Migrate to the Android Gradle Plugin's new variant APIs

[jschear]

AGP 4+ contains new APIs for accessing build variants (and the APKs produced for each of them), and the existing APIs have been deprecated.

The main differences appear to be:

• com.android.build.gradle.api.TestVariant has been replaced by com.android.build.api.variant.AndroidTest.
• Instead of using com.android.build.gradle.AppExtension and com.android.build.gradle.TestedExtension to access build variants, one needs to use com.android.build.api.variant.ApplicationAndroidComponentsExtension to access com.android.build.api.variant.ApplicationVariant, which has a androidTest: AndroidTest? property for the corresponding instrumentation test variant. (And com.android.build.api.variant.LibraryAndroidComponentsExtension to access com.android.build.api.variant.LibraryVariant.)
• ApplicationVariant, LibraryVariant, and AndroidTest expose their outputs as com.android.build.api.variant.VariantOutputs, but there's no longer a way to get the path to each APK output via that API. Instead, one has to use the com.android.build.api.artifact.Artifacts API to access a DirectoryProperty for the folder the APKs are placed in, and use BuiltArtifactsLoader to access the outputs within a task action.
  • There's an example here: https://github.com/android/gradle-recipes/blob/agp-7.0/Kotlin/getApksTest/app/build.gradle.kts

I've taken a stab at the update here, but the BuiltArtifactsLoader change is a bit tricky: https://github.com/runningcode/fladle/compare/master...jschear:js/agp_7

[runningcode]

Thanks for filing. This is a good idea. 👍 I'll try to take a look at your solution soon.

[jstewart5000]

👋🏾 @runningcode Curious if there is an ETA on this migration? If you are super swamped @jschear and I might look into making this one happen. Let us know whenever you get a chance 😃

[runningcode]

Hey, sorry there's no ETA on this. Sorry I haven't got a chance to look at it. October is a busy month for me but perhaps later I will be able to take a look at it. Feel free to contribute or pick up the PR.

[jschear]

Sounds good -- thanks for the update. We've been looking at making some other changes (in short: our app uses ABI splits, which fladle/fulladle doesn't handle right now), and were having trouble deciding between implementing them using the old AGP APIs, or upgrading to the new APIs first.