[cloud_firestore] Null in stream on no network, unable to detect data absence or failure

[EArminjon]

What feature would you like to see?

I want to report an issue with Firebase’s stream. When the device is offline (in airplane mode), the stream provides a null value, making it difficult to distinguish between the following scenarios:

• The user has no subscriptions.
• The user has maybe some subscriptions but is currently offline.

This causes an issue where, as a developer, I end up caching the null value when the stream returns null due to the lack of network connection. As a result, users appear to have no subscriptions even though they might actually have them, just offline.

It would be helpful if Firebase could provide a clearer way to handle this, so we can properly differentiate these scenarios and manage caching accordingly.

In the following example handleError is not called on network issue.

  @override
  Stream<List<SubscriptionEntity>> listenUserSubscriptions(String userId) {
    final DocumentReference<Map<String, dynamic>> ref = firestore
        .collection(_usersTable)
        .doc(userId)
        .collection(_purchaseTable)
        .doc(userId);
    return ref
        .snapshots()
        .map((DocumentSnapshot<Map<String, dynamic>> snapshot) {
          return SubscriptionModel.fromJson(snapshot.data() ?? {}).toDomain;
        })
        .handleError((Object err) {
          print("Error: $err");
        });

[SelaseKay]

Hi @EArminjon, thanks for the report. What platform are you experiencing this on?

[EArminjon]

@SelaseKay Hi, Android 15.

[SelaseKay]

Hi @EArminjon, I'm suspecting this could be from the underlying Firebase Android SDK. Have you disabled offline caching for Firebase?

[EArminjon]

@SelaseKay

Yes I've disabled persistence :

 final FirebaseFirestore instance = FirebaseFirestore.instance;
 instance.settings = const Settings(
   persistenceEnabled: false,
   ignoreUndefinedProperties: true,
 );
 FirebaseFirestore.setLoggingEnabled(kDebugMode);

I'm starting to use the code bellow. It works but it's not really maintainable as expected. It could be better with a way to directly get the firebase error code.

  @override
  Stream<List<SubscriptionEntity>> listenUserSubscriptions(String userId) {
    final DocumentReference<Map<String, dynamic>> ref = firestore
        .collection(_usersTable)
        .doc(userId)
        .collection(_purchaseTable)
        .doc(userId);
    return ref.snapshots().map((
      DocumentSnapshot<Map<String, dynamic>> snapshot,
    ) {
      if (!snapshot.exists && snapshot.metadata.isFromCache) {
        // I've disabled Firestore persistance
        // This if condition is used to detect error like network issue
        // https://github.com/firebase/flutterfire/issues/17317
        throw const NetworkException();
      }
      return SubscriptionModel.fromJson(snapshot.data() ?? {}).toDomain;
    });
  }