1 files changed, 67 insertions, 0 deletions
diff --git a/pylint/extensions/comparison_placement.py b/pylint/extensions/comparison_placement.py
new file mode 100644
index 000000000..64c8dee5e
--- /dev/null
+++ b/pylint/extensions/comparison_placement.py
@@ -0,0 +1,67 @@
+# 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
+
+"""
+Checks for yoda comparisons (variable before constant)
+See https://en.wikipedia.org/wiki/Yoda_conditions
+"""
+
+
+from astroid import nodes
+
+from pylint.checkers import BaseChecker, utils
+from pylint.interfaces import IAstroidChecker
+
+REVERSED_COMPS = {"<": ">", "<=": ">=", ">": "<", ">=": "<="}
+COMPARISON_OPERATORS = frozenset(("==", "!=", "<", ">", "<=", ">="))
+
+
+class MisplacedComparisonConstantChecker(BaseChecker):
+    """Checks the placement of constants in comparisons"""
+
+    __implements__ = (IAstroidChecker,)
+
+    # configuration section name
+    name = "comparison-placement"
+    msgs = {
+        "C2201": (
+            "Comparison should be %s",
+            "misplaced-comparison-constant",
+            "Used when the constant is placed on the left side "
+            "of a comparison. It is usually clearer in intent to "
+            "place it in the right hand side of the comparison.",
+            {"old_names": [("C0122", "old-misplaced-comparison-constant")]},
+        )
+    }
+
+    options = ()
+
+    def _check_misplaced_constant(
+        self,
+        node: nodes.Compare,
+        left: nodes.NodeNG,
+        right: nodes.NodeNG,
+        operator: str,
+    ):
+        if isinstance(right, nodes.Const):
+            return
+        operator = REVERSED_COMPS.get(operator, operator)
+        suggestion = f"{right.as_string()} {operator} {left.value!r}"
+        self.add_message("misplaced-comparison-constant", node=node, args=(suggestion,))
+
+    @utils.check_messages("misplaced-comparison-constant")
+    def visit_compare(self, node: nodes.Compare) -> None:
+        # NOTE: this checker only works with binary comparisons like 'x == 42'
+        # but not 'x == y == 42'
+        if len(node.ops) != 1:
+            return
+
+        left = node.left
+        operator, right = node.ops[0]
+        if operator in COMPARISON_OPERATORS and isinstance(left, nodes.Const):
+            self._check_misplaced_constant(node, left, right, operator)
+
+
+def register(linter):
+    """Required method to auto register this checker."""
+    linter.register_checker(MisplacedComparisonConstantChecker(linter))