extend_schema: Do not modify standard directives

Replicates graphql/graphql-js@fdc3555

Author: Cito

src/graphql/utilities/extend_schema.py

@@ -80,6 +80,7 @@
     is_non_null_type,
     is_object_type,
     is_scalar_type,
+    is_specified_directive,
     is_specified_scalar_type,
     is_union_type,
     specified_scalar_types,
@@ -257,6 +258,10 @@ def replace_named_type(self, type_: GraphQLNamedType) -> GraphQLNamedType:
 
     # noinspection PyShadowingNames
     def replace_directive(self, directive: GraphQLDirective) -> GraphQLDirective:
+        if is_specified_directive(directive):
+            # Builtin directives are not extended.
+            return directive
+
         kwargs = directive.to_kwargs()
         return GraphQLDirective(
             **merge_kwargs(

tests/utilities/test_extend_schema.py

@@ -23,6 +23,7 @@
     assert_object_type,
     assert_scalar_type,
     assert_union_type,
+    specified_directives,
     validate_schema,
 )
 from graphql.utilities import build_schema, concat_ast, extend_schema, print_schema
@@ -102,6 +103,38 @@ def can_be_used_for_limited_execution():
         )
         assert result == ({"newField": "123"}, None)
 
+    def does_not_modify_built_in_types_and_directives():
+        schema = build_schema(
+            """
+              type Query {
+                str: String
+                int: Int
+                float: Float
+                id: ID
+                bool: Boolean
+              }
+            """
+        )
+
+        extension_sdl = dedent(
+            """
+            extend type Query {
+              foo: String
+            }
+            """
+        )
+
+        extended_schema = extend_schema(schema, parse(extension_sdl))
+
+        # built-ins are used
+        assert extended_schema.get_type("Int") is GraphQLInt
+        assert extended_schema.get_type("Float") is GraphQLFloat
+        assert extended_schema.get_type("String") is GraphQLString
+        assert extended_schema.get_type("Boolean") is GraphQLBoolean
+        assert extended_schema.get_type("ID") is GraphQLID
+
+        assert extended_schema.directives == specified_directives
+
     def extends_objects_by_adding_new_fields():
         schema = build_schema(
             '''