# 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
from __future__ import annotations
from typing import TYPE_CHECKING
from astroid import nodes
from pylint.checkers import BaseChecker
from pylint.interfaces import HIGH
if TYPE_CHECKING:
from pylint.lint import PyLinter
COMPARISON_OP = frozenset(("<", "<=", ">", ">=", "!=", "=="))
IDENTITY_OP = frozenset(("is", "is not"))
MEMBERSHIP_OP = frozenset(("in", "not in"))
class BadChainedComparisonChecker(BaseChecker):
"""Checks for unintentional usage of chained comparison."""
name = "bad-chained-comparison"
msgs = {
"W3601": (
"Suspicious %s-part chained comparison using semantically incompatible operators (%s)",
"bad-chained-comparison",
"Used when there is a chained comparison where one expression is part "
"of two comparisons that belong to different semantic groups "
'("<" does not mean the same thing as "is", chaining them in '
'"0 < x is None" is probably a mistake).',
)
}
def _has_diff_semantic_groups(self, operators: list[str]) -> bool:
# Check if comparison operators are in the same semantic group
for semantic_group in (COMPARISON_OP, IDENTITY_OP, MEMBERSHIP_OP):
if operators[0] in semantic_group:
group = semantic_group
return not all(o in group for o in operators)
def visit_compare(self, node: nodes.Compare) -> None:
operators = sorted({op[0] for op in node.ops})
if self._has_diff_semantic_groups(operators):
num_parts = f"{len(node.ops)}"
incompatibles = (
", ".join(f"'{o}'" for o in operators[:-1]) + f" and '{operators[-1]}'"
)
self.add_message(
"bad-chained-comparison",
node=node,
args=(num_parts, incompatibles),
confidence=HIGH,
)
def register(linter: PyLinter) -> None:
linter.register_checker(BadChainedComparisonChecker(linter))
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