Firebaseui-android: TransformException: Error while generating the main dex list.

[emarc-m]

• Android device: Pixel 2
• Android OS version: 8.1.0
• GMS Plugin Version: 4.0.1
• Firebase Auth: 16.0.1
• Firebase Core: 16.0.0
• Firebase Database: 16.0.1
• Firebase Invites: 16.0.0
• Firebase Messaging: 17.0.0
• FirebaseUI version: 4.0.1

Build fails when using firebase ui version 4.0.1, works on version 3.3.1

Observed Results:

```
com.android.build.api.transform.TransformException: Error while generating the main dex list.

Error while generating the main dex list.
com.android.tools.r8.errors.CompilationError: Program type already present: android.arch.core.util.Function
Program type already present: android.arch.core.util.Function
```

Please see: SO post

[emptyway]

same here. my workaround was to downgrade the support library version to 27.0.2

[samtstern]

Thank you both for flagging this. Reading on StackOverflow this seems to be an issue with Firebase libraries / Support libraries. It only appeared in FirebaseUI 4.0 because we updated transitive dependencies. For that reason I will close this issue and move discussion to the SO thread. Should be fixed with future deps/tooling updates.