render_with_debug

render_with_debug.rb

# config/initializers/render_with_debug.rb
if Rails.env.development?
  ActionView::Base.class_eval do
    alias_method :original_render, :render

    def render(options = {}, locals = {}, &block)
      if self.respond_to?(:render_with_debug)
        self.render_with_debug(options, locals, &block)
      else
        original_render(options, locals, &block)
      end
    end

    def render_with_debug(options = {}, locals = {}, &block)
    if Rails.env.development?
      partial_name = options.is_a?(Hash) ? options[:partial] : options
      debug_start_comment = "<!-- Start of #{partial_name} partial -->\n"
      debug_end_comment = "\n<!-- End of #{partial_name} partial -->"

      if block_given?
        raw(debug_start_comment) + original_render(options, locals, &block) + raw(debug_end_comment)
      else
        raw(debug_start_comment) + original_render(options, locals) + raw(debug_end_comment)
      end
    else
      render(options, locals, &block)
    end
  end
  end
end