From: "chucke (Tiago Cardoso) via ruby-core" <ruby-core@...>
Date: 2025-08-11T13:26:23+00:00
Subject: [ruby-core:122945] [Ruby Bug#21538] initialize_dup not called when duping class/module

Issue #21538 has been reported by chucke (Tiago Cardoso).

----------------------------------------
Bug #21538: initialize_dup not called when duping class/module
https://bugs.ruby-lang.org/issues/21538

* Author: chucke (Tiago Cardoso)
* Status: Open
* ruby -v: 3.4.5
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
Not sure whether this is expected behaviour or not, but just leaving it here to start the debate on whether callbacks like `initialize_dup` are supposed to be called when a module or class is duped (the same happens with `initialize_copy` and `initialize_clone` btw):

    class A
      def initialize_dup(_)
        puts "dup instance"
        super
      end
      def self.initialize_dup(_)
        puts "dup class"
        super
      end
    end

    A.new.dup #=> "dup instance"
    A.dup #=> nothing



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