Remove unused queryId after fetchMore

CHANGELOG.md

@@ -23,6 +23,9 @@
 - Avoid updating (and later invalidating) cache watches when `fetchPolicy` is `'no-cache'`. <br/>
   [@bradleyayers](https://github.com/bradleyayers) in [PR #4573](https://github.com/apollographql/apollo-client/pull/4573), part of [issue #3452](https://github.com/apollographql/apollo-client/issues/3452)
 
+- Remove temporary `queryId` after `fetchMore` completes. <br/>
+  [@doomsower](https://github.com/doomsower) in [#4440](https://github.com/apollographql/apollo-client/pull/4440)
+
 ### Apollo Cache In-Memory
 
 - Support `new InMemoryCache({ freezeResults: true })` to help enforce immutability. <br/>

packages/apollo-client/src/__tests__/fetchMore.ts

@@ -473,6 +473,41 @@ describe('fetchMore on an observable query', () => {
       },
     });
   });
+
+  it('will not leak fetchMore query', () => {
+    latestResult = null;
+    var beforeQueryCount;
+    return setup({
+      request: {
+        query,
+        variables: variablesMore,
+      },
+      result: resultMore,
+    })
+      .then(watchedQuery => {
+        beforeQueryCount = Object.keys(
+          client.queryManager.queryStore.getStore(),
+        ).length;
+        return watchedQuery.fetchMore({
+          variables: { start: 10 }, // rely on the fact that the original variables had limit: 10
+          updateQuery: (prev, options) => {
+            const state = cloneDeep(prev) as any;
+            state.entry.comments = [
+              ...state.entry.comments,
+              ...(options.fetchMoreResult as any).entry.comments,
+            ];
+            return state;
+          },
+        });
+      })
+      .then(data => {
+        var afterQueryCount = Object.keys(
+          client.queryManager.queryStore.getStore(),
+        ).length;
+        expect(afterQueryCount).toBe(beforeQueryCount);
+        unsetup();
+      });
+  });
 });
 
 describe('fetchMore on an observable query with connection', () => {

packages/apollo-client/src/core/ObservableQuery.ts

@@ -343,11 +343,10 @@ export class ObservableQuery<
     );
 
     let combinedOptions: any;
+    const qid = this.queryManager.generateQueryId();
 
     return Promise.resolve()
       .then(() => {
-        const qid = this.queryManager.generateQueryId();
-
         if (fetchMoreOptions.query) {
           // fetch a new query
           combinedOptions = fetchMoreOptions;
@@ -381,7 +380,13 @@ export class ObservableQuery<
           }),
         );
 
+        this.queryManager.stopQuery(qid);
+
         return fetchMoreResult as ApolloQueryResult<TData>;
+
+      }, error => {
+        this.queryManager.stopQuery(qid);
+        throw error;
       });
   }