set up new directive

Author: robrichard

src/type/directives.js

@@ -192,6 +192,30 @@ export const GraphQLDeferDirective = new GraphQLDirective({
   },
 });
 
+/**
+ * Used to conditionally defer fragments.
+ */
+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: GraphQLNonNull(GraphQLString),
+      description: 'Unique name',
+    },
+    initial_count: {
+      type: GraphQLNonNull(GraphQLInt),
+      description: 'Number of items to return immediately',
+    },
+  },
+});
+
 /**
  * Constant string used for default reason for a deprecation.
  */
@@ -220,7 +244,6 @@ export const GraphQLDeprecatedDirective = new GraphQLDirective({
 export const specifiedDirectives = Object.freeze([
   GraphQLIncludeDirective,
   GraphQLSkipDirective,
-  GraphQLDeferDirective,
   GraphQLDeprecatedDirective,
 ]);
 

src/type/index.js

@@ -79,6 +79,7 @@ export {
   GraphQLIncludeDirective,
   GraphQLSkipDirective,
   GraphQLDeferDirective,
+  GraphQLStreamDirective,
   GraphQLDeprecatedDirective,
   // Constant Deprecation Reason
   DEFAULT_DEPRECATION_REASON,

src/type/schema.js

@@ -24,6 +24,8 @@ import {
 import { __Schema } from './introspection';
 import {
   GraphQLDirective,
+  GraphQLStreamDirective,
+  GraphQLDeferDirective,
   isDirective,
   specifiedDirectives,
 } from './directives';
@@ -136,6 +138,7 @@ export class GraphQLSchema {
   __validationErrors: ?$ReadOnlyArray<GraphQLError>;
   // Referenced by execute()
   __experimentalDeferFragmentSpreads: boolean;
+  __experimentalStream: boolean;
 
   constructor(config: $ReadOnly<GraphQLSchemaConfig>): void {
     // If this schema was built from a source known to be valid, then it may be
@@ -163,14 +166,27 @@ export class GraphQLSchema {
     this.astNode = config.astNode;
     this.extensionASTNodes = config.extensionASTNodes;
 
-    this.__experimentalDeferFragmentSpreads =
-      config.experimentalDeferFragmentSpreads || false;
+    this.__experimentalStream = config.experimentalStream || false;
     this._queryType = config.query;
     this._mutationType = config.mutation;
     this._subscriptionType = config.subscription;
     // Provide specified directives (e.g. @include and @skip) by default.
     this._directives = config.directives || specifiedDirectives;
 
+    if (config.experimentalDeferFragmentSpreads) {
+      this.__experimentalDeferFragmentSpreads = true;
+      this._directives = [].concat(this._directives, [GraphQLDeferDirective]);
+    } else {
+      this.__experimentalDeferFragmentSpreads = false;
+    }
+
+    if (config.experimentalStream) {
+      this.__experimentalStream = true;
+      this._directives = [].concat(this._directives, [GraphQLStreamDirective]);
+    } else {
+      this.__experimentalStream = false;
+    }
+
     // Build type map now to detect any errors within this schema.
     const initialTypes: Array<?GraphQLNamedType> = [
       this._queryType,
@@ -320,6 +336,18 @@ export type GraphQLSchemaValidationOptions = {|
    * Default: false
    */
   experimentalDeferFragmentSpreads?: boolean,
+
+  /**
+   *
+   * EXPERIMENTAL:
+   *
+   * If enabled, items from a plural fields with @stream directive
+   * are not returned from the iniital query and each item is returned
+   * in a patch after the initial result from the synchronous query.
+   *
+   * Default: false
+   */
+  experimentalStream?: boolean,
 |};
 
 export type GraphQLSchemaConfig = {|

src/utilities/__tests__/findBreakingChanges-test.js

@@ -7,6 +7,7 @@ import { GraphQLSchema } from '../../type/schema';
 import {
   GraphQLSkipDirective,
   GraphQLDeferDirective,
+  GraphQLStreamDirective,
   GraphQLIncludeDirective,
   GraphQLDeprecatedDirective,
 } from '../../type/directives';
@@ -795,6 +796,7 @@ describe('findBreakingChanges', () => {
         GraphQLSkipDirective,
         GraphQLIncludeDirective,
         GraphQLDeferDirective,
+        GraphQLStreamDirective,
       ],
     });
 

src/utilities/buildASTSchema.js

@@ -17,6 +17,7 @@ import {
   GraphQLSkipDirective,
   GraphQLIncludeDirective,
   GraphQLDeferDirective,
+  GraphQLStreamDirective,
   GraphQLDeprecatedDirective,
 } from '../type/directives';
 
@@ -110,6 +111,10 @@ export function buildASTSchema(
     directives.push(GraphQLDeferDirective);
   }
 
+  if (!directives.some(directive => directive.name === 'stream')) {
+    directives.push(GraphQLStreamDirective);
+  }
+
   if (!directives.some(directive => directive.name === 'deprecated')) {
     directives.push(GraphQLDeprecatedDirective);
   }

src/validation/__tests__/harness.js

@@ -12,6 +12,7 @@ import {
   GraphQLIncludeDirective,
   GraphQLSkipDirective,
   GraphQLDeferDirective,
+  GraphQLStreamDirective,
 } from '../../type/directives';
 import {
   GraphQLInt,
@@ -364,6 +365,7 @@ export const testSchema = new GraphQLSchema({
     GraphQLIncludeDirective,
     GraphQLSkipDirective,
     GraphQLDeferDirective,
+    GraphQLStreamDirective,
     new GraphQLDirective({
       name: 'onQuery',
       locations: ['QUERY'],