when looking at a rendered html page, it's often hard to tell where the code of a partial lives inside the views directory.

in order to simplify the process of finding the proper file, i find myself dropping this extension into my rails projects:

if Rails.env.development?
  module My
    module PartialRenderer
      def render(context, options, block)
        msg = "rendering '#{options[:partial]}' with locals '#{(options[:locals] || {}).keys}'"
        "<!-- start #{msg}-->\n#{super(context, options, block)}\n<!-- end #{msg}-->\n".html_safe
      end
    end
  end

  ActionView::PartialRenderer.prepend(My::PartialRenderer)
end

this will generate comments around the partial, so it's easy to spot the right files while looking at the html source:

<!-- start rendering 'some_partial' with locals '[:all, :assigned, :locals]'-->
<div class="hello">
    <div class="world">
      [...]
    </div>
</div>
<!-- end rendering 'some_partial' with locals '[:all, :assigned, :locals]'-->

i would like to propose a PR that adds this functionality to rails, but beforehand, i would like to discuss the best approach of integrating this and whether this has a chance of getting merged into master.