From e896c0ab2d36740207f91086262e9feb4fc1c32d Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Wed, 25 Jul 2012 15:58:45 +0200
Subject: Adds method askForResponse

Adds method askForResponse which returns a response immediately instead of waiting for a result. That way, one can wait for an ask's result using a timeout.
---
 .../scala/tools/nsc/interactive/CompilerControl.scala     | 15 ++++++++++++++-
 src/compiler/scala/tools/nsc/util/InterruptReq.scala      | 11 +++++++++++
 src/compiler/scala/tools/nsc/util/WorkScheduler.scala     |  7 ++++++-
 3 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/src/compiler/scala/tools/nsc/interactive/CompilerControl.scala b/src/compiler/scala/tools/nsc/interactive/CompilerControl.scala
index 801b4ad22b..aab1c8fb7e 100644
--- a/src/compiler/scala/tools/nsc/interactive/CompilerControl.scala
+++ b/src/compiler/scala/tools/nsc/interactive/CompilerControl.scala
@@ -252,6 +252,19 @@ trait CompilerControl { self: Global =>
   /** Asks for a computation to be done quickly on the presentation compiler thread */
   def ask[A](op: () => A): A = if (self.onCompilerThread) op() else scheduler doQuickly op
 
+  /** Asks for a computation to be done on presentation compiler thread, returning
+   *  a response with the result or an exception
+   */
+  def askForResponse[A](op: () => A): Response[A] = {
+    val r = new Response[A]
+    val ir = scheduler askDoQuickly op
+    ir onComplete {
+      case Left(result) => r set result
+      case Right(exc) => r raise exc
+    }
+    r
+  }
+
   def onCompilerThread = Thread.currentThread == compileRunner
 
   /** Info given for every member found by completion
@@ -390,7 +403,7 @@ trait CompilerControl { self: Global =>
         case _ => println("don't know what to do with this " + action.getClass)
       }
     }
-    
+
     override def doQuickly[A](op: () => A): A = {
       throw new FailedInterrupt(new Exception("Posted a work item to a compiler that's shutting down"))
     }
diff --git a/src/compiler/scala/tools/nsc/util/InterruptReq.scala b/src/compiler/scala/tools/nsc/util/InterruptReq.scala
index 61aaa1bdcb..816d16f767 100644
--- a/src/compiler/scala/tools/nsc/util/InterruptReq.scala
+++ b/src/compiler/scala/tools/nsc/util/InterruptReq.scala
@@ -2,6 +2,7 @@ package scala.tools.nsc
 package util
 
 /** A class of work items to be used in interrupt requests.
+ *  Todo: we should replace the Eithers by Futures or Try's.
  */
 abstract class InterruptReq {
   /** The result type of the operation
@@ -11,9 +12,14 @@ abstract class InterruptReq {
   /** The operation to be performed */
   protected val todo: () => R
 
+  type Continuation = Either[R, Throwable] => Unit
+
   /** The result provided */
   private var result: Option[Either[R, Throwable]] = None
 
+  /** The continuations waiting asynchronously on a provided result */
+  private var waiting: List[Continuation] = Nil
+
   /** To be called from interrupted server to execute demanded task */
   def execute(): Unit = synchronized {
     try {
@@ -22,6 +28,7 @@ abstract class InterruptReq {
       case t: Throwable => result = Some(Right(t))
     } finally {
       notify()
+      for (k <- waiting.reverse) k(result.get)
     }
   }
 
@@ -38,6 +45,10 @@ abstract class InterruptReq {
       case Right(t) => throw new FailedInterrupt(t)
     }
   }
+
+  def onComplete(k: Continuation) = synchronized {
+    waiting = k :: waiting
+  }
 }
 
 class FailedInterrupt(cause: Throwable) extends Exception("Compiler exception during call to 'ask'", cause)
diff --git a/src/compiler/scala/tools/nsc/util/WorkScheduler.scala b/src/compiler/scala/tools/nsc/util/WorkScheduler.scala
index 8c037cbda5..b1f4696d3e 100644
--- a/src/compiler/scala/tools/nsc/util/WorkScheduler.scala
+++ b/src/compiler/scala/tools/nsc/util/WorkScheduler.scala
@@ -54,6 +54,11 @@ class WorkScheduler {
 
   /** Called from client: have interrupt executed by server and return result */
   def doQuickly[A](op: () => A): A = {
+    val ir = askDoQuickly(op)
+    ir.getResult()
+  }
+
+  def askDoQuickly[A](op: () => A): InterruptReq { type R = A } = {
     val ir = new InterruptReq {
       type R = A
       val todo = op
@@ -62,7 +67,7 @@ class WorkScheduler {
       interruptReqs enqueue ir
       notify()
     }
-    ir.getResult()
+    ir
   }
 
   /** Called from client: have action executed by server */
-- 
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