Issue 4878 - Start using ESLint for adblockpluscore

lib/elemHide.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/>.
  */
 
+"use strict";
+
 /**
  * @fileOverview Element hiding implementation.
  */
 
 let {Utils} = require("utils");
 let {ElemHideException} = require("filterClasses");
 let {FilterNotifier} = require("filterNotifier");
 
 /**
  * Lookup table, filters by their associated key
- * @type Object
+ * @type {Object}
  */
-var filterByKey = [];
+let filterByKey = [];
 
 /**
  * Lookup table, keys of the filters by filter text
- * @type Object
+ * @type {Object}
  */
-var keyByFilter = Object.create(null);
+let keyByFilter = Object.create(null);
 
 /**
  * Nested lookup table, filter (or false if inactive) by filter key by domain.
  * (Only contains filters that aren't unconditionally matched for all domains.)
- * @type Object
+ * @type {Object}
  */
-var filtersByDomain = Object.create(null);
+let filtersByDomain = Object.create(null);
 
 /**
  * Lookup table, filter key by selector. (Only used for selectors that are
  * unconditionally matched for all domains.)
  */
-var filterKeyBySelector = Object.create(null);
+let filterKeyBySelector = Object.create(null);
 
 /**
  * This array caches the keys of filterKeyBySelector table (selectors which
  * unconditionally apply on all domains). It will be null if the cache needs to
  * be rebuilt.
  */
-var unconditionalSelectors = null;
+let unconditionalSelectors = null;
 
 /**
  * This array caches the values of filterKeyBySelector table (filterIds for
  * selectors which unconditionally apply on all domains). It will be null if the
  * cache needs to be rebuilt.
  */
-var unconditionalFilterKeys = null;
+let unconditionalFilterKeys = null;
 
 /**
  * Object to be used instead when a filter has a blank domains property.
  */
-var defaultDomains = Object.create(null);
+let defaultDomains = Object.create(null);
 defaultDomains[""] = true;
 
 /**
  * Lookup table, keys are known element hiding exceptions
- * @type Object
+ * @type {Object}
  */
-var knownExceptions = Object.create(null);
+let knownExceptions = Object.create(null);
 
 /**
  * Lookup table, lists of element hiding exceptions by selector
- * @type Object
+ * @type {Object}
  */
-var exceptions = Object.create(null);
+let exceptions = Object.create(null);
 
 /**
  * Container for element hiding filters
  * @class
  */
-var ElemHide = exports.ElemHide =
-{
+let ElemHide = exports.ElemHide = {
   /**
    * Removes all known filters
    */
-  clear: function()
+  clear()
   {
     filterByKey = [];
     keyByFilter = Object.create(null);
     filtersByDomain = Object.create(null);
     filterKeyBySelector = Object.create(null);
     unconditionalSelectors = unconditionalFilterKeys = null;
     knownExceptions = Object.create(null);
     exceptions = Object.create(null);
     FilterNotifier.emit("elemhideupdate");
   },
 
-  _addToFiltersByDomain: function(key, filter)
+  _addToFiltersByDomain(key, filter)
   {
     let domains = filter.domains || defaultDomains;
     for (let domain in domains)
     {
       let filters = filtersByDomain[domain];
       if (!filters)
         filters = filtersByDomain[domain] = Object.create(null);
 
       if (domains[domain])
         filters[key] = filter;
       else
         filters[key] = false;
     }
   },
 
   /**
    * Add a new element hiding filter
    * @param {ElemHideFilter} filter
    */
-  add: function(filter)
+  add(filter)
   {
     if (filter instanceof ElemHideException)
     {
       if (filter.text in knownExceptions)
         return;
 
-      let selector = filter.selector;
+      let {selector} = filter;
       if (!(selector in exceptions))
         exceptions[selector] = [];
       exceptions[selector].push(filter);
 
       // If this is the first exception for a previously unconditionally
       // applied element hiding selector we need to take care to update the
       // lookups.
       let filterKey = filterKeyBySelector[selector];
       if (typeof filterKey != "undefined")
       {
@@ skipping 21 matching lines @@
       else
       {
         // The new filter's selector only applies to some domains
         this._addToFiltersByDomain(key, filter);
       }
     }
 
     FilterNotifier.emit("elemhideupdate");
   },
 
-  _removeFilterKey: function(key, filter)
+  _removeFilterKey(key, filter)
   {
     if (filterKeyBySelector[filter.selector] == key)
     {
       delete filterKeyBySelector[filter.selector];
       unconditionalSelectors = unconditionalFilterKeys = null;
       return;
     }
 
     // We haven't found this filter in unconditional filters, look in
     // filtersByDomain.
     let domains = filter.domains || defaultDomains;
     for (let domain in domains)
     {
       let filters = filtersByDomain[domain];
       if (filters)
         delete filters[key];
     }
   },
 
   /**
    * Removes an element hiding filter
    * @param {ElemHideFilter} filter
    */
-  remove: function(filter)
+  remove(filter)
   {
     if (filter instanceof ElemHideException)
     {
       if (!(filter.text in knownExceptions))
         return;
 
       let list = exceptions[filter.selector];
       let index = list.indexOf(filter);
       if (index >= 0)
         list.splice(index, 1);
       delete knownExceptions[filter.text];
     }
     else
     {
       if (!(filter.text in keyByFilter))
         return;
 
       let key = keyByFilter[filter.text];
       delete filterByKey[key];
       delete keyByFilter[filter.text];
       this._removeFilterKey(key, filter);
     }
 
