Issue 4871 - Have ESLint pass for the messageResponder

messageResponder.js

Index: messageResponder.js
diff --git a/messageResponder.js b/messageResponder.js
index e8b911a4519f8a20e86cb53a04d9b330753b127f..aba044e0f87e6e66dac01a75b8c1247095e4d0c6 100644
--- a/messageResponder.js
+++ b/messageResponder.js
@@ -18,7 +18,8 @@
 "use strict";
 
 {
-  var ext = ext || require("ext_background");
+  if (typeof ext == "undefined")

[kzar, 2017/02/08 08:39:24]

(This change is required since we'll be using `let` instead of `var` to declare
`ext` in adblockpluschrome when the related ESLint changes land there.)

+    window.ext = require("ext_background");
 
   const {port} = require("messaging");
   const {Prefs} = require("prefs");
@@ -78,28 +79,25 @@
   let listenedPreferences = Object.create(null);
   let listenedFilterChanges = Object.create(null);
   let messageTypes = {
-    "app": "app.respond",
-    "filter": "filters.respond",
-    "pref": "prefs.respond",
-    "subscription": "subscriptions.respond"
+    app: "app.respond",
+    filter: "filters.respond",
+    pref: "prefs.respond",
+    subscription: "subscriptions.respond"
   };
 
-  function sendMessage(type, action)
+  function sendMessage(type, action, ...args)
   {
     let pages = changeListeners.keys();
     if (pages.length == 0)
       return;
 
-    let args = [];
-    for (let i = 2; i < arguments.length; i++)
+    for (let i = 0; i < args.length; i++)

[Thomas Greiner, 2017/02/08 10:11:09]

Why not use a for-of loop instead to simplify the code?

[kzar, 2017/02/08 10:27:24]

Since we need to replace some arguments in place.

[Thomas Greiner, 2017/02/08 10:37:26]

Ah, don't know how I overlooked that. :p You're of course absolutely right.

Usually we'd use `Array.map()` for that instead of a for-loop so not sure why it
wasn't used here. Anyway, no need to make this change if you consider it to be
out of scope for this review.

     {
-      let arg = arguments[i];
+      let arg = args[i];
       if (arg instanceof Subscription)
-        args.push(convertSubscription(arg));
+        args[i] = convertSubscription(arg);
       else if (arg instanceof Filter)
-        args.push(convertFilter(arg));
-      else
-        args.push(arg);
+        args[i] = convertFilter(arg);
     }
 
     for (let page of pages)
@@ -110,14 +108,14 @@
       {
         page.sendMessage({
           type: messageTypes[type],
-          action: action,
-          args: args
+          action,
+          args
         });
       }
     }
   }
 
-  function addFilterListeners(type, actions)
+  function addFilterListeners(type, actions, ...args)
   {
     for (let action of actions)
     {
@@ -130,12 +128,9 @@
       if (!(name in listenedFilterChanges))
       {
         listenedFilterChanges[name] = null;
-        FilterNotifier.on(name, function()
+        FilterNotifier.on(name, () =>
         {
-          let args = [type, action];
-          for (let arg of arguments)
-            args.push(arg);
-          sendMessage.apply(null, args);
+          sendMessage(...[type, action].concat(args));

[Thomas Greiner, 2017/02/08 10:11:09]

Looks like a more complicated way of writing `sendMessage(type, action,
...args)`.

[kzar, 2017/02/08 10:27:24]

Good point, Done.

         });
       }
     }
@@ -158,7 +153,8 @@
     {
       let subscriptionInit = tryRequire("subscriptionInit");
       return {
-        filterlistsReinitialized: subscriptionInit ? subscriptionInit.reinitialized : false
+        filterlistsReinitialized: subscriptionInit
+          ? subscriptionInit.reinitialized : false
       };
     }
 
@@ -169,11 +165,16 @@
     {
       let bidiDir;
       if ("chromeRegistry" in Utils)
-        bidiDir = Utils.chromeRegistry.isLocaleRTL("adblockplus") ? "rtl" : "ltr";
+      {
+        let rtl = Utils.chromeRegistry.isLocaleRTL("adblockplus");

[Thomas Greiner, 2017/02/08 10:11:09]

Detail: It'd be great if the variable name would reflect that it's a boolean by
calling it `isRtl` or `isRTL`.

[kzar, 2017/02/08 10:27:24]

Done.

+        bidiDir = rtl ? "rtl" : "ltr";
+      }
       else
+      {
         bidiDir = ext.i18n.getMessage("@@bidi_dir");
+      }
 
-      return {locale: Utils.appLocale, bidiDir: bidiDir};
+      return {locale: Utils.appLocale, bidiDir};
     }
 
     if (message.what == "features")
@@ -229,7 +230,7 @@
                             RegExpFilter.typeMap.DOCUMENT |
                             RegExpFilter.typeMap.ELEMHIDE))
       {
-        let hostname = sender.frame.url.hostname;
+        let {hostname} = sender.frame.url;
         filters = ElemHideEmulation.getRulesForDomain(hostname);
         filters = filters.map(filter =>
         {
@@ -280,7 +281,7 @@
       for (let j = subscription.filters.length - 1; j >= 0; j--)
       {
         let filter = subscription.filters[j];
-        if (/^@@\|\|([^\/:]+)\^\$document$/.test(filter.text))
+        if (/^@@\|\|([^/:]+)\^\$document$/.test(filter.text))
           continue;
 
         if (!(filter.text in seenFilter))
@@ -359,7 +360,8 @@
       subscription.disabled = false;
       FilterStorage.addSubscription(subscription);
 
-      if (subscription instanceof DownloadableSubscription && !subscription.lastDownload)
+      if (subscription instanceof DownloadableSubscription &&
+          !subscription.lastDownload)
         Synchronizer.execute(subscription);
     }
   });
@@ -416,8 +418,8 @@
 
   port.on("subscriptions.update", (message, sender) =>
   {
-    let subscriptions = message.url ? [Subscription.fromURL(message.url)] :
-                        FilterStorage.subscriptions;
+    let subscriptions = message.url ? [Subscription.fromURL(message.url)]
+                        : FilterStorage.subscriptions;
     for (let subscription of subscriptions)
     {
       if (subscription instanceof DownloadableSubscription)