Fixed the error passing situation with query merging

CHANGELOG.md

@@ -5,7 +5,7 @@ Expect active development and potentially significant breaking changes in the `0
 ### vNEXT
 
 - Avoid extra `assign` when there are no optimistic updates present. [PR #597]((https://github.com/apollostack/apollo-client/pull/597)
-- ...
+- Fixed issue with error passing with query merging. [PR #589](https://github.com/apollostack/apollo-client/pull/589) and [Issue #551](https://github.com/apollostack/apollo-client/issues/551).
 
 ### v0.4.13
 

src/batching/queryMerging.ts

@@ -109,7 +109,7 @@ export function unpackMergedResult(
       topLevel: true,
     });
 
-    return { data: unpackedData };
+    return assign({}, result, { data: unpackedData });
   });
 
   return resultArray;

test/queryMerging.ts

@@ -831,6 +831,39 @@ describe('Query merging', () => {
     assert.deepEqual(unpackedResults[1], { data: secondResult });
   });
 
+  it('should unpack with errors in the result', () => {
+    const query = gql`
+      query authorNames {
+        author {
+          firstName
+          lastName
+        }
+      }`;
+    const graphQLError = new Error('This is some kind of graphql error.');
+    const result = {
+      data: {
+        author: {
+          firstName: 'Dhaivat',
+          lastName: 'Pandya',
+        },
+      },
+      errors: [ graphQLError ],
+    };
+    const composedResult = {
+      data: {
+        ___authorNames___requestIndex_0___fieldIndex_0: {
+          firstName: 'Dhaivat',
+          lastName: 'Pandya',
+        },
+      },
+      errors: [ graphQLError ],
+    };
+    const requests = [{ query }];
+    const unpackedResults = unpackMergedResult(composedResult, requests);
+    assert.equal(unpackedResults.length, 1);
+    assert.deepEqual(unpackedResults[0], result);
+  });
+
   describe('unpackDataForRequest', () => {
     const unpackQueryResult = (query: Document, data: Object) => {
       return unpackDataForRequest({
@@ -1210,5 +1243,6 @@ describe('Query merging', () => {
       });
       assert.deepEqual(unpackedData, result);
     });
+
   });
 });