From d2fe2b323820f4fbce268ade71435d58088118bb Mon Sep 17 00:00:00 2001
From: Alexander Early <alexander.early@gmail.com>
Date: Sun, 6 Mar 2016 17:33:08 -0800
Subject: defend against multiple callbacks

---
 lib/waterfall.js | 34 +++++++++++++++++++---------------
 1 file changed, 19 insertions(+), 15 deletions(-)

(limited to 'lib/waterfall.js')

diff --git a/lib/waterfall.js b/lib/waterfall.js
index 8867c87..e25f629 100644
--- a/lib/waterfall.js
+++ b/lib/waterfall.js
@@ -5,28 +5,32 @@ import noop from 'lodash/noop';
 import once from 'lodash/once';
 import rest from 'lodash/rest';
 
-import ensureAsync from './ensureAsync';
-import iterator from './iterator';
+import onlyOnce from './internal/onlyOnce';
 
 export default  function(tasks, cb) {
     cb = once(cb || noop);
     if (!isArray(tasks)) return cb(new Error('First argument to waterfall must be an array of functions'));
     if (!tasks.length) return cb();
+    var taskIndex = 0;
 
-    function wrapIterator(iterator) {
-        return rest(function(err, args) {
+    function nextTask(args) {
+        if (taskIndex === tasks.length) {
+            return cb.apply(null, [null].concat(args));
+        }
+        var task = tasks[taskIndex];
+        taskIndex++;
+
+        var taskCallback = onlyOnce(rest(function(err, args) {
             if (err) {
-                cb.apply(null, [err].concat(args));
-            } else {
-                var next = iterator.next();
-                if (next) {
-                    args.push(wrapIterator(next));
-                } else {
-                    args.push(cb);
-                }
-                ensureAsync(iterator).apply(null, args);
+                return cb.apply(null, [err].concat(args));
             }
-        });
+            nextTask(args);
+        }));
+
+        args.push(taskCallback);
+
+        task.apply(null, args);
     }
-    wrapIterator(iterator(tasks))();
+
+    nextTask([]);
 }
-- 
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