From: "byroot (Jean Boussier) via ruby-core" <ruby-core@...>
Date: 2023-05-20T18:15:13+00:00
Subject: [ruby-core:113565] [Ruby master Bug#19681] The final classpath of partially named modules is sometimes inconsistent once permanently named

Issue #19681 has been updated by byroot (Jean Boussier).


> it's not 100% certain not clearing it on remove_const was a feature or an oversight.

Interesting datapoint on this part:

```ruby
A = Class.new
B = A
Object.send(:remove_const, :A)
p B.name
```

From `1.8` to `2.3` -> `"B"`
Since `2.4` -> `"A"`

So there was indeed a behavior change at some point, again not clear if intended or an oversight.

Additionally:

```ruby
A = Class.new
A.name
B = A
Object.send(:remove_const, :A)
p B.name
```

Always returned `"A"`. So somehow, even on 1.8, once the `name` had been accessed once, it was permanent. 

----------------------------------------
Bug #19681: The final classpath of partially named modules is sometimes inconsistent once permanently named
https://bugs.ruby-lang.org/issues/19681#change-103198

* 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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