.only_required_for_messages("unreachable", "lost-exception")
def visit_return(self, node: nodes.Return) -> None:
"""Return node visitor.
1 - check if the node has a right sibling (if so, that's some
unreachable code)
2 - check if the node is inside the 'finally' clause of a 'try...finally'
block
"""
self._check_unreachable(node)
# Is it inside final body of a try...finally block ?
self._check_not_in_finally(node, "return", (nodes.FunctionDef,))
@utils.only_required_for_messages("unreachable")
def visit_continue(self, node: nodes.Continue) -> None:
"""Check is the node has a right sibling (if so, that's some unreachable
code).
"""
self._check_unreachable(node)
@utils.only_required_for_messages("unreachable", "lost-exception")
def visit_break(self, node: nodes.Break) -> None:
"""Break node visitor.
1 - check if the node has a right sibling (if so, that's some
unreachable code)
2 - check if the node is inside the 'finally' clause of a 'try...finally'
block
"""
# 1 - Is it right sibling ?
self._check_unreachable(node)
# 2 - Is it inside final body of a try...finally block ?
self._check_not_in_finally(node, "break", (nodes.For, nodes.While))
@utils.only_required_for_messages("unreachable")
def visit_raise(self, node: nodes.Raise) -> None:
"""Check if the node has a right sibling (if so, that's some unreachable
code).
"""
self._check_unreachable(node)
def _check_misplaced_format_function(self, call_node: nodes.Call) -> None:
if not isinstance(call_node.func, nodes.Attribute):
return
if call_node.func.attrname != "format":
return
expr = utils.safe_infer(call_node.func.expr)
if isinstance(expr, util.UninferableBase):
return
if not expr:
# we are doubtful on inferred type of node, so here just check if format
# was called on print()
call_expr = call_node.func.expr
if not isinstance(call_expr, nodes.Call):
return
if (
isinstance(call_expr.func, nodes.Name)
and call_expr.func.name == "print"
):
self.add_message("misplaced-format-function", node=call_node)
@utils.only_required_for_messages(
"eval-used",
"exec-used",
"bad-reversed-sequence",
"misplaced-format-function",
"unreachable",
)
def visit_call(self, node: nodes.Call) -> None:
"""Visit a Call node."""
if utils.is_terminating_func(node):
self._check_unreachable(node, confidence=INFERENCE)
self._check_misplaced_format_function(node)
if isinstance(node.func, nodes.Name):
name = node.func.name
# ignore the name if it's not a builtin (i.e. not defined in the
# locals nor globals scope)
if not (name in node.frame(future=True) or name in node.root()):
if name == "exec":
self.add_message("exec-used", node=node)
elif name == "reversed":
self._check_reversed(node)
elif name == "eval":
self.add_message("eval-used", node=node)
@utils.only_required_for_messages("assert-on-tuple", "assert-on-string-literal")
def visit_assert(self, node: nodes.Assert) -> None:
"""Check whether assert is used on a tuple or string literal."""
if isinstance(node.test, nodes.Tuple) and len(node.test.elts) > 0:
self.add_message("assert-on-tuple", node=node, confidence=HIGH)
if isinstance(node.test, nodes.Const) and isinstance(node.test.value, str):
if node.test.value:
when = "never"
else:
when = "always"
self.add_message("assert-on-string-literal", node=node, args=(when,))
@utils.only_required_for_messages("duplicate-key")
def visit_dict(self, node: nodes.Dict) -> None:
"""Check duplicate key in dictionary."""
keys = set()
for k, _ in node.items:
if isinstance(k, nodes.Const):
key = k.value
elif isinstance(k, nodes.Attribute):
key = k.as_string()
else:
continue
if key in keys:
self.add_message("duplicate-key", node=node, args=key)
keys.add(key)
@utils.only_required_for_messages("duplicate-value")
def visit_set(self, node: nodes.Set) -> None:
"""Check duplicate value in set."""
values = set()
for v in node.elts:
if isinstance(v, nodes.Const):
value = v.value
else:
continue
if value in values:
self.add_message(
"duplicate-value", node=node, args=value, confidence=HIGH
)
values.add(value)
def visit_tryfinally(self, node: nodes.TryFinally) -> None:
"""Update try...finally flag."""
assert self._tryfinallys is not None
self._tryfinallys.append(node)
def leave_tryfinally(self, _: nodes.TryFinally) -> None:
"""Update try...finally flag."""
assert self._tryfinallys is not None
self._tryfinallys.pop()
def _check_unreachable(
self,
node: nodes.Return | nodes.Continue | nodes.Break | nodes.Raise | nodes.Call,
confidence: Confidence = HIGH,
) -> None:
"""Check unreachable code."""
unreachable_statement = node.next_sibling()
if unreachable_statement is not None:
if (
isinstance(node, nodes.Return)
and isinstance(unreachable_statement, nodes.Expr)
and isinstance(unreachable_statement.value, nodes.Yield)
):
# Don't add 'unreachable' for empty generators.
# Only add warning if 'yield' is followed by another node.
unreachable_statement = unreachable_statement.next_sibling()
if unreachable_statement is None:
return
self.add_message(
"unreachable", node=unreachable_statement, confidence=confidence
)
def _check_not_in_finally(
self,
node: nodes.Break | nodes.Return,
node_name: str,
breaker_classes: tuple[nodes.NodeNG, ...] = (),
) -> None:
"""Check that a node is not inside a 'finally' clause of a
'try...finally' statement.
