Issue 7016 - Convert serialization functions into generators

lib/subscriptionClasses.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 249 matching lines @@
    */
   defaults: null,
 
   /**
    * Tests whether a filter should be added to this group by default
    * @param {Filter} filter filter to be tested
    * @return {boolean}
    */
   isDefaultFor(filter)
   {
-    if (this.defaults)
+    if (this.defaults && this.defaults.length)
     {
       for (let type of this.defaults)
       {
         if (filter instanceof SpecialSubscription.defaultsMap.get(type))
           return true;
         if (!(filter instanceof ActiveFilter) && type == "blacklist")
           return true;
       }
     }
 
     return false;
   },
 
   /**
    * See Subscription.serialize()
    * @inheritdoc
    */
   *serialize()
   {
     let {defaults, _lastDownload} = this;
 
     yield* Subscription.prototype.serialize.call(this);
 
-    if (defaults && defaults.length)
+    if (defaults)
     {
       yield "defaults=" +
             defaults.filter(
               type => SpecialSubscription.defaultsMap.has(type)
             ).join(" ");
     }
     if (_lastDownload)
       yield "lastDownload=" + _lastDownload;
   }
 });
@@ skipping 277 matching lines @@
     if (errors)
       yield "errors=" + errors;
     if (version)
       yield "version=" + version;
     if (requiredVersion)
       yield "requiredVersion=" + requiredVersion;
     if (downloadCount)
       yield "downloadCount=" + downloadCount;
   }
 });