parse_formatted_request_parameters does not respect parameters[:format]

I have been working on a project where I need to parse various flavors of XML that are POSTed from various SMS message aggregators into request_parameters. I tried to take advantage of the built in ActionController::Base.param_parsers but ran into some serious problems.

Since I can't control the aggregators' HTTP Content-Type headers to resolve the Mime::Type, I need to rely on the ':format' idiom in Rails routes. So instead of an HTTP POST to '/sms_messages.xml' I POST to '/sms_messages.clickatell'. Unfortunately the format parameter isn't parsed out of the request until after the param_parser is selected:

http://github.com/rails/rails/tr...

It appears that the content_type variable can only resolved from the Content-Type header at this point and not from params[:format] (or any other parameters for this matter). I need rails to respect the format of the request over the Content-Type header on a POST or PUT.