Reset query store errors via ObservableQuery.resetQueryStoreErrors (#4941)

* Reset query store errors via `ObservableQuery.resetQueryStoreErrors`

React Apollo relies on the `ObervableQuery->getCurrentResult`
method to retrieve query results to show within its components.
When an error occurs while fetching results, that error is stored
in the query store that each `ObservableQuery` instance is
configured to use. Unfortunately, `getCurrentResult` will only
retrieve subsequent results if no error exists in the query store.
`ObservableQuery` doesn't currently provide a way to clear out
query store errors, which means when React Apollo originating
requests that cause an error occur, the error is stored, and
future valid requests can no longer be processed.

This commit adds a `resetQueryStoreErrors` method to the
`ObservableQuery` public API, that will allow React Apollo (and
other consumers) to be able to clear out query store errors.

Related to: apollographql/react-apollo#3090

* Changelog update

* Remove unnecessary expect

Author: hwillson

CHANGELOG.md

@@ -4,6 +4,9 @@
 
 ### Apollo Client (vNext)
 
+- A new `ObservableQuery.resetQueryStoreErrors()` method is now available that
+  can be used to clear out `ObservableQuery` query store errors.  <br/>
+  [@hwillson](https://github.com/hwillson) in [#4941](https://github.com/apollographql/apollo-client/pull/4941)
 - Documentation updates.  <br/>
   [@michael-watson](https://github.com/michael-watson) in [#4940](https://github.com/apollographql/apollo-client/pull/4940)  <br/>
   [@hwillson](https://github.com/hwillson) in [#4969](https://github.com/apollographql/apollo-client/pull/4969)

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

@@ -280,6 +280,14 @@ export class ObservableQuery<
     this.isTornDown = false;
   }
 
+  public resetQueryStoreErrors() {
+    const queryStore = this.queryManager.queryStore.get(this.queryId);
+    if (queryStore) {
+      queryStore.networkError = null;
+      queryStore.graphQLErrors = [];
+    }
+  }
+
   /**
    * Update the variables of this observable query, and fetch the new results.
    * This method should be preferred over `setVariables` in most use cases.

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

@@ -4,6 +4,7 @@ import {
   InMemoryCache,
   IntrospectionFragmentMatcher,
 } from 'apollo-cache-inmemory';
+import { GraphQLError } from 'graphql';
 
 import mockQueryManager from '../../__mocks__/mockQueryManager';
 import mockWatchQuery from '../../__mocks__/mockWatchQuery';
@@ -1998,4 +1999,48 @@ describe('ObservableQuery', () => {
       });
     });
   });
+
+  describe('resetQueryStoreErrors', () => {
+    it("should remove any GraphQLError's stored in the query store", (done) => {
+      const graphQLError = new GraphQLError('oh no!');
+
+      const observable: ObservableQuery<any> = mockWatchQuery({
+        request: { query, variables },
+        result: { errors: [graphQLError] },
+      });
+
+      observable.subscribe({
+        error() {
+          const { queryManager } = (observable as any);
+          const queryStore = queryManager.queryStore.get(observable.queryId);
+          expect(queryStore.graphQLErrors).toEqual([graphQLError]);
+
+          observable.resetQueryStoreErrors();
+          expect(queryStore.graphQLErrors).toEqual([]);
+
+          done();
+        }
+      });
+    });
+
+    it("should remove network error's stored in the query store", (done) => {
+      const networkError = new Error('oh no!');
+
+      const observable: ObservableQuery<any> = mockWatchQuery({
+        request: { query, variables },
+        result: { data: dataOne },
+      });
+
+      observable.subscribe({
+        next() {
+          const { queryManager } = (observable as any);
+          const queryStore = queryManager.queryStore.get(observable.queryId);
+          queryStore.networkError = networkError;
+          observable.resetQueryStoreErrors();
+          expect(queryStore.networkError).toBeNull();
+          done();
+        }
+      });
+    });
+  });
 });