# File lib/sprockets/helpers.rb, line 154
    def asset_tag(source, options = {}, &block)
      raise ::ArgumentError, 'block missing' unless block
      options = { :expand => !!Helpers.debug || !!Helpers.expand, :debug => Helpers.debug }.merge(options)

      path = asset_path(source, options)
      output = if options[:expand] && path.respond_to?(:map)
        "\n<!-- Expanded from #{source} -->\n" + path.map(&block).join("\n")
      else
        yield path
      end

      output = output.html_safe if output.respond_to?(:html_safe)
      output
    end