From: "fxn (Xavier Noria) via ruby-core" <ruby-core@...>
Date: 2024-01-17T07:39:46+00:00
Subject: [ruby-core:116265] [Ruby master Feature#19742] Introduce `Module#anonymous?`

Issue #19742 has been updated by fxn (Xavier Noria).


I have all these matters in my head pretty clearly (and I am writing a book about constants), but in case someone is reading and is not used to the orthogonality of all this, you can even have a permanent set that is not reachable even when created:

```ruby
M = Module.new
N = M

Object.send(:remove_const, :M)

N::C = Class.new
N::C.name # => "M::C"

module N
  class D
  end
end

N::D.name # => "M::D"
```

The reason is that the resolution algorithms determine on which class or module **object** you are creating the constants. The answer is "in the one **stored** in the `N` constant stored in the class object stored in the `Object` constant". OK, you got an object. It has a name attribute, and from that string you derive a new string.

It is all quite orthogonal.

----------------------------------------
Feature #19742: Introduce `Module#anonymous?`
https://bugs.ruby-lang.org/issues/19742#change-106287

* 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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