Exclude stubbed classes from subclasses after teardown

[GCorbel]

This fix https://github.com/rspec/rspec-mocks/issues/1568.

Stubbed classes are excluded from parent subclasses after each spec.

The original issue :

begin
  require "bundler/inline"
rescue LoadError => e
  $stderr.puts "Bundler version 1.10 or later is required. Please update your Bundler"
  raise e
end

gemfile(true) do
  source "https://rubygems.org"

  gem "rspec", "3.12.0" # Activate the gem and version you are reporting the issue against.
  gem 'rspec-mocks', '3.12.6'
end

puts "Ruby version is: #{RUBY_VERSION}" # Ruby version is: 3.1.4

class Something; end

describe 'Test' do
  before(:each) do
    class A < Something; end
    stub_const('B', Class.new(Something))
  end

  it 'something' do
    puts Something.subclasses # => [B, A]
  end

  it 'something else' do
    puts Something.subclasses # => [B, B, A]
    # Only one occurence of B should be listed
  end
end

Now, Something.subclasses always return [B, A].

[GCorbel]

I’m skeptical, however, to include it for everyone. There might be some performance impact, and since this can introduce flakiness due to the GC race condition and an exception is not reassuring.

I understand your worries. I would like to find a better solution but wasn't able.

Maybe we can use a config as excluded_stubbed_const_from_subclasses or enable it by default and do a config as thread_safe_garabage_collection ?

[GCorbel]

The more I think, the more I'm in favor of a config flag. Maybe a warning message that say the flag have to be switched should be displayed when there is an error.

[pirj]

I support your idea of opting in for this with a flag.

[pirj]

We could conditionally require weakref if this option is on.

[GCorbel]

Should we have the option on by default ?

[pirj]

No. But we’re working in RSpec 4, and we can think about enabling it there unless performance considerations come up.

[GCorbel]

I change to run specs only for Ruby 3.1 and ahead as in https://github.com/rails/rails/blob/v7.0.8/activesupport/lib/active_support/ruby_features.rb

[GCorbel]

Sorry, my latest commit was completely broke. I fixed it.

[GCorbel]

I fixed the code for Ruby <= 2.4

[GCorbel]

The CI pass except for "ruby-head" which is not to my commit

[GCorbel]

I fixed a flap on specs. Now the CI should pass.

[GCorbel]

I finally succeeded to install Ruby 3.4-dev locally and confirm that the error on the CI is not related to the PR. It also fail on the main branch.

[GCorbel]

Hello, I don't want to bother you but is it possible to have a quick review, at least on the global behavior? I'm waiting for this to be able to move forward on the project I'm working on.

[GCorbel]

Please accept my apologies for the wait. The code is mostly good, thanks!

No problem, it's open source. You don't even have to reply.

[GCorbel]

@JonRowe can you give a look at this request ?

[JonRowe]

I'd like to apologise for leaving this hanging for so long, its been on my review list for ages but I just haven't been able to get around to it, I had a couple of concerns about weak ref and other such behaviour but following on from the discussion in #1568 I'm going to close this. Sorry to have wasted your time.