From: "fxn (Xavier Noria) via ruby-core" <ruby-core@...>
Date: 2023-05-20T12:17:27+00:00
Subject: [ruby-core:113553] [Ruby master Bug#19681] The final classpath of partially named modules is sometimes inconsistent once permanently named

Issue #19681 has been updated by fxn (Xavier Noria).


Oh yes, what I wanted to mean is that TruffleRuby has things modeled so that what I believe is the correct behaviour is easy to implement. You grab the object, if its name is not permanent ask for its basename and make it permanent, the constant is irrelevant.

Regarding "checking if the constant path exists", that is something Ruby does not check:

```
M = Module/new
X = M

Object.send(:remove_const :M)

X::C = Class.new
```

That is fine, `X::C.name` is "M::C", Ruby does verify if the constant is reachable. So, no need for that to be a criteria here either.

What happens in Ruby is that if you got a "M" in your name, it is going to be an "M" forever. That is the invariant. And that is why I believe this patch is good.

----------------------------------------
Bug #19681: The final classpath of partially named modules is sometimes inconsistent once permanently named
https://bugs.ruby-lang.org/issues/19681#change-103183

* Author: byroot (Jean Boussier)
* Status: Open
* Priority: Normal
* Backport: 3.0: WONTFIX, 3.1: REQUIRED, 3.2: REQUIRED
----------------------------------------
Reported to me by @fxn 

```ruby
m = Module.new

class m::C; end
p m::C.name # => "#<Module:0x000000010789fbe0>::C"

m::D = m::C
p m::D.name # => "#<Module:0x000000010789fbe0>::C"

M = m
p M::C.name # => "M::D"
```

Expected behavior:

```ruby
p M::C.name # => "M::C"
```

### Reason

When the parent is assigned its permanent classpath, we iterate over its `const_table` to recursively give a permanent name to all the constant it owns.

However, `const_table` is an `id_table` so it doesn't retain the insertion order, which means that if the constant was aliased,
we can no longer distinguish between the original name and its aliases, and whichever comes first in the `const_table` will be used as the permanent name.

### Potential solution

I have a tentative fix for it in https://github.com/ruby/ruby/pull/7829. Instead of relying on the `const_table` key, it extract the original name from the temporary classpath.
It does feel a bit wrong to do a string search in such a place, but it does work.

 



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