Detect args passed to directive without args (fixes #63)

Author: Cito

README.md

@@ -16,7 +16,7 @@ The current version 3.0.0b0 of GraphQL-core is up-to-date
 with GraphQL.js version 14.5.0.
 
 All parts of the API are covered by an extensive test suite
-of currently 1981 unit tests.
+of currently 1983 unit tests.
 
 
 ## Documentation

src/graphql/validation/rules/known_argument_names.py

@@ -60,7 +60,7 @@ def __init__(self, context: Union[ValidationContext, SDLValidationContext]) -> N
     def enter_directive(self, directive_node: DirectiveNode, *_args):
         directive_name = directive_node.name.value
         known_args = self.directive_args.get(directive_name)
-        if directive_node.arguments and known_args:
+        if directive_node.arguments and known_args is not None:
             for arg_node in directive_node.arguments:
                 arg_name = arg_node.name.value
                 if arg_name not in known_args:

tests/validation/test_known_argument_names.py

@@ -120,6 +120,25 @@ def field_args_are_invalid():
             [unknown_directive_arg("unless", "skip", [], 3, 25)],
         )
 
+    def directive_without_args_is_valid():
+        assert_valid(
+            """
+            {
+                dog @onField
+            }
+            """
+        )
+
+    def arg_passed_to_directive_without_args_is_reported():
+        assert_errors(
+            """
+            {
+                dog @onField(if: true)
+            }
+            """,
+            [unknown_directive_arg("if", "onField", [], 3, 30)],
+        )
+
     def misspelled_directive_args_are_reported():
         assert_errors(
             """