title: Cloud Firestore collection while offline returns empty
body: <p>I am testing the behavior of my React Native app offline. I am using Expo and a Cloud Firestore database. The code that I am using to update the screen is something like:</p>
  <pre><code>useEffect(() =&gt; {
  const unsubscribe = db
    .collection('myCol1')
    .doc('myDoc1)
    .collection('myCol2')
    .onSnapshot((snapshot) =&gt; {
      // Update state based on snapshot.docs
      // But snapshot.docs is empty when offline
    });
  return unsubscribe; }, []);
  </code></pre>
  <p>While online, everything is working great. Offline however, the collection that is fetched is empty. Is there something obvious that I am missing in terms of how caching works with Cloud Firestore? I am also not sure how to debug that. Thanks!</p>