null default args in introspection query

Author: jaemk

graphql/execution/executor.py

@@ -10,7 +10,7 @@
 from ..error import GraphQLError, GraphQLLocatedError
 from ..pyutils.default_ordered_dict import DefaultOrderedDict
 from ..pyutils.ordereddict import OrderedDict
-from ..utils.undefined import Undefined
+from ..utils.undefined import Undefined, UndefinedDefaultValue
 from ..type import (GraphQLEnumType, GraphQLInterfaceType, GraphQLList,
                     GraphQLNonNull, GraphQLObjectType, GraphQLScalarType,
                     GraphQLSchema, GraphQLUnionType)
@@ -239,6 +239,9 @@ def resolve_field(exe_context, parent_type, source, field_asts, parent_info):
     executor = exe_context.executor
     result = resolve_or_error(resolve_fn_middleware, source, info, args, executor)
 
+    if result is UndefinedDefaultValue:
+        return Undefined
+
     return complete_value_catching_error(
         exe_context,
         return_type,

graphql/type/introspection.py

@@ -2,6 +2,7 @@
 
 from ..language.printer import print_ast
 from ..utils.ast_from_value import ast_from_value
+from ..utils.undefined import UndefinedDefaultValue
 from .definition import (GraphQLArgument, GraphQLEnumType, GraphQLEnumValue,
                          GraphQLField, GraphQLInputObjectType,
                          GraphQLInterfaceType, GraphQLList, GraphQLNonNull,
@@ -333,6 +334,15 @@ def input_fields(type, info):
     ])
 )
 
+
+def _resolve_default_value(input_value, *_):
+    if input_value.default_value is UndefinedDefaultValue:
+        return UndefinedDefaultValue
+    if input_value.default_value is None:
+        return None
+    return print_ast(ast_from_value(input_value.default_value, input_value))
+
+
 __InputValue = GraphQLObjectType(
     '__InputValue',
     description='Arguments provided to Fields or Directives and the input fields of an '
@@ -344,9 +354,7 @@ def input_fields(type, info):
         ('type', GraphQLField(GraphQLNonNull(__Type))),
         ('defaultValue', GraphQLField(
             type=GraphQLString,
-            resolver=lambda input_val, *_:
-            None if input_val.default_value is None
-            else print_ast(ast_from_value(input_val.default_value, input_val))
+            resolver=_resolve_default_value,
         ))
     ]))
 

graphql/utils/tests/test_build_client_schema.py

@@ -54,6 +54,9 @@ def test_builds_a_simple_schema_with_both_operation_types():
         fields={
             'setString': GraphQLField(GraphQLString, description='Set the string field', args={
                 'value': GraphQLArgument(GraphQLString)
+            }),
+            'setStringDefault': GraphQLField(GraphQLString, description='Set the string field', args={
+                'value_default': GraphQLArgument(GraphQLString, default_value=None)
             })
         }
     )
@@ -387,6 +390,15 @@ def test_builds_a_schema_with_field_arguments_with_default_values():
                         )
                     }
                 )),
+                ('defaultNullInt', GraphQLField(
+                    GraphQLString,
+                    args={
+                        'intArg': GraphQLArgument(
+                            GraphQLInt,
+                            default_value=None
+                        )
+                    }
+                )),
                 ('defaultList', GraphQLField(
                     GraphQLString,
                     args={