Pass dependencies symbolically to WireTask for better Gradle caching

[swankjesse]

Right now we pass dependencies to WireTask as the absolute paths to the resolved artifact, like so:

/Users/jwilson/.m2/repository/com/squareup/wire/dinosaur/all-protos/1.0/all-protos-1.0.jar

This won’t work for shared Gradle caches. We should instead use a symbolic identifier like com.squareup.wire.dinosaur:all-protos:1.0 that is independent of the current environment’s artifact directory.

[martinbonnin]

At the end of the day, I think the task inputs should be ConfigurableFileCollection everywhere. ConfigurableFileCollections can contain:

• a local zipTree
• a fileTree folder + include rules
• or a configuration with project() dependencies.

Which I think covers all the use cases? Then the task could be trimmed down to just:

abstract class WireTask @Inject constructor(
  objects: ObjectFactory,
  private val fileOperations: FileOperations,
) : DefaultTask() {

  @get:InputFiles
  @SkipWhenEmpty
  @get:PathSensitive(PathSensitivity.RELATIVE)
  abstract val protoSourceFiles: ConfigurableFileCollection

  @InputFiles
  @PathSensitive(PathSensitivity.RELATIVE)
  abstract val protoPathFiles: ConfigurableFileCollection

  // ...
}

(I thought SourceTask was needed for @SkipWhenEmpty but turns out it's not so it brings very little value compared to DefaultTask)

The nice bonus is that ConfigurableFileCollections are "lazy". They won't try to resolve their configurations until the task starts executing.