gh-102558: [Enum] better handling of non-Enum EnumType classes (GH-103060)

(cherry picked from commit f4ed2c6)

Co-authored-by: Ethan Furman <[email protected]>

Author: miss-islington

Lib/enum.py

@@ -936,7 +936,7 @@ def _convert_(cls, name, module, filter, source=None, *, boundary=None, as_globa
     def _check_for_existing_members_(mcls, class_name, bases):
         for chain in bases:
             for base in chain.__mro__:
-                if issubclass(base, Enum) and base._member_names_:
+                if isinstance(base, EnumType) and base._member_names_:
                     raise TypeError(
                             "<enum %r> cannot extend %r"
                             % (class_name, base)
@@ -958,7 +958,7 @@ def _get_mixins_(mcls, class_name, bases):
         # ensure final parent class is an Enum derivative, find any concrete
         # data type, and check that Enum has no members
         first_enum = bases[-1]
-        if not issubclass(first_enum, Enum):
+        if not isinstance(first_enum, EnumType):
             raise TypeError("new enumerations should be created as "
                     "`EnumName([mixin_type, ...] [data_type,] enum_type)`")
         member_type = mcls._find_data_type_(class_name, bases) or object
@@ -970,7 +970,7 @@ def _find_data_repr_(mcls, class_name, bases):
             for base in chain.__mro__:
                 if base is object:
                     continue
-                elif issubclass(base, Enum):
+                elif isinstance(base, EnumType):
                     # if we hit an Enum, use it's _value_repr_
                     return base._value_repr_
                 elif '__repr__' in base.__dict__:
@@ -988,12 +988,12 @@ def _find_data_type_(mcls, class_name, bases):
                 base_chain.add(base)
                 if base is object:
                     continue
-                elif issubclass(base, Enum):
+                elif isinstance(base, EnumType):
                     if base._member_type_ is not object:
                         data_types.add(base._member_type_)
                         break
                 elif '__new__' in base.__dict__ or '__init__' in base.__dict__:
-                    if issubclass(base, Enum):
+                    if isinstance(base, EnumType):
                         continue
                     data_types.add(candidate or base)
                     break
@@ -1187,8 +1187,6 @@ def _missing_(cls, value):
         return None
 
     def __repr__(self):
-        if not isinstance(self, Enum):
-            return repr(self)
         v_repr = self.__class__._value_repr_ or repr
         return "<%s.%s: %s>" % (self.__class__.__name__, self._name_, v_repr(self._value_))
 

Lib/test/test_enum.py

@@ -1321,7 +1321,6 @@ def repr(self):
             class Huh(MyStr, MyInt, Enum):
                 One = 1
 
-
     def test_pickle_enum(self):
         if isinstance(Stooges, Exception):
             raise Stooges