sbt/tasks-standard/src/test/scala/TaskRunnerCircular.scala

package sbt

import org.scalacheck._
import Prop._
import TaskGen._

object TaskRunnerCircularTest extends Properties("TaskRunner Circular") {
  property("Catches circular references") = forAll(MaxTasksGen, MaxWorkersGen) { checkCircularReferences _ }
  property("Allows references to completed tasks") = forAllNoShrink(MaxTasksGen, MaxWorkersGen) { allowedReference _ }
  final def allowedReference(intermediate: Int, workers: Int) =
    {
      val top = task(intermediate).named("top")
      def iterate(tk: Task[Int]): Task[Int] =
        tk flatMap { t =>
          if (t <= 0)
            top
          else
            iterate(task(t - 1).named((t - 1).toString))
        }
      try { checkResult(tryRun(iterate(top), true, workers), intermediate) }
      catch { case i: Incomplete if cyclic(i) => ("Unexpected cyclic exception: " + i) |: false }
    }
  final def checkCircularReferences(intermediate: Int, workers: Int) =
    {
      lazy val top = iterate(task(intermediate).named("bottom"), intermediate)
      def iterate(tk: Task[Int], i: Int): Task[Int] =
        tk flatMap { t =>
          if (t <= 0)
            top
          else
            iterate(task(t - 1).named((t - 1).toString), i - 1)
        }
      try { tryRun(top, true, workers); false }
      catch { case i: Incomplete => cyclic(i) }
    }
  def cyclic(i: Incomplete) = Incomplete.allExceptions(i).exists(_.isInstanceOf[Execute[({ type A[_] <: AnyRef })#A]#CyclicException[_]])
}