Issue 491 - Validate custom filters

background.js

Index: background.js
===================================================================
--- a/background.js
+++ b/background.js
@@ -21,6 +21,7 @@
   this.RegExpFilter = RegExpFilter;
   this.BlockingFilter = BlockingFilter;
   this.WhitelistFilter = WhitelistFilter;
+  this.InvalidFilter = InvalidFilter;
 }
 with(require("subscriptionClasses"))
 {
@@ -524,11 +525,23 @@
       }
       break;
     case "add-filters":
-      if (msg.filters && msg.filters.length)
+      var filters = [];
+

[kzar, 2014/11/18 16:32:10]

How come you don't check that msg.filters and msg.filters.length are truthy here
any more?

[Sebastian Noack, 2014/11/18 17:42:55]

There was no point in checking it in the first place, since this message is
always send with an array, and whether it is empty or not doesn't matter.

+      for (var i = 0; i < msg.filters.length; i++)
       {
-        for (var i = 0; i < msg.filters.length; i++)
-          FilterStorage.addFilter(Filter.fromText(msg.filters[i]));
+        var filter = Filter.fromText(msg.filters[i], true);

[kzar, 2014/11/18 16:32:10]

Instead of having this separate filter variable how about pushing the filter
onto the filters array straight away? Then you could check if filters[i] was an
instance of InvalidFilter before proceeding.

[Sebastian Noack, 2014/11/18 17:42:55]

We have to access the filter object 3 times (or 2 times if directly pushed to
the array). So accessing that object via an array index, is neither more
readable nor efficient.

+        if (filter instanceof InvalidFilter)
+        {
+          sendResponse({status: "invalid", error: filter.reason});
+          return;
+        }
+        filters.push(filter);
       }
+
+      for (var i = 0; i < filters.length; i++)

[kzar, 2014/11/18 16:32:10]

You've re-declared the `i` variable here.

+        FilterStorage.addFilter(filters[i]);
+
+      sendResponse({status: "ok"});
       break;
     case "add-subscription":
       ext.showOptions(function(page)