🐛 [firebase_core] Support Gradle 8

[guidezpl]

Bug report

Describe the bug
Gradle 8 is not supported.

Steps to reproduce

Steps to reproduce the behavior:

1. Update a Flutter's build.gradle to use classpath 'com.android.tools.build:gradle:8.0.0'
2. Try to build
3. See error:

A problem occurred configuring project ':firebase_core'.
> Could not create an instance of type com.android.build.api.variant.impl.LibraryVariantBuilderImpl.
   > Namespace not specified. Please specify a namespace in the module's build.gradle file like so:

android {
    namespace 'com.example.namespace'
}

* Try:
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.

Expected behavior

No errors

Sample project

https://github.com/flutter/gallery

[darshankawar]

Similar issue in flutter repo for more details: flutter/flutter#125181

flutter/flutter#125181 (comment)

[darshankawar]

/cc @Lyokone

[vbuberen]

Would like to share some of experience of trying to update to AGP 8 and Gradle 8 for one of packages: ajinasokan/flutter_displaymode#21

The issue is in missing namespace only. However, I would suggest to not remove package tag for now (till integration_tests package supports the new namespace property) from AndroidManifest to not fail integration tests as it happens here: https://github.com/fluttercommunity/plus_plugins/actions/runs/4756241629/jobs/8451506112?pr=1699
Finally, Flutter 3.7.12 is required to build the project after updates or, otherwise, there will be errors pointing to flutter_tools, like I had yesterday before moving from 3.7.11:

FAILURE: Build failed with an exception.
* Where:
Script '/Users/vb/Development/flutter/packages/flutter_tools/gradle/flutter.gradle' line: 912

[Lyokone]

Support for AGP 8.0 will be rolled out in a couple of hours. Please note that some of our dependencies (like GRPC Java) are not fully compatible yet. So if you are using Firestore / Database or Performance) you should probably wait a bit on AGP 7.4.2 till every dependency is compatible.

[Lyokone]

After some more investigation, it seems that adding the

  integration_test:
    sdk: flutter

is what is causing the R8 errors. Till integration_test is, not fully updated you should stay on 7.4.2 if your are using integration testing.