Fix build after #1467 (#2014)

Author: IvanGoncharov

src/subscription/__tests__/subscribe-test.js

@@ -434,9 +434,9 @@ describe('Subscription Initialization Phase', () => {
 
   it('resolves to an error for source event stream resolver errors', async () => {
     // Returning an error
-    const subscriptionReturningErrorSchema = emailSchemaWithResolvers(() => {
-      return new Error('test error');
-    });
+    const subscriptionReturningErrorSchema = emailSchemaWithResolvers(
+      () => new Error('test error'),
+    );
     await testReportsError(subscriptionReturningErrorSchema);
 
     // Throwing an error
@@ -446,10 +446,8 @@ describe('Subscription Initialization Phase', () => {
     await testReportsError(subscriptionThrowingErrorSchema);
 
     // Resolving to an error
-    const subscriptionResolvingErrorSchema = emailSchemaWithResolvers(
-      async () => {
-        return new Error('test error');
-      },
+    const subscriptionResolvingErrorSchema = emailSchemaWithResolvers(() =>
+      Promise.resolve(new Error('test error')),
     );
     await testReportsError(subscriptionResolvingErrorSchema);
 
@@ -1013,6 +1011,7 @@ describe('Subscription Publish Phase', () => {
       `),
     );
 
+    // $FlowFixMe
     const payload1 = await subscription.next();
     expect(payload1).to.deep.equal({
       done: false,

src/subscription/subscribe.js

@@ -151,16 +151,15 @@ function subscribeImpl(
 
   // Resolve the Source Stream, then map every source value to a
   // ExecutionResult value as described above.
-  return sourcePromise.then(
-    resultOrStream =>
-      // Note: Flow can't refine isAsyncIterable, so explicit casts are used.
-      isAsyncIterable(resultOrStream)
-        ? mapAsyncIterator(
-            ((resultOrStream: any): AsyncIterable<mixed>),
-            mapSourceToResponse,
-            reportGraphQLError,
-          )
-        : ((resultOrStream: any): ExecutionResult),
+  return sourcePromise.then(resultOrStream =>
+    // Note: Flow can't refine isAsyncIterable, so explicit casts are used.
+    isAsyncIterable(resultOrStream)
+      ? mapAsyncIterator(
+          ((resultOrStream: any): AsyncIterable<mixed>),
+          mapSourceToResponse,
+          reportGraphQLError,
+        )
+      : ((resultOrStream: any): ExecutionResult),
   );
 }