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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
"""Variables checkers for Python code."""
from __future__ import annotations
import collections
import copy
import itertools
import os
import re
import sys
from collections import defaultdict
from collections.abc import Generator, Iterable, Iterator
from enum import Enum
from functools import lru_cache
from typing import TYPE_CHECKING, Any, NamedTuple
import astroid
from astroid import bases, extract_node, nodes, util
from astroid.nodes import _base_nodes
from astroid.typing import InferenceResult
from pylint.checkers import BaseChecker, utils
from pylint.checkers.utils import (
in_type_checking_block,
is_postponed_evaluation_enabled,
is_sys_guard,
)
from pylint.constants import PY39_PLUS, TYPING_NEVER, TYPING_NORETURN
from pylint.interfaces import CONTROL_FLOW, HIGH, INFERENCE, INFERENCE_FAILURE
from pylint.typing import MessageDefinitionTuple
if sys.version_info >= (3, 8):
from functools import cached_property
else:
from astroid.decorators import cachedproperty as cached_property
if TYPE_CHECKING:
from pylint.lint import PyLinter
SPECIAL_OBJ = re.compile("^_{2}[a-z]+_{2}$")
FUTURE = "__future__"
# regexp for ignored argument name
IGNORED_ARGUMENT_NAMES = re.compile("_.*|^ignored_|^unused_")
# In Python 3.7 abc has a Python implementation which is preferred
# by astroid. Unfortunately this also messes up our explicit checks
# for `abc`
METACLASS_NAME_TRANSFORMS = {"_py_abc": "abc"}
BUILTIN_RANGE = "builtins.range"
TYPING_MODULE = "typing"
TYPING_NAMES = frozenset(
{
"Any",
"Callable",
"ClassVar",
"Generic",
"Optional",
"Tuple",
"Type",
"TypeVar",
"Union",
"AbstractSet",
"ByteString",
"Container",
"ContextManager",
"Hashable",
"ItemsView",
"Iterable",
"Iterator",
"KeysView",
"Mapping",
"MappingView",
"MutableMapping",
"MutableSequence",
"MutableSet",
"Sequence",
"Sized",
"ValuesView",
"Awaitable",
"AsyncIterator",
"AsyncIterable",
"Coroutine",
"Collection",
"AsyncGenerator",
"AsyncContextManager",
"Reversible",
"SupportsAbs",
"SupportsBytes",
"SupportsComplex",
"SupportsFloat",
"SupportsInt",
"SupportsRound",
"Counter",
"Deque",
"Dict",
"DefaultDict",
"List",
"Set",
"FrozenSet",
"NamedTuple",
"Generator",
"AnyStr",
"Text",
"Pattern",
"BinaryIO",
}
)
DICT_TYPES = (
astroid.objects.DictValues,
astroid.objects.DictKeys,
astroid.objects.DictItems,
astroid.nodes.node_classes.Dict,
)
NODES_WITH_VALUE_ATTR = (
nodes.Assign,
nodes.AnnAssign,
nodes.AugAssign,
nodes.Expr,
nodes.Return,
nodes.Match,
)
class VariableVisitConsumerAction(Enum):
"""Reported by _check_consumer() and its sub-methods to determine the
subsequent action to take in _undefined_and_used_before_checker().
Continue -> continue loop to next consumer
Return -> return and thereby break the loop
"""
CONTINUE = 0
RETURN = 1
def _is_from_future_import(stmt: nodes.ImportFrom, name: str) -> bool | None:
"""Check if the name is a future import from another module."""
try:
module = stmt.do_import_module(stmt.modname)
except astroid.AstroidBuildingException:
return None
for local_node in module.locals.get(name, []):
if isinstance(local_node, nodes.ImportFrom) and local_node.modname == FUTURE:
return True
return None
@lru_cache(maxsize=1000)
def overridden_method(
klass: nodes.LocalsDictNodeNG, name: str | None
) -> nodes.FunctionDef | None:
"""Get overridden method if any."""
try:
parent = next(klass.local_attr_ancestors(name))
except (StopIteration, KeyError):
return None
try:
meth_node = parent[name]
except KeyError:
# We have found an ancestor defining <name> but it's not in the local
# dictionary. This may happen with astroid built from living objects.
return None
if isinstance(meth_node, nodes.FunctionDef):
return meth_node
return None
def _get_unpacking_extra_info(node: nodes.Assign, inferred: InferenceResult) -> str:
"""Return extra information to add to the message for unpacking-non-sequence
and unbalanced-tuple/dict-unpacking errors.
"""
more = ""
if isinstance(inferred, DICT_TYPES):
if isinstance(node, nodes.Assign):
more = node.value.as_string()
elif isinstance(node, nodes.For):
more = node.iter.as_string()
return more
inferred_module = inferred.root().name
if node.root().name == inferred_module:
if node.lineno == inferred.lineno:
more = f"'{inferred.as_string()}'"
elif inferred.lineno:
more = f"defined at line {inferred.lineno}"
elif inferred.lineno:
more = f"defined at line {inferred.lineno} of {inferred_module}"
return more
def _detect_global_scope(
node: nodes.Name, frame: nodes.LocalsDictNodeNG, defframe: nodes.LocalsDictNodeNG
) -> bool:
"""Detect that the given frames share a global scope.
Two frames share a global scope when neither
of them are hidden under a function scope, as well
as any parent scope of them, until the root scope.
In this case, depending from something defined later on
will only work if guarded by a nested function definition.
Example:
class A:
# B has the same global scope as `C`, leading to a NameError.
# Return True to indicate a shared scope.
class B(C): ...
class C: ...
Whereas this does not lead to a NameError:
class A:
def guard():
# Return False to indicate no scope sharing.
class B(C): ...
class C: ...
"""
def_scope = scope = None
if frame and frame.parent:
scope = frame.parent.scope()
if defframe and defframe.parent:
def_scope = defframe.parent.scope()
if (
isinstance(frame, nodes.ClassDef)
and scope is not def_scope
and scope is utils.get_node_first_ancestor_of_type(node, nodes.FunctionDef)
):
# If the current node's scope is a class nested under a function,
# and the def_scope is something else, then they aren't shared.
return False
if isinstance(frame, nodes.FunctionDef):
# If the parent of the current node is a
# function, then it can be under its scope (defined in); or
# the `->` part of annotations. The same goes
# for annotations of function arguments, they'll have
# their parent the Arguments node.
if frame.parent_of(defframe):
return node.lineno < defframe.lineno # type: ignore[no-any-return]
if not isinstance(node.parent, (nodes.FunctionDef, nodes.Arguments)):
return False
elif any(
not isinstance(f, (nodes.ClassDef, nodes.Module)) for f in (frame, defframe)
):
# Not interested in other frames, since they are already
# not in a global scope.
return False
break_scopes = []
for current_scope in (scope, def_scope):
# Look for parent scopes. If there is anything different
# than a module or a class scope, then they frames don't
# share a global scope.
parent_scope = current_scope
while parent_scope:
if not isinstance(parent_scope, (nodes.ClassDef, nodes.Module)):
break_scopes.append(parent_scope)
break
if parent_scope.parent:
parent_scope = parent_scope.parent.scope()
else:
break
if break_scopes and len(set(break_scopes)) != 1:
# Store different scopes than expected.
# If the stored scopes are, in fact, the very same, then it means
# that the two frames (frame and defframe) share the same scope,
# and we could apply our lineno analysis over them.
# For instance, this works when they are inside a function, the node
# that uses a definition and the definition itself.
return False
# At this point, we are certain that frame and defframe share a scope
# and the definition of the first depends on the second.
return frame.lineno < defframe.lineno # type: ignore[no-any-return]
def _infer_name_module(
node: nodes.Import, name: str
) -> Generator[InferenceResult, None, None]:
context = astroid.context.InferenceContext()
context.lookupname = name
return node.infer(context, asname=False) # type: ignore[no-any-return]
def _fix_dot_imports(
not_consumed: dict[str, list[nodes.NodeNG]]
) -> list[tuple[str, _base_nodes.ImportNode]]:
"""Try to fix imports with multiple dots, by returning a dictionary
with the import names expanded.
The function unflattens root imports,
like 'xml' (when we have both 'xml.etree' and 'xml.sax'), to 'xml.etree'
and 'xml.sax' respectively.
"""
names: dict[str, _base_nodes.ImportNode] = {}
for name, stmts in not_consumed.items():
if any(
isinstance(stmt, nodes.AssignName)
and isinstance(stmt.assign_type(), nodes.AugAssign)
for stmt in stmts
):
continue
for stmt in stmts:
if not isinstance(stmt, (nodes.ImportFrom, nodes.Import)):
continue
for imports in stmt.names:
second_name = None
import_module_name = imports[0]
if import_module_name == "*":
# In case of wildcard imports,
# pick the name from inside the imported module.
second_name = name
else:
name_matches_dotted_import = False
if (
import_module_name.startswith(name)
and import_module_name.find(".") > -1
):
name_matches_dotted_import = True
if name_matches_dotted_import or name in imports:
# Most likely something like 'xml.etree',
# which will appear in the .locals as 'xml'.
# Only pick the name if it wasn't consumed.
second_name = import_module_name
if second_name and second_name not in names:
names[second_name] = stmt
return sorted(names.items(), key=lambda a: a[1].fromlineno) # type: ignore[no-any-return]
def _find_frame_imports(name: str, frame: nodes.LocalsDictNodeNG) -> bool:
"""Detect imports in the frame, with the required *name*.
Such imports can be considered assignments if they are not globals.
Returns True if an import for the given name was found.
"""
if name in _flattened_scope_names(frame.nodes_of_class(nodes.Global)):
return False
imports = frame.nodes_of_class((nodes.Import, nodes.ImportFrom))
for import_node in imports:
for import_name, import_alias in import_node.names:
# If the import uses an alias, check only that.
# Otherwise, check only the import name.
if import_alias:
if import_alias == name:
return True
elif import_name and import_name == name:
return True
return False
def _import_name_is_global(
stmt: nodes.Global | _base_nodes.ImportNode, global_names: set[str]
) -> bool:
for import_name, import_alias in stmt.names:
# If the import uses an alias, check only that.
# Otherwise, check only the import name.
if import_alias:
if import_alias in global_names:
return True
elif import_name in global_names:
return True
return False
def _flattened_scope_names(
iterator: Iterator[nodes.Global | nodes.Nonlocal],
) -> set[str]:
values = (set(stmt.names) for stmt in iterator)
return set(itertools.chain.from_iterable(values))
def _assigned_locally(name_node: nodes.Name) -> bool:
"""Checks if name_node has corresponding assign statement in same scope."""
