[ruby-core:123992] [Ruby Bug#21760] Ruby::Box: a couple of require-related problems

3 Dec 2025

      Issue #21760 has been reported by zverok (Victor Shepelev).

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Bug #21760: Ruby::Box: a couple of require-related problems
https://bugs.ruby-lang.org/issues/21760

* Author: zverok (Victor Shepelev)
* Status: Open
* ruby -v: 4.0.0dev (2025-12-03T05:16:03Z master 4762f429f4) +PRISM [x86_64-linux]
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
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I am not sure whether all the problems have the same nature, but putting them together for now.

**1. Enabling box breaks `gem`+`require`**

Minimal reproducible example:

`test.rb`:

```ruby
gem 'faraday', '= 2.14.0'
require 'faraday'
p Faraday::VERSION
```

(Note that there is no explicit use of `Ruby::Box`)

Running it with and without `RUBY_BOX`:

```sh
$ ruby test.rb
"2.14.0"

$ RUBY_BOX=1 ruby test.rb 
ruby: warning: Ruby::Box is experimental, and the behavior may change in the future!
See doc/box.md for known issues, etc.
test.rb:2:in 'Kernel#require': cannot load such file -- faraday (LoadError)
	from test.rb:2:in 'Ruby::Box::Loader#require'
	from test.rb:2:in '<main>'
test.rb:2:in 'Kernel#require': cannot load such file -- faraday (LoadError)
	from test.rb:2:in 'Ruby::Box::Loader#require'
	from test.rb:2:in '<main>'
```
(sic, the error is printed twice)

**2. requiring the same gem from `Box`-loaded file and the main file**

`box.rb`:
```ruby
require 'faraday'
p "In a box: #{Faraday::VERSION}"
```

`main.rb`
```ruby
b = Ruby::Box.new

b.load('box.rb')

require 'faraday'
```

```sh
$ RUBY_BOX=1 ruby main.rb
ruby: warning: Ruby::Box is experimental, and the behavior may change in the future!
See doc/box.md for known issues, etc.
"In a box: 2.14.0"
main.rb:5:in 'Kernel#require': cannot load such file -- faraday (LoadError)
	from main.rb:5:in 'Ruby::Box::Loader#require'
	from main.rb:5:in '<main>'
main.rb:5:in 'Kernel#require': cannot load such file -- faraday (LoadError)
	from main.rb:5:in 'Ruby::Box::Loader#require'
	from main.rb:5:in '<main>'
```

**3. `Box#require` seem to not be aware of gems**

In the example above, we see that Box-loaded file can require a gem.

This also works:
```ruby
b = Ruby::Box.new

b.eval(<<~RUBY)
  require "faraday"

  p Faraday::VERSION
RUBY
```
(prints "2.14.0" as expected)

But this doesn't:

```ruby
b = Ruby::Box.new

b.require('faraday')
```

```sh
$ RUBY_BOX=1 ruby test.rb 
ruby: warning: Ruby::Box is experimental, and the behavior may change in the future!
See doc/language/box.md for known issues, etc.
test.rb:3:in 'Ruby::Box#require': cannot load such file -- faraday (LoadError)
	from test.rb:3:in '<main>'
```

-- 
https://bugs.ruby-lang.org/