From 9eea47fcc3721d2f0d5918e171c4d73ac2a4b9e3 Mon Sep 17 00:00:00 2001
From: carmelid <carmelid@gmail.com>
Date: Tue, 16 Jul 2019 16:33:28 +0200
Subject: [PATCH] fix: default merged resolver behavior for nullable fields

---
 src/stitching/defaultMergedResolver.ts | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/stitching/defaultMergedResolver.ts b/src/stitching/defaultMergedResolver.ts
index cbf754a03a8..5e5ca3822ea 100644
--- a/src/stitching/defaultMergedResolver.ts
+++ b/src/stitching/defaultMergedResolver.ts
@@ -1,4 +1,4 @@
-import { GraphQLFieldResolver, responsePathAsArray } from 'graphql';
+import { GraphQLFieldResolver, GraphQLNonNull, responsePathAsArray } from 'graphql';
 import { locatedError } from 'graphql/error';
 import { getErrorsFromParent, annotateWithChildrenErrors } from './errors';
 import { getResponseKeyFromInfo } from './getResponseKeyFromInfo';
@@ -20,7 +20,8 @@ const defaultMergedResolver: GraphQLFieldResolver<any, any> = (parent, args, con
 
   let result = parent[responseKey];
 
-  if (result == null) {
+  // Only replace the aliased result with the parent result if the field is non-nullable
+  if (result == null && info.returnType instanceof GraphQLNonNull) {
     result = parent[info.fieldName];
   }