Add Template Identification HTML Comments to ERB output in Rails

template_identification.rb

# Add Template Identification HTML Comments to ERB output
module ::ActionView
  module TemplateHandlers
    class ERB < TemplateHandler
      include Compilable
      cattr_accessor :erb_trim_mode
      self.erb_trim_mode = '-'
      def compile(template)
        buf = <<-HTML
          <% unless request and request.xhr? %>
            <% __in_erb_template=true %>\n
            <!-- // BEGIN #{ template } -->\n
          <% end %>
            #{ template.source }\n
          <% unless request and request.xhr? %>
            <!-- // END #{ template } -->\n
          <% end %>
        HTML
        src = ::ERB.new(buf, nil, erb_trim_mode, '@output_buffer').src
        RUBY_VERSION >= '1.9' ? src.sub(/\A#coding:.*\n/, '') : src
      end
    end
  end
end