A Thor task to watch a (directory of .haml templates and compile them to another directory. See usage.md at the bottom.

haml_watcher.thor

# Script to watch a directory for any changes to a haml file
# and compile it.
# Copyright © 2013 Gyula László. Code released under the DWTFYW License.
 
require 'fssm'
require 'haml'



class HamlWatch < Thor

  include Thor::Actions


  desc 'compile FROM TO', 'Compile the haml files in FROM to TO'
  method_option :extension, type: :string, default: '', 
    desc: 'The new extension to append to the file name instead of .haml'
  method_option :encoding, type: :string, default: 'UTF-8',
    desc: 'The default encoding to use'
  method_option :glob, type: :string, default: '**/*.haml',
    desc: 'The glob for the files to look for'
  def compile from, to

    watched_dir = File.join(File.dirname(__FILE__), from)
    output_path = File.join(File.dirname(__FILE__), to)
    opts = options

    say_status "HamlWatch", "Monitoring for changes to '#{from}'..."
    haml_watch = self

    glob = options[:glob]

    Dir[ File.join( watched_dir, glob ) ].each do |f|
      rel_path = f.gsub watched_dir, ''
      on_file_recompile watched_dir, rel_path, output_path
    end

    FSSM.monitor(watched_dir, glob ) do
      update { |base, relative| haml_watch.on_file_recompile( base, relative, output_path ) }
      create { |base, relative| haml_watch.on_file_recompile( base, relative, output_path ) }
    end
  end


  no_tasks do
    # Helper for unifying calls to compilations from fs events
    def on_file_recompile base, relative, output_path
        input   = File.join(base, relative)
        # remove the haml extension and replace it with the options provided
        output  = File.join output_path, relative.gsub!('.haml', options[:extension])
        compile_haml_file input, output, encoding: options[:encoding]
    end

    # Helper for compiling a HAML template to an Html one
    # it simply wraps the creation for the output
    # and forwards it to run_haml_compiler
    def compile_haml_file in_path, out_path, opts={}
      opts = { create_directory: true }.merge opts
      if opts[:create_directory]
        base_path = File.dirname(out_path)
        # Create the directory for the output file
        empty_directory base_path, verbose: false
      end
      run_haml_compiler in_path, out_path, opts
    end

    # Helper method for wrapping the HAML compiler.
    def run_haml_compiler in_path, out_path, opts={}
      opts = { format: :html5, create_directory: true, encoding: 'UTF-8'}.merge opts
      # Convert the format to sym so haml wont throw an error
      opts[:format] = opts[:format].to_sym
      nice_paths = [in_path, out_path].map {|p| p.gsub(File.dirname(__FILE__), '')}
      # Load and compile the template
      template = ""
      begin
        File.open(in_path, "r:#{opts[:encoding]}") { |f| template = f.read }
        haml_engine = Haml::Engine.new(template, opts)
        File.open(out_path, "w:#{opts[:encoding]}") { |f| f.puts haml_engine.render }
        # Try to write out nice paths
        say_status "HAML", "[#{Time.now.strftime("%H:%M")}] #{nice_paths[0]} -> #{nice_paths[1]}"
      rescue Exception => e
        say_status "ERROR", "[#{Time.now.strftime("%H:%M")}] #{nice_paths[0]} -> #{nice_paths[1]}"
        puts e
      end
    end

  end
end

usage.md

Usage:

Install requirements

  $ gem install fssm thor

Get some help about options

  $ thor help haml_watch:help

Compile the .hbs.haml templates in templates/haml to handlebars (.hbs) templates in templates/hbs

  $ thor haml_watch:compile templates/haml templates/hbs