Smurf

Smurf is a Rails plugin that does Javascript and CSS minification the way you would expect. See, with Rails 2.x we got this cool new :cache option on javascript_include_tag and stylesheet_link_tag, but no option for minifying the cached file(s).

Smurf ends that. Smurf - if installed and when caching is enabled for the environment - will nab the concatenated file content from Rails just before it saves it and minifies the content using either JSmin or a custom CSS compressor.

Some cool things about Smurf, which also allude to the reasons I wrote it:

Smurf will only run when Rails needs to cache new files
It will never run on its own
It requires absolutely no configuration
Other than installing it, you don't need to do anything
It just gets out of your way

Smurf will work with most versions of Rails 2.3.x and above; including Rails 3.0.0.beta1.

JSmin

The Javascript is minified with the Google Closure Compiler.

Smurf CSS Compressor

The following are the rules I applied, gathered from various perusals around the Internets

Replace consecutive whitespace characters with a single space
Remove whitespace around opening brackets
Remove whitespace in front of closing brackets
Remove the semi-colon just before the closing bracket
Remove comments between /* ... */ - this could be a problem (esp. for CSS hacks)
Remove spaces around ;, :, and , characters
Ensure whitespace between closing brackets and periods

Installation

You install Smurf as a gem:

sudo gem install smurf

Because this latest version is intended to work with Rails 3 and above, you'll need to update your Gemfile ad add:

gem 'smurf'

Then, wherever you define javascript_include_tag or stylesheet_link_tag, make sure to add the standard :cache => true or :cache => 'some_bundle' options.

Also make sure to at least have this setting in your production.rb:

config.perform_caching = true

Small suggestion

bcarpenter reminded all of us that Rails will generate real files if you set config.action_controller.perform_caching to true. If you happen to do this while developing your fantastic Rails app you may also accidentally commit them to your development repository. This is not what you want as it can send you and your awesome developer friends down the wrong rabbit hole ... and then when you figure out the problem you may be understandably and misguidedly pissed at Smurf :)

bcarpenter didn't seem too mad since he reached out to me (whew!) and suggested I add a little comment about making sure to ignore the generated cache files/directories in your SCM of choice. If you happen to be using git, be sure to do something to the effect of the following in your .gitignore file:

public/*/cache/*

Testing

Simple:

rake

If you want to play around with different versions, you'll need to update the Gemfile version of rails. While Smurf itself should work as is with Rails 3 and Rails 2.3.x, the test setup is different enough between 3 and 2.3.x that I can't make guarantees. If you need a previous version, look for the appropriate tag in the source code.