Scala Error Handling and Debugging

Main.scala

import scala.concurrent.Future
import scala.concurrent.ExecutionContext.Implicits.global

object Main extends App {
  Console.println("Running")
  val future = Future.successful(1)
  val future2 = Future.successful(2)

  def wrapFuture(future: Future[Int]) = future.flatMap{ a => 
    if(a == 1){
      Future.successful(a)
    } else {
      Future.failed(new Throwable())
    }
  }
  
  val composedFuture = for {
    a <- wrapFuture(future)
    b <- wrapFuture(future2)
  } yield {
    a + b
  }

  composedFuture onFailure {
    case t => Console.println(t.getStackTrace.mkString("\n"))
  }
}

output.txt

$ scala Main
Running
Main$$anonfun$wrapFuture$1.apply(test.scala:13)
Main$$anonfun$wrapFuture$1.apply(test.scala:9)
scala.concurrent.Future$$anonfun$flatMap$1.apply(Future.scala:253)
scala.concurrent.Future$$anonfun$flatMap$1.apply(Future.scala:251)
scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
scala.concurrent.impl.ExecutionContextImpl$AdaptedForkJoinTask.exec(ExecutionContextImpl.scala:121)
scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)