Cruller compiles and caches CoffeeScript in a way that is friendly to deploying in a production environment
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Cruller is a gem for nicely dealing with CoffeeScript files in a Sinatra app that you might want to deploy on a production system, and thus don't want CoffeeScript compiling all the time, or your evil sysadmin might not want to install Node (no idea why!).

It deals best in the following situation:

  • In development, all requests are being handled directly by Sinatra including static files
  • In production, some requests (e.g. for /public/ files) are handled by the web server in front of Sinatra.

In this ideal situation it will nicely compile cached copies for you in development, but be bypassed in production.



First, you'll need to configure Cruller (unless you are happy with it's defaults):

Cruller.configure {:source => "path/to/coffeescripts",
                   :destination => "path/to/javascript/output",
                   :path => "/url/for/javascripts",
                   :compile => "auto"}

Cruller takes 4 parameters:

  • source: the location where your CoffeeScript files are located.
  • destination: where you want the compiled Javascript to be written to. Any existing Javascript files will be served from here too.
  • path: The URL for your Javascripts.
  • compile: Whether you want to always compile CoffeeScript when a request is made, automatically compile it based on modified time, or never compile the CoffeeScript and only ever serve cached files.

Now, you can brew CoffeeScript! The command is simple:


It doesn't matter if the name has .coffee or .js in it. Cruller will strip that away. The command returns either the string of CoffeeScript, or false if Cruller couldn't find anything to brew or return to you.


Cruller has some middleware that you can use in your Rack app which will allow you to compile CoffeeScript to a folder normally handled directly by the Rack server (e.g. the public directory):

use Cruller::Server

to your file before your actual Rack app, and then configure Cruller before your app serves any requests (otherwise it will use default settings) using Cruller.configure.


In Sinatra you can use the middleware by adding the configuration + use call in your configure block. The following example would stop Cruller being used in production (reverting to the cache)

configure do |app|
  Cruller.configure( {:source => "views/coffeescripts",
                      :destination => "public/javascripts"} )

  app.use Cruller::Server if settings.environment == :development

Ruby on Rails

With Rails 3 you can either put the use line in your file as above or you can add a config line in application.rb or development.rb if you just want Cruller to compile CoffeeScript in development:

config.middleware.use Cruller::Server

Then you can configure Cruller wherever you like. I add a file called cruller.rb to my initializers folder:

  :source => "app/views/coffeescripts",
  :destination => "public/javascripts",
  :path => "/javascripts",
  :compile => "auto"

Contributing to Cruller

  • Check out the latest master to make sure the feature hasn't been implemented or the bug hasn't been fixed yet
  • Check out the issue tracker to make sure someone already hasn't requested it and/or contributed it
  • Fork the project
  • Start a feature/bugfix branch
  • Commit and push until you are happy with your contribution
  • Make sure to add tests for it. This is important so I don't break it in a future version unintentionally.
  • Please try not to mess with the Rakefile, version, or history. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so I can cherry-pick around it.


Copyright (c) 2011 David Somers. See LICENSE.txt for further details.