Simplified Union implementation

graphene/types/union.py

@@ -1,38 +1,14 @@
-import six
-
-from ..utils.is_base_type import is_base_type
-from ..utils.trim_docstring import trim_docstring
-from .options import Options
 from .unmountedtype import UnmountedType
+from .objecttype import ObjectType
+
+from .base import BaseOptions, BaseType
 
 
-class UnionMeta(type):
+class UnionOptions(BaseOptions):
-
+    types = ()  # type: List[Type[ObjectType]]
-    def __new__(cls, name, bases, attrs):
-        # Also ensure initialization is only performed for subclasses of
-        # Union
-        if not is_base_type(bases, UnionMeta):
-            return type.__new__(cls, name, bases, attrs)
-
-        options = Options(
-            attrs.pop('Meta', None),
-            name=name,
-            description=trim_docstring(attrs.get('__doc__')),
-            types=(),
-        )
-
-        assert (
-            isinstance(options.types, (list, tuple)) and
-            len(options.types) > 0
-        ), 'Must provide types for Union {}.'.format(options.name)
-
-        return type.__new__(cls, name, bases, dict(attrs, _meta=options))
-
-    def __str__(cls):  # noqa: N805
-        return cls._meta.name
 
 
-class Union(six.with_metaclass(UnionMeta, UnmountedType)):
+class Union(UnmountedType, BaseType):
     '''
     Union Type Definition
 
@@ -40,6 +16,16 @@ class Union(six.with_metaclass(UnionMeta, UnmountedType)):
     is used to describe what types are possible as well as providing a function
     to determine which type is actually used when the field is resolved.
     '''
+    @classmethod
+    def __init_subclass_with_meta__(cls, types=None, **options):
+        assert (
+            isinstance(types, (list, tuple)) and
+            len(types) > 0
+        ), 'Must provide types for Union {name}.'.format(name=cls.__name__)
+
+        _meta = UnionOptions(cls)
+        _meta.types = types
+        super(Union, cls).__init_subclass_with_meta__(_meta=_meta, **options)
 
     @classmethod
     def get_type(cls):