From: "Eregon (Benoit Daloze)" <noreply@...>
Date: 2022-08-18T09:35:59+00:00
Subject: [ruby-core:109541] [Ruby master Bug#18729] Method#owner and UnboundMethod#owner are incorrect after using Module#public/protected/private

Issue #18729 has been updated by Eregon (Benoit Daloze).


To explain my mental model:
I think Method/UnboundMethod captures a given method, and that should never change (even if someone monkey patches or remove/add methods).
This currently holds, except for ZSUPER methods, so the change will fix that.
(note: java.lang.reflect.Method is the opposite, it just captures the name and not a method entry)

I think public and alias should both "copy" the method entry.
Some people think public should instead just change visibility and delegate to super method (current semantics).
Because code is very unlikely to monkey-patch a method after making it public, both mental models work in practice.

----------------------------------------
Bug #18729: Method#owner and UnboundMethod#owner are incorrect after using Module#public/protected/private
https://bugs.ruby-lang.org/issues/18729#change-98712

* Author: Eregon (Benoit Daloze)
* Status: Open
* Priority: Normal
* Assignee: Eregon (Benoit Daloze)
* ruby -v: ruby 3.1.1p18 (2022-02-18 revision 53f5fc4236) [x86_64-linux]
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
The #owner should be "the class or module that defines the method".
Or in other words, the owner is the module which has the method table containing that method.

This generally holds, and it seems very likely this assumption is relied upon (e.g., when decorating a method, undefining it, etc).
But the returned value on CRuby is incorrect for this case:
```ruby
class A
  protected def foo
    :A
  end
end

class B < A
  p [instance_method(:foo), instance_method(:foo).owner, instance_methods(false), A.instance_methods(false)]
  public :foo
  p [instance_method(:foo), instance_method(:foo).owner, instance_methods(false), A.instance_methods(false)]
end
```

It gives:
```
[#<UnboundMethod: B(A)#foo() owner.rb:2>, A, [], [:foo]]
[#<UnboundMethod: B(A)#foo() owner.rb:2>, A, [:foo], [:foo]]
```

So `UnboundMethod#owner` says `A`, but clearly there is a :foo method entry in B created by `public :foo`, and that is shown through `B.instance_methods(false)`.

The expected output is:

```
[#<UnboundMethod: B(A)#foo() owner.rb:2>, A, [], [:foo]]
[#<UnboundMethod: B#foo() owner.rb:2>, B, [:foo], [:foo]]
```



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