feat: Canceling flows (#1542)

* cancelable foreach

* cancelable waterfall

* cancellable auto

* fix lint

* fix tests

* cancelable whilst/until/during/forever

* fix waterfall test.  It WILL get there

* docs

* auto should not start other tasks once canceled

* simplify waterfall, add test for arrays

* simplify eachOf

* cancelable retry

* cancelable eachOf for arrays

* revert test tweak

1 files changed, 7 insertions, 1 deletions

diff --git a/lib/auto.js b/lib/auto.js
index a6150aa..500620a 100644
--- a/lib/auto.js
+++ b/lib/auto.js
@@ -102,6 +102,7 @@ export default function (tasks, concurrency, callback) {
 
     var results = {};
     var runningTasks = 0;
+    var canceled = false;
     var hasError = false;
 
     var listeners = Object.create(null);
@@ -156,6 +157,7 @@ export default function (tasks, concurrency, callback) {
     }
 
     function processQueue() {
+        if (canceled) return
         if (readyTasks.length === 0 && runningTasks === 0) {
             return callback(null, results);
         }
@@ -189,6 +191,10 @@ export default function (tasks, concurrency, callback) {
 
         var taskCallback = onlyOnce(function(err, result) {
             runningTasks--;
+            if (err === false) {
+                canceled = true
+                return
+            }
             if (arguments.length > 2) {
                 result = slice(arguments, 1);
             }
@@ -200,7 +206,7 @@ export default function (tasks, concurrency, callback) {
                 safeResults[key] = result;
                 hasError = true;
                 listeners = Object.create(null);
-
+                if (canceled) return
                 callback(err, safeResults);
             } else {
                 results[key] = result;