IE7's Accept Header And Rails respond

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: <pre class="terminal">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)</pre> 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. 2009-10-28T01:26:06Z IE7 doesn't explicitly specify what format it expects in the accept header. This causes Rails to render the first format in the respond_to block. 37 rails, respond_to, ie, ie7, format, bug true ie7-accept-header-and-rails-respon-to-bug IE7's Accept Header And Rails respond_to Bug

2009-10-28T01:26:30Z