Issue 5137 - [emscripten] Added basic filter storage implementation

lib/filterStorage.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
- * Copyright (C) 2006-2017 eyeo GmbH
+ * 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
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 "use strict";
 
 const {FilterStorage} = require("compiled");
 const {Subscription, SpecialSubscription} = require("subscriptionClasses");
-const {ActiveFilter} = require("filterClasses");
-const {Prefs} = require("prefs");
 
 // Backwards compatibility
 FilterStorage.getGroupForFilter = FilterStorage.getSubscriptionForFilter;
 
 /**
  * This property allows iterating over the list of subscriptions. It will delete
  * references automatically at the end of the current loop iteration. If you
  * need persistent references or element access by position you should use
  * FilterStorage.subscriptionAt() instead.
  * @type {Iterable}
  */
 FilterStorage.subscriptions = {
-  [Symbol.iterator]: function*()
+  *[Symbol.iterator]()
   {
     for (let i = 0, l = FilterStorage.subscriptionCount; i < l; i++)
     {
       let subscription = FilterStorage.subscriptionAt(i);
       try
       {
         yield subscription;
       }
       finally
       {
         subscription.delete();
       }
     }
   }
 };
 
 /**
  * Adds a user-defined filter to the most suitable subscription in the list,
  * creates one if none found.
  * @param {Filter} filter
+ * @returns {boolean}
+ *    false if the filter was already in the list and no adding was performed
  */
 FilterStorage.addFilter = function(filter)
 {
   for (let subscription of this.subscriptions)
     if (!subscription.disabled && subscription.indexOfFilter(filter) >= 0)
-      return;
+      return false;
 
   let subscription = this.getSubscriptionForFilter(filter);
-  if (!subscription)
+  try
   {
-    subscription = Subscription.fromURL(null);
-    subscription.makeDefaultFor(filter);
-    this.addSubscription(subscription);
+    if (!subscription)
+    {
+      subscription = Subscription.fromURL(null);
+      subscription.makeDefaultFor(filter);
+      this.addSubscription(subscription);
+    }
+    subscription.insertFilterAt(filter, subscription.filterCount);
   }
-  subscription.insertFilterAt(filter, subscription.filterCount);
-  subscription.delete();

[sergei, 2017/05/08 10:54:39]

strictly speaking it should be in finally block, but I'm not sure that we follow
that rule.

[Wladimir Palant, 2017/05/08 12:55:41]

You are correct. I tend to be too comfortable for unit test code, but for
production code we should get used to that pattern.

+  finally
+  {
+    if (subscription)
+      subscription.delete();
+  }
   return true;
 };
 
 /**
  * Removes a user-defined filter from the list
  * @param {Filter} filter
  */
 FilterStorage.removeFilter = function(filter)
 {
   for (let subscription of this.subscriptions)
   {
     if (subscription instanceof SpecialSubscription)
     {
       while (true)

[sergei, 2017/05/08 10:54:39]

Is this loop to remove duplicates of the filter in the same subscription? I
guess that a subscription is a set of unique filters, isn't it?

[Wladimir Palant, 2017/05/08 12:55:41]

No, a subscription can contain the same filter multiple times, we don't impose
any such restrictions (any more, since around Adblock Plus 0.7). This is
particularly important for comments, filter list authors tend to use comments as
separators - and these are identical then.

       {
         let index = subscription.indexOfFilter(filter);
         if (index >= 0)
           subscription.removeFilterAt(index);
         else
           break;
       }
     }
   }
 };
 
 exports.FilterStorage = FilterStorage;