If we find a parent which type is in breaker_classes before
a 'try...finally' block we skip the whole check.
"""
# if self._tryfinallys is empty, we're not an in try...finally block
if not self._tryfinallys:
return
# the node could be a grand-grand...-child of the 'try...finally'
_parent = node.parent
_node = node
while _parent and not isinstance(_parent, breaker_classes):
if hasattr(_parent, "finalbody") and _node in _parent.finalbody:
self.add_message("lost-exception", node=node, args=node_name)
return
_node = _parent
_parent = _node.parent
def _check_reversed(self, node: nodes.Call) -> None:
"""Check that the argument to `reversed` is a sequence."""
try:
argument = utils.safe_infer(utils.get_argument_from_call(node, position=0))
except utils.NoSuchArgumentError:
pass
else:
if isinstance(argument, util.UninferableBase):
return
if argument is None:
# Nothing was inferred.
# Try to see if we have iter().
if isinstance(node.args[0], nodes.Call):
try:
func = next(node.args[0].func.infer())
except astroid.InferenceError:
return
if getattr(
func, "name", None
) == "iter" and utils.is_builtin_object(func):
self.add_message("bad-reversed-sequence", node=node)
return
if isinstance(argument, (nodes.List, nodes.Tuple)):
return
# dicts are reversible, but only from Python 3.8 onward. Prior to
# that, any class based on dict must explicitly provide a
# __reversed__ method
if not self._py38_plus and isinstance(argument, astroid.Instance):
if any(
ancestor.name == "dict" and utils.is_builtin_object(ancestor)
for ancestor in itertools.chain(
(argument._proxied,), argument._proxied.ancestors()
)
):
try:
argument.locals[REVERSED_PROTOCOL_METHOD]
except KeyError:
self.add_message("bad-reversed-sequence", node=node)
return
if hasattr(argument, "getattr"):
# everything else is not a proper sequence for reversed()
for methods in REVERSED_METHODS:
for meth in methods:
try:
argument.getattr(meth)
except astroid.NotFoundError:
break
else:
break
else:
self.add_message("bad-reversed-sequence", node=node)
else:
self.add_message("bad-reversed-sequence", node=node)
@utils.only_required_for_messages("confusing-with-statement")
def visit_with(self, node: nodes.With) -> None:
# a "with" statement with multiple managers corresponds
# to one AST "With" node with multiple items
pairs = node.items
if pairs:
for prev_pair, pair in zip(pairs, pairs[1:]):
if isinstance(prev_pair[1], nodes.AssignName) and (
pair[1] is None and not isinstance(pair[0], nodes.Call)
):
# Don't emit a message if the second is a function call
# there's no way that can be mistaken for a name assignment.
# If the line number doesn't match
# we assume it's a nested "with".
self.add_message("confusing-with-statement", node=node)
def _check_self_assigning_variable(self, node: nodes.Assign) -> None:
# Detect assigning to the same variable.
scope = node.scope()
scope_locals = scope.locals
rhs_names = []
targets = node.targets
if isinstance(targets[0], nodes.Tuple):
if len(targets) != 1:
# A complex assignment, so bail out early.
return
targets = targets[0].elts
if len(targets) == 1:
# Unpacking a variable into the same name.
return
if isinstance(node.value, nodes.Name):
if len(targets) != 1:
return
rhs_names = [node.value]
elif isinstance(node.value, nodes.Tuple):
rhs_count = len(node.value.elts)
if len(targets) != rhs_count or rhs_count == 1:
return
rhs_names = node.value.elts
for target, lhs_name in zip(targets, rhs_names):
if not isinstance(lhs_name, nodes.Name):
continue
if not isinstance(target, nodes.AssignName):
continue
# Check that the scope is different from a class level, which is usually
# a pattern to expose module level attributes as class level ones.
if isinstance(scope, nodes.ClassDef) and target.name in scope_locals:
continue
if target.name == lhs_name.name:
self.add_message(
"self-assigning-variable", args=(target.name,), node=target
)
def _check_redeclared_assign_name(self, targets: list[nodes.NodeNG | None]) -> None:
dummy_variables_rgx = self.linter.config.dummy_variables_rgx
for target in targets:
if not isinstance(target, nodes.Tuple):
continue
found_names = []
for element in target.elts:
if isinstance(element, nodes.Tuple):
self._check_redeclared_assign_name([element])
elif isinstance(element, nodes.AssignName) and element.name != "_":
if dummy_variables_rgx and dummy_variables_rgx.match(element.name):
return
found_names.append(element.name)
names = collections.Counter(found_names)
for name, count in names.most_common():
if count > 1:
self.add_message(
"redeclared-assigned-name", args=(name,), node=target
)
@utils.only_required_for_messages(
"self-assigning-variable", "redeclared-assigned-name"
)
def visit_assign(self, node: nodes.Assign) -> None:
self._check_self_assigning_variable(node)
self._check_redeclared_assign_name(node.targets)
@utils.only_required_for_messages("redeclared-assigned-name")
def visit_for(self, node: nodes.For) -> None:
self._check_redeclared_assign_name([node.target])
|