resourceGenerators in Compile does not run on compile (but does run on Run)

start a new sbt project:

build.sbt:

resourceGenerators in Compile <+=
  (resourceManaged in Compile, name, version) map { (dir, n, v) =>
    println("saving git hash to resource - this should happen (only) upon compile")
    val file = dir / "version"
    val contents = Process("git rev-parse HEAD").lines.head
    IO.write(file, contents)
    Seq(file)
  }

hw.scala:

object Hi {
  def main(args: Array[String]) = {
    println("Hi!")
    val version = getClass.getResource("version")
    println(s"running from git hash ${scala.io.Source.fromURL(version).mkString}")
  }
}

Setup git: git init git add . git commit -am "initial commit"

sbt compile it, you see only:

[info] Compiling 1 Scala source to target/scala-2.10/classes...
[success] Total time: 1 s, completed Jan 30, 2015 11:37:20 AM

sbt run it, you see:

saving git hash to resource - this should happen (only) upon compile
[info] Running Hi 
Hi!
running from git hash 83931d8fec29fab2e26e7107b743adfd5d51df88

System setup:

Java HotSpot™ 64-Bit Server VM, Java 1.7.0_76)

[info] This is sbt 0.13.7 [info] The current project is built against Scala 2.10.4 [info] Available Plugins: sbt.plugins.IvyPlugin, sbt.plugins.JvmPlugin, sbt.plugins.CorePlugin, sbt.plugins.JUnitXmlReportPlugin, com.typesafe.sbteclipse.plugin.EclipsePlugin [info] sbt, sbt plugins, and build definitions are using Scala 2.10.4

(Ubuntu 14.04.1)

Related issues: https://github.com/sbt/sbt/issues/1046 https://github.com/sbt/sbt-buildinfo/issues/46 http://stackoverflow.com/questions/28223663/humane-guidance-for-sbt-dsl

[muuki88]

This is how we solved this:

• define a task that we add to the resourceGenerators
• trigger task when compile is being called

val yarnBuild: TaskKey[Seq[File]] = taskKey[Seq[File]](
  "run yarn build:prod and returns the generated assets"
)

// in settings
yarnBuild := { ... },
// add to resourceGenerators
Compile / resourceGenerators += yarnBuild.taskValue,
// trigger on compile for hot reloading, e.g. ~reStart
yarnBuild := yarnBuild.triggeredBy(Compile / compile).value

[larsrh]

@jsuereth You mentioned attaching triggers to the compile task, could you sketch what that would look like?