ES6-ify codebase (#1553)

* cancelable foreach

* cancelable waterfall

* cancellable auto

* fix lint

* fix tests

* cancelable whilst/until/during/forever

* fix waterfall test.  It WILL get there

* docs

* use rest params instead of slice

* clean up internals

* remove property func

* clarify uses of createTester

* happy path async funtions in asyncify

* stop using arguments

* DLL to class

* moar arrows

* fix merge issues

* remove forOwn

* moar arrows

* fix merge mistake

* even more arrows, what can stop him

* mo more fn.apply(null,...)

* remove more spurious uses of apply

* update lint config

* just when you thought there couldn't possibly be more arrows

* use eslint:recommended

* even less uses or aguments

* get rid of prototype cuteness

* fix concat tests

* fix more tests

1 files changed, 14 insertions, 18 deletions

diff --git a/lib/auto.js b/lib/auto.js
index 500620a..adfdfa1 100644
--- a/lib/auto.js
+++ b/lib/auto.js
@@ -1,7 +1,5 @@
 import noop from './internal/noop';
 
-import forOwn from './internal/forOwn';
-import slice from './internal/slice';
 import once from './internal/once';
 import onlyOnce from './internal/onlyOnce';
 import wrapAsync from './internal/wrapAsync';
@@ -114,7 +112,8 @@ export default function (tasks, concurrency, callback) {
     // without the possibility of returning to an ancestor task
     var uncheckedDependencies = {};
 
-    forOwn(tasks, function (task, key) {
+    Object.keys(tasks).forEach(key => {
+        var task = tasks[key]
         if (!Array.isArray(task)) {
             // no dependencies
             enqueueTask(key, [task]);
@@ -131,14 +130,14 @@ export default function (tasks, concurrency, callback) {
         }
         uncheckedDependencies[key] = remainingDependencies;
 
-        dependencies.forEach(function (dependencyName) {
+        dependencies.forEach(dependencyName => {
             if (!tasks[dependencyName]) {
                 throw new Error('async.auto task `' + key +
                     '` has a non-existent dependency `' +
                     dependencyName + '` in ' +
                     dependencies.join(', '));
             }
-            addListener(dependencyName, function () {
+            addListener(dependencyName, () => {
                 remainingDependencies--;
                 if (remainingDependencies === 0) {
                     enqueueTask(key, task);
@@ -151,9 +150,7 @@ export default function (tasks, concurrency, callback) {
     processQueue();
 
     function enqueueTask(key, task) {
-        readyTasks.push(function () {
-            runTask(key, task);
-        });
+        readyTasks.push(() => runTask(key, task));
     }
 
     function processQueue() {
@@ -179,9 +176,7 @@ export default function (tasks, concurrency, callback) {
 
     function taskComplete(taskName) {
         var taskListeners = listeners[taskName] || [];
-        taskListeners.forEach(function (fn) {
-            fn();
-        });
+        taskListeners.forEach(fn => fn());
         processQueue();
     }
 
@@ -189,19 +184,19 @@ export default function (tasks, concurrency, callback) {
     function runTask(key, task) {
         if (hasError) return;
 
-        var taskCallback = onlyOnce(function(err, result) {
+        var taskCallback = onlyOnce((err, ...result) => {
             runningTasks--;
             if (err === false) {
                 canceled = true
                 return
             }
-            if (arguments.length > 2) {
-                result = slice(arguments, 1);
+            if (result.length < 2) {
+                result = result[0];
             }
             if (err) {
                 var safeResults = {};
-                forOwn(results, function(val, rkey) {
-                    safeResults[rkey] = val;
+                Object.keys(results).forEach(rkey => {
+                    safeResults[rkey] = results[rkey];
                 });
                 safeResults[key] = result;
                 hasError = true;
@@ -232,7 +227,7 @@ export default function (tasks, concurrency, callback) {
         while (readyToCheck.length) {
             currentTask = readyToCheck.pop();
             counter++;
-            getDependents(currentTask).forEach(function (dependent) {
+            getDependents(currentTask).forEach(dependent => {
                 if (--uncheckedDependencies[dependent] === 0) {
                     readyToCheck.push(dependent);
                 }
@@ -248,7 +243,8 @@ export default function (tasks, concurrency, callback) {
 
     function getDependents(taskName) {
         var result = [];
-        forOwn(tasks, function (task, key) {
+        Object.keys(tasks).forEach(key => {
+            const task = tasks[key]
             if (Array.isArray(task) && task.indexOf(taskName) >= 0) {
                 result.push(key);
             }