TestChanged.scala

// WIP based on the similar sbt plugin in Alpakka

package com.tzavellas

import scala.collection.immutable
import scala.sys.process._

import sbt._
import sbt.Keys._

object TestChanged extends AutoPlugin {

  override def trigger = allRequirements
  override def requires = plugins.JvmPlugin

  val diffTarget = settingKey[String]("The branch to diff against")
  val subprojectRoot = settingKey[String]("The root directory for sub-projects")
  val onlyScala = settingKey[Boolean]("Whether only changed Scala files trigger tests")

  val changedDirectories = taskKey[immutable.Set[String]]("List of touched modules in this PR branch")
  val changedSubprojects = taskKey[immutable.Set[String]]("List of touched modules in this PR branch")
  val testChanged = taskKey[Unit]("Test all subprojects with changes compared to master")

  private val scalaFileExtensions = Seq(".java", ".scala", ".sbt", ".routes")

  override lazy val buildSettings = Seq(
    diffTarget := "origin/production",
    subprojectRoot := "",
    onlyScala := true,
    changedDirectories := {
      val log = streams.value.log
      val target = diffTarget.value

      val diffOutput = s"git diff $target --name-only".!!.split("\n")

      val changedDirectories =
        diffOutput
          .map(_.trim)
          .filter(f => !onlyScala.value || scalaFileExtensions.exists(f.endsWith))
          .map(f =>
            if (subprojectRoot.value.isEmpty) f.takeWhile(_ != '/')
            else if (!f.startsWith(subprojectRoot.value)) f.takeWhile(_ != '/')
            else subprojectRoot.value + "/" + f.replaceAll(subprojectRoot.value + "/", "").takeWhile(_ != '/'))
          .map(new File(_))
          .map(file => if (file.isDirectory) file.toString else ".")
          .toSet

      log.info("Detected changes in directories: " + changedDirectories.mkString("[", ", ", "]"))
      changedDirectories
    },
    changedSubprojects := {
      val log = streams.value.log
      val transitiveClasspath = buildDependencies.value.classpathTransitive
      val changedDirs = changedDirectories.value
      val changedSubprojects = transitiveClasspath.filter { case (pr, deps) =>
        shouldBuild(pr.project, changedDirs) ||
          deps.exists(dep => shouldBuild(dep.project, changedDirs))
      }.map(_._1.project).toSet
      log.info("Detected changes in subprojects: " + changedSubprojects.mkString("[", ", ", "]"))
      changedSubprojects
    }
  )

  override lazy val projectSettings = Seq(
    testChanged := Def.taskDyn {
      val skip = Def.setting { task(()) }
      if (changedSubprojects.value.contains(name.value)) test in Test
      else skip
    }.value
  )

  private def shouldBuild(projectName: String, changedDirectories: Set[String]) =
      changedDirectories.exists(_.endsWith(projectName)) || // project files changed
        changedDirectories.contains(".") || changedDirectories.contains("project") // sbt changed
}