make sure types can default to null

Author: jaemk

graphql/utils/is_valid_literal_value.py

@@ -17,7 +17,7 @@ def is_valid_literal_value(type, value_ast):
     if not value_ast:
         return _empty_list
 
-    if isinstance(value_ast, ast.Variable):
+    if isinstance(value_ast, (ast.Variable, ast.NullValue)):
         return _empty_list
 
     if isinstance(type, GraphQLList):
@@ -60,9 +60,6 @@ def get_field_ast_value(field_name):
 
     assert isinstance(type, (GraphQLScalarType, GraphQLEnumType)), 'Must be input type'
 
-    if isinstance(value_ast, ast.NullValue):
-        return _empty_list
-
     parse_result = type.parse_literal(value_ast)
     if parse_result is None:
         return [u'Expected type "{}", found {}.'.format(type.name, print_ast(value_ast))]

graphql/validation/tests/test_default_values_of_correct_type.py

@@ -44,7 +44,9 @@ def test_variables_with_valid_default_values():
     query WithDefaultValues(
         $a: Int = 1,
         $b: String = "ok",
-        $c: ComplexInput = { requiredField: true, intField: 3 }
+        $c: ComplexInput = { requiredField: true, intField: 3 },
+        $d: ComplexInputl = null,
+        $d: [Int] = null
     ) {
         dog { name }
     }