Deal with 'is not' but exclude 'is not None'

Author: cdce8p

pylint/extensions/code_style.py

@@ -379,8 +379,10 @@ def _can_be_inverted(values: list[nodes.NodeNG]) -> InvertibleValues:
         invertible = InvertibleValues.NO
         for node in values:
             match node:
-                case nodes.UnaryOp(op="not") | nodes.Compare(
-                    ops=[("!=" | "not in", _)]
+                case nodes.UnaryOp(op="not"):
+                    invertible |= InvertibleValues.EXPLICIT_NEGATION
+                case nodes.Compare(ops=[("!=" | "not in" | "is not" as op, n)]) if not (
+                    op == "is not" and isinstance(n, nodes.Const) and n.value is None
                 ):
                     invertible |= InvertibleValues.EXPLICIT_NEGATION
                 case nodes.Compare(
@@ -405,6 +407,8 @@ def _invert_node(node: nodes.NodeNG) -> nodes.NodeNG:
                         new_op = "=="
                     case "not in":
                         new_op = "in"
+                    case "is not":
+                        new_op = "is"
                     case "<":
                         new_op = ">="
                     case "<=":

tests/functional/ext/code_style/cs_improve_conditionals.py

@@ -1,4 +1,4 @@
-# pylint: disable=missing-docstring
+# pylint: disable=missing-docstring,too-many-branches
 
 def f1(expr, node_cls, x, y, z):
     if isinstance(expr, node_cls) and expr.attrname == "__init__":
@@ -19,10 +19,17 @@ def f1(expr, node_cls, x, y, z):
     elif x < 0 or y <= 1:
         ...
 
+    if x is not None or y is not None:
+        ...
+    elif not isinstance(expr, node_cls) or x is not None:
+        ...
+
     if not isinstance(expr, node_cls) or expr.attrname != "__init__":  # [improve-conditionals]
         ...
     elif not x or y not in z:  # [improve-conditionals]
         ...
+    elif not x or y is not z:  # [improve-conditionals]
+        ...
     elif not (not x or not y):  # [improve-conditionals]
         ...
     elif x and (not y or not z):  # [improve-conditionals]

tests/functional/ext/code_style/cs_improve_conditionals.txt

@@ -1,4 +1,5 @@
-improve-conditionals:22:7:22:68:f1:Rewrite conditional expression to 'not (isinstance(expr, node_cls) and expr.attrname == '__init__')':HIGH
-improve-conditionals:24:9:24:28:f1:Rewrite conditional expression to 'not (x and y in z)':HIGH
-improve-conditionals:26:9:26:29:f1:Rewrite conditional expression to 'x and y':HIGH
-improve-conditionals:28:16:28:30:f1:Rewrite conditional expression to 'not (y and z)':HIGH
+improve-conditionals:27:7:27:68:f1:Rewrite conditional expression to 'not (isinstance(expr, node_cls) and expr.attrname == '__init__')':HIGH
+improve-conditionals:29:9:29:28:f1:Rewrite conditional expression to 'not (x and y in z)':HIGH
+improve-conditionals:31:9:31:28:f1:Rewrite conditional expression to 'not (x and y is z)':HIGH
+improve-conditionals:33:9:33:29:f1:Rewrite conditional expression to 'x and y':HIGH
+improve-conditionals:35:16:35:30:f1:Rewrite conditional expression to 'not (y and z)':HIGH