Issue 2824 - Only consider ads subscriptions in chooseFilterSubscription

lib/subscriptionInit.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 63 matching lines @@
 
     if (subscription instanceof SpecialSubscription &&
         subscription.filters.length > 0)
       return false;
   }
 
   return true;
 }
 
 /**
+ * Finds the element for the default ad blocking filter subscription based
+ * on the user's locale.
+ *
+ * @param {HTMLCollection} subscriptions
+ * @return {Element}
+ */
+function chooseFilterSubscription(subscriptions)
+{
+  let selectedItem = null;
+  let selectedPrefix = null;
+  let matchCount = 0;
+  for (let subscription of subscriptions)
+  {
+    if (!selectedItem)
+      selectedItem = subscription;
+
+    let prefixes = subscription.getAttribute("prefixes");
+    let prefix = prefixes && prefixes.split(",").find(
+      lang => new RegExp("^" + lang + "\\b").test(Utils.appLocale)
+    );
+
+    let subscriptionType = subscription.getAttribute("type");
+
+    if (prefix && subscriptionType == "ads")
+    {
+      if (!selectedPrefix || selectedPrefix.length < prefix.length)
+      {
+        selectedItem = subscription;
+        selectedPrefix = prefix;
+        matchCount = 1;
+      }
+      else if (selectedPrefix && selectedPrefix.length == prefix.length)
+      {
+        matchCount++;
+
+        // If multiple items have a matching prefix of the same length:
+        // Select one of the items randomly, probability should be the same
+        // for all items. So we replace the previous match here with
+        // probability 1/N (N being the number of matches).
+        if (Math.random() * matchCount < 1)
+        {
+          selectedItem = subscription;
+          selectedPrefix = prefix;
+        }
+      }
+    }
+  }
+  return selectedItem;
+}
+
+/**
  * Gets the filter subscriptions to be added when the extnesion is loaded.
  *
  * @return {Promise|Subscription[]}
  */
 function getSubscriptions()
 {
   let subscriptions = [];
 
   // Add pre-configured subscriptions
   for (let url of Prefs.additional_subscriptions)
@@ skipping 18 matching lines @@
   // Add default ad blocking subscription (e.g. EasyList)
   if (shouldAddDefaultSubscription())
   {
     return fetch("subscriptions.xml")
       .then(response => response.text())
       .then(text =>
       {
         let doc = new DOMParser().parseFromString(text, "application/xml");
         let nodes = doc.getElementsByTagName("subscription");
 
-        let node = Utils.chooseFilterSubscription(nodes);
+        let node = chooseFilterSubscription(nodes);
         if (node)
         {
           let url = node.getAttribute("url");
           if (url)
           {
             let subscription = Subscription.fromURL(url);
             subscription.disabled = false;
             subscription.title = node.getAttribute("title");
             subscription.homepage = node.getAttribute("homepage");
             subscriptions.push(subscription);
@@ skipping 44 matching lines @@
  * Sets a callback that is called with an array of subscriptions to be added
  * during initialization. The callback must return an array of subscriptions
  * that will effectively be added.
  *
  * @param {function} callback
  */
 exports.setSubscriptionsCallback = callback =>
 {
   subscriptionsCallback = callback;
 };