Issue 4864 - Start using ESLint for adblockpluschrome

include.preload.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+/* globals ElemHideEmulation, splitSelector */
+
 "use strict";
 
-const typeMap = {
-  "img": "IMAGE",
-  "input": "IMAGE",
-  "picture": "IMAGE",
-  "audio": "MEDIA",
-  "video": "MEDIA",
-  "frame": "SUBDOCUMENT",
-  "iframe": "SUBDOCUMENT",
-  "object": "OBJECT",
-  "embed": "OBJECT"
-};
+// This variable is also used by our other content scripts.
+let elemhide;
+
+const typeMap = new Map([
+  ["img", "IMAGE"],
+  ["input", "IMAGE"],
+  ["picture", "IMAGE"],
+  ["audio", "MEDIA"],
+  ["video", "MEDIA"],
+  ["frame", "SUBDOCUMENT"],
+  ["iframe", "SUBDOCUMENT"],
+  ["object", "OBJECT"],
+  ["embed", "OBJECT"]
+]);
 
 function getURLsFromObjectElement(element)
 {
   let url = element.getAttribute("data");
   if (url)
     return [url];
 
   for (let child of element.children)
   {
     if (child.localName != "param")
       continue;
 
     let name = child.getAttribute("name");
-    if (name != "movie"  && // Adobe Flash
+    if (name != "movie" &&  // Adobe Flash
         name != "source" && // Silverlight
-        name != "src"    && // Real Media + Quicktime
+        name != "src" &&    // Real Media + Quicktime
         name != "FileName") // Windows Media
       continue;
 
     let value = child.getAttribute("value");
     if (!value)
       continue;
 
     return [value];
   }
 
@@ skipping 20 matching lines @@
   return urls;
 }
 
 function getURLsFromMediaElement(element)
 {
   let urls = getURLsFromAttributes(element);
 
   for (let child of element.children)
   {
     if (child.localName == "source" || child.localName == "track")
-      urls.push.apply(urls, getURLsFromAttributes(child));
+      urls.push(...getURLsFromAttributes(child));
   }
 
   if (element.poster)
     urls.push(element.poster);
 
   return urls;
 }
 
 function getURLsFromElement(element)
 {
@@ skipping 19 matching lines @@
   {
     if (/^(?!https?:)[\w-]+:/i.test(urls[i]))
       urls.splice(i--, 1);
   }
 
   return urls;
 }
 
 function checkCollapse(element)
 {
-  let mediatype = typeMap[element.localName];
+  let mediatype = typeMap.get(element.localName);
   if (!mediatype)
     return;
 
   let urls = getURLsFromElement(element);
   if (urls.length == 0)
     return;
 
   ext.backgroundPage.sendMessage(
     {
       type: "filters.collapse",
-      urls: urls,
-      mediatype: mediatype,
+      urls,
+      mediatype,
       baseURL: document.location.href
     },
 
     collapse =>
     {
       function collapseElement()
       {
         let propertyName = "display";
         let propertyValue = "none";
         if (element.localName == "frame")
@@ skipping 22 matching lines @@
   );
 }
 
 function checkSitekey()
 {
   let attr = document.documentElement.getAttribute("data-adblockkey");
   if (attr)
     ext.backgroundPage.sendMessage({type: "filters.addKey", token: attr});
 }
 
-function getContentDocument(element)
-{
-  try
-  {
-    return element.contentDocument;
-  }
-  catch (e)
-  {
-    return null;
-  }
-}
-
 function ElementHidingTracer()
 {
   this.selectors = [];
   this.filters = [];
 
   this.changedNodes = [];
   this.timeout = null;
 
   this.observer = new MutationObserver(this.observe.bind(this));
   this.trace = this.trace.bind(this);
@@ skipping 31 matching lines @@
           if (getComputedStyle(element).display == "none")
           {
             matchedSelectors.push(filters[i].replace(/^.*?##/, ""));
             break nodes;
           }
         }
       }
     }
 
     if (matchedSelectors.length > 0)
+    {
       ext.backgroundPage.sendMessage({
         type: "devtools.traceElemHide",
         selectors: matchedSelectors
       });
+    }
   },
 
   onTimeout()
   {
     this.checkNodes(this.changedNodes, this.selectors, this.filters);
     this.changedNodes = [];
     this.timeout = null;
   },
 
   observe(mutations)
@@ skipping 83 matching lines @@
   document.documentElement.removeChild(script);
 }
 
