Add new checker `bad-chained-comparison` (#7990)

Co-authored-by: Pierre Sassoulas <pierre.sassoulas@gmail.com>

1 files changed, 61 insertions, 0 deletions

diff --git a/pylint/checkers/bad_chained_comparison.py b/pylint/checkers/bad_chained_comparison.py
new file mode 100644
index 000000000..fa75c52b2
--- /dev/null
+++ b/pylint/checkers/bad_chained_comparison.py
@@ -0,0 +1,61 @@
+# 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 = {
+        "W3501": (
+            "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))