Rack 2.1.0 breaks ActiveStorage

[thedanbob]

I submitted this issue to Rails and they sent me here.

Rack::File (now Rack::Files) no longer accepts nil as a first parameter per this commit: 8f85307. File.expand_path throws a TypeError.

This breaks the ActiveStorage file server: https://github.com/rails/rails/blob/master/activestorage/app/controllers/concerns/active_storage/file_server.rb#L6

[ioquatix]

What do you think is the right behaviour?

• Do nothing - nil is not a valid root path.
• Allow nil root path - potentially other operations broken (although maybe not in practice).

I'm not quite sure what is the right way forward. We did break backwards compatibility.

[rafaelfranca]

I think we should keep nil being a valid path, at least in 2.1. It works today for Active Storage use case.

[ioquatix]

Okay I can make a PR.

[rafaelfranca]

👍