Add HTML comments to rendered templates and views to discover where content is coming from

view_finder.rb

# Drop this in as a rails initializer and resstart rails
# View the source of pages - you'll see which template and views are used when rendering pages
module ActionView
  class TemplateRenderer
    alias_method :original_render, :render

    def render(context, options)
      rendered_content = original_render(context, options)

      # Random string makes it easier to jump between matching start / stop when viewing source of the page
      random_string = SecureRandom.hex
      template_path = determine_template(options).inspect

      # Single case is overkill - but some day this might handle other types of templates
      case @lookup_context.rendered_format
      when :html
        "<!-- [#{random_string}] Start #{template_path} -->\n #{rendered_content} <!-- [#{random_string}] End #{template_path} -->\n"
      else
        rendered_content
      end
    end
  end

  class Template
    alias_method :original_render, :render

    def render(view, locals, buffer=nil, &block)
      rendered_content = original_render(view, locals, buffer, &block)
      # Inline templates do not have a path or type
      return rendered_content unless type

      # Random string makes it easier to jump between matching start / stop when viewing source of the page
      random_string = SecureRandom.hex
      template_path = self.inspect

      # Single case is overkill - but some day this might handle other types of templates
      case type.to_sym
      when :html
        "<!-- [#{random_string}] Start #{template_path} -->\n".html_safe + rendered_content + "<!-- [#{random_string}] End #{template_path} -->\n".html_safe
      else
        rendered_content
      end
    end
  end
end