Task that aggregate resources from dependencies in SBT 0.11

Build.scala

import sbt._
import Keys._

object ProjectBuild extends Build {
  // setup sub projects
  // ...

  lazy val warproj = Project("war-project", file("."), settings = buildSettings) dependsOn(subproj1, subproj2 /* ... */)

  val buildSettings = {
    // libraryDependencies += ...,
    // other stuff,
    // add task that aggregates resources from dependencies
    Seq(aggrResTask)
  }

  val aggrRes= TaskKey[Seq[File]]("aggr-res", "show aggregate resources")

  val aggrResTask = aggrRes in Compile <<= {
    (thisProjectRef, buildStructure) flatMap aggrResources(resources in Compile)
  }

  def aggrResources[T](key: ScopedTask[Seq[T]])(proj: ProjectRef, struct: Load.BuildStructure) = {
    val deps = collectDeps(_.dependencies.map(_.project))(proj, struct)
    deps.flatMap(key in (_, Compile) get struct.data).join.map(_.flatten)
  }

  def collectDeps(op: ResolvedProject => Seq[ProjectRef])(projRef: ProjectRef, struct: Load.BuildStructure): Seq[ProjectRef] = {
    val deps = Project.getProject(projRef, struct).toSeq.flatMap(op)
    deps.flatMap(ref => ref +: collectDeps(op)(ref, struct)).distinct
  }
}