Add CSS minifier to Sprockets - ruby

Question

I have a web application which uses rack.
The code:
set :assets, (Sprockets::Environment.new { |env|
env.js_compressor = Uglifier.new({
:output => {
:preserve_line => true,
:bracketize => true,
:beautify => true,
:indent_level => 4,
:semicolons => true,
},
:mangle => false
})
env.append_path(APP_ROOT + "/app/assets/images")
env.append_path(APP_ROOT + "/app/assets/javascripts")
env.append_path(APP_ROOT + "/app/assets/stylesheets")
})
I now want to add a CSS minifier to it.
Can someone explain why only javascript files are taken into the JS compressor above?
Can I add something like env.css_compressor = YUI::CssCompressor.new() after the JS_compressor to get my requirement done
UPDATE: Well the second actually worked. But I have no clue how it worked :)

Answer 1

You hadn't set up the Sprockets::Environment.css_compressor variable, so there was no compressor available to run on text/css assets.
puts Sprockets::Environment.methods.inspect
#=> [...#css_compressor, #css_compressor=, #js_compressor, #js_compressor=,...]
To answer your question about how assets are loaded, yes the default is to point to one load path and you can as well manipulate that to include others.
https://github.com/sstephenson/sprockets
The load path is an ordered list of directories that Sprockets uses to
search for assets. To add a directory to your environment's load path, use the append_path and prepend_path methods.