Add @stream directive to schema

Author: robrichard

src/index.ts

@@ -63,6 +63,7 @@ export {
   GraphQLIncludeDirective,
   GraphQLSkipDirective,
   GraphQLDeferDirective,
+  GraphQLStreamDirective,
   GraphQLDeprecatedDirective,
   GraphQLSpecifiedByDirective,
   // "Enum" of Type Kinds

src/type/directives.ts

@@ -18,7 +18,7 @@ import {
   defineArguments,
   GraphQLNonNull,
 } from './definition';
-import { GraphQLBoolean, GraphQLString } from './scalars';
+import { GraphQLBoolean, GraphQLInt, GraphQLString } from './scalars';
 
 /**
  * Test if the given value is a GraphQL directive.
@@ -188,6 +188,31 @@ export const GraphQLDeferDirective = new GraphQLDirective({
   },
 });
 
+/**
+ * Used to conditionally stream list fields.
+ */
+export const GraphQLStreamDirective = new GraphQLDirective({
+  name: 'stream',
+  description:
+    'Directs the executor to stream plural fields when the `if` argument is true or undefined.',
+  locations: [DirectiveLocation.FIELD],
+  args: {
+    if: {
+      type: GraphQLBoolean,
+      description: 'Stream when true or undefined.',
+    },
+    label: {
+      type: GraphQLString,
+      description: 'Unique name',
+    },
+    initialCount: {
+      defaultValue: 0,
+      type: GraphQLInt,
+      description: 'Number of items to return immediately',
+    },
+  },
+});
+
 /**
  * Constant string used for default reason for a deprecation.
  */

src/type/index.ts

@@ -132,6 +132,7 @@ export {
   GraphQLIncludeDirective,
   GraphQLSkipDirective,
   GraphQLDeferDirective,
+  GraphQLStreamDirective,
   GraphQLDeprecatedDirective,
   GraphQLSpecifiedByDirective,
   // Constant Deprecation Reason