Hi @Cova8bitdots

I think the Custom Main Manifest is ON just because Assets/Plugins/Android/AndroidManifest.xm exists. There is actually no flag from Unity API to turn it ON or OFF.

Also, you are correct. Assets/Firebase/Editor/Firebase.Messaging.Editor.dll automatically generate this file because we have custom implementation to forward message from Android service to Android activity (see this code).

Is there a reason why you have to eliminate this file? Are you trying to do so to avoid the error you saw? I think that error is an unrelated issue.

About the error message you mentioned:

Failed to read Firebase options from the app's resources. Either make sure google-services.json is included in your build or specify options explicitly.

This occurs when Firebase SDK was not able to locate google-services.json. Quick question: does this occurs to you on Android only or on iOS as well?

For Android, Firebase.Editor.dll would generated an Android resource google-services.xml from google-services.json under Assets/Plugins/Android/FirebaseApp.androidlib. Please check if that folder exists.

Lastly, could you confirm if the same issue is reproducible using Firebase quickstart?

Please let us know.
Shawn

I think the Custom Main Manifest is ON just because Assets/Plugins/Android/AndroidManifest.xml exists. There is actually no flag from Unity API to turn it ON or OFF.

I have few question.

1. Did your editor script call reflection method to force turning Custom Main Manifest ON ?
2. on Unity2020.3 (Unity2020LTS), it requires customGradleTemplate to build with other firebase plugins ( details are written in description, please check it). I want to know why FCM is only not support using custom GradleTemplate officially ?
3. Have you already confirmed working plugin build with Unity2020.3 ?

Is there a reason why you have to eliminate this file? Are you trying to do so to avoid the error you saw? I think that error is an unrelated issue.

Because we try to upgrade Unity Version from 2019.4 to 2020.3.
From 2020.3 other firebase plugins need to use customGradleTemplate for build Android app, however FCM use AndroidManifest, so we cant migrate CustomAndroidManifest to custom gradle template.

This occurs when Firebase SDK was not able to locate google-services.json. Quick question: does this occurs to you on Android only or on iOS as well?

This happens on Android device.

For Android, Firebase.Editor.dll would generated an Android resource google-services.xml from google-services.json under Assets/Plugins/Android/FirebaseApp.androidlib. Please check if that folder exists.

I know latest version changed folder name from Assets/Plugins/Android/FirebaseApp.android to Assets/Plugins/Android/FirebaseApp.androidlib.
However, with plugin v6.15.2, it does NOT generate folder Assets/Plugins/Android/FirebaseApp.androidlib but Assets/Plugins/Android/FirebaseApp.android.
We can rename folder temporally, but if UnityEditor try to re-import assets, Assets/Plugins/Android/FirebaseApp.android folder will re-generated.

Lastly, could you confirm if the same issue is reproducible using Firebase quickstart?
I have not enough time to check sample. so it takes long time to check sample again.

What I want to tell you is FCM with other firebase plugins on Unity2019LTS, Android build using CustomAndroidManifest works well, but FCM with other firebase plugins on Unity2020LTS, Android build using custom gradleTemplate does NOT work.

1. Did your editor script call reflection method to force turning Custom Main Manifest ON ?

Firebase.Messaging.Editor.dll generates Assets/Plugins/Android/AndroidManifest.xml. When the file exists, you will see Custom Main Manifest be turned on. There is actually no Unity API to flip the switch AFAIK.
However, if Assets/Plugins/Android/AndroidManifest.xml exists in your project before you import Firebase SDK, Firebase.Messaging.Editor.dll will NOT override it. That means you will need to add com.google.firebase.MessagingUnityPlayerActivity activity yourself. We do not have a good way to merge it for you yet. One possible way is to delete this AndroidManifest.xml from your project, let Firebase.Messaging.Editor.dll to generate one and use version-control diff tool to merge the change.

2. on Unity2020.3 (Unity2020LTS), it requires customGradleTemplate to build with other firebase plugins ( details are written in description, please check it). I want to know why FCM is only not support using custom GradleTemplate officially ?

By customGradleTemplate, do you mean Custom Main Gradle Template, which generates Assets/Plugins/Android/mainTemplate.gradle? If so, FCM should support this with no issue. However, since Unity changed Gradle project structure, you will need to enable Custom Gradle Properties Template as well in order to enable Jetifier. If this is not enabled, you should see a log started with Resolution Failed with this piece of detail in it.

3. Have you already confirmed working plugin build with Unity2020.3 ?

Yes. As a matter of fact, I just built FCM quickstart with Firebase Unity SDK 8.0.0 and Unity 2020.3.14f1, installed to my own phone and sent a message from Firebase console. It worked as intended.

You might encounter some obstacles to build it though.

1. As mentioned, you need to turn on Custom Gradle Properties Template if you want to use Custom Main Gradle Template.
2. You need to turn on Minify. Unfortunately Unity did not update their doc to explain the new options. Basically you need to check Release and/or Debug under Minify section. By default, Unity uses their in-house minification or Proguard (unfortunately this is not explained anywhere in public doc). If you want to use R8, developed by Google, check Use R8 as well. Either option should work as I tested.

Here is my Player Settings

Note that the generated Assets/Plugins/Android/AndroidManifest.xml is required to forward Intent from Android service to Android activity to make FirebaseMessaging.MessageReceived event works properly. You can definitely implement your own way to handle Intent. More details here.

Also, I would recommend you to upgrade to the latest Firebase SDK. We fixed a couple of issues for the breaking changes from Unity, ex. Assets/Plugins/Android/FirebaseApp without .androidlib simply won't work in Unity 2020.

I recommend you to try FCM quickstart and see if you can reproduce the issue with it.

If not, please provide a minimum-viable-project to us for debugging, since we were not able to reproduce it from our end.

Hey @Cova8bitdots. We need more information to resolve this issue but there hasn't been an update in 5 weekdays. I'm marking the issue as stale and if there are no new updates in the next 5 days I will close it automatically.

If you have more information that will help us get to the bottom of this, just add a comment!

Since there haven't been any recent updates here, I am going to close this issue.

@Cova8bitdots if you're still experiencing this problem and want to continue the discussion just leave a comment here and we are happy to re-open this.