[ruby-core:103372] [Ruby master Feature#17753] Add Module#namespace

[fxn@hashref.com]

Issue #17753 has been updated by fxn (Xavier Noria).


 Let me add some edge cases that are possible, also for the archives:

```ruby
module M
  module N
  end
end

M::N.namespace # => A::B::C, parent module name does not match
```

```ruby
M.namespace # => M, module is namespace of itself
```

```ruby
M::N.namespace # => M
M.namespace    # => N, cycles of arbitrary depth
```

```ruby
M::N.namespace # => The module that was once in M has been garbage collected
```

I am sure I can come with more if I think more about it.

The Ruby model of this is extremely flexible and decoupled, and that is the public interface. Constant assignment, constants API, instantiation of anonymous modules, etc.


----------------------------------------
Feature #17753: Add Module#namespace
https://bugs.ruby-lang.org/issues/17753#change-91465

* 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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