name_node_scope = name_node.scope()
assign_stmts = name_node_scope.nodes_of_class(nodes.AssignName)
return any(a.name == name_node.name for a in assign_stmts) or _find_frame_imports(
name_node.name, name_node_scope
)
def _has_locals_call_after_node(stmt: nodes.NodeNG, scope: nodes.FunctionDef) -> bool:
skip_nodes = (
nodes.FunctionDef,
nodes.ClassDef,
nodes.Import,
nodes.ImportFrom,
)
for call in scope.nodes_of_class(nodes.Call, skip_klass=skip_nodes):
inferred = utils.safe_infer(call.func)
if (
utils.is_builtin_object(inferred)
and getattr(inferred, "name", None) == "locals"
):
if stmt.lineno < call.lineno:
return True
return False
MSGS: dict[str, MessageDefinitionTuple] = {
"E0601": (
"Using variable %r before assignment",
"used-before-assignment",
"Emitted when a local variable is accessed before its assignment took place. "
"Assignments in try blocks are assumed not to have occurred when evaluating "
"associated except/finally blocks. Assignments in except blocks are assumed "
"not to have occurred when evaluating statements outside the block, except "
"when the associated try block contains a return statement.",
),
"E0602": (
"Undefined variable %r",
"undefined-variable",
"Used when an undefined variable is accessed.",
),
"E0603": (
"Undefined variable name %r in __all__",
"undefined-all-variable",
"Used when an undefined variable name is referenced in __all__.",
),
"E0604": (
"Invalid object %r in __all__, must contain only strings",
"invalid-all-object",
"Used when an invalid (non-string) object occurs in __all__.",
),
"E0605": (
"Invalid format for __all__, must be tuple or list",
"invalid-all-format",
"Used when __all__ has an invalid format.",
),
"E0611": (
"No name %r in module %r",
"no-name-in-module",
"Used when a name cannot be found in a module.",
),
"W0601": (
"Global variable %r undefined at the module level",
"global-variable-undefined",
'Used when a variable is defined through the "global" statement '
"but the variable is not defined in the module scope.",
),
"W0602": (
"Using global for %r but no assignment is done",
"global-variable-not-assigned",
"When a variable defined in the global scope is modified in an inner scope, "
"the 'global' keyword is required in the inner scope only if there is an "
"assignment operation done in the inner scope.",
),
"W0603": (
"Using the global statement", # W0121
"global-statement",
'Used when you use the "global" statement to update a global '
"variable. Pylint discourages its usage. That doesn't mean you cannot "
"use it!",
),
"W0604": (
"Using the global statement at the module level", # W0103
"global-at-module-level",
'Used when you use the "global" statement at the module level '
"since it has no effect.",
),
"W0611": (
"Unused %s",
"unused-import",
"Used when an imported module or variable is not used.",
),
"W0612": (
"Unused variable %r",
"unused-variable",
"Used when a variable is defined but not used.",
),
"W0613": (
"Unused argument %r",
"unused-argument",
"Used when a function or method argument is not used.",
),
"W0614": (
"Unused import(s) %s from wildcard import of %s",
"unused-wildcard-import",
"Used when an imported module or variable is not used from a "
"`'from X import *'` style import.",
),
"W0621": (
"Redefining name %r from outer scope (line %s)",
"redefined-outer-name",
"Used when a variable's name hides a name defined in an outer scope or except handler.",
),
"W0622": (
"Redefining built-in %r",
"redefined-builtin",
"Used when a variable or function override a built-in.",
),
"W0631": (
"Using possibly undefined loop variable %r",
"undefined-loop-variable",
"Used when a loop variable (i.e. defined by a for loop or "
"a list comprehension or a generator expression) is used outside "
"the loop.",
),
"W0632": (
"Possible unbalanced tuple unpacking with sequence %s: left side has %d "
"label%s, right side has %d value%s",
"unbalanced-tuple-unpacking",
"Used when there is an unbalanced tuple unpacking in assignment",
{"old_names": [("E0632", "old-unbalanced-tuple-unpacking")]},
),
"E0633": (
"Attempting to unpack a non-sequence%s",
"unpacking-non-sequence",
"Used when something which is not a sequence is used in an unpack assignment",
{"old_names": [("W0633", "old-unpacking-non-sequence")]},
),
"W0640": (
"Cell variable %s defined in loop",
"cell-var-from-loop",
"A variable used in a closure is defined in a loop. "
"This will result in all closures using the same value for "
"the closed-over variable.",
),
"W0641": (
"Possibly unused variable %r",
"possibly-unused-variable",
"Used when a variable is defined but might not be used. "
"The possibility comes from the fact that locals() might be used, "
"which could consume or not the said variable",
),
"W0642": (
"Invalid assignment to %s in method",
"self-cls-assignment",
"Invalid assignment to self or cls in instance or class method "
"respectively.",
),
"E0643": (
"Invalid index for iterable length",
"potential-index-error",
"Emitted when an index used on an iterable goes beyond the length of that "
"iterable.",
),
"W0644": (
"Possible unbalanced dict unpacking with %s: "
"left side has %d label%s, right side has %d value%s",
"unbalanced-dict-unpacking",
"Used when there is an unbalanced dict unpacking in assignment or for loop",
),
}
class ScopeConsumer(NamedTuple):
"""Store nodes and their consumption states."""
to_consume: dict[str, list[nodes.NodeNG]]
consumed: dict[str, list[nodes.NodeNG]]
consumed_uncertain: defaultdict[str, list[nodes.NodeNG]]
scope_type: str
class NamesConsumer:
"""A simple class to handle consumed, to consume and scope type info of node locals."""
def __init__(self, node: nodes.NodeNG, scope_type: str) -> None:
self._atomic = ScopeConsumer(
copy.copy(node.locals), {}, collections.defaultdict(list), scope_type
)
self.node = node
self._if_nodes_deemed_uncertain: set[nodes.If] = set()
def __repr__(self) -> str:
_to_consumes = [f"{k}->{v}" for k, v in self._atomic.to_consume.items()]
_consumed = [f"{k}->{v}" for k, v in self._atomic.consumed.items()]
_consumed_uncertain = [
f"{k}->{v}" for k, v in self._atomic.consumed_uncertain.items()
]
to_consumes = ", ".join(_to_consumes)
consumed = ", ".join(_consumed)
consumed_uncertain = ", ".join(_consumed_uncertain)
return f"""
to_consume : {to_consumes}
consumed : {consumed}
consumed_uncertain: {consumed_uncertain}
scope_type : {self._atomic.scope_type}
"""
def __iter__(self) -> Iterator[Any]:
return iter(self._atomic)
@property
def to_consume(self) -> dict[str, list[nodes.NodeNG]]:
return self._atomic.to_consume
@property
def consumed(self) -> dict[str, list[nodes.NodeNG]]:
return self._atomic.consumed
@property
def consumed_uncertain(self) -> defaultdict[str, list[nodes.NodeNG]]:
"""Retrieves nodes filtered out by get_next_to_consume() that may not
have executed.
These include nodes such as statements in except blocks, or statements
in try blocks (when evaluating their corresponding except and finally
blocks). Checkers that want to treat the statements as executed
(e.g. for unused-variable) may need to add them back.
"""
return self._atomic.consumed_uncertain
@property
def scope_type(self) -> str:
return self._atomic.scope_type
def mark_as_consumed(self, name: str, consumed_nodes: list[nodes.NodeNG]) -> None:
"""Mark the given nodes as consumed for the name.
If all of the nodes for the name were consumed, delete the name from
the to_consume dictionary
"""
unconsumed = [n for n in self.to_consume[name] if n not in set(consumed_nodes)]
self.consumed[name] = consumed_nodes
if unconsumed:
self.to_consume[name] = unconsumed
else:
del self.to_consume[name]
def get_next_to_consume(self, node: nodes.Name) -> list[nodes.NodeNG] | None:
"""Return a list of the nodes that define `node` from this scope.
If it is uncertain whether a node will be consumed, such as for statements in
except blocks, add it to self.consumed_uncertain instead of returning it.
Return None to indicate a special case that needs to be handled by the caller.
"""
name = node.name
parent_node = node.parent
found_nodes = self.to_consume.get(name)
node_statement = node.statement(future=True)
if (
found_nodes
and isinstance(parent_node, nodes.Assign)
and parent_node == found_nodes[0].parent
):
lhs = found_nodes[0].parent.targets[0]
if lhs.name == name: # this name is defined in this very statement
found_nodes = None
if (
found_nodes
and isinstance(parent_node, nodes.For)
and parent_node.iter == node
and parent_node.target in found_nodes
):
found_nodes = None
# Before filtering, check that this node's name is not a nonlocal
if any(
isinstance(child, nodes.Nonlocal) and node.name in child.names
for child in node.frame(future=True).get_children()
):
return found_nodes
# And no comprehension is under the node's frame
if VariablesChecker._comprehension_between_frame_and_node(node):
return found_nodes
# Filter out assignments guarded by always false conditions
if found_nodes:
uncertain_nodes = self._uncertain_nodes_in_false_tests(found_nodes, node)
self.consumed_uncertain[node.name] += uncertain_nodes
uncertain_nodes_set = set(uncertain_nodes)
found_nodes = [n for n in found_nodes if n not in uncertain_nodes_set]
# Filter out assignments in ExceptHandlers that node is not contained in
if found_nodes:
found_nodes = [
n
for n in found_nodes
if not isinstance(n.statement(future=True), nodes.ExceptHandler)
or n.statement(future=True).parent_of(node)
]
# Filter out assignments in an Except clause that the node is not
# contained in, assuming they may fail
if found_nodes:
uncertain_nodes = self._uncertain_nodes_in_except_blocks(
found_nodes, node, node_statement
)
self.consumed_uncertain[node.name] += uncertain_nodes
uncertain_nodes_set = set(uncertain_nodes)
found_nodes = [n for n in found_nodes if n not in uncertain_nodes_set]
# If this node is in a Finally block of a Try/Finally,
# filter out assignments in the try portion, assuming they may fail
if found_nodes:
uncertain_nodes = (
self._uncertain_nodes_in_try_blocks_when_evaluating_finally_blocks(
found_nodes, node_statement
)
)
self.consumed_uncertain[node.name] += uncertain_nodes
uncertain_nodes_set = set(uncertain_nodes)
found_nodes = [n for n in found_nodes if n not in uncertain_nodes_set]
# If this node is in an ExceptHandler,
# filter out assignments in the try portion, assuming they may fail
if found_nodes:
uncertain_nodes = (
self._uncertain_nodes_in_try_blocks_when_evaluating_except_blocks(
found_nodes, node_statement
)
)
self.consumed_uncertain[node.name] += uncertain_nodes
uncertain_nodes_set = set(uncertain_nodes)
found_nodes = [n for n in found_nodes if n not in uncertain_nodes_set]
return found_nodes
@staticmethod
def _exhaustively_define_name_raise_or_return(
name: str, node: nodes.NodeNG
) -> bool:
"""Return True if there is a collectively exhaustive set of paths under
this `if_node` that define `name`, raise, or return.
"""
# Handle try and with
if isinstance(node, (nodes.TryExcept, nodes.TryFinally)):
# Allow either a path through try/else/finally OR a path through ALL except handlers
return (
NamesConsumer._defines_name_raises_or_returns_recursive(name, node)
or isinstance(node, nodes.TryExcept)
and all(
NamesConsumer._defines_name_raises_or_returns_recursive(
name, handler
)
for handler in node.handlers
)
)
if isinstance(node, nodes.With):
return NamesConsumer._defines_name_raises_or_returns_recursive(name, node)
if not isinstance(node, nodes.If):
return False
# Be permissive if there is a break
if any(node.nodes_of_class(nodes.Break)):
return True
# Is there an assignment in this node itself, e.g. in named expression?
if NamesConsumer._defines_name_raises_or_returns(name, node):
return True
# If there is no else, then there is no collectively exhaustive set of paths
if not node.orelse:
return False
return NamesConsumer._branch_handles_name(
name, node.body
) and NamesConsumer._branch_handles_name(name, node.orelse)
@staticmethod
def _branch_handles_name(name: str, body: Iterable[nodes.NodeNG]) -> bool:
return any(
NamesConsumer._defines_name_raises_or_returns(name, if_body_stmt)
or isinstance(
if_body_stmt,
(nodes.If, nodes.TryExcept, nodes.TryFinally, nodes.With),
)
and NamesConsumer._exhaustively_define_name_raise_or_return(
name, if_body_stmt
)
for if_body_stmt in body
)
def _uncertain_nodes_in_false_tests(
self, found_nodes: list[nodes.NodeNG], node: nodes.NodeNG
) -> list[nodes.NodeNG]:
"""Identify nodes of uncertain execution because they are defined under
tests that evaluate false.
Don't identify a node if there is a collectively exhaustive set of paths
that define the name, raise, or return (e.g. every if/else branch).
"""
uncertain_nodes = []
for other_node in found_nodes:
if in_type_checking_block(other_node):
continue
if not isinstance(other_node, nodes.AssignName):
continue
closest_if = utils.get_node_first_ancestor_of_type(other_node, nodes.If)
if closest_if is None:
continue
if node.frame() is not closest_if.frame():
continue
if closest_if is not None and closest_if.parent_of(node):
continue
# Name defined in every if/else branch
if NamesConsumer._exhaustively_define_name_raise_or_return(
other_node.name, closest_if
):
continue
# Higher-level if already determined to be always false
if any(
if_node.parent_of(closest_if)
for if_node in self._if_nodes_deemed_uncertain
):
uncertain_nodes.append(other_node)
continue
# All inferred values must test false
if isinstance(closest_if.test, nodes.NamedExpr):
test = closest_if.test.value
else:
test = closest_if.test
all_inferred = utils.infer_all(test)
if not all_inferred or not all(
isinstance(inferred, nodes.Const) and not inferred.value
for inferred in all_inferred
):
continue
uncertain_nodes.append(other_node)
self._if_nodes_deemed_uncertain.add(closest_if)
return uncertain_nodes
@staticmethod
def _uncertain_nodes_in_except_blocks(
found_nodes: list[nodes.NodeNG],
node: nodes.NodeNG,
node_statement: nodes.Statement,
) -> list[nodes.NodeNG]:
"""Return any nodes in ``found_nodes`` that should be treated as uncertain
because they are in an except block.
