scala - Await.result(...) Scala 2.10 中 fatal error 和异常处理之间的区别

Question

为什么 Await.result(f, t) 会重新抛出 f 引发的异常，而不会重新抛出 fatal error ？

这是错误还是预期的行为？

以下 REPL 序列重现了该行为:

scala> import scala.concurrent.duration._
import scala.concurrent.duration._

scala> import scala.concurrent._
import scala.concurrent._

scala> val ec = scala.concurrent.ExecutionContext.global
ec: scala.concurrent.ExecutionContextExecutor = scala.concurrent.impl.ExecutionContextImpl@2d2217da

scala> Await.result(Future{throw new RuntimeException()}(ec), Duration.Inf)
java.lang.RuntimeException
    at $anonfun$1.apply(<console>:15)
    at $anonfun$1.apply(<console>:15)
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24)
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24)
    at scala.concurrent.impl.ExecutionContextImpl$$anon$3.exec(ExecutionContextImpl.scala:107)
    at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
    at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
    at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
    at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)


scala> Await.result(Future{throw new LinkageError()}(ec), Duration.Inf)
scala.NotImplementedError: an implementation is missing
    at $line28.$read$$iw$$iw$$iw$$iw$$iw$$iw$$anonfun$1.apply(<console>:15)
    at $line28.$read$$iw$$iw$$iw$$iw$$iw$$iw$$anonfun$1.apply(<console>:15)
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24)
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24)
    at scala.concurrent.impl.ExecutionContextImpl$$anon$3.exec(ExecutionContextImpl.scala:107)
    at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
    at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
    at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
    at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
    (hanging - needs ctrl-c)

两次执行之间的区别在于第一次执行将终止执行，第二次将打印堆栈跟踪然后挂起，永远等待(虽然不确定是什么)。

Edit1:将 NotImplementedError 替换为 LinkageError，因为 NotImplementedError 行为已在 2.11.1 中修改，而 LinkageError 保留一样。

Edit2:添加“致命”来描述问题中的错误。

Answer 1

发生这种情况是因为 scala.util.NonFatal(在 Future 的实现中使用)与 NotImplementedError 不匹配，导致它被视为致命的。在 2.11 中，这发生了变化，NotImplementedError 不再是 fatal error 。参见 this commit .