Android app works fine when using debug JS bundle, but has horrible bug in release JS bundle.

[Tochukwuibe]

I'm getting ready to release my companies' app for internal beta testing. I noticed this issue when i tried to run a release build for my app by using android studio or running the commend: react-native run-android --variant=release.
What happens next is that my app then gets stuck on my initial loading screen (using react navigation for my app). It seems as though a certain portion of my app is not executing, which is the part where i am checking to see if the user is authenticated (using react-native-firebse) and then deciding whether to send them into the main page or the login screen.
This logic runs in a redux saga, where i use an event channel (a wrapper around the firebase onAuthStateChange realtime listener) to monitor the users auth status and route them as i mentioned above. Using Alerts i was able to isolate the exact part of the saga where for some reason it never resolves the async value of the onAuthStateChange listener. I have put a label above the line of code in question.

I have tested both the debug and release JS bundle using the command to generate an offline bundle, and I am certain that the issue is in the release bundle alone.

NOTE: At first i was having this issue with react-native 0.59.9 on Both Android and IOS platform. I decided to update to the latest version 0.60.5 hoping that it would fix it. Now I am only experiencing this on the Android platform.

React Native version:
System:
OS: macOS 10.14.6
CPU: (8) x64 Intel(R) Core(TM) i7-4870HQ CPU @ 2.50GHz
Memory: 2.07 GB / 16.00 GB
Shell: 3.2.57 - /bin/bash
Binaries:
Node: 10.16.2 - ~/.nvm/versions/node/v10.16.2/bin/node
npm: 6.9.0 - ~/.nvm/versions/node/v10.16.2/bin/npm
Watchman: 4.9.0 - /usr/local/bin/watchman
SDKs:
iOS SDK:
Platforms: iOS 12.4, macOS 10.14, tvOS 12.4, watchOS 5.3
Android SDK:
API Levels: 27, 28, 29
Build Tools: 28.0.3, 29.0.2
System Images: android-27 | Google Play Intel x86 Atom
IDEs:
Android Studio: 3.4 AI-183.6156.11.34.5692245
Xcode: 10.3/10G8 - /usr/bin/xcodebuild
npmPackages:
react: 16.8.6 => 16.8.6
react-native: 0.60.5 => 0.60.5
npmGlobalPackages:
react-native-cli: 2.0.1

Steps To Reproduce

1. Create app
2. include firebase
3. include redux saga
4. Use event channel to listen for authstateChanges
5. Create a release build of the app
6. See bug.

Describe what you expected to happen:
The app should run fine like it does in debug mode.

Snack, code example, screenshot, or link to a repository:

function* checkAuthStatus() {
    try {


        const authChan = yield call(eventChannel$, AppAuthService.currentUser$);
        const navigation = yield call(getTopLevelNavigator);

        while (true) {

           // HERE IS THE LINE OF CODE THAT NEVER RESOLVES
            const { user } = yield take(authChan);  

            if (!!user) {

                const { claims } = yield call(AppAuthService.getIdTokenResult);
                yield put(AuthActions.userAuthenticated({ user, claims }));

                if (!user.emailVerified || !claims.v2Verified) {


                    navigation.navigate('Auth/Authenticate', { view: 'verify' })

                } else {

                    navigation.navigate('Tabs');
                }


            } else {
                navigation.navigate('Intro');

                yield put(AuthActions.userUnAuthenticated());
            }
        }
    } finally {

    }
}

[Tochukwuibe]

Ps, im pretty sure its not the fault of redux saga or react-native-firebase, because they both work fine in Android debug build and on IOS release build. However, I could be wrong.

[kaloncheung124]

Have you tried disabling Hermes in your app/build.gradle? We had this same problem, and we didn't catch it until after it was deployed to Google Play. After some debugging, disabling Hermes fixed our issue.

Related issue: #25927

[Tochukwuibe]

Hermes was never enabled. I found a hack around the issue, though I can't explain why it works. I was wrapping the firebase onAuthState change with an event channel, which is something that redux-saga provides for handling continuous asynchronous listeners. There was a line of code that i was using to emit the value returned by the firebase onAuthStateChange (similar to resolve in Promise). I had to wrap it in a set timeout set to 0 for it to work. like so:

function authChannel(){
  return eventChannel(emitter => {
       firebase.auth().onAuthStateChange(user => {

                // wont work in release build without settimeout
               setTimeout(() =>  emitter(user), 0)

        })
   })
}