From: "hsbt (Hiroshi SHIBATA) via ruby-core" <ruby-core@...>
Date: 2026-08-30T23:20:52+00:00
Subject: [ruby-core:126548] [Ruby Bug#21830] Ruby::Box and Kernel#require

Issue #21830 has been updated by hsbt (Hiroshi SHIBATA).

Status changed from Open to Closed

@fxn Thank you for your following up. I merged https://github.com/ruby/ruby/pull/18534, so `rails s` is now working with `RUBY_BOX=1`.

I'm traking the support status of RubyGems and Ruby::Box at https://bugs.ruby-lang.org/issues/22275

----------------------------------------
Bug #21830: Ruby::Box and Kernel#require
https://bugs.ruby-lang.org/issues/21830#change-118734

* Author: fxn (Xavier Noria)
* Status: Closed
* Assignee: tagomoris (Satoshi Tagomori)
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN
----------------------------------------
If you enable `Ruby::Box`, decorations to `Kernel#require` do not work.

For example, given _foo.rb_:

```ruby
module M
  def require(_path)
    puts 'decorated'
    super
  end
end

Kernel.prepend(M)

p require 'tsort'
```

the decoration works normally:

```
% ruby -v foo.rb
ruby 4.0.0 (2025-12-25 revision 553f1675f3) +YJIT +PRISM [arm64-darwin25]
decorated
true
```

but it does not with the feature enabled:

```
% RUBY_BOX=1 ruby -v foo.rb
ruby 4.0.0 (2025-12-25 revision 553f1675f3) +YJIT +PRISM [arm64-darwin25]
ruby: warning: Ruby::Box is experimental, and the behavior may change in the future!
See https://docs.ruby-lang.org/en/4.0/Ruby/Box.html for known issues, etc.
true
```

With this, Zeitwerk cannot work because it totally depends on a decoration of `Kernel#require` (done [here](https://github.com/fxn/zeitwerk/blob/main/lib/zeitwerk/core_ext/kernel.rb)).

Bootsnap also depends on the ability of decorating `Kernel#require` (done [here](https://github.com/rails/bootsnap/blob/main/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb)).

On one hand, these gems are walking a fine line in the border of the public interface of Ruby. On the other hand, it is a goal of boxes to be transparent to the code being loaded under them.

@tagomoris (Satoshi Tagomori) what should be the way to go in your opinion?

/cc @byroot (Jean Boussier)



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