Fix observeFragment triggering unhandled rejections on network error (#4885)

Summary:
This PR fixes an issue where `observeFragment` triggers unhandled rejections on network error, which happens because of the dangling promise created and dropped.

Pull Request resolved: #4885

Reviewed By: tyao1

Differential Revision: D68505423

Pulled By: captbaritone

fbshipit-source-id: 2df4afa40e140de7baea04e811f5c5b06f658a4f

Author: XiNiHa

packages/relay-runtime/store/__tests__/__generated__/observeFragmentTestNetworkErrorFragment.graphql.js

@@ -145,6 +145,35 @@ test('Missing required data', async () => {
   });
 });
 
+test('Keep loading on network error', async () => {
+  const query = graphql`
+    query observeFragmentTestNetworkErrorQuery {
+      ...observeFragmentTestNetworkErrorFragment
+    }
+  `;
+
+  const fragment = graphql`
+    fragment observeFragmentTestNetworkErrorFragment on Query {
+      me {
+        name
+      }
+    }
+  `;
+
+  const environment = createMockEnvironment();
+  const variables = {};
+  const operation = createOperationDescriptor(query, variables);
+  fetchQuery(environment, query, variables).subscribe({});
+  const {data} = environment.lookup(operation.fragment);
+  // $FlowFixMe Data is untyped
+  const observable = observeFragment(environment, fragment, data);
+  withObservableValues(observable, results => {
+    expect(results).toEqual([{state: 'loading'}]);
+    environment.mock.reject(operation, new Error('Network error'));
+    expect(results).toEqual([{state: 'loading'}]);
+  });
+});
+
 test('Field error with @throwOnFieldError', async () => {
   const query = graphql`
     query observeFragmentTestThrowOnFieldErrorQuery {

packages/relay-runtime/store/__tests__/__generated__/observeFragmentTestNetworkErrorQuery.graphql.js

@@ -20,8 +20,8 @@ import type {
 } from 'relay-runtime';
 
 const Observable = require('../network/RelayObservable');
+const {getObservableForActiveRequest} = require('../query/fetchQueryInternal');
 const {getFragment} = require('../query/GraphQLTag');
-const getPendingOperationsForFragment = require('../util/getPendingOperationsForFragment');
 const {
   handlePotentialSnapshotErrors,
 } = require('../util/handlePotentialSnapshotErrors');
@@ -241,12 +241,12 @@ function snapshotToFragmentState<TFragmentType: FragmentType, TData>(
   }
 
   if (snapshot.isMissingData) {
-    const pendingOperations = getPendingOperationsForFragment(
-      environment,
-      fragmentNode,
-      owner,
-    );
-    if (pendingOperations != null) {
+    if (
+      getObservableForActiveRequest(environment, owner) != null ||
+      environment
+        .getOperationTracker()
+        .getPendingOperationsAffectingOwner(owner) != null
+    ) {
       return {state: 'loading'};
     }
   }