Routing for multiple subdomains

I'm trying to specify routes (specifically, the root route), dependent on what the current subdomain. I want to route to controller#action1 if the subdomain is subdomain; to controller#action2 if the subdomain is present but not subdomain or www; and to controller#action3 if the subdomain is www or not given.

I tried the following:

MyApp::Application.routes.draw do
  scope :constraints => { :subdomain => "subdomain" } do
    match "/" => "controller#action1"
  end

  scope :constraints => lambda {|req| req.subdomain.present? && !%w(subdomain www).include?(req.subdomain) } do
    match "/" => "controller#action2"  
  end

  root :to => "controller#action3"
end

Browsing to subdomain.myapp.com and other.myapp.com both work as expected (going to action1 and action2, respectively). However, when I try myapp.com or www.myapp.com, I get:

Routing Error
No route matches [GET] "/"

When I run rake routes, I see

   开发者_JAVA百科   / {:subdomain=>"subdomain", :controller=>"controller", :action=>"action1"}
      / {:controller=>"controller", :action=>"action2"}
root  / {:controller=>"controller", :action=>"action3"}

So I guess (speculating) that because there are two routes for / that don't specify a subdomain, my fallback route tries to match the second but then doesn't meet the constraints and fails? What can I do to get this working properly?

This seems to have been a bug in the routing-filter gem, and seems to be fixed as of more recent versions of the gem and the routing changes in Rails 3.2.