combining input task with dynamic task in sbt

Question

I\'d like to make an input task that proceed user input and generate bunch of subtasks to run. Here is the example:

import sbt._
import Keys._
import Def.Initial         


        

Answer 1

Trial and error method gave me the answer but non a single bit of understanding. Here it is:

import sbt._
import Keys._
import Def.Initialize
import complete.DefaultParsers._

object TestBuild extends Build {
  val sampleInput = inputKey[Seq[String]]("sample dynamic input task")
  val sampleDynamic = taskKey[Seq[String]]("sample dynamic task")

  override lazy val settings = super.settings ++ Seq(
    sampleDynamic := Def.taskDyn {
      val sources = Seq("ab", "csd", "efda")
      sources.map(sampleTaskFor _).joinWith(_.join)
    }.value,
    sampleInput := Def.inputTaskDyn {
      val sources = spaceDelimited("").parsed
      sampleTaskAll(sources)
    }.evaluated
  )

  private def sampleTaskFor(source : String) : Initialize[Task[String]] = Def.task {
    source + " : " + source
  }

  private def sampleTaskAll(sources : Seq[String]) : Initialize[Task[Seq[String]]] = Def.taskDyn {
    sources.map(sampleTaskFor _).joinWith(_.join)
  }
}

For a reason I can not comprehend you should isolate creating multitask out of sequence of single tasks in a separate method.