subscribe: once execution starts....

src/execution/__tests__/subscribe-test.ts

@@ -427,6 +427,7 @@ describe('Subscription Initialization Phase', () => {
 
     const result = subscribe({ schema, document });
     expectJSON(result).toDeepEqual({
+      data: null,
       errors: [
         {
           message:
@@ -451,6 +452,7 @@ describe('Subscription Initialization Phase', () => {
 
     const result = subscribe({ schema, document });
     expectJSON(result).toDeepEqual({
+      data: null,
       errors: [
         {
           message: 'The subscription field "unknownField" is not defined.',
@@ -477,6 +479,7 @@ describe('Subscription Initialization Phase', () => {
 
   it('throws an error if subscribe does not return an iterator', async () => {
     const expectedResult = {
+      data: null,
       errors: [
         {
           message:
@@ -498,6 +501,7 @@ describe('Subscription Initialization Phase', () => {
 
   it('resolves to an error for subscription resolver errors', async () => {
     const expectedResult = {
+      data: null,
       errors: [
         {
           message: 'test error',

src/execution/execute.ts

@@ -1141,12 +1141,15 @@ export function createSourceEventStream(
   try {
     const eventStream = executeSubscription(exeContext);
     if (isPromise(eventStream)) {
-      return eventStream.then(undefined, (error) => ({ errors: [error] }));
+      return eventStream.then(undefined, (error) => ({
+        data: null,
+        errors: [error],
+      }));
     }
 
     return eventStream;
   } catch (error) {
-    return { errors: [error] };
+    return { data: null, errors: [error] };
   }
 }