How to get the list of subprojects dynamically in sbt 0.13 - sbt

Question

How can I programmatically (in build.sbt) find all the subprojects of the current root project in sbt 0.13?
(I have not tried Project.componentProjects yet, because it's new in sbt 1.0).
lazy val root = (project in file(".") ... )
val myTask = taskKey[Unit]("some description")
myTask := {
val masterRoot = baseDirectory.value
// This does not work
// val subProjects: Seq[ProjectReference] = root.aggregate
// So I tried to specify the subproject list explicitly; still does not work
val subProjects = Seq[Project](subPrj1)
subProjects.foreach { subproject =>
// All of this works if the "subproject" is hard-coded to "subPrj1"
val subprojectTarget = target.in(subproject).value / "classes"
val cp = (dependencyClasspath in(subproject, Compile, compile)).value
}
}
Got these errors:
build.sbt: error: Illegal dynamic reference: subproject
val subprojectTarget = target.in(subproject).value / "classes"
^
build.sbt: error: Illegal dynamic reference: subproject
val cp = (dependencyClasspath in(subproject, Compile, compile)).value

Answer 1

You can access a list of all subprojects via buildStructure.value.allProjectRefs.
The other part is of your problem is an aweful issue that I've also faced quite often. I was able to work around such problems by first creating a List[Task[A] and then using a recursive function to lift it into a Task[List[A]].
def flattenTasks[A](tasks: Seq[Def.Initialize[Task[A]]]): Def.Initialize[Task[List[A]]] =
tasks.toList match {
case Nil => Def.task { Nil }
case x :: xs => Def.taskDyn {
flattenTasks(xs) map (x.value :: _)
}
}
myTask := {
val classDirectories: List[File] = Def.taskDyn {
flattenTasks {
for (project ← buildStructure.value.allProjectRefs)
yield Def.task { (target in project).value / "classes" }
}
}.value
}
I've used this approach e.g. here: utility methods actual usage