[help wanted] Firestore will not return a response after a long time since you started using it.

Overview (Required)

• We can not use favorite!! 😭
• I can fix it clear app data. So probably, app internal problem.
• I can’t fix this by force stop app.
• It occurred release and debug
• If it occurred, FavoriteFirestoreDatabase “Firestore:setupFavoritesDocument” is logged, But “Firestore:setupFavoritesDocument onComplete” is not logged.

https://github.com/DroidKaigi/conference-app-2018/blob/master/app/src/main/java/io/github/droidkaigi/confsched2018/data/db/FavoriteFirestoreDatabase.kt#L100

    @CheckResult
    private fun setupFavoritesDocument(currentUser: FirebaseUser): Single<FirebaseUser> {
        return Single.create({ e: SingleEmitter<FirebaseUser> ->
            if (DEBUG) Timber.d("Firestore:setupFavoritesDocument")
            val database = FirebaseFirestore.getInstance()
            val favorites = database.collection("users/" + currentUser.uid + "/favorites")
            favorites.get().addOnCompleteListener { task ->
                if (DEBUG) Timber.d("Firestore:setupFavoritesDocument onComplete")

[kakajika]

Hello 🙋 First comment on this project!

I think it’s a problem about Firestore’s behavior when device is regarded as offline.

The official document of Firestore says:

If you get a document while the device is offline, Cloud Firestore returns data from the cache. If the cache does not contain data for that document, or the document does not exist, the get call returns an error.

https://firebase.google.com/docs/firestore/manage-data/enable-offline#get_offline_data

So, if the document is empty, favorites.get() cause error and return nothing. We should use favorites.addSnapshotListener(...) instead.

    @CheckResult
    private fun setupFavoritesDocument(currentUser: FirebaseUser): Single<FirebaseUser> {
        val database = FirebaseFirestore.getInstance()
        val favorites = database.collection("users/" + currentUser.uid + "/favorites")

        return Single.create({ e: SingleEmitter<QuerySnapshot> ->
            if (DEBUG) Timber.d("Firestore:setupFavoritesDocument")
            val listener = favorites.addSnapshotListener { querySnapshot, exception ->
                if (DEBUG) Timber.d("Firestore:setupFavoritesDocument onComplete")
                if (exception != null) {
                    Timber.e(exception, "Firestore:setupFavoritesDocument onComplete fail ")
                    e.onError(exception)
                } else {
                    e.onSuccess(querySnapshot)
                }
            }
            e.setCancellable {
                listener.remove()
            }

        // To avoid [ get -> write -> get -> ... ] loop, make task split.
        }).flatMap { querySnapshot ->
            Single.create<FirebaseUser> { e ->
                if (querySnapshot.isEmpty) {
                    favorites.add(mapOf("initialized" to true)).addOnCompleteListener {
                        if (DEBUG) Timber.d("Firestore:create document for listing")
                        e.onSuccess(currentUser)
                    }
                } else {
                    if (DEBUG) Timber.d("Firestore:document already exists")
                    e.onSuccess(currentUser)
                }
            }
        }
    }

I tried code above, and it seems to work well. If It’s OK, I create PR! 😃

[Kesin11]

I did reproduce this issue may be. In my case, same behaviour occurs when launch app without network connection.

1. Turn off wifi
2. Launch app
3. Turn on wifi
4. Touch favorite icon in AllSessionsFragment. Icon is turned on
5. Go to session detail
6. Favorite icon is still turned off

I tried to repeat step 4 to 6 after turned on wifi, it still same result. But after about 1 minutes, it revived suddenly. However, I can not see any log in setupFavoritesDocument()