[ruby-core:121950] [Ruby Bug#21316] Namespaces leak with permanent names

[ruby-core:121950] [Ruby Bug#21316] Namespaces leak with permanent names

[fxn (Xavier Noria) via ruby-core]

Issue #21316 has been reported by fxn (Xavier Noria).

----------------------------------------
Bug #21316: Namespaces leak with permanent names
https://bugs.ruby-lang.org/issues/21316

* Author: fxn (Xavier Noria)
* Status: Open
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
Namespaces are not transparent for this program

```ruby
C = Class.new
C.name == 'C'
```

because under a non-main user namespace, the name of `C` has the namespace as a prefix.



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[ruby-core:121962] [Ruby Bug#21316] Namespaces leak with permanent names

[mame (Yusuke Endoh) via ruby-core]

Issue #21316 has been updated by mame (Yusuke Endoh).


This is definitely not ideal. `Class#name` could end up referring to a different constant.

```ruby
# main.rb
NS = Namespace.new
NS.require "./sub"

# sub.rb
class C; end
p C #=> expected: C
    #=> actual: NS::C ← This could refer to a different constant, which is problematic
```

@tagomoris suggested that `Class#name` should behave as follows:

* If the current namespace is at the front, omit it and just return `"C"`
* Otherwise, return something like `"#<Namespace: ...>::C"`

```ruby
# main.rb
NS = Namespace.new
NS.require "./sub"
p NS::C #=> #<Namespace: ...>::C

# sub.rb
class C; end
p C #=> C
```


----------------------------------------
Bug #21316: Namespaces leak with permanent names
https://bugs.ruby-lang.org/issues/21316#change-113078

* Author: fxn (Xavier Noria)
* Status: Open
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
Namespaces are not transparent for this program

```ruby
C = Class.new
C.name == 'C'
```

because under a non-main user namespace, the name of `C` has the namespace as a prefix.



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[ruby-core:121964] [Ruby Bug#21316] Namespaces leak with permanent names

[fxn (Xavier Noria) via ruby-core]

Issue #21316 has been updated by fxn (Xavier Noria).


Main problem here is that there are many programs that depend on that name. They may store it somewhere for later `const_get` (for example polymorphic Active Record associations), passed to a callback (for example `on_load` callbacks in Zeitwerk), etc.

That the name matches the constant path of the class or module being defined is a strong property of the language people rely on.

----------------------------------------
Bug #21316: Namespaces leak with permanent names
https://bugs.ruby-lang.org/issues/21316#change-113080

* Author: fxn (Xavier Noria)
* Status: Open
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
Namespaces are not transparent for this program

```ruby
C = Class.new
C.name == 'C'
```

because under a non-main user namespace, the name of `C` has the namespace as a prefix.



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[ruby-core:121983] [Ruby Bug#21316] Namespaces leak with permanent names

[Eregon (Benoit Daloze) via ruby-core]

Issue #21316 has been updated by Eregon (Benoit Daloze).


Right I think in the namespace defining the class/module the `Module#name` needs to not have a prefix, or it will break many gems.
OTOH when used outside, it could be very confusing without a prefix.

> suggested that Class#name should behave as follows:

Yeah, that's probably the best trade-off, although of course it means the Module#name for a given Module changes based on which Namespace is the current one.

---

BTW, I think the main namespace constants should also be prefixed when seen in another namespace, currently it's not the case:
```
$ RUBY_NAMESPACE=1 ruby -ve 'main = Namespace.current; ns = Namespace.new; class C; end; ns::MAIN_C = C; File.write "ns.rb", "p MAIN_C; p eval(MAIN_C.name)"; ns.require "./ns"'
ruby 3.5.0dev (2025-05-10T07:50:29Z namespace-on-read-.. bd4f57f96b) +PRISM [x86_64-linux]
ruby: warning: Namespace is experimental, and the behavior may change in the future!
See doc/namespace.md for know issues, etc.
C
(eval at /home/eregon/ns.rb:1):1:in '<top (required)>': uninitialized constant #<Namespace:24,user,optional>::C (NameError)
	from /home/eregon/ns.rb:1:in 'Kernel#eval'
	from /home/eregon/ns.rb:1:in '<top (required)>'
	from -e:1:in 'Namespace#require'
	from -e:1:in '<main>'
```

----------------------------------------
Bug #21316: Namespaces leak with permanent names
https://bugs.ruby-lang.org/issues/21316#change-113099

* Author: fxn (Xavier Noria)
* Status: Open
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
Namespaces are not transparent for this program

```ruby
C = Class.new
C.name == 'C'
```

because under a non-main user namespace, the name of `C` has the namespace as a prefix.



