Ruby

This code comes from a Rails test case, so we can change it if needed. However, there might be other cases to consider.

This only triggers the TypeError for the top-level module Namespace, not when it’s nested inside another module.

$ ruby -ve 'module Foo; module Namespace; end; end' ruby 3.5.0dev (2025-05-15T08:25:56Z master 427ede2dde) +PRISM [x86_64-linux] 

$ RUBY_NAMESPACE=1 ruby -ve 'module Foo; module Namespace; end; end' ruby 3.5.0dev (2025-05-15T08:25:56Z master 427ede2dde) +PRISM [x86_64-linux] ruby: warning: Namespace is experimental, and the behavior may change in the future! See doc/namespace.md for known issues, etc. $ 

It looks intentional to me:

Namespace.new
(irb):1:in 'Namespace#initialize': Namespace is disabled. Set RUBY_NAMESPACE=1 environment variable to use Namespace. (RuntimeError)

But the incompatibility may not have been considered since toplevel Ruby used to warn in 3.4 for Ruby::VERSION and others.

But the incompatibility may not have been considered since toplevel Ruby used to warn in 3.4 for Ruby::VERSION and others.

Yes, we likely need to emit a deprecation warning when a top-level Namespace constant is defined.

I guess I found a widely used real-world app that defines a toplevel Namespace class, and it seems very difficult for them to resolve this conflict...
https://github.com/gitlabhq/gitlabhq/blob/master/app/models/namespace.rb

Perhaps we should better rename our namespace to Ruby::Namespace or something?

I want to let Matz determine how to handle this problem :D