middleman/middleman-core/lib/middleman-core/renderers/less.rb

require 'less'

module Middleman
  module Renderers
    # Sass renderer
    module Less
      # Setup extension
      class << self
        # Once registered
        def registered(app)
          # Default less options
          app.config.define_setting :less, {}, 'LESS compiler options'

          app.before_configuration do
            template_extensions less: :css
          end

          app.after_configuration do
            ::Less.paths << File.join(source_dir, config[:css_dir])
          end

          # Tell Tilt to use it as well (for inline sass blocks)
          ::Tilt.register 'less', LocalLoadingLessTemplate
          ::Tilt.prefer(LocalLoadingLessTemplate)
        end

        alias_method :included, :registered
      end

      # A SassTemplate for Tilt which outputs debug messages
      class LocalLoadingLessTemplate < ::Tilt::LessTemplate
        def prepare
          if ::Less.const_defined? :Engine
            @engine = ::Less::Engine.new(data)
          else
            parser  = ::Less::Parser.new(options.merge filename: eval_file, line: line, paths: ['.', File.dirname(eval_file)])
            @engine = parser.parse(data)
          end
        end
      end
    end
  end
end