1 files changed, 7 insertions, 6 deletions
diff --git a/lib/auto.js b/lib/auto.js
index b06e3c5..ad92d74 100644
--- a/lib/auto.js
+++ b/lib/auto.js
@@ -1,8 +1,7 @@
-import noop from './internal/noop';
-
 import once from './internal/once';
 import onlyOnce from './internal/onlyOnce';
 import wrapAsync from './internal/wrapAsync';
+import { promiseCallback, PROMISE_SYMBOL } from './internal/promiseCallback'
 
 /**
  * Determines the best order for running the {@link AsyncFunction}s in `tasks`, based on
@@ -42,7 +41,7 @@ import wrapAsync from './internal/wrapAsync';
  * pass an error to their callback. Results are always returned; however, if an
  * error occurs, no further `tasks` will be performed, and the results object
  * will only contain partial results. Invoked with (err, results).
- * @returns undefined
+ * @returns {Promise} a promise, if a callback is not passed
  * @example
  *
  * async.auto({
@@ -83,13 +82,13 @@ import wrapAsync from './internal/wrapAsync';
  *     console.log('results = ', results);
  * });
  */
-export default function (tasks, concurrency, callback) {
-    if (typeof concurrency === 'function') {
+export default function auto(tasks, concurrency, callback) {
+    if (typeof concurrency !== 'number') {
         // concurrency is optional, shift the args.
         callback = concurrency;
         concurrency = null;
     }
-    callback = once(callback || noop);
+    callback = once(callback || promiseCallback());
     var numTasks = Object.keys(tasks).length;
     if (!numTasks) {
         return callback(null);
@@ -251,4 +250,6 @@ export default function (tasks, concurrency, callback) {
         });
         return result;
     }
+
+    return callback[PROMISE_SYMBOL]
 }