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@brentmc79

@brentmc79

Full-time web developer. Part-time smart ass.

I'm Brent Collier.

After a year and a half as an engineer on Twitter's Trust & Safety team, I'm looking for my next gig. Contact me if you know of something interesting.

#

IE7's Accept Header And Rails respond_to Bug

Posted on 10/28/2009

Earlier this afternoon, I was debugging an ajax call that consistently resulted in an error, but only in IE.  Checking the log file, I found this:

Processing ApplicationController#index (for 192.168.1.108 at 2009-10-27 14:37:03) [GET]
Session ID: ddde16cf83baca85a81e9fb0772c2844
Parameters: {"format"=>"js", "page"=>"1"}


ActionController::MethodNotAllowed (Only get, head, post, put, and delete requests are allowed.):
/vendor/rails/actionpack/lib/action_controller/routing/recognition_optimisation.rb:65:in `recognize_path'
/vendor/rails/actionpack/lib/action_controller/routing/route_set.rb:384:in `recognize'
/vendor/rails/actionpack/lib/action_controller/dispatcher.rb:154:in `handle_request'
/vendor/rails/actionpack/lib/action_controller/dispatcher.rb:107:in `dispatch'
/vendor/rails/actionpack/lib/action_controller/dispatcher.rb:104:in `synchronize'
/vendor/rails/actionpack/lib/action_controller/dispatcher.rb:104:in `dispatch'
/vendor/rails/actionpack/lib/action_controller/dispatcher.rb:120:in `dispatch_cgi'
/vendor/rails/actionpack/lib/action_controller/dispatcher.rb:35:in `dispatch'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/railz/request_handler.rb:50:in `process_request'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/abstract_request_handler.rb:207:in `main_loop'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/railz/application_spawner.rb:378:in `start_request_handler'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/railz/application_spawner.rb:336:in `handle_spawn_application'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/utils.rb:183:in `safe_fork'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/railz/application_spawner.rb:334:in `handle_spawn_application'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/abstract_server.rb:352:in `__send__'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/abstract_server.rb:352:in `main_loop'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/abstract_server.rb:196:in `start_synchronously'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/abstract_server.rb:163:in `start'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/railz/application_spawner.rb:213:in `start'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/spawn_manager.rb:262:in `spawn_rails_application'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/abstract_server_collection.rb:126:in `lookup_or_add'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/spawn_manager.rb:256:in `spawn_rails_application'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/abstract_server_collection.rb:80:in `synchronize'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/abstract_server_collection.rb:79:in `synchronize'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/spawn_manager.rb:255:in `spawn_rails_application'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/spawn_manager.rb:154:in `spawn_application'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/spawn_manager.rb:287:in `handle_spawn_application'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/abstract_server.rb:352:in `__send__'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/abstract_server.rb:352:in `main_loop'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/lib/phusion_passenger/abstract_server.rb:196:in `start_synchronously'
/Library/Ruby/Gems/1.8/gems/passenger-2.2.5/bin/passenger-spawn-server:61

Rendering /Users/brent/Intridea/project/vendor/rails/actionpack/lib/action_controller/templates/rescues/layout.erb (method_not_allowed)

WTF?  That told me a whole lotta nothing.

First of all, it was blowing up before it even got into the application code, which was was strange because it worked just fine in Firefox, Safari, etc.  Second, I checked the response body and it was returning html.  Html?  The format is clearly specified as "js" in the request parameters.  Double-checking the controller code, there was definitely a respond_to block with format.js, so why was it returning html?

I showed this to one of my coworkers and he asked if I had tried switching the format calls in the respond_to block.  There were two, one for html and one for javascript.  I switched them up, and put the format.js first.  I reloaded the page, and what do you know, it worked!  No error.  Again, wtf?  He told me that this same bug had kicked his ass on a previous project.

Aparently, IE7 isn't specific about what sort of response it expects in the accept header.  This causes Rails to merely return the first format that it comes to.  In my case, the html.

So if you're not seeing the format that you're expecting when testing with IE7, try reordering the format calls in the respond_to block.