[ruby-core:113990] [Ruby master Feature#19742] Introduce `Module#anonymous?`

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


Oh, I thought you meant that the module has a name and had not been assigned to a constant.

If the module has a name, then not being considered to be anonymous is the least surprising definition to me.

You could also have

```ruby
class C
  def self.name
    nil
  end
end
```

However, I think overriding such a core method for an attribute that is out of reach, managed internally by Ruby, is questionable and predicates may be well-defined for the common case, and obviate situations like this. With this definition, can you say an anonymous module was never assigned to a constant? No, no more. However, you can add "without an overwritten name" to make the statement hold.

We could say that an empty array has 0 size. Can people override `Array#size` to return 7? Yes, they can. But API docs do not need to cover such possibilities. If you override, you're on your own with the consequences.

----------------------------------------
Feature #19742: Introduce `Module#anonymous?`
https://bugs.ruby-lang.org/issues/19742#change-103648

* 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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