Adds support for the Android Feature plugin

[josh-burton]

The feature plugin is a new plugin type used in Instant Apps.

[evant]

Looks good, can we get a test for this? See https://github.com/evant/gradle-retrolambda/blob/master/gradle-retrolambda/src/test/java/me/tatarka/AndroidLibPluginTest.java for an example.

[josh-burton]

Hey Evan, I've added tests but they are currently failing.

The UI tests (or the sample projects) are failing due to issues with flavor selection in the latest AGP plugin: https://issuetracker.google.com/issues/62170415

I'm unsure why the unit tests are failing. I am getting the following error: lambda expressions are not supported in -source 1.7

Perhaps an environment setup issue?

[evant]

Hm, yep I'm getting the same error. Adding

compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
}

seems to cause I new error

com.sun.tools.javac.code.Symbol$CompletionFailure: class file for java.lang.invoke.MethodType not found

I'm getting that error running trying to run the sample app too.

[evant]

Figured it out, apprently features have a feature varaint and a library variant. Adding

android.libraryVariants.all { BaseVariant variant ->
    configureCompileJavaTask(project, variant, transform)
}

seems to fix it.

[josh-burton]

Did you add the compile options to the test projects? I'm still getting a myriad of errors with both changes 😕

[evant]

The remaining tests I see failing don't seem to be related to this change. If this is the case you are seeing, I can merge this and make a sepreate pr for the tests.

[josh-burton]

ah ok I think that may be the case. I'm happy for this to be merged.