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[ruby-core:122045] [Ruby Bug#21316] Namespaces leak with permanent names

[make_now_just (Hiroya Fujinami) via ruby-core]

Issue #21316 has been updated by make_now_just (Hiroya Fujinami).


I found an issue on `Marshal` and `Namespace` maybe related to this ticket.

When dumping an object defined in a namespace using Marshal, the result will vary depending on whether the namespace is held as a variable or constant, and whether `Marshal.dump` is performed inside or outside the namespace.

In other words, we have the following files:

`ns.rb`:
```ruby
class Foo
  def dump_in_ns = Marshal.dump(self)
end
```

`main.rb`:
```ruby
ns = Namespace.new
ns.require("./ns.rb")

NS = Namespace.new
NS.require("./ns.rb")

puts "var / in ns"
begin
  ns::Foo.new.dump
  p :ok
rescue => ex
  p :error
  p ex
end
puts

puts "const / in ns"
begin
  NS::Foo.new.dump
  p :ok
rescue => ex
  p :error
  p ex
end
puts

puts "var / out ns"
begin
  Marshal.dump(ns::Foo.new)
  p :ok
rescue => ex
  p :error
  p ex
end
puts

puts "const / out ns"
begin
  Marshal.dump(NS::Foo.new)
  p :ok
rescue => ex
  p :error
  p ex
end
```
Then, the result is as follows:
```console
$ RUBY_NAMESPACE=1 ruby main.rb
var / in ns
:error
#<NoMethodError: undefined method 'dump' for an instance of #<Namespace:0x000000012018ed88>::Foo>

const / in ns
:error
#<NoMethodError: undefined method 'dump' for an instance of NS::Foo>

var / out ns
:error
#<TypeError: can't dump anonymous class #<Namespace:0x000000012018ed88>::Foo>

const / out ns
:ok
```

I'm not sure this issue is completely related to this ticket,  but `Marshal.dump` should work in any case.

----------------------------------------
Bug #21316: Namespaces leak with permanent names
https://bugs.ruby-lang.org/issues/21316#change-113195

* Author: fxn (Xavier Noria)
* Status: Open
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
Namespaces are not transparent for this program

```ruby
C = Class.new
C.name == 'C'
```

because under a non-main user namespace, the name of `C` has the namespace as a prefix.



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[ruby-core:122049] [Ruby Bug#21316] Namespaces leak with permanent names

[Eregon (Benoit Daloze) via ruby-core]

Issue #21316 has been updated by Eregon (Benoit Daloze).


@make_now_just In the first two cases, it should be `.dump_in_ns` not `.dump`

----------------------------------------
Bug #21316: Namespaces leak with permanent names
https://bugs.ruby-lang.org/issues/21316#change-113199

* Author: fxn (Xavier Noria)
* Status: Open
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
Namespaces are not transparent for this program

```ruby
C = Class.new
C.name == 'C'
```

because under a non-main user namespace, the name of `C` has the namespace as a prefix.



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[ruby-core:122050] [Ruby Bug#21316] Namespaces leak with permanent names

[make_now_just (Hiroya Fujinami) via ruby-core]

Issue #21316 has been updated by make_now_just (Hiroya Fujinami).


@Eregon It has already been fixed. Thank you.

----------------------------------------
Bug #21316: Namespaces leak with permanent names
https://bugs.ruby-lang.org/issues/21316#change-113200

* Author: fxn (Xavier Noria)
* Status: Open
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
Namespaces are not transparent for this program

```ruby
C = Class.new
C.name == 'C'
```

because under a non-main user namespace, the name of `C` has the namespace as a prefix.



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