Use argument's default_value regardless if the input field is required (#1326)

* Use argument's default value regardless if the input field is required

* Add a test

* Format code

graphene/types/schema.py

@@ -26,7 +26,6 @@ from graphql import (
     GraphQLObjectType,
     GraphQLSchema,
     GraphQLString,
-    Undefined,
 )
 from graphql.execution import ExecutionContext
 from graphql.execution.values import get_argument_values
@@ -313,9 +312,7 @@ class TypeMap(dict):
                         arg_type,
                         out_name=arg_name,
                         description=arg.description,
-                        default_value=Undefined
-                        if isinstance(arg.type, NonNull)
-                        else arg.default_value,
+                        default_value=arg.default_value,
                     )
                 subscribe = field.wrap_subscribe(
                     self.get_function_for_type(

graphene/types/tests/test_type_map.py

@@ -6,6 +6,7 @@ from graphql.type import (
     GraphQLInputField,
     GraphQLInputObjectType,
     GraphQLInterfaceType,
+    GraphQLNonNull,
     GraphQLObjectType,
     GraphQLString,
 )
@@ -94,6 +95,21 @@ def test_objecttype():
     }
 
 
+def test_required_argument_with_default_value():
+    class MyObjectType(ObjectType):
+        foo = String(bar=String(required=True, default_value="x"))
+
+    type_map = create_type_map([MyObjectType])
+
+    graphql_type = type_map["MyObjectType"]
+    foo_field = graphql_type.fields["foo"]
+
+    bar_argument = foo_field.args["bar"]
+    assert bar_argument.default_value == "x"
+    assert isinstance(bar_argument.type, GraphQLNonNull)
+    assert bar_argument.type.of_type == GraphQLString
+
+
 def test_dynamic_objecttype():
     class MyObjectType(ObjectType):
         """Description"""