[ruby-core:103422] [Ruby master Feature#17753] Add Module#namespace

Issue #17753 has been updated by Eregon (Benoit Daloze).


I see, the name `namespace` is what we're disagreeing on.
Maybe you have another suggestion for the name of that method?

Maybe `outer_module`/`outer_scope` would work too, but I feel `namespace` is nicer.
All these 3 names imply some kind of lexical relationship. And even though that can be broken, in most cases it is respected and the intent of the user using this new method is clearly to go one step up in the lexical relationship.
So we should mention in the docs this might return unusual results for e.g. anonymous modules that are later assigned to a constant.

FWIW internally that's named "lexical parent module" in TruffleRuby, but that doesn't make a nice method name.
Indeed, it's not always "lexical" but in the vast majority of cases the intent is that and we would say `A::B` is `namespaced` or `defined under` (`rb_define_module_under)` module/class `A`.

The way I see it is modules are the closest thing to a namespace that Ruby has. And therefore Module#namespace feels natural to me.
From the other direction, I agree namespaces often have different/stricter semantics than Ruby modules in other languages.
Yet I think it's OK to have a slightly different meaning for namespace in Ruby, and that seems already established in docs.

----------------------------------------
Feature #17753: Add Module#namespace
https://bugs.ruby-lang.org/issues/17753#change-91513

* Author: tenderlovemaking (Aaron Patterson)
* Status: Open
* Priority: Normal
----------------------------------------
Given code like this:

```ruby
module A
  module B
    class C; end
    class D; end
  end
end
```

We can get from `C` to `B` like `C.outer_scope`, or to `A` like
`C.outer_scope.outer_scope`.

I want to use this in cases where I don't know the outer scope, but I
want to find constants that are "siblings" of a constant.  For example,
I can do `A::B::C.outer_scope.constants` to find the list of "sibling"
constants to `C`.  I want to use this feature when walking objects and
introspecting.  For example:

```ruby
ObjectSpace.each_object(Class) do |k|
  p siblings: k.outer_scope.constants
end
```

I've attached a patch that implements this feature, and there is a pull request on GitHub [here](https://github.com/ruby/ruby/pull/4326).

---Files--------------------------------
0001-Add-Module-outer_scope.patch (5.93 KB)
0001-Add-Module-namespace.patch (5.89 KB)


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