[cloud_firestore] Have snapshots() method emit errors for devs to handle!

[sentd94]

When listening to realtime updates of a collection, no errors / exceptions are emitted to the stream (for example if the client cannot get a connection to the server):

db
    .collection('stuff')
    .where("someBool", isEqualTo: false)
    .snapshots()
    .listen((snap) { ...  }, onError: (e) {
         //never called...
         debugPrint(e.toString());
     });

Why is this important?

Sometimes you need to differentiate if a collection currently has no documents OR the internet is down and therefore your snapshot is empty.

Note

For getting data just once using get() method there is a getOptions parameter which you can use to enable error throwing (by passing GetOptions(source: Source.server)). For snapshots() you don't have that option.