Fix an issue where useSuspenseQuery would not respond to cache upda…

…tes when using a cache-first fetch policy with data in the cache when the hook is mounted (#10651)

This fixes an issue where `useSuspenseQuery` would not respond to cache updates
when using a cache-first `fetchPolicy` after the hook was mounted with data
already in the cache.

This is due to the fact that this hook manages the fetching lifecycle
(via `reobserve`) rather than the subscription. We disable fetching when
subscribing to the observable since we kick off the fetch in the first render.
This however has some downstream issues, since `reobserve` is necessary to set
some internal state updates on `ObservableQuery` and `QueryInfo`. In cases where
we can fulfill the result via the cache immediately, we avoid calling
`reobserve` by subscribing (via the `fetchOnFirstSubscribe` option) to avoid the
network request, but this means the interal state updates do not happen.

In this case, `QueryInfo`, is initialized with a `networkStatus` of 1, but
because we don't call `reobserve`, this value never gets updated to 7 even
though `observableQuery.getCurrentResult()` is able to correctly set this value
to 7. This caused issues where `broadcastQueries` was not sending notifications
since `queryInfo` avoids broadcasting to in-flight queries for fetch policies
other than cache-only and cache-and-network.

This attempts to patch the behavior expected from in `reobserve` by
marking the queryInfo as ready if we detect that the result is also
ready.

Co-authored-by: Alessia Bellisario <alessia@apollographql.com>

.changeset/funny-peas-change.md

@@ -0,0 +1,5 @@
+---
+'@apollo/client': patch
+---
+
+Fixes an issue where `useSuspenseQuery` would not respond to cache updates when using a cache-first `fetchPolicy` after the hook was mounted with data already in the cache.

src/react/hooks/__tests__/useSuspenseQuery.test.tsx

@@ -1810,6 +1810,47 @@ describe('useSuspenseQuery', () => {
     }
   );
 
+  // https://github.com/apollographql/apollo-client/issues/10478
+  it('responds to cache updates when data is already in the cache while using a cache-first fetch policy', async () => {
+    const { query, mocks } = useSimpleQueryCase();
+
+    const client = new ApolloClient({
+      cache: new InMemoryCache(),
+      link: new MockLink(mocks),
+    });
+
+    client.writeQuery({
+      query,
+      data: { greeting: 'Hello from cache' },
+    });
+
+    const { result } = renderSuspenseHook(
+      () => useSuspenseQuery(query, { fetchPolicy: 'cache-first' }),
+      { client }
+    );
+
+    expect(result.current.data).toEqual({ greeting: 'Hello from cache' });
+
+    // Allow time for the subscription in the hook to set itself up since it is
+    // wrapped in a setTimeout (to handle Strict mode bugs). Without this
+    // `wait`, `subscribe` isn't called until after our test updates the cache
+    // via `writeQuery`, which then emits the most recent result, which is the
+    // updated value.
+    await wait(0);
+
+    client.writeQuery({
+      query,
+      data: { greeting: 'Updated hello' },
+    });
+
+    await waitFor(() => {
+      expect(result.current).toMatchObject({
+        data: { greeting: 'Updated hello' },
+        error: undefined,
+      });
+    });
+  });
+
   it('uses the default fetch policy from the client when none provided in options', async () => {
     const { query, mocks } = useSimpleQueryCase();
 

src/react/hooks/useSuspenseQuery.ts

@@ -11,6 +11,7 @@ import {
   TypedDocumentNode,
   WatchQueryOptions,
   WatchQueryFetchPolicy,
+  NetworkStatus,
 } from '../../core';
 import {
   compact,
@@ -373,6 +374,43 @@ function useObservableQueryResult<TData>(observable: ObservableQuery<TData>) {
             next: handleUpdate,
             error: handleUpdate,
           });
+
+          // Fixes an issue where mounting this hook with data already in the
+          // cache while using a cache-first fetch policy did not respond to
+          // cache updates.
+          //
+          // This is due to the fact that this hook manages the
+          // fetching lifecycle (via `reobserve`) rather than the subscription.
+          // We disable fetching when subscribing to the observable since we
+          // kick off the fetch in the first render. This however has some
+          // downstream issues, since `reobserve` is necessary to set some
+          // internal state updates on `ObservableQuery` and `QueryInfo`. In
+          // cases where we can fulfill the result via the cache immediately, we
+          // avoid calling `reobserve` by subscribing (via the
+          // `fetchOnFirstSubscribe` option) to avoid the network request, but
+          // this means the interal state updates do not happen.
+          //
+          // In this case, `QueryInfo`, is initialized with a `networkStatus` of
+          // 1, but because we don't call `reobserve`, this value never gets
+          // updated to 7 even though `observableQuery.getCurrentResult()` is
+          // able to correctly set this value to 7. This caused issues where
+          // `broadcastQueries` was not sending notifications since `queryInfo`
+          // avoids broadcasting to in-flight queries for fetch policies other
+          // than cache-only and cache-and-network.
+          //
+          // This attempts to patch the behavior expected from `reobserve` by
+          // marking the queryInfo as ready if we detect that the result is also
+          // ready.
+          //
+          // Related to https://github.com/apollographql/apollo-client/issues/10478
+          const result = resultRef.current!;
+
+          if (
+            result.networkStatus !== observable['queryInfo'].networkStatus &&
+            result.networkStatus === NetworkStatus.ready
+          ) {
+            observable['queryInfo'].markReady();
+          }
         });
 
         return () => {