Make generated Metal bits a pure rack endpoint application (not middleware)

Instead of calling super to pass the request on, return a 404.
The modified app looks like this:

  # app/metal/poller.rb
  class Poller
    def self.call(env)
      if env["PATH_INFO"] =~ /^\/poller/
        [200, {"Content-Type" => "text/html"}, "Hello, World!"]
      else
        [404, {"Content-Type" => "text/html"}, "Not Found"]
      end
    end
  end

But you aren't locked in to just Rails:

  # app/metal/api.rb
  require 'sinatra'
  Sinatra::Application.default_options.merge!(:run => false, :env => :production)
  Api = Sinatra.application unless defined? Api

  get '/interesting/new/ideas' do
    'Hello Sinatra!'
  end

1 files changed, 4 insertions, 4 deletions

diff --git a/railties/lib/rails_generator/generators/components/metal/templates/metal.rb b/railties/lib/rails_generator/generators/components/metal/templates/metal.rb
index 39487263df..e94982b69a 100644
--- a/railties/lib/rails_generator/generators/components/metal/templates/metal.rb
+++ b/railties/lib/rails_generator/generators/components/metal/templates/metal.rb
@@ -1,12 +1,12 @@
 # Allow the metal piece to run in isolation
 require(File.dirname(__FILE__) + "/../../config/environment") unless defined?(Rails)
 
-class <%= class_name %> < Rails::Rack::Metal
-  def call(env)
+class <%= class_name %>
+  def self.call(env)
     if env["PATH_INFO"] =~ /^\/<%= file_name %>/
-      [200, {"Content-Type" => "text/html"}, "Hello, World!"]
+      [200, {"Content-Type" => "text/html"}, ["Hello, World!"]]
     else
-      super
+      [404, {"Content-Type" => "text/html"}, ["Not Found"]]
     end
   end
 end