Thank you for replying to give more context.

You have some courage to go to a Ruby project and try to upgrade Rails from 4 to 7. I hope it will go as smoothly as possible. Props to you!

I am not sure if it helps and maybe you know these, but just in case here are 3 URLs I keep at hand when I upgrade Rails:

1. https://railsdiff.org (where it shows diff from sources)

2. https://www.fastruby.io/blog/tags/upgrades (they have some great articles in cases of some upgrades)

3. https://guides.rubyonrails.org/v6.1/upgrading_ruby_on_rails.... (there is page for each version just replace v6.1 with the major version that you need)

And also if you have not already started may I suggest you don't go directly from Rails 4 to Rails 7 but just try to go to each major(ish) version:

   Rails 4.0 -> 4.1.x
   Rails 4.1 -> 5.0.x
   Rails 5.0 -> 5.1.x
   Rails 5.1 -> 5.2.x
   Rails 5.2 -> 6.0.x
   Rails 6.0 -> 6.1.6.1
   Rails 6.1 -> 7.0.x

For each version there is an upgrade page. Eg:

- https://guides.rubyonrails.org/v4.1/upgrading_ruby_on_rails....

- https://guides.rubyonrails.org/v5.0/upgrading_ruby_on_rails....

- https://guides.rubyonrails.org/v5.1/upgrading_ruby_on_rails....

You might want to give a try to this gem: https://github.com/fastruby/next_rails. I did not used it so far but I would have a Rails 4 app I will probably try to use it.