Rake Task to convert ERB to Slim using html2slim gem.

erb2slim.rake

# Rake convert:erb2:slim converts every ERB files under `/app/views/**`.
# Original ERB files will be kept otherwise `delete` option is passed like:
# `$ rake "convert:erb2:slim[delete]"` .

namespace :convert do
  namespace :erb2 do
    ERBS = FileList["#{Rails.root}/app/views/**/*.erb"]
    ### Slim
    require 'html2slim'
    # generate tasks for slim files
    slims = ERBS.map do |erb|
      slim = erb.sub(/\.erb$/, '.slim')
      file slim, [:option] => [erb] do |_task, args|
        puts "conventing #{erb} .."
        File.open erb, 'r' do |f|
          content = HTML2Slim.convert!(f, :erb)
          IO.write(slim, content)
        end
        puts "convented to #{slim} ."

        if args[:option] == 'delete'
          File.delete(erb)
          puts "deleted #{erb} ."
        end
      end
      slim
    end
    desc 'Convert erb tempaltes to slim. `rake "convert:erb2:slim[delete]"` to delete source erb files'
    task :slim, [:option] => slims
  end
end