"""
uncertain_nodes = []
for other_node in found_nodes:
other_node_statement = other_node.statement(future=True)
# Only testing for statements in the except block of TryExcept
closest_except_handler = utils.get_node_first_ancestor_of_type(
other_node_statement, nodes.ExceptHandler
)
if not closest_except_handler:
continue
# If the other node is in the same scope as this node, assume it executes
if closest_except_handler.parent_of(node):
continue
closest_try_except: nodes.TryExcept = closest_except_handler.parent
# If the try or else blocks return, assume the except blocks execute.
try_block_returns = any(
isinstance(try_statement, nodes.Return)
for try_statement in closest_try_except.body
)
else_block_returns = any(
isinstance(else_statement, nodes.Return)
for else_statement in closest_try_except.orelse
)
else_block_exits = any(
isinstance(else_statement, nodes.Expr)
and isinstance(else_statement.value, nodes.Call)
and utils.is_terminating_func(else_statement.value)
for else_statement in closest_try_except.orelse
)
if try_block_returns or else_block_returns or else_block_exits:
# Exception: if this node is in the final block of the other_node_statement,
# it will execute before returning. Assume the except statements are uncertain.
if (
isinstance(node_statement.parent, nodes.TryFinally)
and node_statement in node_statement.parent.finalbody
and closest_try_except.parent.parent_of(node_statement)
):
uncertain_nodes.append(other_node)
# Or the node_statement is in the else block of the relevant TryExcept
elif (
isinstance(node_statement.parent, nodes.TryExcept)
and node_statement in node_statement.parent.orelse
and closest_try_except.parent.parent_of(node_statement)
):
uncertain_nodes.append(other_node)
# Assume the except blocks execute, so long as each handler
# defines the name, raises, or returns.
elif all(
NamesConsumer._defines_name_raises_or_returns_recursive(
node.name, handler
)
for handler in closest_try_except.handlers
):
continue
if NamesConsumer._check_loop_finishes_via_except(node, closest_try_except):
continue
# Passed all tests for uncertain execution
uncertain_nodes.append(other_node)
return uncertain_nodes
@staticmethod
def _defines_name_raises_or_returns(name: str, node: nodes.NodeNG) -> bool:
if isinstance(node, (nodes.Raise, nodes.Assert, nodes.Return)):
return True
if (
isinstance(node, nodes.AnnAssign)
and node.value
and isinstance(node.target, nodes.AssignName)
and node.target.name == name
):
return True
if isinstance(node, nodes.Assign):
for target in node.targets:
for elt in utils.get_all_elements(target):
if isinstance(elt, nodes.Starred):
elt = elt.value
if isinstance(elt, nodes.AssignName) and elt.name == name:
return True
if isinstance(node, nodes.If):
if any(
child_named_expr.target.name == name
for child_named_expr in node.nodes_of_class(nodes.NamedExpr)
):
return True
return False
@staticmethod
def _defines_name_raises_or_returns_recursive(
name: str, node: nodes.NodeNG
) -> bool:
"""Return True if some child of `node` defines the name `name`,
raises, or returns.
"""
for stmt in node.get_children():
if NamesConsumer._defines_name_raises_or_returns(name, stmt):
return True
if isinstance(stmt, (nodes.If, nodes.With)):
if any(
NamesConsumer._defines_name_raises_or_returns(name, nested_stmt)
for nested_stmt in stmt.get_children()
):
return True
return False
@staticmethod
def _check_loop_finishes_via_except(
node: nodes.NodeNG, other_node_try_except: nodes.TryExcept
) -> bool:
"""Check for a case described in https://github.com/PyCQA/pylint/issues/5683.
It consists of a specific control flow scenario where the only
non-break exit from a loop consists of the very except handler we are
examining, such that code in the `else` branch of the loop can depend on it
being assigned.
Example:
for _ in range(3):
try:
do_something()
except:
name = 1 <-- only non-break exit from loop
else:
break
else:
print(name)
"""
if not other_node_try_except.orelse:
return False
closest_loop: None | (
nodes.For | nodes.While
) = utils.get_node_first_ancestor_of_type(node, (nodes.For, nodes.While))
if closest_loop is None:
return False
if not any(
else_statement is node or else_statement.parent_of(node)
for else_statement in closest_loop.orelse
):
# `node` not guarded by `else`
return False
for inner_else_statement in other_node_try_except.orelse:
if isinstance(inner_else_statement, nodes.Break):
break_stmt = inner_else_statement
break
else:
# No break statement
return False
def _try_in_loop_body(
other_node_try_except: nodes.TryExcept, loop: nodes.For | nodes.While
) -> bool:
"""Return True if `other_node_try_except` is a descendant of `loop`."""
return any(
loop_body_statement is other_node_try_except
or loop_body_statement.parent_of(other_node_try_except)
for loop_body_statement in loop.body
)
if not _try_in_loop_body(other_node_try_except, closest_loop):
for ancestor in closest_loop.node_ancestors():
if isinstance(ancestor, (nodes.For, nodes.While)):
if _try_in_loop_body(other_node_try_except, ancestor):
break
else:
# `other_node_try_except` didn't have a shared ancestor loop
return False
for loop_stmt in closest_loop.body:
if NamesConsumer._recursive_search_for_continue_before_break(
loop_stmt, break_stmt
):
break
else:
# No continue found, so we arrived at our special case!
return True
return False
@staticmethod
def _recursive_search_for_continue_before_break(
stmt: nodes.Statement, break_stmt: nodes.Break
) -> bool:
"""Return True if any Continue node can be found in descendants of `stmt`
before encountering `break_stmt`, ignoring any nested loops.
"""
if stmt is break_stmt:
return False
if isinstance(stmt, nodes.Continue):
return True
for child in stmt.get_children():
if isinstance(stmt, (nodes.For, nodes.While)):
continue
if NamesConsumer._recursive_search_for_continue_before_break(
child, break_stmt
):
return True
return False
@staticmethod
def _uncertain_nodes_in_try_blocks_when_evaluating_except_blocks(
found_nodes: list[nodes.NodeNG], node_statement: nodes.Statement
) -> list[nodes.NodeNG]:
"""Return any nodes in ``found_nodes`` that should be treated as uncertain.
Nodes are uncertain when they are in a try block and the ``node_statement``
being evaluated is in one of its except handlers.
"""
uncertain_nodes: list[nodes.NodeNG] = []
closest_except_handler = utils.get_node_first_ancestor_of_type(
node_statement, nodes.ExceptHandler
)
if closest_except_handler is None:
return uncertain_nodes
for other_node in found_nodes:
other_node_statement = other_node.statement(future=True)
# If the other statement is the except handler guarding `node`, it executes
if other_node_statement is closest_except_handler:
continue
# Ensure other_node is in a try block
(
other_node_try_ancestor,
other_node_try_ancestor_visited_child,
) = utils.get_node_first_ancestor_of_type_and_its_child(
other_node_statement, nodes.TryExcept
)
if other_node_try_ancestor is None:
continue
if (
other_node_try_ancestor_visited_child
not in other_node_try_ancestor.body
):
continue
# Make sure nesting is correct -- there should be at least one
# except handler that is a sibling attached to the try ancestor,
# or is an ancestor of the try ancestor.
if not any(
closest_except_handler in other_node_try_ancestor.handlers
or other_node_try_ancestor_except_handler
in closest_except_handler.node_ancestors()
for other_node_try_ancestor_except_handler in other_node_try_ancestor.handlers
):
continue
# Passed all tests for uncertain execution
uncertain_nodes.append(other_node)
return uncertain_nodes
@staticmethod
def _uncertain_nodes_in_try_blocks_when_evaluating_finally_blocks(
found_nodes: list[nodes.NodeNG], node_statement: nodes.Statement
) -> list[nodes.NodeNG]:
uncertain_nodes: list[nodes.NodeNG] = []
(
closest_try_finally_ancestor,
child_of_closest_try_finally_ancestor,
) = utils.get_node_first_ancestor_of_type_and_its_child(
node_statement, nodes.TryFinally
)
if closest_try_finally_ancestor is None:
return uncertain_nodes
if (
child_of_closest_try_finally_ancestor
not in closest_try_finally_ancestor.finalbody
):
return uncertain_nodes
for other_node in found_nodes:
other_node_statement = other_node.statement(future=True)
(
other_node_try_finally_ancestor,
child_of_other_node_try_finally_ancestor,
) = utils.get_node_first_ancestor_of_type_and_its_child(
other_node_statement, nodes.TryFinally
)
if other_node_try_finally_ancestor is None:
continue
# other_node needs to descend from the try of a try/finally.
if (
child_of_other_node_try_finally_ancestor
not in other_node_try_finally_ancestor.body
):
continue
# If the two try/finally ancestors are not the same, then
# node_statement's closest try/finally ancestor needs to be in
# the final body of other_node's try/finally ancestor, or
# descend from one of the statements in that final body.
if (
other_node_try_finally_ancestor is not closest_try_finally_ancestor
and not any(
other_node_final_statement is closest_try_finally_ancestor
or other_node_final_statement.parent_of(
closest_try_finally_ancestor
)
for other_node_final_statement in other_node_try_finally_ancestor.finalbody
)
):
continue
# Passed all tests for uncertain execution
uncertain_nodes.append(other_node)
return uncertain_nodes
# pylint: disable=too-many-public-methods
class VariablesChecker(BaseChecker):
"""BaseChecker for variables.
Checks for
* unused variables / imports
* undefined variables
* redefinition of variable from builtins or from an outer scope or except handler
* use of variable before assignment
* __all__ consistency
* self/cls assignment
"""
name = "variables"
msgs = MSGS
options = (
(
"init-import",
{
"default": False,
"type": "yn",
"metavar": "<y or n>",
"help": "Tells whether we should check for unused import in "
"__init__ files.",
},
),
(
"dummy-variables-rgx",
{
"default": "_+$|(_[a-zA-Z0-9_]*[a-zA-Z0-9]+?$)|dummy|^ignored_|^unused_",
"type": "regexp",
"metavar": "<regexp>",
"help": "A regular expression matching the name of dummy "
"variables (i.e. expected to not be used).",
},
),
(
"additional-builtins",
{
"default": (),
"type": "csv",
"metavar": "<comma separated list>",
"help": "List of additional names supposed to be defined in "
"builtins. Remember that you should avoid defining new builtins "
"when possible.",
},
),
(
"callbacks",
{
"default": ("cb_", "_cb"),
"type": "csv",
"metavar": "<callbacks>",
"help": "List of strings which can identify a callback "
"function by name. A callback name must start or "
"end with one of those strings.",
},
),
(
"redefining-builtins-modules",
{
"default": (
"six.moves",
"past.builtins",
"future.builtins",
"builtins",
"io",
),
"type": "csv",
"metavar": "<comma separated list>",
"help": "List of qualified module names which can have objects "
"that can redefine builtins.",
},
),
(
"ignored-argument-names",
{
"default": IGNORED_ARGUMENT_NAMES,
"type": "regexp",
"metavar": "<regexp>",
"help": "Argument names that match this expression will be ignored.",
},
),
(
"allow-global-unused-variables",
{
"default": True,
"type": "yn",
"metavar": "<y or n>",
"help": "Tells whether unused global variables should be treated as a violation.",
},
),
(
"allowed-redefined-builtins",
{
"default": (),
"type": "csv",
"metavar": "<comma separated list>",
"help": "List of names allowed to shadow builtins",
},
),
)
def __init__(self, linter: PyLinter) -> None:
super().__init__(linter)
self._to_consume: list[NamesConsumer] = []
self._type_annotation_names: list[str] = []
self._except_handler_names_queue: list[
tuple[nodes.ExceptHandler, nodes.AssignName]
] = []
"""This is a queue, last in first out."""
self._postponed_evaluation_enabled = False
@utils.only_required_for_messages(
"unbalanced-dict-unpacking",
)
def visit_for(self, node: nodes.For) -> None:
if not isinstance(node.target, nodes.Tuple):
return
targets = node.target.elts
inferred = utils.safe_infer(node.iter)
if not isinstance(inferred, DICT_TYPES):
return
values = self._nodes_to_unpack(inferred)
if not values:
# no dict items returned
return
if isinstance(inferred, astroid.objects.DictItems):
# dict.items() is a bit special because values will be a tuple
# So as long as there are always 2 targets and values each are
# a tuple with two items, this will unpack correctly.
# Example: `for key, val in {1: 2, 3: 4}.items()`
if len(targets) == 2 and all(len(x.elts) == 2 for x in values):
return
# Starred nodes indicate ambiguous unpacking
# if `dict.items()` is used so we won't flag them.
if any(isinstance(target, nodes.Starred) for target in targets):
return
if len(targets) != len(values):
details = _get_unpacking_extra_info(node, inferred)
self._report_unbalanced_unpacking(node, inferred, targets, values, details)
def leave_for(self, node: nodes.For) -> None:
self._store_type_annotation_names(node)
def visit_module(self, node: nodes.Module) -> None:
"""Visit module : update consumption analysis variable
checks globals doesn't overrides builtins.
