Fixed flexible resolving in return type

graphene/types/interface.py

@@ -48,7 +48,11 @@ class Interface(six.with_metaclass(InterfaceMeta)):
     when the field is resolved.
     '''
 
-    resolve_type = None
+    @classmethod
+    def resolve_type(cls, instance, context, info):
+        from .objecttype import ObjectType
+        if isinstance(instance, ObjectType):
+            return type(instance)
 
     def __init__(self, *args, **kwargs):
         raise Exception("An Interface cannot be intitialized")

graphene/types/objecttype.py

@@ -63,10 +63,7 @@ class ObjectType(six.with_metaclass(ObjectTypeMeta)):
     have a name, but most importantly describe their fields.
     '''
 
-    @classmethod
-    def is_type_of(cls, root, context, info):
-        if isinstance(root, cls):
-            return True
+    is_type_of = None
 
     def __init__(self, *args, **kwargs):
         # ObjectType acting as container

graphene/types/tests/test_query.py

@@ -41,6 +41,10 @@ def test_query_wrong_default_value():
     class MyType(ObjectType):
         field = String()
 
+        @classmethod
+        def is_type_of(cls, root, context, info):
+            return isinstance(root, MyType)
+
     class Query(ObjectType):
         hello = Field(MyType, default_value='hello')
 
@@ -153,6 +157,30 @@ def test_query_middlewares():
     assert executed.data == {'hello': 'dlroW', 'other': 'rehto'}
 
 
+def test_objecttype_on_instances():
+    class Ship:
+        def __init__(self, name):
+            self.name = name
+
+    class ShipType(ObjectType):
+        name = String(description="Ship name", required=True)
+
+        def resolve_name(self, context, args, info):
+            # Here self will be the Ship instance returned in resolve_ship
+            return self.name
+
+    class Query(ObjectType):
+        ship = Field(ShipType)
+
+        def resolve_ship(self, context, args, info):
+            return Ship(name='xwing')
+
+    schema = Schema(query=Query)
+    executed = schema.execute('{ ship { name } }')
+    assert not executed.errors
+    assert executed.data == {'ship': {'name': 'xwing'}}
+
+
 def test_big_list_query_benchmark(benchmark):
     big_list = range(10000)
 

graphene/types/typemap.py

@@ -6,6 +6,7 @@ from graphql import (GraphQLArgument, GraphQLBoolean, GraphQLField,
                      GraphQLFloat, GraphQLID, GraphQLInputObjectField,
                      GraphQLInt, GraphQLList, GraphQLNonNull, GraphQLString)
 from graphql.type import GraphQLEnumValue
+from graphql.execution.executor import get_default_resolve_type_fn
 from graphql.type.typemap import GraphQLTypeMap
 
 from ..utils.str_converters import to_camel_case
@@ -26,11 +27,14 @@ def is_graphene_type(_type):
         return True
 
 
-def resolve_type(resolve_type_func, map, root, args, info):
-    _type = resolve_type_func(root, args, info)
+def resolve_type(resolve_type_func, map, root, context, info):
+    _type = resolve_type_func(root, context, info)
     # assert inspect.isclass(_type) and issubclass(_type, ObjectType), (
     #     'Received incompatible type "{}".'.format(_type)
     # )
+    if not _type:
+        return get_default_resolve_type_fn(root, context, info, info.return_type)
+
     if inspect.isclass(_type) and issubclass(_type, ObjectType):
         graphql_type = map.get(_type._meta.name)
         assert graphql_type and graphql_type.graphene_type == _type