From 68cc30c1dfe8ae8ceb2dc9f3ea3e5836119acc4f Mon Sep 17 00:00:00 2001
From: Keegan McAllister <kmcallister@mozilla.com>
Date: Fri, 6 Dec 2013 16:39:59 -0800
Subject: [PATCH] Add a helper for sending a message on task failure

---
 src/components/util/task.rs | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/components/util/task.rs b/src/components/util/task.rs
index 20dc2b6ad6f..49b22348dfa 100644
--- a/src/components/util/task.rs
+++ b/src/components/util/task.rs
@@ -3,9 +3,23 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use std::task;
+use std::comm::SharedChan;
+use std::task::TaskBuilder;
 
 pub fn spawn_named<S: IntoSendStr>(name: S, f: proc()) {
     let mut builder = task::task();
     builder.name(name);
     builder.spawn(f);
 }
+
+/// Arrange to send a particular message to a channel if the task built by
+/// this `TaskBuilder` fails.
+pub fn send_on_failure<T: Send>(builder: &mut TaskBuilder, msg: T, dest: SharedChan<T>) {
+    let port = builder.future_result();
+    do spawn {
+        match port.recv() {
+            Ok(()) => (),
+            Err(..) => dest.send(msg),
+        }
+    }
+}