Fix Android behaviour with Android Gradle Plugin >=4.2.0

[bwindsor]

React Native 0.65 upgraded the Android Gradle Plugin to 4.2.1, which causes anything using react-native-config to fail with the following error:

The value for property 'buildConfigFields' is final and cannot be changed any further.

Gradle has multiple phases: https://docs.gradle.org/current/userguide/build_lifecycle.html. The reason for this error is that Gradle executes the contents of task.doFirst during the execution phase. However, during execution then buildConfigFields is final so cannot be modified. It can only be modified during the configure phase.

This PR removes the task.doFirst callback, and simply executes the code inside the callback immediately during the configure phase. This has been tested by myself and some other users (see #567) and still works with multiple build types and multiple flavors, both with gradle plugin 4.1.x and 4.2.x.

My assumption as to why this upgrade broke react-native-config is that Gradle decided to strictly enforce that buildConfigFields is final during the execution phase, whereas in previous versions it probably wasn't enforced but should have been. Google are aware of this change in behaviour (https://issuetracker.google.com/issues/172657565) and closed the issue with a Won't fix (intended behaviour) response. So it's up to react-native-config to change to be compatible with this new behaviour.

Fixes #567
Fixes #578
Fixes #608

[octsiri]

May I know which version of gradle plugin you use for this fixing? For RN-0.65.1 they used 4.2.1. I try to implement but still got some errors, Need help, thanks

[mlazari]

May I know which version of gradle plugin you use for this fixing? For RN-0.65.1 they used 4.2.1. I try to implement but still got some errors, Need help, thanks

I've verified this with classpath 'com.android.tools.build:gradle:4.2.1', distributionUrl=https\://services.gradle.org/distributions/gradle-6.9-all.zip and worked fine for me.

[bwindsor]

@octsiri I'm using the same as @mlazari is using. It's the same versions as RN-0.65.1 uses. You also get errors when updating to 4.2.x if you're using an old version of Android Studio, make sure you're on the latest. I expect your errors are likely due to something different. If you're using the "quick fix" way of editing a file in node_modules to implement this PR just to see if it works, make sure you clean your build to ensure the changes are definitely picked up as well.

[bwindsor]

@sanduluca Thanks for approving - what needs to be done to merge this?

[luancurti]

Thank you @bwindsor

[virajverlekar-tm]

When will this change be added to a release tag?

[luancurti]

Published 🚀