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Nanoc3 and CoffeeScript

Nanoc3 is a pretty awesome static site generator. It works by running your content through “filters” to create the final static site. It comes with a lot of built in filters – Haml, Sass, rubypants, markdown, and more! Nothing for Javascript though. Which is sad because I really like CoffeeScript. It’s ok! I wrote my own filter, shared here for your enjoyment.

Bang this in your lib folder:

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require 'open3'
require 'win32/open3' if RUBY_PLATFORM.match /win32/

class CoffeeFilter < Nanoc3::Filter
  identifier :coffee

  def run(content, params = {})
    output = ''
    error = ''
    command = 'coffee -s -p -l'
    Open3.popen3(command) do |stdin, stdout, stderr|
      stdin.puts content
      stdin.close
      output = stdout.read.strip
      error = stderr.read.strip
      [stdout, stderr].each { |io| io.close }
    end

    if error.length > 0
      raise("Compilation error:\n#{error}")
    else
      output
    end
  end
end

To use it, a compilation rule like the following is pretty neat:

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# Compile both coffee and js, co-mingled in the same directory
compile '/js/*' do
  case item[:extension]
    when 'coffee'
      filter :coffee
    when 'js'
      # Nothing
  end
end

Don’t forget to add ‘coffee’ to the list of text extensions in your config.yaml!

Protip: You can use the above pattern to filter content through any command line program. Figlet anyone?

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