Debug option versus deprecated code in running websites

@bastianallgeier:

Please publish a PHP script that lists all necessary changes of a Kirby website 3.x, e.g. migrated from a formerly Kirby 2.x website, (please don’t let the script change anything!!!), so that after this changes this website will work with Kirby 3.3.0+, if the debug option is enabled.
This should also examine all parts of the website that lead to error messages not visible in the browser source code but avoids showing the webpage because of that error.
So far I have found in my website code some plugins and panel-based code which do not cause any visible error messages in the normal browser source code.

Suggestion:
Maybe it would be helpful to uncouple the corresponding error messages from the debug option, because for me it was sometimes difficult to find the respective parts in foreign code. Troubleshooting live running Kirby 3.x sites and deprecated code may be two different things in existing sites than in development sites…
I’m thinking of an additional option that suppresses deprecated code in the debug option.

You can find the list of breaking changes and deprecated methods in the changelog: https://github.com/getkirby/kirby/releases

It is never advisable to update a live website without testing on a local or staging server first.

This list is unfortunately not complete according to my experiences or (wrong or missing) understanding, see one of my last posts here in the forum, https://forum.getkirby.com/t/kirby-helpsection-plugin/13198/11 and https://forum.getkirby.com/t/custom-plugin-the-json-response-from-the-api-could-not-be-parsed/16078/6

Much more difficult is it for me as (already long-term) Kirby developer (without corresponding basic training) to debug foreign code, which shows in the normal browser page source code no error message, because it is uses e.g. Javascript code or leads in any background processes such as models or controllers or plugins to errors.

[Added:]
If I have a “normal” error in my code, I cannot debug it, if I have “deprecated code” in that (development) website.

Those deprecated methods are documented in the changelog. A search in your codebased for those methods should do the job. All visible/invisible and related methods were already deprecated from Kirby 3.0 (https://getkirby.com/docs/cookbook/setup/migrate-site#frontend__page-status)

Such a script would also help any plugin author to update his code, which would help all users of this plugin.
Therefore I am looking forward to the decision of @bastianallgeier about my script wish as well as my suggestion.