From: "dpepper (Daniel Pepper) via ruby-core" <ruby-core@...>
Date: 2023-06-05T03:53:36+00:00
Subject: [ruby-core:113760] [Ruby master Bug#19711] NoMethodError "private method `new' called for class" since bebd05fb51ea65bc57344b67100748200f8311eb

Issue #19711 has been updated by dpepper (Daniel Pepper).


Looks like https://github.com/rails/rails/blob/main/activesupport/test/deprecation_test.rb calls `.new` on the Deprecation Singleton a bunch of places.  This behavior _should_ not be possible on a singleton, however `.new` is explicitly marked as public in InstanceDelegator.

```ruby
module ActiveSupport
  class Deprecation
    include Singleton
    include InstanceDelegator  # <==
```


```ruby
module ActiveSupport
  class Deprecation
    module InstanceDelegator # :nodoc:
      def self.included(base)
        ...
        base.public_class_method :new  # <== makes otherwise private method public again
      end
```
https://github.com/rails/rails/blob/main/activesupport/lib/active_support/deprecation/instance_delegator.rb#L10


Essentially, this is what's happening:
```ruby
klass = Class.new do
  include Singleton
  public_class_method :new
end

Class.new(klass).new  # <== used to work but explodes after the change
```

The Singleton PR inadvertently changed `.new` to be marked private in both included and inherited (priorly just the when included), hence `.new` was made private, public, then unexpectedly private again.  I agree with ioquatix in wondering why `.new` is called on a singleton, but happy to scope down the Singleton change to avoid changing behavior until we want to do that explicitly.

----------------------------------------
Bug #19711: NoMethodError "private method `new' called for class" since bebd05fb51ea65bc57344b67100748200f8311eb
https://bugs.ruby-lang.org/issues/19711#change-103406

* Author: yahonda (Yasuo Honda)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.3.0dev (2023-06-03T00:35:18Z master bebd05fb51) [x86_64-linux]
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
Rails CI against ruby3.3.0dev has been failing https://buildkite.com/rails/rails/builds/96929#0188841c-cf1f-46d6-b48b-f510a5675262/1069-1078
According to git bisect, this change has been triggered via bebd05fb51ea65bc57344b67100748200f8311eb

### Steps to reproduce (that may not be minimum though)

```
$ gem install activesupport
$irb
require 'active_support/deprecation'
klass = Class.new(ActiveSupport::Deprecation)
deprecator = klass.new
```

### Expected behavior
It should successfully work as the previous commit does.

```
$ ruby -v
ruby 3.3.0dev (2023-06-02T21:16:52Z master 4e26ae3cb9) [x86_64-linux]
$ gem install activesupport
Successfully installed activesupport-7.0.5
Parsing documentation for activesupport-7.0.5
Done installing documentation for activesupport after 1 seconds
1 gem installed
$ irb
irb(main):001:0> require 'active_support/deprecation'
=> true
irb(main):002:0> klass = Class.new(ActiveSupport::Deprecation)
=> #<Class:0x00007f683e01a5b0>
irb(main):003:0> deprecator = klass.new
=>
#<#<Class:0x00007f683e01a5b0>:0x00007f683e2207b0
...
irb(main):004:0>
```

### Actual behavior

It gets "(irb):5:in `<main>': private method `new' called for class #<Class:0x00007fbd57dd9b10> (NoMethodError)"

```
$ ruby -v
ruby 3.3.0dev (2023-06-03T00:35:18Z master bebd05fb51) [x86_64-linux]
$ gem install activesupport
Successfully installed activesupport-7.0.5
Parsing documentation for activesupport-7.0.5
Done installing documentation for activesupport after 1 seconds
1 gem installed
$ irb
irb(main):001:0> require 'active_support/deprecation'
=> true
irb(main):002:0> klass = Class.new(ActiveSupport::Deprecation)
irb(main):003:0> deprecator = klass.new
(irb):3:in `<main>': private method `new' called for class #<Class:0x00007f7e13282bc8> (NoMethodError)
	from <internal:kernel>:187:in `loop'
	from /home/yahonda/.rbenv/versions/trunk/lib/ruby/gems/3.3.0+0/gems/irb-1.7.0/exe/irb:9:in `<top (required)>'
	from /home/yahonda/.rbenv/versions/trunk/bin/irb:25:in `load'
	from /home/yahonda/.rbenv/versions/trunk/bin/irb:25:in `<main>'
irb(main):004:0>
irb(main):003:0> require 'active_support/deprecation'
=> true
irb(main):004:0>       klass = Class.new(ActiveSupport::Deprecation)
=> #<Class:0x00007fbd57dd9b10>
irb(main):005:0>       deprecator = klass.new
(irb):5:in `<main>': private method `new' called for class #<Class:0x00007fbd57dd9b10> (NoMethodError)
	from <internal:kernel>:187:in `loop'
	from /home/yahonda/.rbenv/versions/trunk/lib/ruby/gems/3.3.0+0/gems/irb-1.7.0/exe/irb:9:in `<top (required)>'
	from /home/yahonda/.rbenv/versions/trunk/bin/irb:25:in `load'
	from /home/yahonda/.rbenv/versions/trunk/bin/irb:25:in `<main>'
irb(main):006:0>



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