1 files changed, 39 insertions, 18 deletions

diff --git a/lib/auto.js b/lib/auto.js
index 327383b..0e9d108 100644
--- a/lib/auto.js
+++ b/lib/auto.js
@@ -34,13 +34,16 @@ export default function (tasks, concurrency, callback) {
     var hasError = false;
 
     var listeners = [];
+
     function addListener(fn) {
         listeners.unshift(fn);
     }
+
     function removeListener(fn) {
         var idx = indexOf(listeners, fn);
         if (idx >= 0) listeners.splice(idx, 1);
     }
+
     function taskComplete() {
         remainingTasks--;
         arrayEach(listeners.slice(), function (fn) {
@@ -69,6 +72,7 @@ export default function (tasks, concurrency, callback) {
                 });
                 safeResults[k] = args;
                 hasError = true;
+                listeners = [];
 
                 callback(err, safeResults);
             }
@@ -77,37 +81,54 @@ export default function (tasks, concurrency, callback) {
                 setImmediate(taskComplete);
             }
         });
+
         var requires = task.slice(0, task.length - 1);
-        // prevent dead-locks
-        var len = requires.length;
-        var dep;
-        while (len--) {
-            if (!(dep = tasks[requires[len]])) {
-                throw new Error('Has non-existent dependency in ' +
-                    requires.join(', '));
-            }
-            if (isArray(dep) && indexOf(dep, k) >= 0) {
-                throw new Error('Has cyclic dependencies');
+
+        checkForDeadlocks();
+
+        if (ready()) {
+            startNext();
+        } else {
+            addListener(listener);
+        }
+
+        function checkForDeadlocks() {
+            var len = requires.length;
+            var dep;
+            while (len--) {
+                if (!(dep = tasks[requires[len]])) {
+                    throw new Error('Has non-existent dependency in ' +
+                        requires.join(', '));
+                }
+                if (isArray(dep) && indexOf(dep, k) >= 0) {
+                    throw new Error('Has cyclic dependencies');
+                }
             }
         }
+
         function ready() {
-            return runningTasks < concurrency && !baseHas(results, k) &&
+            return runningTasks < concurrency &&
+                !baseHas(results, k) &&
+                !hasError &&
                 arrayEvery(requires, function (x) {
                     return baseHas(results, x);
                 });
         }
-        if (ready()) {
+
+        function startNext() {
             runningTasks++;
-            task[task.length - 1](taskCallback, results);
-        }
-        else {
-            addListener(listener);
+            var taskFn = task[task.length - 1];
+            if (requires.length > 0) {
+                taskFn(results, taskCallback);
+            } else {
+                taskFn(taskCallback);
+            }
         }
+
         function listener() {
             if (ready()) {
-                runningTasks++;
                 removeListener(listener);
-                task[task.length - 1](taskCallback, results);
+                startNext();
             }
         }
     });