be gracious on Enums that are not recognized by DRF #500

drf_spectacular/plumbing.py

@@ -970,10 +970,11 @@ def resolve_type_hint(hint):
             schema.update(build_basic_type(type(args[0])))
         return schema
     elif inspect.isclass(hint) and issubclass(hint, Enum):
-        return {
-            'enum': [item.value for item in hint],
-            **build_basic_type([t for t in hint.__mro__ if is_basic_type(t)][0])
-        }
+        schema = {'enum': [item.value for item in hint]}
+        mixin_base_types = [t for t in hint.__mro__ if is_basic_type(t)]
+        if mixin_base_types:
+            schema.update(build_basic_type(mixin_base_types[0]))
+        return schema
     elif hasattr(typing, 'TypedDict') and isinstance(hint, typing._TypedDictMeta):
         return build_object_type(
             properties={

tests/test_plumbing.py

@@ -96,6 +96,13 @@ class LanguageEnum(str, Enum):
     DE = 'de'
 
 
+# Make sure we can deal with plain Enums that are not handled by DRF.
+# The second base class makes this work for DRF.
+class InvalidLanguageEnum(Enum):
+    EN = 'en'
+    DE = 'de'
+
+
 TYPE_HINT_TEST_PARAMS = [
     (
         typing.Optional[int],
@@ -139,13 +146,15 @@ class LanguageEnum(str, Enum):
     ), (
         typing.Optional[typing.Union[str, int]],
         {'oneOf': [{'type': 'string'}, {'type': 'integer'}], 'nullable': True}
+    ), (
+        LanguageEnum,
+        {'enum': ['en', 'de'], 'type': 'string'}
+    ), (
+        InvalidLanguageEnum,
+        {'enum': ['en', 'de']}
     )
 ]
 
-TYPE_HINT_TEST_PARAMS.append((
-    LanguageEnum,
-    {'enum': ['en', 'de'], 'type': 'string'}
-))
 
 if DJANGO_VERSION > '3':
     from django.db.models.enums import TextChoices  # only available in Django>3