Add test for oneOf support and fix linting

Author: Cito

pyproject.toml

@@ -294,6 +294,7 @@ disallow_untyped_defs = false
 [tool.pyright]
 reportIncompatibleVariableOverride = false
 reportMissingTypeArgument = false
+reportReturnType = false
 reportUnknownArgumentType = false
 reportUnknownMemberType = false
 reportUnknownParameterType = false

src/graphql/utilities/build_client_schema.py

@@ -256,7 +256,7 @@ def build_input_object_def(
             fields=lambda: build_input_value_def_map(
                 input_object_introspection["inputFields"]
             ),
-            is_one_of=input_object_introspection.get("isOneOf"),
+            is_one_of=input_object_introspection.get("isOneOf", False),
         )
 
     type_builders: dict[str, Callable[[IntrospectionType], GraphQLNamedType]] = {

tests/utilities/test_build_client_schema.py

@@ -594,6 +594,22 @@ def builds_a_schema_with_specified_by_url():
 
         assert cycle_introspection(sdl) == sdl
 
+    def builds_a_schema_with_one_of_directive():
+        sdl = dedent(
+            """
+            type Query {
+              someField(someArg: SomeInputObject): String
+            }
+
+            input SomeInputObject @oneOf {
+              someInputField1: String
+              someInputField2: String
+            }
+            """
+        )
+
+        assert cycle_introspection(sdl) == sdl
+
     def can_use_client_schema_for_limited_execution():
         schema = build_schema(
             """

tests/utilities/test_get_introspection_query.py

@@ -2,6 +2,7 @@
 
 import re
 from typing import Pattern
+
 from graphql.language import parse
 from graphql.utilities import build_schema, get_introspection_query
 from graphql.validation import validate