[ruby-core:113362] [Ruby master Feature#19520] Support for `Module.new(name)` and `Class.new(superclass, name)`.

27 Apr 2023

      Issue #19520 has been updated by Eregon (Benoit Daloze).

Dan0042 (Daniel DeLorme) wrote in #note-35:
...
But let's say it really is too slow to do a `rb_funcall` for each nested namespace;
Module#name is cached (and returns a frozen string) and should likely remain cached.
But you are not suggesting to change Module#name anyway.

However on a case such as a NoMethodError, there is no notion of parent namespace.
We would just call `inspect` on the class/module.
It is the responsibility of that class/module `inspect` to show the parent namespaces, like the default Module#inspect does.

So I don't see any performance issue here, besides having to call `inspect` on the Module (if overridden) for NoMethodError#message.
That is indeed a potential concern, see #18285, but it seems less problematic than `object.inspect` which was done previously.

----------------------------------------
Feature #19520: Support for `Module.new(name)` and `Class.new(superclass, name)`.
https://bugs.ruby-lang.org/issues/19520#change-102925

* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
----------------------------------------
See <https://bugs.ruby-lang.org/issues/19450> for previous discussion and motivation.

[This proposal](https://github.com/ruby/ruby/pull/7376) introduces the `name` parameter to `Class.new` and `Module.new`:

```ruby
Class.new(superclass, name)
Module.new(name)
```

As a slight change, we could use keyword arguments instead.

## Example usage

The current Ruby test suite has code which shows the usefulness of this new method:

```ruby
  def labeled_module(name, &block)
    Module.new do
      singleton_class.class_eval {
        define_method(:to_s) {name}
        alias inspect to_s
        alias name to_s
      }
      class_eval(&block) if block
    end
  end
  module_function :labeled_module

  def labeled_class(name, superclass = Object, &block)
    Class.new(superclass) do
      singleton_class.class_eval {
        define_method(:to_s) {name}
        alias inspect to_s
        alias name to_s
      }
      class_eval(&block) if block
    end
  end
  module_function :labeled_class
```

The updated code would look like this:

```ruby
  def labeled_module(name, &block)
    Module.new(name, &block)
  end

  def labeled_class(name, superclass = Object, &block)
    Class.new(superclass, name, &block)
  end
  module_function :labeled_class
```

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