From 75c8ac33b48775e80f832b0cf34f42c4bf60f4ca Mon Sep 17 00:00:00 2001
From: Roland <rk@rkuhn.info>
Date: Tue, 29 Nov 2011 16:37:48 +0100
Subject: [PATCH] =?UTF-8?q?make=20next=20state=E2=80=99s=20data=20availabl?=
 =?UTF-8?q?e=20in=20onTransition=20blocks,=20fixes=20#1422?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

cherry-picked from release-1.3
---
 .../scala/akka/actor/FSMTransitionSpec.scala  | 25 +++++++++++++++++++
 .../src/main/scala/akka/actor/FSM.scala       |  7 ++++++
 2 files changed, 32 insertions(+)

diff --git a/akka-actor-tests/src/test/scala/akka/actor/FSMTransitionSpec.scala b/akka-actor-tests/src/test/scala/akka/actor/FSMTransitionSpec.scala
index afdf9da5eb..7c67d8e1e1 100644
--- a/akka-actor-tests/src/test/scala/akka/actor/FSMTransitionSpec.scala
+++ b/akka-actor-tests/src/test/scala/akka/actor/FSMTransitionSpec.scala
@@ -29,6 +29,19 @@ object FSMTransitionSpec {
     override def preRestart(reason: Throwable, msg: Option[Any]) { target ! "restarted" }
   }
 
+  class OtherFSM(target: ActorRef) extends Actor with FSM[Int, Int] {
+    startWith(0, 0)
+    when(0) {
+      case Ev("tick") ⇒ goto(1) using (1)
+    }
+    when(1) {
+      case Ev(_) ⇒ stay
+    }
+    onTransition {
+      case 0 -> 1 ⇒ target ! ((stateData, nextStateData))
+    }
+  }
+
   class Forwarder(target: ActorRef) extends Actor {
     def receive = { case x ⇒ target ! x }
   }
@@ -72,4 +85,16 @@ class FSMTransitionSpec extends AkkaSpec with ImplicitSender {
     }
   }
 
+  "A FSM" must {
+
+    "make previous and next state data available in onTransition" in {
+      val fsm = system.actorOf(new OtherFSM(testActor))
+      within(300 millis) {
+        fsm ! "tick"
+        expectMsg((0, 1))
+      }
+    }
+
+  }
+
 }
diff --git a/akka-actor/src/main/scala/akka/actor/FSM.scala b/akka-actor/src/main/scala/akka/actor/FSM.scala
index e4ca89770a..9419fccc60 100644
--- a/akka-actor/src/main/scala/akka/actor/FSM.scala
+++ b/akka-actor/src/main/scala/akka/actor/FSM.scala
@@ -382,6 +382,11 @@ trait FSM[S, D] extends ListenerManagement {
    */
   protected[akka] def stateData: D = currentState.stateData
 
+  /**
+   * Return next state data (available in onTransition handlers)
+   */
+  protected[akka] def nextStateData = nextState.stateData
+
   /*
    * ****************************************************************
    *                PRIVATE IMPLEMENTATION DETAILS
@@ -393,6 +398,7 @@ trait FSM[S, D] extends ListenerManagement {
    */
   private var currentState: State = _
   private var timeoutFuture: Option[Cancellable] = None
+  private var nextState: State = _
   private var generation: Long = 0L
 
   /*
@@ -515,6 +521,7 @@ trait FSM[S, D] extends ListenerManagement {
     } else {
       nextState.replies.reverse foreach { r ⇒ sender ! r }
       if (currentState.stateName != nextState.stateName) {
+        this.nextState = nextState
         handleTransition(currentState.stateName, nextState.stateName)
         notifyListeners(Transition(self, currentState.stateName, nextState.stateName))
       }