How to embed a Sinatra app inside a Rails app through a plugin (not Metal)

gistfile1.rb

script/generate plugin HelloWorld

# vendor/plugins/hello_world/init.rb
Rails.configuration.gem "sinatra"
Rails.configuration.middleware.insert_before("ActionController::Failsafe", "HelloWorld")

# vendor/plugins/hello_world/lib/hello_world.rb
# your sinatra app goes here...
require 'sinatra/base'
class HelloWorld < Sinatra::Base
  get "/hello" do
    "Hello World!"
  end
  #this hackeration is required for sinatra to be a nice rack citizen
  error 404 do
    @app.call(env)
  end
end

@cobbr2 I'm not entirely sure this is required anymore. This is old 2.3.x stuff... not sure if it's useful in rails 3 or even newer versions of rack and sinatra. I wrote this pre-sinatra 1.0