sinatra/mount

sinatra-mount.rb

require 'sinatra/base'

module Sinatra
  module Mount

    def mount(app, route="/#{app.name.downcase}")
      before "#{route}*" do
        halt app.call(
          env.merge(
            'SCRIPT_NAME' => route.split('/').last,
            'PATH_INFO'   =>  params.delete('splat').join('/')
          )
        )
      end
    end

  end
  register Mount
end

class Bar < Sinatra::Base
  get '/' do
    'bar'
  end
  
  get %r{^/(?<bar>[^/]+)$} do
    "bar: #{params[:bar]}"
  end
end


class Foo < Sinatra::Base
  register Sinatra::Mount
  
  get '/' do
    'foo'
  end
  
  p mount Bar, '/:foo/bars'
  
  get %r{^/(?<foo>[^/]+)$} do
    "foo: #{params[:foo]}"
  end
end

Foo.run!

Also usable implementation of mount.