From: marcandre-ruby-core@...
Date: 2020-10-20T10:00:24+00:00
Subject: [ruby-core:100444] [Ruby master Feature#17145] Ractor-aware	`Object#deep_freeze`

Issue #17145 has been updated by marcandre (Marc-Andre Lafortune).


ko1 (Koichi Sasada) wrote in #note-17:
> I never realized that so many `freeze` redefinition are used. Checking the code, some of them freeze attribute objects, which they are frozen with `deep_freeze`. I can find some cases to calculate lazy (?).

Indeed, I imagine that the majority are used to do a deep-freeze, so calling `#freeze` or not will not make a difference.

An example of lazy computation I can remember writing is a [generic memoization module in DeepCover](https://github.com/deep-cover/deep-cover/blob/master/core_gem/lib/deep_cover/memoize.rb) which is then used [in different places](https://github.com/deep-cover/deep-cover/blob/master/core_gem/lib/deep_cover/coverage/analysis.rb#L6-L7). Yes, I'm lazy enough that I factorized the `@cache ||= ` pattern ����

> I still not sure we can remain the half-frozen state, so I want to ask other comments.

How about 3 pass?
1) Collect reachable objects; abort on non-freezable.
2) Call `#freeze` on reachable objects. Exception due to custom method failing => half frozen state (just write better code ����)
3) On success, mark all objects as Ractor shareable. 




----------------------------------------
Feature #17145: Ractor-aware `Object#deep_freeze`
https://bugs.ruby-lang.org/issues/17145#change-88063

* Author: marcandre (Marc-Andre Lafortune)
* Status: Open
* Priority: Normal
----------------------------------------
I'd like to propose `Object#deep_freeze`:

Freezes recursively the contents of the receiver (by calling `deep_freeze`) and
then the receiver itself (by calling `freeze`).
Values that are shareable via `Ractor` (e.g. classes) are never frozen this way.

```ruby
# freezes recursively:
ast = [:hash, [:pair, [:str, 'hello'], [:sym, :world]]].deep_freeze
ast.dig(1, 1) # => [:str, 'hello']
ast.dig(1, 1).compact! # => FrozenError

# does not freeze classes:
[[String]].deep_freeze
String.frozen? # => false

# calls `freeze`:
class Foo
  def freeze
    build_cache!
    puts "Ready for freeze"
    super
  end
  # ...
end
[[[Foo.new]]].deep_freeze # => Outputs "Ready for freeze"
```


I think a variant `deep_freeze!` that raises an exception if the result isn't Ractor-shareable would be useful too:

```ruby
class Fire
  def freeze
    # do not call super
  end
end

x = [Fire.new]
x.deep_freeze! # => "Could not be deeply-frozen: #<Fire:0x00007ff151994748>"
```



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