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# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
# For details: https://github.com/pylint-dev/pylint/blob/main/LICENSE
# Copyright (c) https://github.com/pylint-dev/pylint/blob/main/CONTRIBUTORS.txt
"""Optional checker to warn when loop variables are overwritten in the loop's body."""
from __future__ import annotations
from astroid import nodes
from pylint import checkers
from pylint.checkers import utils
from pylint.interfaces import HIGH
from pylint.lint import PyLinter
class RedefinedLoopNameChecker(checkers.BaseChecker):
name = "redefined-loop-name"
msgs = {
"W2901": (
"Redefining %r from loop (line %s)",
"redefined-loop-name",
"Used when a loop variable is overwritten in the loop body.",
),
}
def __init__(self, linter: PyLinter) -> None:
super().__init__(linter)
self._loop_variables: list[
tuple[nodes.For, list[str], nodes.LocalsDictNodeNG]
] = []
@utils.only_required_for_messages("redefined-loop-name")
def visit_assignname(self, node: nodes.AssignName) -> None:
assign_type = node.assign_type()
if not isinstance(assign_type, (nodes.Assign, nodes.AugAssign)):
return
node_scope = node.scope()
for outer_for, outer_variables, outer_for_scope in self._loop_variables:
if node_scope is not outer_for_scope:
continue
if node.name in outer_variables and not utils.in_for_else_branch(
outer_for, node
):
self.add_message(
"redefined-loop-name",
args=(node.name, outer_for.fromlineno),
node=node,
confidence=HIGH,
)
break
@utils.only_required_for_messages("redefined-loop-name")
def visit_for(self, node: nodes.For) -> None:
assigned_to = [a.name for a in node.target.nodes_of_class(nodes.AssignName)]
# Only check variables that are used
assigned_to = [
var
for var in assigned_to
if not self.linter.config.dummy_variables_rgx.match(var)
]
node_scope = node.scope()
for variable in assigned_to:
for outer_for, outer_variables, outer_for_scope in self._loop_variables:
if node_scope is not outer_for_scope:
continue
if variable in outer_variables and not utils.in_for_else_branch(
outer_for, node
):
self.add_message(
"redefined-loop-name",
args=(variable, outer_for.fromlineno),
node=node,
confidence=HIGH,
)
break
self._loop_variables.append((node, assigned_to, node.scope()))
@utils.only_required_for_messages("redefined-loop-name")
def leave_for(self, node: nodes.For) -> None: # pylint: disable=unused-argument
self._loop_variables.pop()
def register(linter: PyLinter) -> None:
linter.register_checker(RedefinedLoopNameChecker(linter))
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