 // Chrome doesn't allow us to intercept WebSockets[1], and therefore
 // some ad networks are misusing them as a way to serve adverts and circumvent
 // us. As a workaround we wrap WebSocket, preventing blocked WebSocket
 // connections from being opened.
 // [1] - https://bugs.chromium.org/p/chromium/issues/detail?id=129353
 function wrapWebSocket()
 {
-  let eventName = "abpws-" + Math.random().toString(36).substr(2);
+  let randomEventName = "abpws-" + Math.random().toString(36).substr(2);
 
-  document.addEventListener(eventName, event =>
+  document.addEventListener(randomEventName, event =>
   {
     ext.backgroundPage.sendMessage({
       type: "request.websocket",
       url: event.detail.url
     }, block =>
     {
-      document.dispatchEvent(
-        new CustomEvent(eventName + "-" + event.detail.url, {detail: block})
-      );
+      document.dispatchEvent(new CustomEvent(
+        randomEventName + "-" + event.detail.url, {detail: block}
+      ));
     });
   });
 
   runInPageContext(eventName =>
   {
     // As far as possible we must track everything we use that could be
     // sabotaged by the website later in order to circumvent us.
     let RealWebSocket = WebSocket;
-    let closeWebSocket = Function.prototype.call.bind(RealWebSocket.prototype.close);
+    let RealCustomEvent = window.CustomEvent;
+    let closeWebSocket = Function.prototype.call.bind(
+      RealWebSocket.prototype.close
+    );
     let addEventListener = document.addEventListener.bind(document);
     let removeEventListener = document.removeEventListener.bind(document);
     let dispatchEvent = document.dispatchEvent.bind(document);
-    let CustomEvent = window.CustomEvent;
 
     function checkRequest(url, callback)
     {
       let incomingEventName = eventName + "-" + url;
       function listener(event)
       {
         callback(event.detail);
         removeEventListener(incomingEventName, listener);
       }
       addEventListener(incomingEventName, listener);
 
-      dispatchEvent(new CustomEvent(eventName, {
-        detail: {url: url}
-      }));
+      dispatchEvent(new RealCustomEvent(eventName, {detail: {url}}));
     }
 
-    function WrappedWebSocket(url)
+    function WrappedWebSocket(url, ...args)
     {
       // Throw correct exceptions if the constructor is used improperly.
       if (!(this instanceof WrappedWebSocket)) return RealWebSocket();
       if (arguments.length < 1) return new RealWebSocket();
 
       let websocket;
       if (arguments.length == 1)
         websocket = new RealWebSocket(url);
       else
-        websocket = new RealWebSocket(url, arguments[1]);
+        websocket = new RealWebSocket(url, args[0]);

[Wladimir Palant, 2017/03/14 13:03:24]

From the look of it, this should really be:

  let websocket = new RealWebSocket(url, ...args);

The if block no longer serves a purpose.

[kzar, 2017/03/15 04:57:45]

Done.

 
       checkRequest(websocket.url, blocked =>
       {
         if (blocked)
           closeWebSocket(websocket);
       });
 
       return websocket;
     }
     WrappedWebSocket.prototype = RealWebSocket.prototype;
-    WebSocket = WrappedWebSocket.bind();
+    window.WebSocket = WrappedWebSocket.bind();
     Object.defineProperties(WebSocket, {
       CONNECTING: {value: RealWebSocket.CONNECTING, enumerable: true},
       OPEN: {value: RealWebSocket.OPEN, enumerable: true},
       CLOSING: {value: RealWebSocket.CLOSING, enumerable: true},
       CLOSED: {value: RealWebSocket.CLOSED, enumerable: true},
       prototype: {value: RealWebSocket.prototype}
     });
 
     RealWebSocket.prototype.constructor = WebSocket;
-  }, eventName);
+  }, randomEventName);
 }
 
 function ElemHide()
 {
   this.shadow = this.createShadowTree();
   this.style = null;
   this.tracer = null;
 
   this.elemHideEmulation = new ElemHideEmulation(
     window,
@@ skipping 32 matching lines @@
     shadow.appendChild(document.createElement("shadow"));
 
