Make updateQuery option of subscribeToMore optional

CHANGELOG.md

@@ -5,7 +5,7 @@ Expect active development and potentially significant breaking changes in the `0
 ### vNEXT
 - Added `HTTPBatchedNetworkInterface` as an index export to make it easier
 to subclass externally, consistent with `HTTPFetchNetworkInterface`. [PR #1446](https://github.com/apollographql/apollo-client/pull/1446)
-
+- Make `updateQuery` option of `subscribeToMore` optional [PR #1455](https://github.com/apollographql/apollo-client/pull/1455)
 
 ### 1.0.0-rc.5
 - Fix: Revert PR that caused uncaught promise rejections [PR #1133](https://github.com/apollographql/apollo-client/pull/1133)

src/core/ObservableQuery.ts

@@ -262,19 +262,20 @@ export class ObservableQuery<T> extends Observable<ApolloQueryResult<T>> {
       variables: options.variables,
     });
 
-    const reducer = options.updateQuery;
-
     const subscription = observable.subscribe({
       next: (data) => {
-        const mapFn = (previousResult: Object, { variables }: { variables: Object }) => {
-          return reducer(
-            previousResult, {
-              subscriptionData: { data },
-              variables,
-            },
-          );
-        };
-        this.updateQuery(mapFn);
+        if (options.updateQuery) {
+          const reducer = options.updateQuery;
+          const mapFn = (previousResult: Object, { variables }: { variables: Object }) => {
+            return reducer(
+              previousResult, {
+                subscriptionData: { data },
+                variables,
+              },
+            );
+          };
+          this.updateQuery(mapFn);
+        }
       },
       error: (err) => {
         if (options.onError) {

src/core/watchQueryOptions.ts

@@ -84,7 +84,7 @@ export interface FetchMoreQueryOptions {
 export type SubscribeToMoreOptions = {
   document: DocumentNode;
   variables?: { [key: string]: any };
-  updateQuery: (previousQueryResult: Object, options: {
+  updateQuery?: (previousQueryResult: Object, options: {
     subscriptionData: { data: any },
     variables: { [key: string]: any },
   }) => Object;

test/subscribeToMore.ts

@@ -77,6 +77,22 @@ describe('subscribeToMore', () => {
     results: [...results3],
   };
 
+  const results4 = ['Vyacheslav Kim', 'Changping Chen'].map(
+    name => ({ result: { name: name }, delay: 10 }),
+  );
+
+  const sub4 = {
+    request: {
+      query: gql`
+        subscription newValues {
+          name
+        }
+      `,
+    },
+    id: 0,
+    results: [...results4],
+  };
+
   it('triggers new result from subscription data', (done) => {
     let latestResult: any = null;
     const networkInterface = mockSubscriptionNetworkInterface([sub1], req1);
@@ -226,5 +242,55 @@ describe('subscribeToMore', () => {
     }
   });
 
+  it('updates new result from subscription via a reducer in watchQuery options', (done) => {
+    let latestResult: any = null;
+    const networkInterface = mockSubscriptionNetworkInterface([sub4], req1);
+    let counter = 0;
+
+    const client = new ApolloClient({
+      networkInterface,
+      addTypename: false,
+    });
+
+    const obsHandle = client.watchQuery({
+      query,
+      reducer: (previousResult, action) => {
+        if (action.type === 'APOLLO_SUBSCRIPTION_RESULT' && action.operationName === 'newValues') {
+          if (action.result.data) {
+            return { entry: { value: action.result.data.name } };
+          }
+        }
+        return previousResult;
+      },
+    });
+    const sub = obsHandle.subscribe({
+      next(queryResult) {
+        latestResult = queryResult;
+        counter++;
+      },
+    });
+
+    obsHandle.subscribeToMore({
+      document: gql`
+        subscription newValues {
+          name
+        }
+      `,
+    });
+
+    setTimeout(() => {
+      sub.unsubscribe();
+      assert.equal(counter, 3);
+      assert.deepEqual(
+        latestResult,
+        { data: { entry: { value: 'Changping Chen' } }, loading: false, networkStatus: 7, stale: false },
+      );
+      done();
+    }, 50);
+
+    for (let i = 0; i < 2; i++) {
+      networkInterface.fireResult(0); // 0 is the id of the subscription for the NI
+    }
+  });
   // TODO add a test that checks that subscriptions are cancelled when obs is unsubscribed from.
 });