Ruby1.9: submitted string form parameters with non-ASCII characters cause encoding errors

In our projects (Rails 2.3.5) we're currently using something like this to solve the problem with params:

  before_filter :force_utf8_params
  
  def force_utf8_params
    traverse = lambda do |object, block|
      if object.kind_of?(Hash)
        object.each_value { |o| traverse.call(o, block) }
      elsif object.kind_of?(Array)
        object.each { |o| traverse.call(o, block) }
      else
        block.call(object)
      end
      object
    end
    force_encoding = lambda do |o|
      o.force_encoding(Encoding::UTF_8) if o.respond_to?(:force_encoding)
    end
    traverse.call(params, force_encoding)
  end

but we want to move it into a middleware as well.

Jeremy, I think this middleware should not blindly do force_encoding("utf8") because browser could send data in other encoding without telling which. It could be really in ISO-8859-1 and forcing UTF8 will damage the string. Maybe the middleware should use some heuristics to guess encoding if HTTP encoding header wasn't set. Wycats wrote in one if his recent posts that there are some ideas for such a middleware. Do you know if anyone tried to do sth with it?
I'm willing to help as this is real PITA for me at the moment.

@Szymon Nowak

Thanks! It works fine for me!

@Szymon

Thanks! It works pretty well so far.

My first attempt at creating a rails 3 project hit this one. @Szymon solution works, if a bit hackish. :)