ParallelTask

Given a momoized Task,

import com.thoughtworks.zerocost.task._
val futureA: Task[String] = Task.execute("a").toFuture.toTask

and two ParallelTasks that throw exceptions,

import com.thoughtworks.zerocost.parallel.Parallel
def futureB(a: String): ParallelTask[String] = Parallel(Task.execute { throw new Exception("b failed"); a + "b" })
def futureC(a: String): ParallelTask[String] = Parallel(Task.execute { throw new Exception("c failed"); a + "c" })

and a Task that depends on two String values.

def futureD(b: String, c: String): Task[String] = Task.execute(b + c + "d")

When combining those futures together,

val futureResult = futureA.flatMap { a =>
  val Parallel(tupled) = futureB(a) product futureC(a)
  tupled.flatMap { case (b, c) =>
    futureD(b, c)
  }
}

then multiple exceptions should be handled together.

futureResult.handleError {
  case MultipleException(throwables) if throwables.map(_.getMessage) == Set("b failed", "c failed") =>
    "Multiple exceptions handled"
}.map {
  _ should be("Multiple exceptions handled")
}.toFuture