"""
self._to_consume = [NamesConsumer(node, "module")]
self._postponed_evaluation_enabled = is_postponed_evaluation_enabled(node)
for name, stmts in node.locals.items():
if utils.is_builtin(name):
if self._should_ignore_redefined_builtin(stmts[0]) or name == "__doc__":
continue
self.add_message("redefined-builtin", args=name, node=stmts[0])
@utils.only_required_for_messages(
"unused-import",
"unused-wildcard-import",
"redefined-builtin",
"undefined-all-variable",
"invalid-all-object",
"invalid-all-format",
"unused-variable",
"undefined-variable",
)
def leave_module(self, node: nodes.Module) -> None:
"""Leave module: check globals."""
assert len(self._to_consume) == 1
self._check_metaclasses(node)
not_consumed = self._to_consume.pop().to_consume
# attempt to check for __all__ if defined
if "__all__" in node.locals:
self._check_all(node, not_consumed)
# check for unused globals
self._check_globals(not_consumed)
# don't check unused imports in __init__ files
if not self.linter.config.init_import and node.package:
return
self._check_imports(not_consumed)
self._type_annotation_names = []
def visit_classdef(self, node: nodes.ClassDef) -> None:
"""Visit class: update consumption analysis variable."""
self._to_consume.append(NamesConsumer(node, "class"))
def leave_classdef(self, node: nodes.ClassDef) -> None:
"""Leave class: update consumption analysis variable."""
# Check for hidden ancestor names
# e.g. "six" in: Class X(six.with_metaclass(ABCMeta, object)):
for name_node in node.nodes_of_class(nodes.Name):
if (
isinstance(name_node.parent, nodes.Call)
and isinstance(name_node.parent.func, nodes.Attribute)
and isinstance(name_node.parent.func.expr, nodes.Name)
):
hidden_name_node = name_node.parent.func.expr
for consumer in self._to_consume:
if hidden_name_node.name in consumer.to_consume:
consumer.mark_as_consumed(
hidden_name_node.name,
consumer.to_consume[hidden_name_node.name],
)
break
self._to_consume.pop()
def visit_lambda(self, node: nodes.Lambda) -> None:
"""Visit lambda: update consumption analysis variable."""
self._to_consume.append(NamesConsumer(node, "lambda"))
def leave_lambda(self, _: nodes.Lambda) -> None:
"""Leave lambda: update consumption analysis variable."""
# do not check for not used locals here
self._to_consume.pop()
def visit_generatorexp(self, node: nodes.GeneratorExp) -> None:
"""Visit genexpr: update consumption analysis variable."""
self._to_consume.append(NamesConsumer(node, "comprehension"))
def leave_generatorexp(self, _: nodes.GeneratorExp) -> None:
"""Leave genexpr: update consumption analysis variable."""
# do not check for not used locals here
self._to_consume.pop()
def visit_dictcomp(self, node: nodes.DictComp) -> None:
"""Visit dictcomp: update consumption analysis variable."""
self._to_consume.append(NamesConsumer(node, "comprehension"))
def leave_dictcomp(self, _: nodes.DictComp) -> None:
"""Leave dictcomp: update consumption analysis variable."""
# do not check for not used locals here
self._to_consume.pop()
def visit_setcomp(self, node: nodes.SetComp) -> None:
"""Visit setcomp: update consumption analysis variable."""
self._to_consume.append(NamesConsumer(node, "comprehension"))
def leave_setcomp(self, _: nodes.SetComp) -> None:
"""Leave setcomp: update consumption analysis variable."""
# do not check for not used locals here
self._to_consume.pop()
def visit_functiondef(self, node: nodes.FunctionDef) -> None:
"""Visit function: update consumption analysis variable and check locals."""
self._to_consume.append(NamesConsumer(node, "function"))
if not (
self.linter.is_message_enabled("redefined-outer-name")
or self.linter.is_message_enabled("redefined-builtin")
):
return
globs = node.root().globals
for name, stmt in node.items():
if name in globs and not isinstance(stmt, nodes.Global):
definition = globs[name][0]
if (
isinstance(definition, nodes.ImportFrom)
and definition.modname == FUTURE
):
# It is a __future__ directive, not a symbol.
continue
# Do not take in account redefined names for the purpose
# of type checking.:
if any(
in_type_checking_block(definition) for definition in globs[name]
):
continue
line = definition.fromlineno
if not self._is_name_ignored(stmt, name):
self.add_message(
"redefined-outer-name", args=(name, line), node=stmt
)
elif (
utils.is_builtin(name)
and not self._allowed_redefined_builtin(name)
and not self._should_ignore_redefined_builtin(stmt)
):
# do not print Redefining builtin for additional builtins
self.add_message("redefined-builtin", args=name, node=stmt)
def leave_functiondef(self, node: nodes.FunctionDef) -> None:
"""Leave function: check function's locals are consumed."""
self._check_metaclasses(node)
if node.type_comment_returns:
self._store_type_annotation_node(node.type_comment_returns)
if node.type_comment_args:
for argument_annotation in node.type_comment_args:
self._store_type_annotation_node(argument_annotation)
not_consumed = self._to_consume.pop().to_consume
if not (
self.linter.is_message_enabled("unused-variable")
or self.linter.is_message_enabled("possibly-unused-variable")
or self.linter.is_message_enabled("unused-argument")
):
return
# Don't check arguments of function which are only raising an exception.
if utils.is_error(node):
return
# Don't check arguments of abstract methods or within an interface.
is_method = node.is_method()
if is_method and node.is_abstract():
return
global_names = _flattened_scope_names(node.nodes_of_class(nodes.Global))
nonlocal_names = _flattened_scope_names(node.nodes_of_class(nodes.Nonlocal))
comprehension_target_names: set[str] = set()
for comprehension_scope in node.nodes_of_class(nodes.ComprehensionScope):
for generator in comprehension_scope.generators:
for name in utils.find_assigned_names_recursive(generator.target):
comprehension_target_names.add(name)
for name, stmts in not_consumed.items():
self._check_is_unused(
name,
node,
stmts[0],
global_names,
nonlocal_names,
comprehension_target_names,
)
visit_asyncfunctiondef = visit_functiondef
leave_asyncfunctiondef = leave_functiondef
@utils.only_required_for_messages(
"global-variable-undefined",
"global-variable-not-assigned",
"global-statement",
"global-at-module-level",
"redefined-builtin",
)
def visit_global(self, node: nodes.Global) -> None:
"""Check names imported exists in the global scope."""
frame = node.frame(future=True)
if isinstance(frame, nodes.Module):
self.add_message("global-at-module-level", node=node, confidence=HIGH)
return
module = frame.root()
default_message = True
locals_ = node.scope().locals
for name in node.names:
try:
assign_nodes = module.getattr(name)
except astroid.NotFoundError:
# unassigned global, skip
assign_nodes = []
not_defined_locally_by_import = not any(
isinstance(local, (nodes.Import, nodes.ImportFrom))
for local in locals_.get(name, ())
)
if (
not utils.is_reassigned_after_current(node, name)
and not utils.is_deleted_after_current(node, name)
and not_defined_locally_by_import
):
self.add_message(
"global-variable-not-assigned",
args=name,
node=node,
confidence=HIGH,
)
default_message = False
continue
for anode in assign_nodes:
if (
isinstance(anode, nodes.AssignName)
and anode.name in module.special_attributes
):
self.add_message("redefined-builtin", args=name, node=node)
break
if anode.frame(future=True) is module:
# module level assignment
break
if (
isinstance(anode, (nodes.ClassDef, nodes.FunctionDef))
and anode.parent is module
):
# module level function assignment
break
else:
if not_defined_locally_by_import:
# global undefined at the module scope
self.add_message(
"global-variable-undefined",
args=name,
node=node,
confidence=HIGH,
)
default_message = False
if default_message:
self.add_message("global-statement", node=node, confidence=HIGH)
def visit_assignname(self, node: nodes.AssignName) -> None:
if isinstance(node.assign_type(), nodes.AugAssign):
self.visit_name(node)
def visit_delname(self, node: nodes.DelName) -> None:
self.visit_name(node)
def visit_name(self, node: nodes.Name | nodes.AssignName | nodes.DelName) -> None:
"""Don't add the 'utils.only_required_for_messages' decorator here!
It's important that all 'Name' nodes are visited, otherwise the
'NamesConsumers' won't be correct.
"""
stmt = node.statement(future=True)
if stmt.fromlineno is None:
# name node from an astroid built from live code, skip
assert not stmt.root().file.endswith(".py")
return
self._undefined_and_used_before_checker(node, stmt)
self._loopvar_name(node)
@utils.only_required_for_messages("redefined-outer-name")
def visit_excepthandler(self, node: nodes.ExceptHandler) -> None:
if not node.name or not isinstance(node.name, nodes.AssignName):
return
for outer_except, outer_except_assign_name in self._except_handler_names_queue:
if node.name.name == outer_except_assign_name.name:
self.add_message(
"redefined-outer-name",
args=(outer_except_assign_name.name, outer_except.fromlineno),
node=node,
)
break
self._except_handler_names_queue.append((node, node.name))
@utils.only_required_for_messages("redefined-outer-name")
def leave_excepthandler(self, node: nodes.ExceptHandler) -> None:
if not node.name or not isinstance(node.name, nodes.AssignName):
return
self._except_handler_names_queue.pop()
def _undefined_and_used_before_checker(
self, node: nodes.Name, stmt: nodes.NodeNG
) -> None:
frame = stmt.scope()
start_index = len(self._to_consume) - 1
# iterates through parent scopes, from the inner to the outer
base_scope_type = self._to_consume[start_index].scope_type
for i in range(start_index, -1, -1):
current_consumer = self._to_consume[i]
# Certain nodes shouldn't be checked as they get checked another time
if self._should_node_be_skipped(node, current_consumer, i == start_index):
continue
action, nodes_to_consume = self._check_consumer(
node, stmt, frame, current_consumer, base_scope_type
)
if nodes_to_consume:
# Any nodes added to consumed_uncertain by get_next_to_consume()
# should be added back so that they are marked as used.
# They will have already had a chance to emit used-before-assignment.
# We check here instead of before every single return in _check_consumer()
nodes_to_consume += current_consumer.consumed_uncertain[node.name]
current_consumer.mark_as_consumed(node.name, nodes_to_consume)
if action is VariableVisitConsumerAction.CONTINUE:
continue
if action is VariableVisitConsumerAction.RETURN:
return
# we have not found the name, if it isn't a builtin, that's an
# undefined name !
if not (
node.name in nodes.Module.scope_attrs
or utils.is_builtin(node.name)
or node.name in self.linter.config.additional_builtins
or (
node.name == "__class__"
and any(
i.is_method()
for i in node.node_ancestors()
if isinstance(i, nodes.FunctionDef)
)
)
) and not utils.node_ignores_exception(node, NameError):
self.add_message("undefined-variable", args=node.name, node=node)
def _should_node_be_skipped(
self, node: nodes.Name, consumer: NamesConsumer, is_start_index: bool
) -> bool:
"""Tests a consumer and node for various conditions in which the node shouldn't
be checked for the undefined-variable and used-before-assignment checks.
