Nasty bug when using your Rails / jQuery powered app with Chrome

February 20th, 2010 · No Comments

Today I ran into a nasty bug which is only reproducible in Google Chrome. In Firefox the very same code worked perfectly fine.

The code was supposed to work like this: After the user clicked the delete icon, jQuery would send an ajax request to the server, which then would delete the list. In the call back the UI gets updated by removing the list entry element. It’s as simple as that. The HTTP method was set to DELETE to be clean. In Firefox that worked great, in Google Chrome not at all. However you didn’t get a client side error, at least not at first, but a Rails error which would look like this:

Error occurred while parsing request parameters.
Contents:
 
[object Object]
/!\ FAILSAFE /!\  Sat Feb 20 18:56:39 +0100 2010
  Status: 500 Internal Server Error
  undefined method `name' for nil:NilClass
    /home/siebel/.gem/ruby/1.8/gems/activesupport-2.3.5/lib/active_support/whiny_nil.rb:52:in `method_missing'
    /home/siebel/.gem/ruby/1.8/gems/activesupport-2.3.5/lib/active_support/xml_mini/rexml.rb:29:in `merge_element!'
    /home/siebel/.gem/ruby/1.8/gems/activesupport-2.3.5/lib/active_support/xml_mini/rexml.rb:18:in `parse'
    /home/siebel/.gem/ruby/1.8/gems/activesupport-2.3.5/lib/active_support/xml_mini.rb:12:in `__send__'
    /home/siebel/.gem/ruby/1.8/gems/activesupport-2.3.5/lib/active_support/xml_mini.rb:12:in `parse'
    /home/siebel/.gem/ruby/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/hash/conversions.rb:164:in `from_xml'
    /home/siebel/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/params_parser.rb:34:in `parse_formatted_parameters'
    /home/siebel/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/params_parser.rb:11:in `call'
    /home/siebel/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/session/cookie_store.rb:93:in `call'
    /home/siebel/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/failsafe.rb:26:in `call'
    /home/siebel/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/lock.rb:11:in `call'
    /home/siebel/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/lock.rb:11:in `synchronize'
    /home/siebel/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/lock.rb:11:in `call'
    /home/siebel/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:114:in `call'
    /home/siebel/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/reloader.rb:34:in `run'
    /home/siebel/.gem/ruby/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:108:in `call'
    /home/siebel/.gem/ruby/1.8/gems/rails-2.3.5/lib/rails/rack/static.rb:31:in `call'
    /home/siebel/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/urlmap.rb:46:in `call'
    /home/siebel/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/urlmap.rb:40:in `each'
    /home/siebel/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/urlmap.rb:40:in `call'
    /home/siebel/.gem/ruby/1.8/gems/rails-2.3.5/lib/rails/rack/log_tailer.rb:17:in `call'
    /home/siebel/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/content_length.rb:13:in `call'
    /home/siebel/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/handler/webrick.rb:50:in `service'
    /usr/lib/ruby/1.8/webrick/httpserver.rb:104:in `service'
    /usr/lib/ruby/1.8/webrick/httpserver.rb:65:in `run'
    /usr/lib/ruby/1.8/webrick/server.rb:173:in `start_thread'
    /usr/lib/ruby/1.8/webrick/server.rb:162:in `start'
    /usr/lib/ruby/1.8/webrick/server.rb:162:in `start_thread'
    /usr/lib/ruby/1.8/webrick/server.rb:95:in `start'
    /usr/lib/ruby/1.8/webrick/server.rb:92:in `each'
    /usr/lib/ruby/1.8/webrick/server.rb:92:in `start'
    /usr/lib/ruby/1.8/webrick/server.rb:23:in `start'
    /usr/lib/ruby/1.8/webrick/server.rb:82:in `start'
    /home/siebel/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/handler/webrick.rb:14:in `run'
    /home/siebel/.gem/ruby/1.8/gems/rails-2.3.5/lib/commands/server.rb:111
    /usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
    /usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `require'
    /home/siebel/projects/Memento/script/server:3
    -e:1:in `load'
    -e:1

Since the server returned a HTTP 500 error, the client side displayed a message to the user that an error occurred. That certainly was ok, but why the hack did Rails throuw an error?

I had to google a while till I found this ticket: Bug in Chromium with GET parameters when doing a POST request

So it looked like something is going wrong when you send URL parameters alongside during a POST, PUT or DELETE. Since I’m using a URL parameter to specify the locale, I first thought that’s the issue: http://localhost:3000/lists/14?locale=en. Sadly removing it didn’t help.
While searching through the code I realized that for non-GET requests I was adding data to the PUT, DELETE, POST URL by this code:

$(document).ajaxSend(function(event, request, settings) {
        settings.data = { SomeParameter: "value" };
});

Once I commented out this one line things started working. I could finally delete the list using Chrome. The question now: How do I send this additional data. Fun thing: I didn’t have to … it was already added by other parts of the code. So the real issue here was that I had two parameters with the same name in my request. This was gracefully handled but Firefox but not by Google Chrome.