[fix] allow renaming of subscription root fields

CHANGELOG.md

@@ -14,6 +14,10 @@
   [@freiksenet](https://github.com/freiksenet) in [#1003](https://github.com/apollographql/graphql-tools/pull/1003)
 * Allow user-provided `buildSchema` options.  <br/>
   [@trevor-scheer](https://github.com/trevor-scheer) in [#1154](https://github.com/apollographql/graphql-tools/pull/1154)
+* Fix `delegateToSchema` to allow delegation to subscriptions with different root field names, allows
+  the use of the `RenameRootFields` transform with subscriptions,
+  pull request [#1104](https://github.com/apollographql/graphql-tools/pull/1104), fixes
+  [#997](https://github.com/apollographql/graphql-tools/issues/997).  <br/>
 
 ### 4.0.4
 

src/stitching/delegateToSchema.ts

@@ -125,12 +125,11 @@ async function delegateToSchemaImplementation(
     // "subscribe" to the subscription result and map the result through the transforms
     return mapAsyncIterator<ExecutionResult, any>(executionResult, result => {
       const transformedResult = applyResultTransforms(result, transforms);
-      const subscriptionKey = Object.keys(result.data)[0];
 
-      // for some reason the returned transformedResult needs to be nested inside the root subscription field
-      // does not work otherwise...
+      // wrap with fieldName to return for an additional round of resolutioon
+      // with payload as rootValue
       return {
-        [subscriptionKey]: transformedResult,
+        [info.fieldName]: transformedResult,
       };
     });
   }

src/test/testAlternateMergeSchemas.ts

@@ -1,15 +1,28 @@
 /* tslint:disable:no-unused-expression */
 
 import { expect } from 'chai';
-import { graphql, GraphQLSchema } from 'graphql';
+import {
+  graphql,
+  GraphQLSchema,
+  ExecutionResult,
+  subscribe,
+  parse,
+} from 'graphql';
 import mergeSchemas from '../stitching/mergeSchemas';
 import {
   transformSchema,
   FilterRootFields,
   RenameTypes,
   RenameRootFields,
 } from '../transforms';
-import { propertySchema, bookingSchema } from './testingSchemas';
+import {
+  propertySchema,
+  bookingSchema,
+  subscriptionSchema,
+  subscriptionPubSub,
+  subscriptionPubSubTrigger,
+} from './testingSchemas';
+import { forAwaitEach } from 'iterall';
 
 let linkSchema = `
   """
@@ -78,11 +91,23 @@ describe('merge schemas through transforms', () => {
         (operation: string, name: string) => `Bookings_${name}`,
       ),
     ]);
+    const transformedSubscriptionSchema = transformSchema(subscriptionSchema, [
+      new FilterRootFields(
+        (operation: string, rootField: string) =>
+          // must include a Query type otherwise graphql will error
+          'Query.notifications' === `${operation}.${rootField}` ||
+          'Subscription.notifications' === `${operation}.${rootField}`,
+      ),
+      new RenameTypes((name: string) => `Subscriptions_${name}`),
+      new RenameRootFields(
+        (operation: string, name: string) => `Subscriptions_${name}`),
+    ]);
 
     mergedSchema = mergeSchemas({
       schemas: [
         transformedPropertySchema,
         transformedBookingSchema,
+        transformedSubscriptionSchema,
         linkSchema,
       ],
       resolvers: {
@@ -234,6 +259,41 @@ describe('merge schemas through transforms', () => {
       },
     });
   });
+
+  it('local subscriptions should work even if root fields are renamed', done => {
+    const originalNotification = {
+      notifications: {
+        text: 'Hello world',
+      },
+    };
+
+    const transformedNotification = {
+      Subscriptions_notifications: originalNotification.notifications
+    };
+
+    const subscription = parse(`
+      subscription Subscription {
+        Subscriptions_notifications {
+          text
+        }
+      }
+    `);
+
+    let notificationCnt = 0;
+    subscribe(mergedSchema, subscription)
+      .then(results => {
+        forAwaitEach(
+          results as AsyncIterable<ExecutionResult>,
+          (result: ExecutionResult) => {
+            expect(result).to.have.property('data');
+            expect(result.data).to.deep.equal(transformedNotification);
+            !notificationCnt++ ? done() : null;
+          },
+        ).catch(done);
+      }).then(() => {
+        subscriptionPubSub.publish(subscriptionPubSubTrigger, originalNotification);
+      }).catch(done);
+  });
 });
 
 describe('interface resolver inheritance', () => {