"""
if consumer.scope_type == "class":
# The list of base classes in the class definition is not part
# of the class body.
# If the current scope is a class scope but it's not the inner
# scope, ignore it. This prevents to access this scope instead of
# the globals one in function members when there are some common
# names.
if utils.is_ancestor_name(consumer.node, node) or (
not is_start_index and self._ignore_class_scope(node)
):
return True
# Ignore inner class scope for keywords in class definition
if isinstance(node.parent, nodes.Keyword) and isinstance(
node.parent.parent, nodes.ClassDef
):
return True
elif consumer.scope_type == "function" and self._defined_in_function_definition(
node, consumer.node
):
# If the name node is used as a function default argument's value or as
# a decorator, then start from the parent frame of the function instead
# of the function frame - and thus open an inner class scope
return True
elif consumer.scope_type == "lambda" and utils.is_default_argument(
node, consumer.node
):
return True
return False
# pylint: disable = too-many-return-statements, too-many-branches
def _check_consumer(
self,
node: nodes.Name,
stmt: nodes.NodeNG,
frame: nodes.LocalsDictNodeNG,
current_consumer: NamesConsumer,
base_scope_type: str,
) -> tuple[VariableVisitConsumerAction, list[nodes.NodeNG] | None]:
"""Checks a consumer for conditions that should trigger messages."""
# If the name has already been consumed, only check it's not a loop
# variable used outside the loop.
if node.name in current_consumer.consumed:
# Avoid the case where there are homonyms inside function scope and
# comprehension current scope (avoid bug #1731)
if utils.is_func_decorator(current_consumer.node) or not isinstance(
node, nodes.ComprehensionScope
):
self._check_late_binding_closure(node)
return (VariableVisitConsumerAction.RETURN, None)
found_nodes = current_consumer.get_next_to_consume(node)
if found_nodes is None:
return (VariableVisitConsumerAction.CONTINUE, None)
if not found_nodes:
if node.name in current_consumer.consumed_uncertain:
confidence = CONTROL_FLOW
else:
confidence = HIGH
self.add_message(
"used-before-assignment",
args=node.name,
node=node,
confidence=confidence,
)
# Mark for consumption any nodes added to consumed_uncertain by
# get_next_to_consume() because they might not have executed.
return (
VariableVisitConsumerAction.RETURN,
current_consumer.consumed_uncertain[node.name],
)
self._check_late_binding_closure(node)
defnode = utils.assign_parent(found_nodes[0])
defstmt = defnode.statement(future=True)
defframe = defstmt.frame(future=True)
# The class reuses itself in the class scope.
is_recursive_klass: bool = (
frame is defframe
and defframe.parent_of(node)
and isinstance(defframe, nodes.ClassDef)
and node.name == defframe.name
)
if (
is_recursive_klass
and utils.get_node_first_ancestor_of_type(node, nodes.Lambda)
and (
not utils.is_default_argument(node)
or node.scope().parent.scope() is not defframe
)
):
# Self-referential class references are fine in lambda's --
# As long as they are not part of the default argument directly
# under the scope of the parent self-referring class.
# Example of valid default argument:
# class MyName3:
# myattr = 1
# mylambda3 = lambda: lambda a=MyName3: a
# Example of invalid default argument:
# class MyName4:
# myattr = 1
# mylambda4 = lambda a=MyName4: lambda: a
# If the above conditional is True,
# there is no possibility of undefined-variable
# Also do not consume class name
# (since consuming blocks subsequent checks)
# -- quit
return (VariableVisitConsumerAction.RETURN, None)
(
maybe_before_assign,
annotation_return,
use_outer_definition,
) = self._is_variable_violation(
node,
defnode,
stmt,
defstmt,
frame,
defframe,
base_scope_type,
is_recursive_klass,
)
if use_outer_definition:
return (VariableVisitConsumerAction.CONTINUE, None)
if (
maybe_before_assign
and not utils.is_defined_before(node)
and not astroid.are_exclusive(stmt, defstmt, ("NameError",))
):
# Used and defined in the same place, e.g `x += 1` and `del x`
defined_by_stmt = defstmt is stmt and isinstance(
node, (nodes.DelName, nodes.AssignName)
)
if (
is_recursive_klass
or defined_by_stmt
or annotation_return
or isinstance(defstmt, nodes.Delete)
):
if not utils.node_ignores_exception(node, NameError):
# Handle postponed evaluation of annotations
if not (
self._postponed_evaluation_enabled
and isinstance(
stmt,
(
nodes.AnnAssign,
nodes.FunctionDef,
nodes.Arguments,
),
)
and node.name in node.root().locals
):
if defined_by_stmt:
return (VariableVisitConsumerAction.CONTINUE, [node])
return (VariableVisitConsumerAction.CONTINUE, None)
elif base_scope_type != "lambda":
# E0601 may *not* occurs in lambda scope.
# Skip postponed evaluation of annotations
# and unevaluated annotations inside a function body
if not (
self._postponed_evaluation_enabled
and isinstance(stmt, (nodes.AnnAssign, nodes.FunctionDef))
) and not (
isinstance(stmt, nodes.AnnAssign)
and utils.get_node_first_ancestor_of_type(stmt, nodes.FunctionDef)
):
self.add_message(
"used-before-assignment",
args=node.name,
node=node,
confidence=HIGH,
)
return (VariableVisitConsumerAction.RETURN, found_nodes)
elif base_scope_type == "lambda":
# E0601 can occur in class-level scope in lambdas, as in
# the following example:
# class A:
# x = lambda attr: f + attr
# f = 42
# We check lineno because doing the following is fine:
# class A:
# x = 42
# y = lambda attr: x + attr
if (
isinstance(frame, nodes.ClassDef)
and node.name in frame.locals
and stmt.fromlineno <= defstmt.fromlineno
):
self.add_message(
"used-before-assignment",
args=node.name,
node=node,
confidence=HIGH,
)
elif self._is_only_type_assignment(node, defstmt):
if node.scope().locals.get(node.name):
self.add_message(
"used-before-assignment", args=node.name, node=node, confidence=HIGH
)
else:
self.add_message(
"undefined-variable", args=node.name, node=node, confidence=HIGH
)
return (VariableVisitConsumerAction.RETURN, found_nodes)
elif isinstance(defstmt, nodes.ClassDef):
return self._is_first_level_self_reference(node, defstmt, found_nodes)
elif isinstance(defnode, nodes.NamedExpr):
if isinstance(defnode.parent, nodes.IfExp):
if self._is_never_evaluated(defnode, defnode.parent):
self.add_message(
"undefined-variable",
args=node.name,
node=node,
confidence=INFERENCE,
)
return (VariableVisitConsumerAction.RETURN, found_nodes)
return (VariableVisitConsumerAction.RETURN, found_nodes)
@utils.only_required_for_messages("no-name-in-module")
def visit_import(self, node: nodes.Import) -> None:
"""Check modules attribute accesses."""
if not self._analyse_fallback_blocks and utils.is_from_fallback_block(node):
# No need to verify this, since ImportError is already
# handled by the client code.
return
# Don't verify import if part of guarded import block
if in_type_checking_block(node):
return
if isinstance(node.parent, nodes.If) and is_sys_guard(node.parent):
return
for name, _ in node.names:
parts = name.split(".")
try:
module = next(_infer_name_module(node, parts[0]))
except astroid.ResolveError:
continue
if not isinstance(module, nodes.Module):
continue
self._check_module_attrs(node, module, parts[1:])
@utils.only_required_for_messages("no-name-in-module")
def visit_importfrom(self, node: nodes.ImportFrom) -> None:
"""Check modules attribute accesses."""
if not self._analyse_fallback_blocks and utils.is_from_fallback_block(node):
# No need to verify this, since ImportError is already
# handled by the client code.
return
# Don't verify import if part of guarded import block
# I.e. `sys.version_info` or `typing.TYPE_CHECKING`
if in_type_checking_block(node):
return
if isinstance(node.parent, nodes.If) and is_sys_guard(node.parent):
return
name_parts = node.modname.split(".")
try:
module = node.do_import_module(name_parts[0])
except astroid.AstroidBuildingException:
return
module = self._check_module_attrs(node, module, name_parts[1:])
if not module:
return
for name, _ in node.names:
if name == "*":
continue
self._check_module_attrs(node, module, name.split("."))
@utils.only_required_for_messages(
"unbalanced-tuple-unpacking",
"unpacking-non-sequence",
"self-cls-assignment",
"unbalanced_dict_unpacking",
)
def visit_assign(self, node: nodes.Assign) -> None:
"""Check unbalanced tuple unpacking for assignments and unpacking
non-sequences as well as in case self/cls get assigned.
"""
self._check_self_cls_assign(node)
if not isinstance(node.targets[0], (nodes.Tuple, nodes.List)):
return
targets = node.targets[0].itered()
# Check if we have starred nodes.
if any(isinstance(target, nodes.Starred) for target in targets):
return
try:
inferred = utils.safe_infer(node.value)
if inferred is not None:
self._check_unpacking(inferred, node, targets)
except astroid.InferenceError:
return
# listcomp have now also their scope
def visit_listcomp(self, node: nodes.ListComp) -> None:
"""Visit listcomp: update consumption analysis variable."""
self._to_consume.append(NamesConsumer(node, "comprehension"))
def leave_listcomp(self, _: nodes.ListComp) -> None:
"""Leave listcomp: update consumption analysis variable."""
# do not check for not used locals here
self._to_consume.pop()
def leave_assign(self, node: nodes.Assign) -> None:
self._store_type_annotation_names(node)
def leave_with(self, node: nodes.With) -> None:
self._store_type_annotation_names(node)
def visit_arguments(self, node: nodes.Arguments) -> None:
for annotation in node.type_comment_args:
self._store_type_annotation_node(annotation)
# Relying on other checker's options, which might not have been initialized yet.
@cached_property
def _analyse_fallback_blocks(self) -> bool:
return bool(self.linter.config.analyse_fallback_blocks)
@cached_property
def _ignored_modules(self) -> Iterable[str]:
return self.linter.config.ignored_modules # type: ignore[no-any-return]
@cached_property
def _allow_global_unused_variables(self) -> bool:
return bool(self.linter.config.allow_global_unused_variables)
@staticmethod
def _defined_in_function_definition(
node: nodes.NodeNG, frame: nodes.NodeNG
) -> bool:
in_annotation_or_default_or_decorator = False
if (
isinstance(frame, nodes.FunctionDef)
and node.statement(future=True) is frame
):
in_annotation_or_default_or_decorator = (
(
node in frame.args.annotations
or node in frame.args.posonlyargs_annotations
or node in frame.args.kwonlyargs_annotations
or node is frame.args.varargannotation
or node is frame.args.kwargannotation
)
or frame.args.parent_of(node)
or (frame.decorators and frame.decorators.parent_of(node))
or (
frame.returns
and (node is frame.returns or frame.returns.parent_of(node))
)
)
return in_annotation_or_default_or_decorator
@staticmethod
def _in_lambda_or_comprehension_body(
node: nodes.NodeNG, frame: nodes.NodeNG
) -> bool:
"""Return True if node within a lambda/comprehension body (or similar) and thus
should not have access to class attributes in frame.
