# 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 """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))