Exempt parents with only annotations from invalid-enum-extension (#8834)

Author: jacobtylerwalls

doc/whatsnew/fragments/8830.false_positive

@@ -0,0 +1,4 @@
+Exempt parents with only type annotations from the ``invalid-enum-extension``
+message.
+
+Closes #8830

pylint/checkers/classes/class_checker.py

@@ -893,12 +893,21 @@ def _check_consistent_mro(self, node: nodes.ClassDef) -> None:
     def _check_enum_base(self, node: nodes.ClassDef, ancestor: nodes.ClassDef) -> None:
         members = ancestor.getattr("__members__")
         if members and isinstance(members[0], nodes.Dict) and members[0].items:
-            self.add_message(
-                "invalid-enum-extension",
-                args=ancestor.name,
-                node=node,
-                confidence=INFERENCE,
-            )
+            for _, name_node in members[0].items:
+                # Exempt type annotations without value assignments
+                if all(
+                    isinstance(item.parent, nodes.AnnAssign)
+                    and item.parent.value is None
+                    for item in ancestor.getattr(name_node.name)
+                ):
+                    continue
+                self.add_message(
+                    "invalid-enum-extension",
+                    args=ancestor.name,
+                    node=node,
+                    confidence=INFERENCE,
+                )
+                break
 
         if ancestor.is_subtype_of("enum.IntFlag"):
             # Collect integer flag assignments present on the class

tests/functional/i/invalid/invalid_enum_extension.py

@@ -21,6 +21,33 @@ class D(C):
     x = 3
 
 
+# Similarly, items that are only type annotations are okay.
+class ColorEnum(Enum):
+    red: int
+    green: int
+    blue: int
+
+    def __init__(self, red: int, green: int, blue: int) -> None:
+        self.red = red
+        self.green = green
+        self.blue = blue
+
+
+class Pastel(ColorEnum):
+    SAGE = (170, 200, 167)
+
+
+class IncorrectColorEnum(Enum):
+    red: None = None
+
+    def __init__(self, red: None) -> None:
+        self.red = red
+
+
+class IncorrectPastel(IncorrectColorEnum):  # [invalid-enum-extension]
+    SOME_COLOR = 170
+
+
 class CustomFlags(IntFlag):
     SUPPORT_OPEN = 1
     SUPPORT_CLOSE = 2

tests/functional/i/invalid/invalid_enum_extension.txt

@@ -1 +1,2 @@
 invalid-enum-extension:12:0:12:7:B:"Extending inherited Enum class ""A""":INFERENCE
+invalid-enum-extension:47:0:47:21:IncorrectPastel:"Extending inherited Enum class ""IncorrectColorEnum""":INFERENCE