Rails plugin to automatically minify JavaScript and CSS when their bundles get cached
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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 any version of Rails 2.x; including Rails 2.2.2.


It's really an adaptation of Uladzislau Latynski's jsmin.rb port of Douglas Crockford's jsmin.c library.

Smurf CSS Compressor

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

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


./script/plugin install git://github.com/thumblemonks/smurf.git

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.action_controller.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:



If you want to test Smurf and you don't want to test with the latest version of Rails, then do something like the following (using 2.2.2 as an example):


This is the mechanism I used for testing that Smurf works for all versions:

rake && rake RAILS_GEM_VERSION=2.2.2


Author: Justin Knowlden gus@thumblemonks.com

Contributions from: Lance Ivy, Scott White, Daniel Schierbeck

See MIT-LICENSE for licensing information