[ruby-core:121424] [Ruby Bug#21193] Inherited callback returns `nil` for `Object.const_source_location`

21 Mar 2025

      Issue #21193 has been updated by fxn (Xavier Noria).

Agree with @mame.

And, looking at that code from Shopify that showed up in nothing, I can imagine some other application loading with Zeitwerk and doing something like this

```ruby
class AbstractConnection
  def self.inherited(base)
    base::Manager.config # ConcreteConnection::Manager is autoloaded here.
  end
end
```

That works today, would not work with the new order.

----------------------------------------
Bug #21193: Inherited callback returns `nil` for `Object.const_source_location`
https://bugs.ruby-lang.org/issues/21193#change-112406

* Author: eileencodes (Eileen Uchitelle)
* Status: Assigned
* Assignee: matz (Yukihiro Matsumoto)
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
Since https://github.com/ruby/ruby/pull/12927 the inherited callback no longer can access the `Object.const_source_location`. A simplified reproduction is the following:

```ruby
class A
  def self.inherited(other)
    super
    p Object.const_source_location(other.name)
  end 
end

class B < A 
end
```

Prior to this change `Object.const_source_location(other.name)` would return `["test.rb", 8]` and now returns `nil`.

Shopify's application uses the `inherited` callback to load configuration classes and since it's unable to find these classes they aren't loaded when they are called. It's not clear if this was intended or if there's a workaround. In chatting with folks at GitHub, they have a similar issue (although that case sounds less straightforward). A more accurate example of what we have (I did strip this down a bunch too):

```ruby

def self.inherited(config)
  return super unless config.superclass == Config

  if (class_name = config.name) &&
    (config_location = Object.const_source_location(class_name)) &&
    (parent_dirname = File.dirname(config_location[0]))
    config_dirname = File.join(parent_dirname, "config")
      config.autoload(:Something, File.join(config_dirname, "something.rb"))
  end

  super
end
```

Original issue: https://bugs.ruby-lang.org/issues/21143

cc/ @byroot @fxn 

-- 
https://bugs.ruby-lang.org/