Revert 27cc028 (#1983) (#2432)

* Revert 27cc028 (#1983)

* Changelog adjustments

* Grammer fix

* Preserve some test changes

Changelog.md

@@ -6,6 +6,16 @@
   provider value is reset to the previous value it had after its children are
   walked. <br/>
   [@mitchellhamilton](https://github.com/mitchellhamilton) in [#2304](https://github.com/apollographql/react-apollo/pull/2304)
+- Revert: <br/>
+  When a query failed on the first result, the query result `data` was being
+  returned as `undefined`. This behavior has been changed so that `data` is
+  returned as an empty object. This makes checking for data (e.g.
+  instead of `data && data.user` you can just check `data.user`) and
+  destructring (e.g. `{ data: { user } }`) easier. **Note:** this could
+  potentially hurt applications that are relying on a falsey check of `data`
+  to see if any query errors have occurred. A better (and supported) way to
+  check for errors is to use the result `errors` property. <br/>
+  [#1983](https://github.com/apollographql/react-apollo/pull/1983)
 
 ## 2.2.1 (September 26, 2018)
 

src/Query.tsx

@@ -74,7 +74,7 @@ export interface QueryResult<TData = any, TVariables = OperationVariables>
   // I'm aware of. So intead we enforce checking for data
   // like so result.data!.user. This tells TS to use TData
   // XXX is there a better way to do this?
-  data: TData | {};
+  data: TData | undefined;
   error?: ApolloError;
   loading: boolean;
   networkStatus: NetworkStatus;
@@ -391,12 +391,9 @@ export default class Query<TData = any, TVariables = OperationVariables> extends
       if (loading) {
         Object.assign(data.data, this.previousData, currentResult.data);
       } else if (error) {
-        const lastResult = this.queryObservable!.getLastResult();
-        if (lastResult) {
-          Object.assign(data, {
-            data: lastResult.data,
-          });
-        }
+        Object.assign(data, {
+          data: (this.queryObservable!.getLastResult() || {}).data,
+        });
       } else {
         const { fetchPolicy } = this.queryObservable!.options;
         const { partialRefetch } = this.props;

test/client/Query.test.tsx

@@ -163,7 +163,6 @@ describe('Query component', () => {
               return null;
             }
             catchAsyncError(done, () => {
-              expect(result.data).toEqual({});
               expect(result.error).toEqual(new Error('Network error: error occurred'));
               done();
             });

test/client/getDataFromTree.test.tsx

@@ -538,11 +538,9 @@ describe('SSR', () => {
 
       class CurrentUserQuery extends Query<Data> {}
 
-      const hasOwn = Object.prototype.hasOwnProperty;
-
       const WrappedElement = () => (
         <CurrentUserQuery query={query}>
-          {({ data, loading }: { data: Data; loading: boolean }) => (
+          {({ data, loading }) => (
             <div>{loading || !data ? 'loading' : data.currentUser!.firstName}</div>
           )}
         </CurrentUserQuery>
@@ -1291,7 +1289,7 @@ describe('SSR', () => {
 
       const Element = (props: { id: string }) => (
         <CurrentUserQuery query={query} ssr={false} variables={props}>
-          {({ data, loading }: { data: Data; loading: boolean }) => (
+          {({ data, loading }) => (
             <div>{loading || !data ? 'loading' : data.currentUser!.firstName}</div>
           )}
         </CurrentUserQuery>