Test that SchemaDirectiveVisitor can be used as a no-op visitor.

src/test/testDirectives.ts

@@ -35,6 +35,8 @@ enum Gender @enumTypeDirective {
   MALE
 }
 
+scalar Date @dateDirective(tz: "utc")
+
 interface Named @interfaceDirective {
   name: String! @interfaceFieldDirective
 }
@@ -108,6 +110,8 @@ describe('@directives', () => {
       ['enumValueDirective'],
     );
 
+    checkDirectives(schema.getType('Date'), ['dateDirective']);
+
     checkDirectives(schema.getType('Named'), ['interfaceDirective'], {
       name: ['interfaceFieldDirective'],
     });
@@ -230,6 +234,32 @@ describe('@directives', () => {
     });
   });
 
+  it('can use SchemaDirectiveVisitor as a no-op visitor', () => {
+    const schema = makeExecutableSchema({ typeDefs });
+
+    // Since SchemaDirectiveVisitor implements no-op versions of all the
+    // visitor methods, this should work, though I'll admit I wrote this test
+    // partly to keep the code coverage tool happy.
+    SchemaDirectiveVisitor.visitSchema(schema, {
+      schemaDirective: SchemaDirectiveVisitor,
+      queryTypeDirective: SchemaDirectiveVisitor,
+      queryFieldDirective: SchemaDirectiveVisitor,
+      enumTypeDirective: SchemaDirectiveVisitor,
+      enumValueDirective: SchemaDirectiveVisitor,
+      dateDirective: SchemaDirectiveVisitor,
+      interfaceDirective: SchemaDirectiveVisitor,
+      interfaceFieldDirective: SchemaDirectiveVisitor,
+      inputTypeDirective: SchemaDirectiveVisitor,
+      inputFieldDirective: SchemaDirectiveVisitor,
+      mutationTypeDirective: SchemaDirectiveVisitor,
+      mutationArgumentDirective: SchemaDirectiveVisitor,
+      mutationMethodDirective: SchemaDirectiveVisitor,
+      objectTypeDirective: SchemaDirectiveVisitor,
+      objectFieldDirective: SchemaDirectiveVisitor,
+      unionDirective: SchemaDirectiveVisitor,
+    });
+  });
+
   it('can handle all kinds of undeclared arguments', () => {
     const schemaText = `
     enum SpineEnum {