Issue 7046 - Defer caching of domain maps

lib/filterClasses.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present 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 429 matching lines @@
   domainSource: null,
 
   /**
    * Separator character used in domainSource property, must be
    * overridden by subclasses
    * @type {string}
    */
   domainSeparator: null,
 
   /**
+   * Number of times {@link ActiveFilter#domains} has been accessed.
+   * @type {number}
+   * @private
+   */
+  _domainsAccessCount: 0,
+
+  /**
+   * Maximum number of times {@link ActiveFilter#domains} can be accessed
+   * before the value is cached.
+   * @type {number}
+   * @private
+   */
+  _domainsAccessCacheThreshold: 3,
+
+  /**
    * Map containing domains that this filter should match on/not match
    * on or null if the filter should match on all domains
    * @type {?Map.<string,boolean>}
    */
   get domains()
   {
+    // For some filter types this property is accessed only rarely, especially
+    // when the subscriptions are initially loaded. We defer any caching for
+    // such filters.
+    let cacheValue = ++this._domainsAccessCount >
+                     this._domainsAccessCacheThreshold;
+
     let domains = null;
 
     if (this.domainSource)
     {
       let source = this.domainSource.toLowerCase();
 
       let knownMap = knownDomainMaps.get(source);
       if (knownMap)
       {
         domains = knownMap;
@@ skipping 30 matching lines @@
             if (!domains)
               domains = new Map();
 
             domains.set(domain, include);
           }
 
           if (domains)
             domains.set("", !hasIncludes);
         }
 
-        if (domains)
+        if (!domains || cacheValue)

[Manish Jethani, 2018/10/15 15:36:59]

There is a change in the semantics here in that we now always cache the value if
it is null. This makes sense; it doesn't make sense to keep regenerating the
value if it amounts to null anyway.

           knownDomainMaps.set(source, domains);
       }
 
-      this.domainSource = null;
+      if (!domains || cacheValue)
+        this.domainSource = null;
     }
 
-    Object.defineProperty(this, "domains", {value: domains});
-    return this.domains;
+    if (!domains || cacheValue)
+      Object.defineProperty(this, "domains", {value: domains});
+
+    return domains;
   },
 
   /**
    * Array containing public keys of websites that this filter should apply to
    * @type {?string[]}
    */
   sitekeys: null,
 
   /**
    * Checks whether this filter is active on a domain.
@@ skipping 712 matching lines @@
 
   /**
    * Script that should be executed
    * @type {string}
    */
   get script()
   {
     return this.body;
   }
 });