"""
child = node
parent = node.parent
while parent is not None:
if parent is frame:
return False
if isinstance(parent, nodes.Lambda) and child is not parent.args:
# Body of lambda should not have access to class attributes.
return True
if isinstance(parent, nodes.Comprehension) and child is not parent.iter:
# Only iter of list/set/dict/generator comprehension should have access.
return True
if isinstance(parent, nodes.ComprehensionScope) and not (
parent.generators and child is parent.generators[0]
):
# Body of list/set/dict/generator comprehension should not have access to class attributes.
# Furthermore, only the first generator (if multiple) in comprehension should have access.
return True
child = parent
parent = parent.parent
return False
# pylint: disable = too-many-branches
@staticmethod
def _is_variable_violation(
node: nodes.Name,
defnode: nodes.NodeNG,
stmt: nodes.Statement,
defstmt: nodes.Statement,
frame: nodes.LocalsDictNodeNG, # scope of statement of node
defframe: nodes.LocalsDictNodeNG,
base_scope_type: str,
is_recursive_klass: bool,
) -> tuple[bool, bool, bool]:
maybe_before_assign = True
annotation_return = False
use_outer_definition = False
if frame is not defframe:
maybe_before_assign = _detect_global_scope(node, frame, defframe)
elif defframe.parent is None:
# we are at the module level, check the name is not
# defined in builtins
if (
node.name in defframe.scope_attrs
or astroid.builtin_lookup(node.name)[1]
):
maybe_before_assign = False
else:
# we are in a local scope, check the name is not
# defined in global or builtin scope
# skip this lookup if name is assigned later in function scope/lambda
# Note: the node.frame() is not the same as the `frame` argument which is
# equivalent to frame.statement().scope()
forbid_lookup = (
isinstance(frame, nodes.FunctionDef)
or isinstance(node.frame(future=True), nodes.Lambda)
) and _assigned_locally(node)
if not forbid_lookup and defframe.root().lookup(node.name)[1]:
maybe_before_assign = False
use_outer_definition = stmt == defstmt and not isinstance(
defnode, nodes.Comprehension
)
# check if we have a nonlocal
elif node.name in defframe.locals:
maybe_before_assign = not any(
isinstance(child, nodes.Nonlocal) and node.name in child.names
for child in defframe.get_children()
)
if (
base_scope_type == "lambda"
and isinstance(frame, nodes.ClassDef)
and node.name in frame.locals
):
# This rule verifies that if the definition node of the
# checked name is an Arguments node and if the name
# is used a default value in the arguments defaults
# and the actual definition of the variable label
# is happening before the Arguments definition.
#
# bar = None
# foo = lambda bar=bar: bar
#
# In this case, maybe_before_assign should be False, otherwise
# it should be True.
maybe_before_assign = not (
isinstance(defnode, nodes.Arguments)
and node in defnode.defaults
and frame.locals[node.name][0].fromlineno < defstmt.fromlineno
)
elif isinstance(defframe, nodes.ClassDef) and isinstance(
frame, nodes.FunctionDef
):
# Special rule for function return annotations,
# using a name defined earlier in the class containing the function.
if node is frame.returns and defframe.parent_of(frame.returns):
annotation_return = True
if (
frame.returns.name in defframe.locals
and defframe.locals[node.name][0].lineno < frame.lineno
):
# Detect class assignments with a name defined earlier in the
# class. In this case, no warning should be raised.
maybe_before_assign = False
else:
maybe_before_assign = True
if isinstance(node.parent, nodes.Arguments):
maybe_before_assign = stmt.fromlineno <= defstmt.fromlineno
elif is_recursive_klass:
maybe_before_assign = True
else:
maybe_before_assign = (
maybe_before_assign and stmt.fromlineno <= defstmt.fromlineno
)
if maybe_before_assign and stmt.fromlineno == defstmt.fromlineno:
if (
isinstance(defframe, nodes.FunctionDef)
and frame is defframe
and defframe.parent_of(node)
and stmt is not defstmt
):
# Single statement function, with the statement on the
# same line as the function definition
maybe_before_assign = False
elif (
isinstance(defstmt, NODES_WITH_VALUE_ATTR)
and VariablesChecker._maybe_used_and_assigned_at_once(defstmt)
and frame is defframe
and defframe.parent_of(node)
and stmt is defstmt
):
# Single statement if, with assignment expression on same
# line as assignment
# x = b if (b := True) else False
maybe_before_assign = False
elif (
isinstance( # pylint: disable=too-many-boolean-expressions
defnode, nodes.NamedExpr
)
and frame is defframe
and defframe.parent_of(stmt)
and stmt is defstmt
and (
(
defnode.lineno == node.lineno
and defnode.col_offset < node.col_offset
)
or (defnode.lineno < node.lineno)
or (
# Issue in the `ast` module until py39
# Nodes in a multiline string have the same lineno
# Could be false-positive without check
not PY39_PLUS
and defnode.lineno == node.lineno
and isinstance(
defstmt,
(
nodes.Assign,
nodes.AnnAssign,
nodes.AugAssign,
nodes.Return,
),
)
and isinstance(defstmt.value, nodes.JoinedStr)
)
)
):
# Relation of a name to the same name in a named expression
# Could be used before assignment if self-referencing:
# (b := b)
# Otherwise, safe if used after assignment:
# (b := 2) and b
maybe_before_assign = defnode.value is node or any(
anc is defnode.value for anc in node.node_ancestors()
)
# Look for type checking definitions inside a type checking guard.
# Relevant for function annotations only, not variable annotations (AnnAssign)
if (
isinstance(defstmt, (nodes.Import, nodes.ImportFrom))
and isinstance(defstmt.parent, nodes.If)
and in_type_checking_block(defstmt)
and not in_type_checking_block(node)
):
defstmt_parent = defstmt.parent
maybe_annotation = utils.get_node_first_ancestor_of_type(
node, nodes.AnnAssign
)
if not (
maybe_annotation
and utils.get_node_first_ancestor_of_type(
maybe_annotation, nodes.FunctionDef
)
):
# Exempt those definitions that are used inside the type checking
# guard or that are defined in any elif/else type checking guard branches.
used_in_branch = defstmt_parent.parent_of(node)
if not used_in_branch:
if defstmt_parent.has_elif_block():
defined_in_or_else = utils.is_defined(
node.name, defstmt_parent.orelse[0]
)
else:
defined_in_or_else = any(
utils.is_defined(node.name, content)
for content in defstmt_parent.orelse
)
if not defined_in_or_else:
maybe_before_assign = True
return maybe_before_assign, annotation_return, use_outer_definition
@staticmethod
def _maybe_used_and_assigned_at_once(defstmt: nodes.Statement) -> bool:
"""Check if `defstmt` has the potential to use and assign a name in the
same statement.
"""
if isinstance(defstmt, nodes.Match):
return any(case.guard for case in defstmt.cases)
if isinstance(defstmt, nodes.IfExp):
return True
if isinstance(defstmt.value, nodes.BaseContainer):
return any(
VariablesChecker._maybe_used_and_assigned_at_once(elt)
for elt in defstmt.value.elts
if isinstance(elt, NODES_WITH_VALUE_ATTR + (nodes.IfExp, nodes.Match))
)
value = defstmt.value
if isinstance(value, nodes.IfExp):
return True
if isinstance(value, nodes.Lambda) and isinstance(value.body, nodes.IfExp):
return True
if isinstance(value, nodes.Dict) and any(
isinstance(item[0], nodes.IfExp) or isinstance(item[1], nodes.IfExp)
for item in value.items
):
return True
if not isinstance(value, nodes.Call):
return False
return any(
any(isinstance(kwarg.value, nodes.IfExp) for kwarg in call.keywords)
or any(isinstance(arg, nodes.IfExp) for arg in call.args)
or (
isinstance(call.func, nodes.Attribute)
and isinstance(call.func.expr, nodes.IfExp)
)
for call in value.nodes_of_class(klass=nodes.Call)
)
def _is_only_type_assignment(
self, node: nodes.Name, defstmt: nodes.Statement
) -> bool:
"""Check if variable only gets assigned a type and never a value."""
if not isinstance(defstmt, nodes.AnnAssign) or defstmt.value:
return False
if node.name in self.linter.config.additional_builtins or utils.is_builtin(
node.name
):
return False
defstmt_frame = defstmt.frame(future=True)
node_frame = node.frame(future=True)
parent = node
while parent is not defstmt_frame.parent:
parent_scope = parent.scope()
# Find out if any nonlocals receive values in nested functions
for inner_func in parent_scope.nodes_of_class(nodes.FunctionDef):
if inner_func is parent_scope:
continue
if any(
node.name in nl.names
for nl in inner_func.nodes_of_class(nodes.Nonlocal)
) and any(
node.name == an.name
for an in inner_func.nodes_of_class(nodes.AssignName)
):
return False
local_refs = parent_scope.locals.get(node.name, [])
for ref_node in local_refs:
# If local ref is in the same frame as our node, but on a later lineno
# we don't actually care about this local ref.
# Local refs are ordered, so we break.
# print(var)
# var = 1 # <- irrelevant
if defstmt_frame == node_frame and ref_node.lineno > node.lineno:
break
# If the parent of the local reference is anything but an AnnAssign
# Or if the AnnAssign adds a value the variable will now have a value
# var = 1 # OR
# var: int = 1
if (
not isinstance(ref_node.parent, nodes.AnnAssign)
or ref_node.parent.value
) and not (
# EXCEPTION: will not have a value if a self-referencing named expression
# var: int
# if (var := var * var) <-- "var" still undefined
isinstance(ref_node.parent, nodes.NamedExpr)
and any(
anc is ref_node.parent.value for anc in node.node_ancestors()
)
):
return False
parent = parent_scope.parent
return True
@staticmethod
def _is_first_level_self_reference(
node: nodes.Name, defstmt: nodes.ClassDef, found_nodes: list[nodes.NodeNG]
) -> tuple[VariableVisitConsumerAction, list[nodes.NodeNG] | None]:
"""Check if a first level method's annotation or default values
refers to its own class, and return a consumer action.
"""
if node.frame(future=True).parent == defstmt and node.statement(
future=True
) == node.frame(future=True):
# Check if used as type annotation
# Break if postponed evaluation is enabled
if utils.is_node_in_type_annotation_context(node):
if not utils.is_postponed_evaluation_enabled(node):
return (VariableVisitConsumerAction.CONTINUE, None)
return (VariableVisitConsumerAction.RETURN, None)
# Check if used as default value by calling the class
if isinstance(node.parent, nodes.Call) and isinstance(
node.parent.parent, nodes.Arguments
):
return (VariableVisitConsumerAction.CONTINUE, None)
return (VariableVisitConsumerAction.RETURN, found_nodes)
@staticmethod
def _is_never_evaluated(
defnode: nodes.NamedExpr, defnode_parent: nodes.IfExp
) -> bool:
"""Check if a NamedExpr is inside a side of if ... else that never
gets evaluated.
"""
inferred_test = utils.safe_infer(defnode_parent.test)
if isinstance(inferred_test, nodes.Const):
if inferred_test.value is True and defnode == defnode_parent.orelse:
return True
if inferred_test.value is False and defnode == defnode_parent.body:
return True
return False
def _ignore_class_scope(self, node: nodes.NodeNG) -> bool:
"""Return True if the node is in a local class scope, as an assignment.
Detect if we are in a local class scope, as an assignment.
For example, the following is fair game.
class A:
b = 1
c = lambda b=b: b * b
class B:
tp = 1
def func(self, arg: tp):
...
class C:
tp = 2
def func(self, arg=tp):
...
class C:
class Tp:
pass
class D(Tp):
...
