Infer user-defined enum classes by checking if the class is a subtype of enum.Enum (#2277)

* Infer user-defined enum classes by checking if the class is a subtype of ``enum.Enum``.

Co-authored-by: Jacob Walls <jacobtylerwalls@gmail.com>

Author: mbyrnepr2

ChangeLog

@@ -221,6 +221,9 @@ Release date: TBA
 
   Closes pylint-dev/pylint#8802
 
+* Infer user-defined enum classes by checking if the class is a subtype of ``enum.Enum``.
+
+  Closes pylint-dev/pylint#8897
 
 * Fix false positives for ``no-member`` and ``invalid-name`` when using the ``_name_``, ``_value_`` and ``_ignore_`` sunders in Enums.
 

astroid/brain/brain_namedtuple_enum.py

@@ -20,19 +20,10 @@
     AstroidTypeError,
     AstroidValueError,
     InferenceError,
-    MroError,
     UseInferenceDefault,
 )
 from astroid.manager import AstroidManager
 
-ENUM_BASE_NAMES = {
-    "Enum",
-    "IntEnum",
-    "enum.Enum",
-    "enum.IntEnum",
-    "IntFlag",
-    "enum.IntFlag",
-}
 ENUM_QNAME: Final[str] = "enum.Enum"
 TYPING_NAMEDTUPLE_QUALIFIED: Final = {
     "typing.NamedTuple",
@@ -653,14 +644,7 @@ def _get_namedtuple_fields(node: nodes.Call) -> str:
 
 def _is_enum_subclass(cls: astroid.ClassDef) -> bool:
     """Return whether cls is a subclass of an Enum."""
-    try:
-        return any(
-            klass.name in ENUM_BASE_NAMES
-            and getattr(klass.root(), "name", None) == "enum"
-            for klass in cls.mro()
-        )
-    except MroError:
-        return False
+    return cls.is_subtype_of("enum.Enum")
 
 
 def register(manager: AstroidManager) -> None:

tests/brain/test_enum.py

@@ -522,6 +522,42 @@ def __init__(self, mass, radius):
         assert mars[1].name == "MARS"
         assert radius[1].name == "radius"
 
+    def test_local_enum_child_class_inference(self) -> None:
+        """Originally reported in https://github.com/pylint-dev/pylint/issues/8897
+
+        Test that a user-defined enum class is inferred when it subclasses
+        another user-defined enum class.
+        """
+        enum_class_node, enum_member_value_node = astroid.extract_node(
+            """
+        import sys
+
+        from enum import Enum
+
+        if sys.version_info >= (3, 11):
+            from enum import StrEnum
+        else:
+            class StrEnum(str, Enum):
+                pass
+
+
+        class Color(StrEnum): #@
+            RED = "red"
+
+
+        Color.RED.value #@
+        """
+        )
+        assert "RED" in enum_class_node.locals
+
+        enum_members = enum_class_node.locals["__members__"][0].items
+        assert len(enum_members) == 1
+        _, name = enum_members[0]
+        assert name.name == "RED"
+
+        inferred_enum_member_value_node = next(enum_member_value_node.infer())
+        assert inferred_enum_member_value_node.value == "red"
+
     def test_enum_with_ignore(self) -> None:
         """Exclude ``_ignore_`` from the ``__members__`` container
         Originally reported in https://github.com/pylint-dev/pylint/issues/9015

tests/test_inference.py

@@ -4944,6 +4944,9 @@ def __class_getitem__(self, value):
         """
         klass = extract_node(code)
         context = InferenceContext()
+        # For this test, we want a fresh inference, rather than a cache hit on
+        # the inference done at brain time in _is_enum_subclass()
+        context.lookupname = "Fresh lookup!"
         _ = klass.getitem(0, context=context)
 
         assert next(iter(context.path))[0].name == "Parent"