From: "ioquatix (Samuel Williams) via ruby-core" <ruby-core@...>
Date: 2024-01-16T23:13:17+00:00
Subject: [ruby-core:116255] [Ruby master Feature#19742] Introduce `Module#anonymous?`

Issue #19742 has been updated by ioquatix (Samuel Williams).


I think we can assume this is a fair definition, but I'd like to confirm it with @matz:

```ruby
class Module
  def permanent?
    if name = self.name
      Object.const_get(self.name).equal?(self)
    end
  rescue NameError
    false
  end

  def anonymous?
    !permanent?
  end
end
```

However, alternatively, we could defer to whether a class has (or had) a permanent name. The problem is, they are subtly different. The former (example) is quite a robust definition, while the latter (depending on whether a permanent name has or was assigned) is more prone to edge cases (like `const_remove` as discussed).

----------------------------------------
Feature #19742: Introduce `Module#anonymous?`
https://bugs.ruby-lang.org/issues/19742#change-106276

* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
----------------------------------------
As a follow-on <from https://bugs.ruby-lang.org/issues/19521>, I'd like propose we introduce `Module#anonymous?`.

In some situations, like logging/formatting, serialisation/deserialization, debugging or meta-programming, we might like to know if a class is a proper constant or not.

However, this brings about some other issues which might need to be discussed.

After assigning a constant, then removing it, the internal state of Ruby still believes that the class name is permanent, even thought it's no longer true.

e.g.

```
m = Module.new
m.anonymous? # true

M = m
m.anonyomous # false

Object.send(:remove_const, :M)
M # uninitialized constant M (NameError)

m.anonymous? # false
```

Because RCLASS data structure is not updated after the constant is removed, internally the state still has a "permanent class name".

I want to use this proposal to discuss this issue and whether there is anything we should do about such behaviour (or even if it's desirable).

Proposed PR: https://github.com/ruby/ruby/pull/7966

cc @fxn



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