Fix bug in does_fragment_condition_match (fix #56)

Author: dittos

graphql/core/execution/base.py

@@ -167,7 +167,7 @@ def should_include_node(ctx, directives):
 
 def does_fragment_condition_match(ctx, fragment, type_):
     conditional_type = type_from_ast(ctx.schema, fragment.type_condition)
-    if type(conditional_type) == type(type_):
+    if conditional_type == type_:
         return True
     if isinstance(conditional_type, (GraphQLInterfaceType, GraphQLUnionType)):
         return conditional_type.is_possible_type(type_)

tests/core_execution/test_union_interface.py

@@ -247,3 +247,25 @@ def test_allows_fragment_conditions_to_be_abstract_types():
             {'__typename': 'Dog', 'name': 'Odie', 'barks': True}
         ]
     }
+
+
+def test_only_include_fields_from_matching_fragment_condition():
+    ast = parse('''
+      {
+        pets { ...PetFields }
+      }
+      fragment PetFields on Pet {
+        __typename
+        ... on Dog {
+          name
+        }
+      }
+    ''')
+    result = execute(schema, john, ast)
+    assert not result.errors
+    assert result.data == {
+        'pets': [
+            {'__typename': 'Cat'},
+            {'__typename': 'Dog', 'name': 'Odie'}
+        ],
+    }