"""
name = node.name
frame = node.statement(future=True).scope()
in_annotation_or_default_or_decorator = self._defined_in_function_definition(
node, frame
)
in_ancestor_list = utils.is_ancestor_name(frame, node)
if in_annotation_or_default_or_decorator or in_ancestor_list:
frame_locals = frame.parent.scope().locals
else:
frame_locals = frame.locals
return not (
(isinstance(frame, nodes.ClassDef) or in_annotation_or_default_or_decorator)
and not self._in_lambda_or_comprehension_body(node, frame)
and name in frame_locals
)
# pylint: disable = too-many-branches
def _loopvar_name(self, node: astroid.Name) -> None:
# filter variables according to node's scope
astmts = [s for s in node.lookup(node.name)[1] if hasattr(s, "assign_type")]
# If this variable usage exists inside a function definition
# that exists in the same loop,
# the usage is safe because the function will not be defined either if
# the variable is not defined.
scope = node.scope()
# FunctionDef subclasses Lambda due to a curious ontology. Check both.
# See https://github.com/PyCQA/astroid/issues/291
# TODO: Revisit when astroid 3.0 includes the change
if isinstance(scope, nodes.Lambda) and any(
asmt.scope().parent_of(scope) for asmt in astmts
):
return
# Filter variables according to their respective scope. Test parent
# and statement to avoid #74747. This is not a total fix, which would
# introduce a mechanism similar to special attribute lookup in
# modules. Also, in order to get correct inference in this case, the
# scope lookup rules would need to be changed to return the initial
# assignment (which does not exist in code per se) as well as any later
# modifications.
if (
not astmts # pylint: disable=too-many-boolean-expressions
or (
astmts[0].parent == astmts[0].root()
and astmts[0].parent.parent_of(node)
)
or (
astmts[0].is_statement
or not isinstance(astmts[0].parent, nodes.Module)
and astmts[0].statement(future=True).parent_of(node)
)
):
_astmts = []
else:
_astmts = astmts[:1]
for i, stmt in enumerate(astmts[1:]):
if astmts[i].statement(future=True).parent_of(
stmt
) and not utils.in_for_else_branch(astmts[i].statement(future=True), stmt):
continue
_astmts.append(stmt)
astmts = _astmts
if len(astmts) != 1:
return
assign = astmts[0].assign_type()
if not (
isinstance(assign, (nodes.For, nodes.Comprehension, nodes.GeneratorExp))
and assign.statement(future=True) is not node.statement(future=True)
):
return
if not isinstance(assign, nodes.For):
self.add_message("undefined-loop-variable", args=node.name, node=node)
return
for else_stmt in assign.orelse:
if isinstance(
else_stmt, (nodes.Return, nodes.Raise, nodes.Break, nodes.Continue)
):
return
# TODO: 2.16: Consider using RefactoringChecker._is_function_def_never_returning
if isinstance(else_stmt, nodes.Expr) and isinstance(
else_stmt.value, nodes.Call
):
inferred_func = utils.safe_infer(else_stmt.value.func)
if (
isinstance(inferred_func, nodes.FunctionDef)
and inferred_func.returns
):
inferred_return = utils.safe_infer(inferred_func.returns)
if isinstance(
inferred_return, nodes.FunctionDef
) and inferred_return.qname() in {
*TYPING_NORETURN,
*TYPING_NEVER,
"typing._SpecialForm",
}:
return
# typing_extensions.NoReturn returns a _SpecialForm
if (
isinstance(inferred_return, bases.Instance)
and inferred_return.qname() == "typing._SpecialForm"
):
return
maybe_walrus = utils.get_node_first_ancestor_of_type(node, nodes.NamedExpr)
if maybe_walrus:
maybe_comprehension = utils.get_node_first_ancestor_of_type(
maybe_walrus, nodes.Comprehension
)
if maybe_comprehension:
comprehension_scope = utils.get_node_first_ancestor_of_type(
maybe_comprehension, nodes.ComprehensionScope
)
if comprehension_scope is None:
# Should not be possible.
pass
elif (
comprehension_scope.parent.scope() is scope
and node.name in comprehension_scope.locals
):
return
# For functions we can do more by inferring the length of the itered object
try:
inferred = next(assign.iter.infer())
# Prefer the target of enumerate() rather than the enumerate object itself
if (
isinstance(inferred, astroid.Instance)
and inferred.qname() == "builtins.enumerate"
):
likely_call = assign.iter
if isinstance(assign.iter, nodes.IfExp):
likely_call = assign.iter.body
if isinstance(likely_call, nodes.Call):
inferred = next(likely_call.args[0].infer())
except astroid.InferenceError:
self.add_message("undefined-loop-variable", args=node.name, node=node)
else:
if (
isinstance(inferred, astroid.Instance)
and inferred.qname() == BUILTIN_RANGE
):
# Consider range() objects safe, even if they might not yield any results.
return
# Consider sequences.
sequences = (
nodes.List,
nodes.Tuple,
nodes.Dict,
nodes.Set,
astroid.objects.FrozenSet,
)
if not isinstance(inferred, sequences):
self.add_message("undefined-loop-variable", args=node.name, node=node)
return
elements = getattr(inferred, "elts", getattr(inferred, "items", []))
if not elements:
self.add_message("undefined-loop-variable", args=node.name, node=node)
# pylint: disable = too-many-branches
def _check_is_unused(
self,
name: str,
node: nodes.FunctionDef,
stmt: nodes.NodeNG,
global_names: set[str],
nonlocal_names: Iterable[str],
comprehension_target_names: Iterable[str],
) -> None:
# Ignore some special names specified by user configuration.
if self._is_name_ignored(stmt, name):
return
# Ignore names that were added dynamically to the Function scope
if (
isinstance(node, nodes.FunctionDef)
and name == "__class__"
and len(node.locals["__class__"]) == 1
and isinstance(node.locals["__class__"][0], nodes.ClassDef)
):
return
# Ignore names imported by the global statement.
if isinstance(stmt, (nodes.Global, nodes.Import, nodes.ImportFrom)):
# Detect imports, assigned to global statements.
if global_names and _import_name_is_global(stmt, global_names):
return
# Ignore names in comprehension targets
if name in comprehension_target_names:
return
# Ignore names in string literal type annotation.
if name in self._type_annotation_names:
return
argnames = node.argnames()
# Care about functions with unknown argument (builtins)
if name in argnames:
if node.name == "__new__":
is_init_def = False
# Look for the `__init__` method in all the methods of the same class.
for n in node.parent.get_children():
is_init_def = hasattr(n, "name") and (n.name == "__init__")
if is_init_def:
break
# Ignore unused arguments check for `__new__` if `__init__` is defined.
if is_init_def:
return
self._check_unused_arguments(name, node, stmt, argnames, nonlocal_names)
else:
if stmt.parent and isinstance(
stmt.parent, (nodes.Assign, nodes.AnnAssign, nodes.Tuple, nodes.For)
):
if name in nonlocal_names:
return
qname = asname = None
if isinstance(stmt, (nodes.Import, nodes.ImportFrom)):
# Need the complete name, which we don't have in .locals.
if len(stmt.names) > 1:
import_names = next(
(names for names in stmt.names if name in names), None
)
else:
import_names = stmt.names[0]
if import_names:
qname, asname = import_names
name = asname or qname
if _has_locals_call_after_node(stmt, node.scope()):
message_name = "possibly-unused-variable"
else:
if isinstance(stmt, nodes.Import):
if asname is not None:
msg = f"{qname} imported as {asname}"
else:
msg = f"import {name}"
self.add_message("unused-import", args=msg, node=stmt)
return
if isinstance(stmt, nodes.ImportFrom):
if asname is not None:
msg = f"{qname} imported from {stmt.modname} as {asname}"
else:
msg = f"{name} imported from {stmt.modname}"
self.add_message("unused-import", args=msg, node=stmt)
return
message_name = "unused-variable"
if isinstance(stmt, nodes.FunctionDef) and stmt.decorators:
return
# Don't check function stubs created only for type information
if utils.is_overload_stub(node):
return
# Special case for exception variable
if isinstance(stmt.parent, nodes.ExceptHandler) and any(
n.name == name for n in stmt.parent.nodes_of_class(nodes.Name)
):
return
self.add_message(message_name, args=name, node=stmt)
def _is_name_ignored(
self, stmt: nodes.NodeNG, name: str
) -> re.Pattern[str] | re.Match[str] | None:
authorized_rgx = self.linter.config.dummy_variables_rgx
if (
isinstance(stmt, nodes.AssignName)
and isinstance(stmt.parent, nodes.Arguments)
or isinstance(stmt, nodes.Arguments)
):
regex: re.Pattern[str] = self.linter.config.ignored_argument_names
else:
regex = authorized_rgx
# See https://stackoverflow.com/a/47007761/2519059 to
# understand what this function return. Please do NOT use
# this elsewhere, this is confusing for no benefit
return regex and regex.match(name)
def _check_unused_arguments(
self,
name: str,
node: nodes.FunctionDef,
stmt: nodes.NodeNG,
argnames: list[str],
nonlocal_names: Iterable[str],
) -> None:
is_method = node.is_method()
klass = node.parent.frame(future=True)
if is_method and isinstance(klass, nodes.ClassDef):
confidence = (
INFERENCE if utils.has_known_bases(klass) else INFERENCE_FAILURE
)
else:
confidence = HIGH
if is_method:
# Don't warn for the first argument of a (non static) method
if node.type != "staticmethod" and name == argnames[0]:
return
# Don't warn for argument of an overridden method
overridden = overridden_method(klass, node.name)
if overridden is not None and name in overridden.argnames():
return
if node.name in utils.PYMETHODS and node.name not in (
"__init__",
"__new__",
):
return
# Don't check callback arguments
if any(
node.name.startswith(cb) or node.name.endswith(cb)
for cb in self.linter.config.callbacks
):
return
# Don't check arguments of singledispatch.register function.
if utils.is_registered_in_singledispatch_function(node):
return
# Don't check function stubs created only for type information
if utils.is_overload_stub(node):
return
# Don't check protocol classes
if utils.is_protocol_class(klass):
return
if name in nonlocal_names:
return
self.add_message("unused-argument", args=name, node=stmt, confidence=confidence)
def _check_late_binding_closure(self, node: nodes.Name) -> None:
"""Check whether node is a cell var that is assigned within a containing loop.
Special cases where we don't care about the error:
1. When the node's function is immediately called, e.g. (lambda: i)()
2. When the node's function is returned from within the loop, e.g. return lambda: i
"""
if not self.linter.is_message_enabled("cell-var-from-loop"):
return
node_scope = node.frame(future=True)
# If node appears in a default argument expression,
# look at the next enclosing frame instead
if utils.is_default_argument(node, node_scope):
node_scope = node_scope.parent.frame(future=True)
# Check if node is a cell var
if (
not isinstance(node_scope, (nodes.Lambda, nodes.FunctionDef))
or node.name in node_scope.locals
):
return
assign_scope, stmts = node.lookup(node.name)
if not stmts or not assign_scope.parent_of(node_scope):
return
if utils.is_comprehension(assign_scope):
self.add_message("cell-var-from-loop", node=node, args=node.name)
else:
# Look for an enclosing For loop.
# Currently, we only consider the first assignment
assignment_node = stmts[0]
maybe_for = assignment_node
while maybe_for and not isinstance(maybe_for, nodes.For):
if maybe_for is assign_scope:
break
maybe_for = maybe_for.parent
else:
if (
maybe_for
and maybe_for.parent_of(node_scope)
and not utils.is_being_called(node_scope)
and node_scope.parent
and not isinstance(node_scope.statement(future=True), nodes.Return)
):
self.add_message("cell-var-from-loop", node=node, args=node.name)
def _should_ignore_redefined_builtin(self, stmt: nodes.NodeNG) -> bool:
if not isinstance(stmt, nodes.ImportFrom):
return False
return stmt.modname in self.linter.config.redefining_builtins_modules
def _allowed_redefined_builtin(self, name: str) -> bool:
return name in self.linter.config.allowed_redefined_builtins
@staticmethod
def _comprehension_between_frame_and_node(node: nodes.Name) -> bool:
"""Return True if a ComprehensionScope intervenes between `node` and its
frame.
"""
closest_comprehension_scope = utils.get_node_first_ancestor_of_type(
node, nodes.ComprehensionScope
)
return closest_comprehension_scope is not None and node.frame(
future=True
).parent_of(closest_comprehension_scope)
def _store_type_annotation_node(self, type_annotation: nodes.NodeNG) -> None:
"""Given a type annotation, store all the name nodes it refers to."""
if isinstance(type_annotation, nodes.Name):
self._type_annotation_names.append(type_annotation.name)
return
if isinstance(type_annotation, nodes.Attribute):
self._store_type_annotation_node(type_annotation.expr)
return
if not isinstance(type_annotation, nodes.Subscript):
return
if (
isinstance(type_annotation.value, nodes.Attribute)
and isinstance(type_annotation.value.expr, nodes.Name)
and type_annotation.value.expr.name == TYPING_MODULE
):
self._type_annotation_names.append(TYPING_MODULE)
return
self._type_annotation_names.extend(
annotation.name for annotation in type_annotation.nodes_of_class(nodes.Name)
)
def _store_type_annotation_names(
self, node: nodes.For | nodes.Assign | nodes.With
) -> None:
type_annotation = node.type_annotation
if not type_annotation:
return
self._store_type_annotation_node(node.type_annotation)
def _check_self_cls_assign(self, node: nodes.Assign) -> None:
"""Check that self/cls don't get assigned."""
assign_names: set[str | None] = set()
for target in node.targets:
if isinstance(target, nodes.AssignName):
assign_names.add(target.name)
elif isinstance(target, nodes.Tuple):
assign_names.update(
elt.name for elt in target.elts if isinstance(elt, nodes.AssignName)
)
scope = node.scope()
nonlocals_with_same_name = any(
child for child in scope.body if isinstance(child, nodes.Nonlocal)
)
if nonlocals_with_same_name:
scope = node.scope().parent.scope()
if not (
isinstance(scope, nodes.FunctionDef)
and scope.is_method()
and "builtins.staticmethod" not in scope.decoratornames()
):
return
argument_names = scope.argnames()
if not argument_names:
return
self_cls_name = argument_names[0]
if self_cls_name in assign_names:
self.add_message("self-cls-assignment", node=node, args=(self_cls_name,))
def _check_unpacking(
self, inferred: InferenceResult, node: nodes.Assign, targets: list[nodes.NodeNG]
) -> None:
"""Check for unbalanced tuple unpacking
and unpacking non sequences.
