Serving XHTML as application/xhtml+xml with Ruby on Rails

Question

I'm trying to get my Rails app to serve XHTML content properly, with the correct content-type of application/xhtml+xml. Ideally with content negotiation so that IE users get a chance to use the site too.

Given that all the HTML generated by Rails is marked at XHTML 1.0 Transitional, I'm a bit surprised that there is no obvious option to make Rails serve markup as XHTML. I found this http://blog.codahale.com/2006/05/23/rails-plugin-xhtml_content_type/, but it seems to be for 1.1.2 and I can't get it working properly under 2.3.8.

Have I missed something here?

Answer 1

Ok, I've got something that works now. Thanks to @danivovich for starting me in the right place. The first thing I had to do was sort out the Mime types in mime_types.rb so that HTML wasn't aliased with XHTML:

module Mime
  remove_const('HTML') # remove this so that we can re-register the types
end

Mime::Type.register "text/html", :html
Mime::Type.register "application/xhtml+xml", :xhtml

The I just added this to my application controller:

  before_filter :negotiate_xhtml
  after_filter :set_content_type

  def negotiate_xhtml
    @serving_polyglot = false
    if params[:format].nil? or request.format == :html
      @serving_polyglot = ((not request.accepts.include? :xhtml) or params[:format] == 'html')
      request.format = :xhtml
    end
  end

  def set_content_type
    if @serving_polyglot
      response.content_type = 'text/html'
    end
  end    

This makes sure that XHTML is always servered as such, unless the client doesn't accept it, or HTML has been explicitly requested. HTML is always just XHTML served as a polyglot. The @serving_polyglot variable is available in the views where any switching is needed.

This is working for me under Chrome, Safari, Firefox, Opera and IE[6-8].