Add @defer directive to schema

src/index.ts

@@ -62,6 +62,7 @@ export {
   specifiedDirectives,
   GraphQLIncludeDirective,
   GraphQLSkipDirective,
+  GraphQLDeferDirective,
   GraphQLDeprecatedDirective,
   GraphQLSpecifiedByDirective,
   // "Enum" of Type Kinds

src/type/directives.ts

@@ -153,6 +153,29 @@ export const GraphQLSkipDirective: GraphQLDirective = new GraphQLDirective({
   },
 });
 
+/**
+ * Used to conditionally defer fragments.
+ */
+export const GraphQLDeferDirective = new GraphQLDirective({
+  name: 'defer',
+  description:
+    'Directs the executor to defer this fragment when the `if` argument is true or undefined.',
+  locations: [
+    DirectiveLocation.FRAGMENT_SPREAD,
+    DirectiveLocation.INLINE_FRAGMENT,
+  ],
+  args: {
+    if: {
+      type: GraphQLBoolean,
+      description: 'Deferred when true or undefined.',
+    },
+    label: {
+      type: GraphQLString,
+      description: 'Unique name',
+    },
+  },
+});
+
 /**
  * Constant string used for default reason for a deprecation.
  */

src/type/index.ts

@@ -133,6 +133,7 @@ export {
   specifiedDirectives,
   GraphQLIncludeDirective,
   GraphQLSkipDirective,
+  GraphQLDeferDirective,
   GraphQLDeprecatedDirective,
   GraphQLSpecifiedByDirective,
   // Constant Deprecation Reason