My friend Ethan Gunderson wrote an article on the beauty of HAML as a substitute for ERB or just plain HTML markup. He’s been singing its praises for a long time now, but I’ve just been too stubborn to listen to his good advice. At first glance, HAML looks like a strange sort of dialect, and indeed it does take a bit to get used to if you’ve been doing ERB or using any other kind of traditional templating markup for awhile.

During a recent project I’ve been working on, I’ve been spending more time than usual doing actual layout and design. I tend to be someone who actually likes to do my design in the browser. After having all kinds of problems with unclosed nested divs and other mal-formked markup, I decided that it was finally time to give HAML a try.

Boy, have I been missing out on something cool. Better late to the party than never I guess.

Anyhoo, unlike LessCSS (a cool CSS tool I use) which has a –watch flag, HAML does not have the same directory watching capability. I wanted something that watches a given directory and recompiles the HAML to HTML whenever the file is updated. Here’s the ruby script I came up with:

# Script to watch a directory for any changes to a haml file
# and compile it.
#
# USAGE: ruby haml_watch.rb <directory_to_watch>
#
require 'rubygems'
require 'fssm'

directory = File.join(File.dirname(__FILE__), ARGV.first)
FSSM.monitor(directory, '**/*.haml') do
  update do |base, relative|
    input = "#{base}/#{relative}"
    output = "#{base}/#{relative.gsub!('.haml', '.html')}"
    command = "haml #{input} #{output}"
    %x{#{command}}
    puts "Regenerated #{input} to #{output}"
  end
end

It’s pretty straightforward. Make sure you have the ‘fssm’ gem installed before you try to run it (gem install fssm). Thanks Ethan for telling me about HAML. :-)

Enjoy!