"""
if utils.is_inside_abstract_class(node):
return
if utils.is_comprehension(node):
return
if isinstance(inferred, util.UninferableBase):
return
if (
isinstance(inferred.parent, nodes.Arguments)
and isinstance(node.value, nodes.Name)
and node.value.name == inferred.parent.vararg
):
# Variable-length argument, we can't determine the length.
return
# Attempt to check unpacking is properly balanced
values = self._nodes_to_unpack(inferred)
details = _get_unpacking_extra_info(node, inferred)
if values is not None:
if len(targets) != len(values):
self._report_unbalanced_unpacking(
node, inferred, targets, values, details
)
# attempt to check unpacking may be possible (i.e. RHS is iterable)
elif not utils.is_iterable(inferred):
self._report_unpacking_non_sequence(node, details)
@staticmethod
def _nodes_to_unpack(node: nodes.NodeNG) -> list[nodes.NodeNG] | None:
"""Return the list of values of the `Assign` node."""
if isinstance(node, (nodes.Tuple, nodes.List) + DICT_TYPES):
return node.itered() # type: ignore[no-any-return]
if isinstance(node, astroid.Instance) and any(
ancestor.qname() == "typing.NamedTuple" for ancestor in node.ancestors()
):
return [i for i in node.values() if isinstance(i, nodes.AssignName)]
return None
def _report_unbalanced_unpacking(
self,
node: nodes.NodeNG,
inferred: InferenceResult,
targets: list[nodes.NodeNG],
values: list[nodes.NodeNG],
details: str,
) -> None:
args = (
details,
len(targets),
"" if len(targets) == 1 else "s",
len(values),
"" if len(values) == 1 else "s",
)
symbol = (
"unbalanced-dict-unpacking"
if isinstance(inferred, DICT_TYPES)
else "unbalanced-tuple-unpacking"
)
self.add_message(symbol, node=node, args=args, confidence=INFERENCE)
def _report_unpacking_non_sequence(self, node: nodes.NodeNG, details: str) -> None:
if details and not details.startswith(" "):
details = f" {details}"
self.add_message("unpacking-non-sequence", node=node, args=details)
def _check_module_attrs(
self,
node: _base_nodes.ImportNode,
module: nodes.Module,
module_names: list[str],
) -> nodes.Module | None:
"""Check that module_names (list of string) are accessible through the
given module, if the latest access name corresponds to a module, return it.
"""
while module_names:
name = module_names.pop(0)
if name == "__dict__":
module = None
break
try:
module = next(module.getattr(name)[0].infer())
if not isinstance(module, nodes.Module):
return None
except astroid.NotFoundError:
if module.name in self._ignored_modules:
return None
self.add_message(
"no-name-in-module", args=(name, module.name), node=node
)
return None
except astroid.InferenceError:
return None
if module_names:
modname = module.name if module else "__dict__"
self.add_message(
"no-name-in-module", node=node, args=(".".join(module_names), modname)
)
return None
if isinstance(module, nodes.Module):
return module
return None
def _check_all(
self, node: nodes.Module, not_consumed: dict[str, list[nodes.NodeNG]]
) -> None:
assigned = next(node.igetattr("__all__"))
if isinstance(assigned, util.UninferableBase):
return
if assigned.pytype() not in {"builtins.list", "builtins.tuple"}:
line, col = assigned.tolineno, assigned.col_offset
self.add_message("invalid-all-format", line=line, col_offset=col, node=node)
return
for elt in getattr(assigned, "elts", ()):
try:
elt_name = next(elt.infer())
except astroid.InferenceError:
continue
if isinstance(elt_name, util.UninferableBase):
continue
if not elt_name.parent:
continue
if not isinstance(elt_name, nodes.Const) or not isinstance(
elt_name.value, str
):
self.add_message("invalid-all-object", args=elt.as_string(), node=elt)
continue
elt_name = elt_name.value
# If elt is in not_consumed, remove it from not_consumed
if elt_name in not_consumed:
del not_consumed[elt_name]
continue
if elt_name not in node.locals:
if not node.package:
self.add_message(
"undefined-all-variable", args=(elt_name,), node=elt
)
else:
basename = os.path.splitext(node.file)[0]
if os.path.basename(basename) == "__init__":
name = node.name + "." + elt_name
try:
astroid.modutils.file_from_modpath(name.split("."))
except ImportError:
self.add_message(
"undefined-all-variable", args=(elt_name,), node=elt
)
except SyntaxError:
# don't yield a syntax-error warning,
# because it will be later yielded
# when the file will be checked
pass
def _check_globals(self, not_consumed: dict[str, nodes.NodeNG]) -> None:
if self._allow_global_unused_variables:
return
for name, node_lst in not_consumed.items():
for node in node_lst:
self.add_message("unused-variable", args=(name,), node=node)
# pylint: disable = too-many-branches
def _check_imports(self, not_consumed: dict[str, list[nodes.NodeNG]]) -> None:
local_names = _fix_dot_imports(not_consumed)
checked = set()
unused_wildcard_imports: defaultdict[
tuple[str, nodes.ImportFrom], list[str]
] = collections.defaultdict(list)
for name, stmt in local_names:
for imports in stmt.names:
real_name = imported_name = imports[0]
if imported_name == "*":
real_name = name
as_name = imports[1]
if real_name in checked:
continue
if name not in (real_name, as_name):
continue
checked.add(real_name)
is_type_annotation_import = (
imported_name in self._type_annotation_names
or as_name in self._type_annotation_names
)
is_dummy_import = (
as_name
and self.linter.config.dummy_variables_rgx
and self.linter.config.dummy_variables_rgx.match(as_name)
)
if isinstance(stmt, nodes.Import) or (
isinstance(stmt, nodes.ImportFrom) and not stmt.modname
):
if isinstance(stmt, nodes.ImportFrom) and SPECIAL_OBJ.search(
imported_name
):
# Filter special objects (__doc__, __all__) etc.,
# because they can be imported for exporting.
continue
if is_type_annotation_import or is_dummy_import:
# Most likely a typing import if it wasn't used so far.
# Also filter dummy variables.
continue
if as_name is None:
msg = f"import {imported_name}"
else:
msg = f"{imported_name} imported as {as_name}"
if not in_type_checking_block(stmt):
self.add_message("unused-import", args=msg, node=stmt)
elif isinstance(stmt, nodes.ImportFrom) and stmt.modname != FUTURE:
if SPECIAL_OBJ.search(imported_name):
# Filter special objects (__doc__, __all__) etc.,
# because they can be imported for exporting.
continue
if _is_from_future_import(stmt, name):
# Check if the name is in fact loaded from a
# __future__ import in another module.
continue
if is_type_annotation_import or is_dummy_import:
# Most likely a typing import if it wasn't used so far.
# Also filter dummy variables.
continue
if imported_name == "*":
unused_wildcard_imports[(stmt.modname, stmt)].append(name)
else:
if as_name is None:
msg = f"{imported_name} imported from {stmt.modname}"
else:
msg = f"{imported_name} imported from {stmt.modname} as {as_name}"
if not in_type_checking_block(stmt):
self.add_message("unused-import", args=msg, node=stmt)
# Construct string for unused-wildcard-import message
for module, unused_list in unused_wildcard_imports.items():
if len(unused_list) == 1:
arg_string = unused_list[0]
else:
arg_string = (
f"{', '.join(i for i in unused_list[:-1])} and {unused_list[-1]}"
)
self.add_message(
"unused-wildcard-import", args=(arg_string, module[0]), node=module[1]
)
del self._to_consume
def _check_metaclasses(self, node: nodes.Module | nodes.FunctionDef) -> None:
"""Update consumption analysis for metaclasses."""
consumed: list[tuple[dict[str, list[nodes.NodeNG]], str]] = []
for child_node in node.get_children():
if isinstance(child_node, nodes.ClassDef):
consumed.extend(self._check_classdef_metaclasses(child_node, node))
# Pop the consumed items, in order to avoid having
# unused-import and unused-variable false positives
for scope_locals, name in consumed:
scope_locals.pop(name, None)
def _check_classdef_metaclasses(
self, klass: nodes.ClassDef, parent_node: nodes.Module | nodes.FunctionDef
) -> list[tuple[dict[str, list[nodes.NodeNG]], str]]:
if not klass._metaclass:
# Skip if this class doesn't use explicitly a metaclass, but inherits it from ancestors
return []
consumed: list[tuple[dict[str, list[nodes.NodeNG]], str]] = []
metaclass = klass.metaclass()
name = ""
if isinstance(klass._metaclass, nodes.Name):
name = klass._metaclass.name
elif isinstance(klass._metaclass, nodes.Attribute) and klass._metaclass.expr:
attr = klass._metaclass.expr
while not isinstance(attr, nodes.Name):
attr = attr.expr
name = attr.name
elif isinstance(klass._metaclass, nodes.Call) and isinstance(
klass._metaclass.func, nodes.Name
):
name = klass._metaclass.func.name
elif metaclass:
name = metaclass.root().name
found = False
name = METACLASS_NAME_TRANSFORMS.get(name, name)
if name:
# check enclosing scopes starting from most local
for scope_locals, _, _, _ in self._to_consume[::-1]:
found_nodes = scope_locals.get(name, [])
for found_node in found_nodes:
if found_node.lineno <= klass.lineno:
consumed.append((scope_locals, name))
found = True
break
# Check parent scope
nodes_in_parent_scope = parent_node.locals.get(name, [])
for found_node_parent in nodes_in_parent_scope:
if found_node_parent.lineno <= klass.lineno:
found = True
break
if (
not found
and not metaclass
and not (
name in nodes.Module.scope_attrs
or utils.is_builtin(name)
or name in self.linter.config.additional_builtins
)
):
self.add_message("undefined-variable", node=klass, args=(name,))
return consumed
def visit_subscript(self, node: nodes.Subscript) -> None:
inferred_slice = utils.safe_infer(node.slice)
self._check_potential_index_error(node, inferred_slice)
def _check_potential_index_error(
self, node: nodes.Subscript, inferred_slice: nodes.NodeNG | None
) -> None:
"""Check for the potential-index-error message."""
# Currently we only check simple slices of a single integer
if not isinstance(inferred_slice, nodes.Const) or not isinstance(
inferred_slice.value, int
):
return
# If the node.value is a Tuple or List without inference it is defined in place
if isinstance(node.value, (nodes.Tuple, nodes.List)):
# Add 1 because iterables are 0-indexed
if len(node.value.elts) < inferred_slice.value + 1:
self.add_message(
"potential-index-error", node=node, confidence=INFERENCE
)
return
@utils.only_required_for_messages(
"unused-import",
"unused-variable",
)
def visit_const(self, node: nodes.Const) -> None:
"""Take note of names that appear inside string literal type annotations
unless the string is a parameter to `typing.Literal` or `typing.Annotation`.
"""
if node.pytype() != "builtins.str":
return
if not utils.is_node_in_type_annotation_context(node):
return
# Check if parent's or grandparent's first child is typing.Literal
parent = node.parent
if isinstance(parent, nodes.Tuple):
parent = parent.parent
if isinstance(parent, nodes.Subscript):
origin = next(parent.get_children(), None)
if origin is not None and utils.is_typing_member(
origin, ("Annotated", "Literal")
):
return
try:
annotation = extract_node(node.value)
self._store_type_annotation_node(annotation)
except ValueError:
# e.g. node.value is white space
pass
except astroid.AstroidSyntaxError:
# e.g. "?" or ":" in typing.Literal["?", ":"]
pass
def register(linter: PyLinter) -> None:
linter.register_checker(VariablesChecker(linter))