     // Stop the website from messing with our shadow root (#4191, #4298).
     if ("shadowRoot" in Element.prototype)
     {
       runInPageContext(() =>
       {
         let ourShadowRoot = document.documentElement.shadowRoot;
         if (!ourShadowRoot)
           return;
-        let desc = Object.getOwnPropertyDescriptor(Element.prototype, "shadowRoot");
+        let desc = Object.getOwnPropertyDescriptor(Element.prototype,
+                                                   "shadowRoot");
         let shadowRoot = Function.prototype.call.bind(desc.get);
 
         Object.defineProperty(Element.prototype, "shadowRoot", {
           configurable: true, enumerable: true, get()
           {
-            let shadow = shadowRoot(this);
-            return shadow == ourShadowRoot ? null : shadow;
+            let thisShadow = shadowRoot(this);
+            return thisShadow == ourShadowRoot ? null : thisShadow;
           }
         });
       }, null);
     }
 
     return shadow;
   },
 
   addSelectors(selectors, filters)
   {
     if (selectors.length == 0)
       return;
 
     if (!this.style)
     {
       // Create <style> element lazily, only if we add styles. Add it to
       // the shadow DOM if possible. Otherwise fallback to the <head> or
       // <html> element. If we have injected a style element before that
       // has been removed (the sheet property is null), create a new one.
       this.style = document.createElement("style");
-      (this.shadow || document.head
-                   || document.documentElement).appendChild(this.style);
+      (this.shadow || document.head ||
+       document.documentElement).appendChild(this.style);

[Wladimir Palant, 2017/03/14 13:03:24]

Please don't use one-space indentation, it's too easy to miss. Maybe something
like that:

  (
    this.shadow || document.head || document.documentElement
  ).appendChild(this.style);

[kzar, 2017/03/15 04:57:46]

How about this?

 
       // It can happen that the frame already navigated to a different
       // document while we were waiting for the background page to respond.
       // In that case the sheet property will stay null, after addind the
       // <style> element to the shadow DOM.
       if (!this.style.sheet)
         return;
     }
 
     // If using shadow DOM, we have to add the ::content pseudo-element
     // before each selector, in order to match elements within the
     // insertion point.
     let preparedSelectors = [];
     if (this.shadow)
     {
       for (let selector of selectors)
       {
         let subSelectors = splitSelector(selector);
         for (let subSelector of subSelectors)
           preparedSelectors.push("::content " + subSelector);
       }
     }
     else
-    {
       preparedSelectors = selectors;
-    }
 
     // Safari only allows 8192 primitive selectors to be injected at once[1], we
     // therefore chunk the inserted selectors into groups of 200 to be safe.
     // (Chrome also has a limit, larger... but we're not certain exactly what it
     //  is! Edge apparently has no such limit.)
     // [1] - https://github.com/WebKit/webkit/blob/1cb2227f6b2a1035f7bdc46e5ab69debb75fc1de/Source/WebCore/css/RuleSet.h#L68
     for (let i = 0; i < preparedSelectors.length; i += this.selectorGroupSize)
     {
-      let selector = preparedSelectors.slice(i, i + this.selectorGroupSize).join(", ");
+      let selector = preparedSelectors.slice(
+        i, i + this.selectorGroupSize
+      ).join(", ");
       this.style.sheet.insertRule(selector + "{display: none !important;}",
                                   this.style.sheet.cssRules.length);
     }
 
     if (this.tracer)
       this.tracer.addSelectors(selectors, filters || selectors);
   },
 
   apply()
   {
@@ skipping 14 matching lines @@
       this.elemHideEmulation.apply();
     });
   }
 };
 
 if (document instanceof HTMLDocument)
 {
   checkSitekey();
   wrapWebSocket();
 
-  // This variable is also used by our other content scripts, outside of the
-  // current scope.
-  var elemhide = new ElemHide();
+  elemhide = new ElemHide();
   elemhide.apply();
 
   document.addEventListener("error", event =>
   {
     checkCollapse(event.target);
   }, true);
 
   document.addEventListener("load", event =>
   {
     let element = event.target;
     if (/^i?frame$/.test(element.localName))
       checkCollapse(element);
   }, true);
 }