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Feature #19362

closed

#dup on Proc doesn't call initialize_dup

Added by zverok (Victor Shepelev) almost 2 years ago. Updated about 1 year ago.

Status:
Closed
Assignee:
-
Target version:
-
[ruby-core:111953]

Description

In #17545, #dup had changed to create an instance of the subclass.
It, though, doesn't invoke initialize_dup of the subclass, unlike other standard classes.

class MyAry < Array
  def initialize_dup(...)
    p(self.class, ...)
    super
  end
end

class MyString < String
  def initialize_dup(...)
    p(self.class, ...)
    super
  end
end

class MyProc < Proc
  def initialize_dup(...)
    p(self.class, ...)
    super
  end
end

MyString.new('test').dup   # prints MyString, "test"
MyAry.new(['test']).dup    # prints MyAry, ["test"]
MyProc.new { 'test' }.dup  # doesn't print anything

This makes the change in #17545 useless: while inheriting from core classes is indeed marginal, one of author's intention might be carrying additional information with the Proc instance, and bypassing #initialize_dup makes it impossible to maintain this information.

It seems that actually #initialize_dup is also invoked on the core classes themselves, but ignored on Proc.

class Array
  def initialize_dup(...)
    p(self.class, ...)
    super
  end
end

class String
  def initialize_dup(...)
    p(self.class, ...)
    super
  end
end

class Proc
  def initialize_dup(...)
    p(self.class, ...)
    super
  end
end

'test'.dup              # prints String, "test"
['test'].dup            # prints Array, ["test"]
Proc.new { 'test' }.dup # doesn't print anything

Which is an even more marginal problem but still an inconsistency.

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