From 6a34b92771d9642203b6e0593802314b81dc0bf9 Mon Sep 17 00:00:00 2001
From: James Long <longster@gmail.com>
Date: Fri, 31 May 2013 15:52:19 -0400
Subject: [PATCH] add the spawn function for ES6 generators

---
 examples/async-generators/3-spawn.js | 27 +++++++++++++++++++++++++++
 q.js                                 | 12 ++++++++++++
 2 files changed, 39 insertions(+)
 create mode 100644 examples/async-generators/3-spawn.js

diff --git a/examples/async-generators/3-spawn.js b/examples/async-generators/3-spawn.js
new file mode 100644
index 00000000..80c6f3d8
--- /dev/null
+++ b/examples/async-generators/3-spawn.js
@@ -0,0 +1,27 @@
+var Q = require('../../q');
+
+function delay(millis, answer) {
+    const deferredResult = Q.defer();
+    setTimeout(function() {
+        deferredResult.resolve(answer);
+    }, millis);
+    return deferredResult.promise;
+}
+
+function foo() {
+    return delay(1000, 5);
+}
+
+function bar() {
+    return delay(1000, 10);
+}
+
+Q.spawn(function*() {
+    var x = yield foo();
+    console.log(x);
+
+    var y = yield bar();
+    console.log(y);
+
+    console.log('result', x + y);
+});
diff --git a/q.js b/q.js
index 374ca851..c726ce0a 100644
--- a/q.js
+++ b/q.js
@@ -1126,6 +1126,18 @@ function async(makeGenerator) {
     };
 }
 
+/**
+ * The spawn function is a small wrapper around async that immediately
+ * calls the generator and also ends the promise chain, so that any
+ * unhandled errors are thrown instead of forwarded to the error
+ * handler. This is useful because it's extremely common to run
+ * generators at the top-level to work with libraries.
+ */
+Q.spawn = spawn;
+function spawn(makeGenerator) {
+    Q.done(Q.async(makeGenerator)());
+}
+
 // FIXME: Remove this interface once ES6 generators are in SpiderMonkey.
 /**
  * Throws a ReturnValue exception to stop an asynchronous generator.