Issue 4450 - Prevent ElemHide filters with empty domains

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
@@ skipping 25 matching lines @@
 var 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
  */
 var filtersByDomain = Object.create(null);
 
 /**
- * Lookup table, filter keys by selector. (Only contains filters that have a
- * selector that is unconditionally matched for all domains.)
+ * Lookup table, filter key by selector. (Only used for selectors that are
+ * unconditionally matched for all domains.)
  */
-var filterKeysBySelector = Object.create(null);
+var filterKeyBySelector = Object.create(null);
 
 /**
- * This array caches the keys of filterKeysBySelector table (selectors which
+ * 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;
 
 /**
- * This array caches the values of filterKeysBySelector table (filterIds for
+ * 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. Note: Only the first filter key for each selector
- * is cached.
+ * cache needs to be rebuilt.
  */
 var unconditionalFilterKeys = null;
 
 /**
  * Object to be used instead when a filter has a blank domains property.
  */
 var defaultDomains = Object.create(null);
 defaultDomains[""] = true;
 
 /**
@@ skipping 15 matching lines @@
 var ElemHide = exports.ElemHide =
 {
   /**
    * Removes all known filters
    */
   clear: function()
   {
     filterByKey = [];
     keyByFilter = Object.create(null);
     filtersByDomain = Object.create(null);
-    filterKeysBySelector = 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)
   {
     let domains = filter.domains || defaultDomains;
     for (let domain in domains)
@@ skipping 21 matching lines @@
         return;
 
       let selector = filter.selector;
       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 filterKeys = filterKeysBySelector[selector];
-      if (filterKeys)
+      let filterKey = filterKeyBySelector[selector];
+      if (filterKey)
       {
-        for (let filterKey of filterKeys)
-          this._addToFiltersByDomain(filterKey, filterByKey[filterKey]);
-        delete filterKeysBySelector[selector];
+        this._addToFiltersByDomain(filterKey, filterByKey[filterKey]);
+        delete filterKeyBySelector[selector];
         unconditionalSelectors = unconditionalFilterKeys = null;
       }
 
       knownExceptions[filter.text] = true;
     }
     else
     {
       if (filter.text in keyByFilter)
         return;
 
       let key = filterByKey.push(filter) - 1;
       keyByFilter[filter.text] = key;
 
       if (!(filter.domains || filter.selector in exceptions))
       {
         // The new filter's selector is unconditionally applied to all domains
-        let filterKeys = filterKeysBySelector[filter.selector];
-        if (filterKeys)
-        {
-          filterKeys.push(key);
-        }
-        else
-        {
-          filterKeysBySelector[filter.selector] = [key];
-          unconditionalSelectors = unconditionalFilterKeys = null;
-        }
+        filterKeyBySelector[filter.selector] = key;
+        unconditionalSelectors = unconditionalFilterKeys = null;
       }
       else
       {
         // The new filter's selector only applies to some domains
         this._addToFiltersByDomain(key, filter);
       }
     }
 
     FilterNotifier.emit("elemhideupdate");
   },
 
   _removeFilterKey: function(key, filter)
   {
-    let filterKeys = filterKeysBySelector[filter.selector];
-    if (filterKeys)
+    if (filterKeyBySelector[filter.selector] == key)
     {
-      let index = filterKeys.indexOf(key);
-      if (index >= 0)
-      {
-        if (filterKeys.length > 1)
-        {
-          filterKeys.splice(index, 1);
-          if (index == 0)
-            unconditionalFilterKeys = null;
-        }
-        else
-        {
-          delete filterKeysBySelector[filter.selector];
-          unconditionalSelectors = unconditionalFilterKeys = null;
-        }
-        return;
-      }
+      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];
@@ skipping 83 matching lines @@
     return domains;
   },
 
   /**
    * Returns a list of selectors that apply on each website unconditionally.
    * @returns {String[]}
    */
   getUnconditionalSelectors: function()
   {
     if (!unconditionalSelectors)
-      unconditionalSelectors = Object.keys(filterKeysBySelector);
+      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()
   {
     if (!unconditionalFilterKeys)
     {
       let selectors = this.getUnconditionalSelectors();
       unconditionalFilterKeys = [];
       for (let selector of selectors)
-        unconditionalFilterKeys.push(filterKeysBySelector[selector][0]);
+        unconditionalFilterKeys.push(filterKeyBySelector[selector]);
     }
     return unconditionalFilterKeys.slice();
   },
 
 
   /**
    * Constant used by getSelectorsForDomain to return all selectors applying to
    * a particular hostname.
    */
   ALL_MATCHING: 0,
@@ skipping 72 matching lines @@
       let nextDot = currentDomain.indexOf(".");
       currentDomain = nextDot == -1 ? "" : currentDomain.substr(nextDot + 1);
     }
 
     if (provideFilterKeys)
       return [selectors, filterKeys];
     else
       return selectors;
   }
 };