Issue 7015 - Serialize subscriptions for *exportData in one loop

lib/filterStorage.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 459 matching lines @@
       return this.saveToDisk();
     });
   }
 
   /**
    * Generator serializing filter data and yielding it line by line.
    * @yields {string}
    */
   *exportData()
   {
-    // Do not persist external subscriptions
-    let subscriptions = [];
-    for (let subscription of this.subscriptions())
-    {
-      if (!(subscription instanceof ExternalSubscription) &&
-          !(subscription instanceof SpecialSubscription &&
-            subscription.filterCount == 0))
-      {
-        subscriptions.push(subscription);
-      }
-    }
-
     yield "# Adblock Plus preferences";
     yield "version=" + this.formatVersion;
 
     let saved = new Set();
 
     // Save subscriptions
-    for (let subscription of subscriptions)
+    for (let subscription of this.subscriptions())
     {
-      yield* subscription.serialize();
-      yield* subscription.serializeFilters();
-    }
+      // Do not persist external subscriptions
+      if (!(subscription instanceof ExternalSubscription) &&
+          !(subscription instanceof SpecialSubscription &&
+            subscription.filters.length == 0))
+      {
+        yield* subscription.serialize();
+        yield* subscription.serializeFilters();
+      }
 
     // Save filter data
     for (let subscription of subscriptions)
     {
       for (let filter of subscription.filters())
       {
+        // Save filter data
         if (!saved.has(filter.text))
         {
           yield* filter.serialize();
           saved.add(filter.text);
         }
       }
     }
   }
 
   /**
@@ skipping 157 matching lines @@
  *   subscription is disconnected from its own filters.
  */
 function disconnectSubscriptionFilters(subscription, filters)
 {
   if (!filterStorage.knownSubscriptions.has(subscription.url))
     return;
 
   for (let filter of filters || subscription.filters())
     filter.removeSubscription(subscription);
 }