Check for __typename of objects (solves #25)

README.md

@@ -13,7 +13,7 @@ a query language for APIs created by Facebook.
 [![Code Style](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/ambv/black)
 
 The current version 1.0.1 of GraphQL-core-next is up-to-date with GraphQL.js version
-14.0.2. All parts of the API are covered by an extensive test suite of currently 1679
+14.0.2. All parts of the API are covered by an extensive test suite of currently 1681
 unit tests.
 
 
@@ -187,9 +187,9 @@ Design goals for the GraphQL-core-next library are:
   library and language versions
 * to be very close to the GraphQL.js reference implementation, while still using a
   Pythonic API and code style
-* making use of Python type hints, similar to how GraphQL.js makes use of Flow
-* using of [black](https://github.com/ambv/black) for automatic code formatting
-* replicate the complete Mocha-based test suite of GraphQL.js using
+* to make extensive use of Python type hints, similar to how GraphQL.js makes use of Flow
+* to use [black](https://github.com/ambv/black) for automatic code formatting
+* to replicate the complete Mocha-based test suite of GraphQL.js using
   [pytest](https://docs.pytest.org/)
 
 Some restrictions (mostly in line with the design goals):

graphql/execution/execute.py

@@ -1108,8 +1108,14 @@ def default_resolve_type_fn(
     """
 
     # First, look for `__typename`.
-    if isinstance(value, dict) and isinstance(value.get("__typename"), str):
-        return value["__typename"]
+    type_name = (
+        value.get("__typename")
+        if isinstance(value, dict)
+        # need to de-mangle the attribute assumed to be "private" in Python
+        else getattr(value, f"_{value.__class__.__name__}__typename", None)
+    )
+    if isinstance(type_name, str):
+        return type_name
 
     # Otherwise, test each possible type.
     possible_types = info.schema.get_possible_types(abstract_type)

tests/utilities/test_build_ast_schema.py

@@ -369,7 +369,8 @@ def can_build_recursive_union():
         msg = str(exc_info.value)
         assert msg == "Hello types must be GraphQLObjectType objects."
 
-    def specifying_union_type_using_typename():
+    def describe_specifying_union_type_using_typename():
+
         schema = build_schema(
             """
             type Query {
@@ -401,19 +402,33 @@ def specifying_union_type_using_typename():
             }
             """
 
-        root = {
-            "fruits": [
-                {"color": "green", "__typename": "Apple"},
-                {"length": 5, "__typename": "Banana"},
-            ]
-        }
+        expected = ({"fruits": [{"color": "green"}, {"length": 5}]}, None)
 
-        assert graphql_sync(schema, query, root) == (
-            {"fruits": [{"color": "green"}, {"length": 5}]},
-            None,
-        )
+        def using_dicts():
+            root = {
+                "fruits": [
+                    {"color": "green", "__typename": "Apple"},
+                    {"length": 5, "__typename": "Banana"},
+                ]
+            }
+
+            assert graphql_sync(schema, query, root) == expected
+
+        def using_objects():
+            class Apple:
+                __typename = "Apple"
+                color = "green"
+
+            class Banana:
+                __typename = "Banana"
+                length = 5
+
+            class Root:
+                fruits = [Apple(), Banana()]
+
+            assert graphql_sync(schema, query, Root()) == expected
 
-    def specifying_interface_type_using_typename():
+    def describe_specifying_interface_type_using_typename():
         schema = build_schema(
             """
             type Query {
@@ -450,18 +465,7 @@ def specifying_interface_type_using_typename():
             }
             """
 
-        root = {
-            "characters": [
-                {"name": "Han Solo", "totalCredits": 10, "__typename": "Human"},
-                {
-                    "name": "R2-D2",
-                    "primaryFunction": "Astromech",
-                    "__typename": "Droid",
-                },
-            ]
-        }
-
-        assert graphql_sync(schema, query, root) == (
+        expected = (
             {
                 "characters": [
                     {"name": "Han Solo", "totalCredits": 10},
@@ -471,6 +475,36 @@ def specifying_interface_type_using_typename():
             None,
         )
 
+        def using_dicts():
+            root = {
+                "characters": [
+                    {"name": "Han Solo", "totalCredits": 10, "__typename": "Human"},
+                    {
+                        "name": "R2-D2",
+                        "primaryFunction": "Astromech",
+                        "__typename": "Droid",
+                    },
+                ]
+            }
+
+            assert graphql_sync(schema, query, root) == expected
+
+        def using_objects():
+            class Human:
+                __typename = "Human"
+                name = "Han Solo"
+                totalCredits = 10
+
+            class Droid:
+                __typename = "Droid"
+                name = "R2-D2"
+                primaryFunction = "Astromech"
+
+            class Root:
+                characters = [Human(), Droid()]
+
+            assert graphql_sync(schema, query, Root()) == expected
+
     def custom_scalar():
         sdl = dedent(
             """