SBT Post compile source generator.

GeneratorPlugin.scala

object GeneratorPlugin extends AutoPlugin {
    object autoImport {
      val generateSource = TaskKey[Seq[File]]("genmysources","Generates sources")
    }
    import autoImport._
    
    lazy val MyGenerator = config("my-generator").extend(Compile)

   override lazy val projectSettings = Seq[Def.Setting[_]](
    ivyConfigurations += MyGenerator
  ) ++ fromScope(Compile)


  def fromScope(scope: Configuration) = inConfig(MyGenerator)(Defaults.configSettings ++ Seq[Def.Setting[_]](
      classDirectory      := (classDirectory in scope).value //I've worked around MyGenerator grating it's own artifact by setting 
                                                             //classDirectory like so
      sourceManaged       := (sourceManaged in scope).value / "myGeneratedSources",
      val generateSource  <<= (javaHome, compilerClasspath,
                                                  fullClasspath in scope, classDirectory,
                                                  sourceManaged, streams) map (doGenerateSources),
      sourceGenerators    += generateSource.taskValue
  )


   def doGenerateSources = ...
}