Bug #14266: Set#clone(freeze: false) makes frozen internal hash

• Status: Closed
• Assignee: knu (Akinori MUSHA)
• Target version: -
• ruby -v: ruby 2.6.0dev (2018-01-01 trunk 61537) [x86_64-darwin16]
• Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN
• Tags: patch, lib

[znz (Kazuhiro NISHIYAMA)]

% irb -r irb/completion --simple-prompt
>> require 'set'
=> true
>> set=Set[].freeze.clone(freeze: false)
=> #<Set: {}>
>> set.frozen?
=> false
>> set.instance_variable_get(:@hash).frozen?
=> true

In Set#initialize_clone, clone hash without freeze keyword argument.
But I think there is no easy way how to know freeze keyword argument value in initialize_clone.

  # Clone internal hash.
  def initialize_clone(orig)
    super
    @hash = orig.instance_variable_get(:@hash).clone
  end

[jeremyevans0 (Jeremy Evans)]

I see two possible ways to fix this:

1. Switch to overriding clone instead of initialize_clone in such cases.

2. Make clone(freeze: false) call initialize_clone(freeze: false), but have clone otherwise call initialize_clone without a keyword argument. Make Object#initialize_clone accept and ignore the freeze keyword. This way, if you override initialize_clone and don't have it accept the freeze keyword, clone(freeze: false) will raise an ArgumentError. That's probably better than returning a unfrozen object with frozen instance variables.

[znz (Kazuhiro NISHIYAMA)]

• Assignee set to knu (Akinori MUSHA)

(ref Fix Set#clone to clone internal hash.)

[jeremyevans0 (Jeremy Evans)]

• Related to Feature #16129: Call initialize_clone with freeze: false if clone called with freeze: false added

• Status changed from Open to Closed

Applied in changeset git|04eb7c7e462d1fcbab9efc7022c1b43636ab878a.

---

Call initialize_clone with freeze: false if clone called with freeze: false

This makes it possible to initialize_clone to correctly not freeze
internal state if the freeze: false keyword is passed to clone.

If clone is called with freeze: true or no keyword, do not pass
a second argument to initialize_clone to keep backwards
compatibility.

This makes it so that external libraries that override
initialize_clone but do not support the freeze keyword will fail
with ArgumentError if passing freeze: false to clone. I think that
is better than the current behavior, which succeeds but results in
an unfrozen object with frozen internals.

Fix related issues in set and delegate in stdlib.

Fixes [Bug #14266]