Issue 6857 - Do not serialize empty special subscriptions

test/filterStorage_readwrite.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 94 matching lines @@
     test.equal(FilterStorage.fileProperties.version, FilterStorage.formatVersion, "File format version");
 
     if (withExternal)
     {
       {
         let subscription = new ExternalSubscription("~external~external subscription ID", "External subscription");
         subscription.filters = [Filter.fromText("foo"), Filter.fromText("bar")];
         FilterStorage.addSubscription(subscription);
       }
 
-      let externalSubscriptions = FilterStorage.subscriptions.filter(subscription => subscription instanceof ExternalSubscription);
+      let externalSubscriptions = [...FilterStorage.subscriptions()].filter(subscription => subscription instanceof ExternalSubscription);
       test.equal(externalSubscriptions.length, 1, "Number of external subscriptions after updateExternalSubscription");
 
       test.equal(externalSubscriptions[0].url, "~external~external subscription ID", "ID of external subscription");
       test.equal(externalSubscriptions[0].filters.length, 2, "Number of filters in external subscription");
     }
 
     if (withEmptySpecial)
     {
       let specialSubscription =
         SpecialSubscription.createForFilter(Filter.fromText("!foo"));
       FilterStorage.addSubscription(specialSubscription);
 
       FilterStorage.removeFilter(Filter.fromText("!foo"), specialSubscription);
 
       test.equal(specialSubscription.filters.length, 0,
                  "No filters in special subscription");
-      test.ok(FilterStorage.subscriptions.indexOf(specialSubscription) != -1,
+      test.ok(new Set(FilterStorage.subscriptions()).has(specialSubscription),
               "Empty special subscription still in storage");
     }
 
     return FilterStorage.saveToDisk();
   }).then(() => testData).then(expected =>
   {
     test.deepEqual(canonize(IO._getFileContents(FilterStorage.sourceFile)),
                canonize(expected), "Read/write result");
   }).catch(unexpectedError.bind(test)).then(() => test.done());
 }
@@ skipping 100 matching lines @@
   }).catch(unexpectedError.bind(test)).then(() => test.done());
 };
 
 exports.testRestoringBackup = function(test)
 {
   Prefs.patternsbackups = 2;
   Prefs.patternsbackupinterval = 24;
 
   FilterStorage.saveToDisk().then(() =>
   {
-    test.equal(FilterStorage.subscriptions[0].filters.length, 1, "Initial filter count");
+    test.equal([...FilterStorage.subscriptions()][0].filters.length, 1, "Initial filter count");
     FilterStorage.addFilter(Filter.fromText("barfoo"));
-    test.equal(FilterStorage.subscriptions[0].filters.length, 2, "Filter count after adding a filter");
+    test.equal([...FilterStorage.subscriptions()][0].filters.length, 2, "Filter count after adding a filter");
     return FilterStorage.saveToDisk();
   }).then(() =>
   {
     return FilterStorage.loadFromDisk();
   }).then(() =>
   {
-    test.equal(FilterStorage.subscriptions[0].filters.length, 2, "Filter count after adding filter and reloading");
+    test.equal([...FilterStorage.subscriptions()][0].filters.length, 2, "Filter count after adding filter and reloading");
     return FilterStorage.restoreBackup(1);
   }).then(() =>
   {
-    test.equal(FilterStorage.subscriptions[0].filters.length, 1, "Filter count after restoring backup");
+    test.equal([...FilterStorage.subscriptions()][0].filters.length, 1, "Filter count after restoring backup");
     return FilterStorage.loadFromDisk();
   }).then(() =>
   {
-    test.equal(FilterStorage.subscriptions[0].filters.length, 1, "Filter count after reloading");
-  }).catch(unexpectedError.bind(test)).then(() => test.done());
-};
+    test.equal([...FilterStorage.subscriptions()][0].filters.length, 1, "Filter count after reloading");
+  }).catch(unexpectedError.bind(test)).then(() => test.done());
+};