     FilterNotifier.emit("elemhideupdate");
   },
 
   /**
    * Checks whether an exception rule is registered for a filter on a particular
    * domain.
+   * @param {Filter} filter
+   * @param {String} docDomain
+   * @return {ElemHideException}
    */
-  getException: function(/**Filter*/ filter, /**String*/ docDomain) /**ElemHideException*/
+  getException(filter, docDomain)
   {
     if (!(filter.selector in exceptions))
       return null;
 
     let list = exceptions[filter.selector];
     for (let i = list.length - 1; i >= 0; i--)
+    {
       if (list[i].isActiveOnDomain(docDomain))
         return list[i];
+    }
 
     return null;
   },
 
   /**
    * Retrieves an element hiding filter by the corresponding protocol key
+   * @param {Number} key
+   * @return {Filter}
    */
-  getFilterByKey: function(/**Number*/ key) /**Filter*/
+  getFilterByKey(key)
   {
     return (key in filterByKey ? filterByKey[key] : null);
   },
 
   /**
    * Returns a list of all selectors as a nested map. On first level, the keys
    * are all values of `ElemHideBase.selectorDomain` (domains on which these
    * selectors should apply, ignoring exceptions). The values are maps again,
    * with the keys being selectors and values the corresponding filter keys.
    * @returns {Map.<String,Map<String,String>>}
    */
-  getSelectors: function()
+  getSelectors()
   {
     let domains = new Map();
     for (let key in filterByKey)
     {
       let filter = filterByKey[key];
-      let selector = filter.selector;
+      let {selector} = filter;

[Sebastian Noack, 2017/02/20 13:14:51]

Perhaps just inline filter.selector, in the two occurrences below. This
temporary variable seems kinda unnecessary.

[kzar, 2017/02/21 06:13:58]

Seems like kind of an unrelated change, would rather leave it.

[Sebastian Noack, 2017/02/21 09:19:30]

Well, it's not unrelated, because in order to make ESLint happy we either have
to use destructing or inline the property lookup. I think the latter is
preferable, here.

[Sebastian Noack, 2017/02/21 09:20:13]

s/it's not related/it's related/

[kzar, 2017/02/21 10:37:00]

Done.

       if (!selector)
         continue;
 
       let domain = filter.selectorDomain || "";
 
       if (!domains.has(domain))
         domains.set(domain, new Map());
       domains.get(domain).set(selector, key);
     }
 
     return domains;
   },
 
   /**
    * Returns a list of selectors that apply on each website unconditionally.
    * @returns {String[]}
    */
-  getUnconditionalSelectors: function()
+  getUnconditionalSelectors()
   {
     if (!unconditionalSelectors)
       unconditionalSelectors = Object.keys(filterKeyBySelector);
     return unconditionalSelectors.slice();
   },
 
   /**
    * Returns a list of filter keys for selectors which apply to all websites
    * without exception.
    * @returns {Number[]}
    */
-  getUnconditionalFilterKeys: function()
+  getUnconditionalFilterKeys()
   {
     if (!unconditionalFilterKeys)
     {
       let selectors = this.getUnconditionalSelectors();
       unconditionalFilterKeys = [];
       for (let selector of selectors)
         unconditionalFilterKeys.push(filterKeyBySelector[selector]);
     }
     return unconditionalFilterKeys.slice();
   },
@@ skipping 25 matching lines @@
    * @param {Number} [criteria]
    *   One of the following: ElemHide.ALL_MATCHING, ElemHide.NO_UNCONDITIONAL or
    *                         ElemHide.SPECIFIC_ONLY.
    * @param {Boolean} [provideFilterKeys]
    *   If true, the function will return a list of corresponding filter keys in
    *   addition to selectors.
    * @returns {string[]|Array.<string[]>}
    *   List of selectors or an array with two elements (list of selectors and
    *   list of corresponding keys) if provideFilterKeys is true.
    */
-  getSelectorsForDomain: function(domain, criteria, provideFilterKeys)
+  getSelectorsForDomain(domain, criteria, provideFilterKeys)
   {
     let filterKeys = [];
     let selectors = [];
 
     if (typeof criteria == "undefined")
       criteria = ElemHide.ALL_MATCHING;
     if (criteria < ElemHide.NO_UNCONDITIONAL)
     {
       selectors = this.getUnconditionalSelectors();
       if (provideFilterKeys)
         filterKeys = this.getUnconditionalFilterKeys();
     }
 
     let specificOnly = (criteria >= ElemHide.SPECIFIC_ONLY);
     let seenFilters = Object.create(null);
     let currentDomain = domain ? domain.toUpperCase() : "";
+    /* eslint-disable no-constant-condition */

[Sebastian Noack, 2017/02/20 13:14:51]

Ugh. Can we please change esling-config-eyeo, configuring no-constant, setting
the checkLoops option to false. There are certainly legit use cases for
while(true) loops.

[kzar, 2017/02/21 06:13:58]

Done. https://codereview.adblockplus.org/29376668/

     while (true)
     {
       if (specificOnly && currentDomain == "")
         break;
 
       let filters = filtersByDomain[currentDomain];
       if (filters)
       {
         for (let filterKey in filters)
         {
@@ skipping 10 matching lines @@
           }
         }
       }
 
       if (currentDomain == "")
         break;
 
       let nextDot = currentDomain.indexOf(".");
       currentDomain = nextDot == -1 ? "" : currentDomain.substr(nextDot + 1);
     }
+    /* eslint-enable no-constant-condition */
 
     if (provideFilterKeys)
       return [selectors, filterKeys];
-    else
-      return selectors;
+    return selectors;
   }
 };