Bug #22267: Active Support tests started failing on ruby master (bisected to [GH-18194])

• Status: Open
• Assignee: ractor
• Target version: -
• ruby -v: ruby 4.1.0dev (2026-08-26T07:05:32Z master 346b261abe) +PRISM [x86_64-linux]
• Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN

[yahonda (Yasuo Honda)]

On ruby-head, the Active Support (Rails) test suite fails with two Ractor-related errors (rails-nightly build 4651, https://buildkite.com/rails/rails-nightly/builds/4651#01a016ac-eada-492d-9548-44089079b973/L8324).

Rails CI failure. To reproduce on the Rails side, build ruby master, then in a rails/rails checkout run the two tests from activesupport/:

$ ruby -v
ruby 4.1.0dev (2026-08-26T07:05:32Z master 346b261abe) +PRISM [x86_64-linux]

$ bundle exec ruby -Ilib:test test/time_zone_test.rb -n test_formatted_offset_in_ractor
#<Thread:...> terminated with exception (report_on_exception is true):
lib/active_support/time_with_zone.rb:78:in 'ActiveSupport::TimeWithZone#period': undefined method 'period_for_utc' for nil (NoMethodError)
        from lib/active_support/time_with_zone.rb:139:in 'ActiveSupport::TimeWithZone#zone'
        from lib/active_support/time_with_zone.rb:59:in 'ActiveSupport::TimeWithZone#initialize'
        from lib/active_support/time_with_zone.rb:535:in 'ActiveSupport::TimeWithZone#marshal_load'

  1) Error:
TimeZoneTest#test_formatted_offset_in_ractor:
Ractor::RemoteError: thrown by remote Ractor.
    lib/active_support/testing/ractors_assertions.rb:15:in 'Ractor#join'
    lib/active_support/testing/ractors_assertions.rb:15:in 'ActiveSupport::Testing::RactorsAssertions#on_ractor'
    test/time_zone_test.rb:895:in 'TimeZoneTest#test_formatted_offset_in_ractor'

$ bundle exec ruby -Ilib:test test/notifications_test.rb -n test_record_and_set_subscriptions_when_using_a_regexp
  1) Error:
Notifications::NotificationSubscriptionTest#test_record_and_set_subscriptions_when_using_a_regexp:
Ractor::Error: can not copy Hash object.
    lib/active_support/ractors.rb:117:in 'Ractor.make_shareable'
    lib/active_support/ractors.rb:117:in 'ActiveSupport::Ractors.make_shareable'
    lib/active_support/ractors.rb:79:in 'ActiveSupport::Ractors.try_make_shareable'
    lib/active_support/notifications.rb:359:in 'ActiveSupport::Notifications.record_subscriptions'
    lib/active_support/notifications.rb:314:in 'ActiveSupport::Notifications.subscribe'
    test/notifications_test.rb:604:in 'block in <class:NotificationSubscriptionTest>'

git bisect points at GH-18194 (Per-Ractor GC). Both reduce to Ractor copy and reproduce without Rails.

Steps to reproduce (pure Ruby).

(1) mirrors TimeZoneTest#test_formatted_offset_in_ractor — an object with a Time ivar (which now forces a Marshal fallback) whose marshal_load reconstructs from state only reachable in the main Ractor:

class Registry
  @zones = { "z" => Object.new }
  def self.find(name) = @zones.fetch(name)   # reads a class-level ivar
end
class Wrapper
  def initialize(name) = (@name = name; @time = Time.now; @zone = Registry.find(name))
  def marshal_dump = @name
  def marshal_load(name) = (@name = name; @time = Time.now; @zone = Registry.find(name))
end
port = Ractor::Port.new
Ractor.new(port, Wrapper.new("z")) { |p, o| p.send :ok }.join
p port.receive

(2) mirrors Notifications...test_record_and_set_subscriptions_when_using_a_regexp — a Hash holding a Set and a shareable Proc:

require "set"
Ractor.make_shareable({ s: Set.new([1, 2]), p: Ractor.shareable_proc {} }, copy: true)

Expected behavior. On Ruby 4.0.6 and before GH-18194 (50745e3e48):

• (1) copies natively, marshal_load is not called, and prints :ok.
• (2) succeeds.

Actual behavior. On current master (346b261abe) and since GH-18194 (4f6c34eea6):

(1):

#<Thread:...> terminated with exception (report_on_exception is true):
-:3:in 'Registry.find': can not get unshareable values from instance variables of classes/modules from non-main Ractors (@zones from Registry) (Ractor::IsolationError)
      from -:8:in 'Wrapper#marshal_load'
-:11:in 'Ractor#join': thrown by remote Ractor. (Ractor::RemoteError)
      from -:11:in '<main>'

marshal_load now runs in the receiver Ractor, where the object cannot reach main-Ractor state. In Active Support the same happens in TimeWithZone#marshal_load; there Time.find_zone rescues this and returns nil, so the Rails trace shows period_for_utc for nil instead.

(2):

-:2:in 'Ractor.make_shareable': can not copy Hash object. (Ractor::Error)
      from -:2:in '<main>'
-:2:in 'Ractor.make_shareable': no _dump_data is defined for class Proc (TypeError)
      from -:2:in '<main>'

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)
• Subject changed from Active Support tests started failing on ruby master (bisected to #18194) to Active Support tests started failing on ruby master (bisected to [GH-18194])

[luke-gru (Luke Gruber)]

• Assignee set to ractor

[jhawthorn (John Hawthorn)]

I'm hoping to solve this with https://github.com/ruby/ruby/pull/18605

[yahonda (Yasuo Honda)]

Testing https://github.com/ruby/ruby/pull/18605 and confirmed 1 of 2 issues are resolved.

$ ruby -v
ruby 4.1.0dev (2026-09-02T22:07:39Z ractor_copy_serial.. cef58b42cf) +PRISM [x86_64-linux]

• 1 of 2 works successfully

$ bundle exec ruby -Ilib:test test/time_zone_test.rb -n test_formatted_offset_in_ractor
Source locally installed gems is ignoring #<Bundler::StubSpecification name=psych version=5.4.0 platform=ruby> because it is missing extensions
Source locally installed gems is ignoring #<Bundler::StubSpecification name=io-console version=0.8.2 platform=ruby> because it is missing extensions
Please switch from -n/--name to -i/--include
Running 579 tests in parallel using 8 processes
Run options: -n test_formatted_offset_in_ractor --seed 5784

# Running:

.

Finished in 0.202319s, 4.9427 runs/s, 4.9427 assertions/s.

1 runs, 1 assertions, 0 failures, 0 errors, 0 skips

• 2 of 2 gets the same error.

$ bundle exec ruby -Ilib:test test/notifications_test.rb -n test_record_and_set_subscriptions_when_using_a_regexp
Source locally installed gems is ignoring #<Bundler::StubSpecification name=psych version=5.4.0 platform=ruby> because it is missing extensions
Source locally installed gems is ignoring #<Bundler::StubSpecification name=io-console version=0.8.2 platform=ruby> because it is missing extensions
Please switch from -n/--name to -i/--include
Running 45 tests in a single process (parallelization threshold is 50)
Run options: -n test_record_and_set_subscriptions_when_using_a_regexp --seed 50428

# Running:

E

Finished in 0.000568s, 1759.7951 runs/s, 0.0000 assertions/s.

  1) Error:
Notifications::NotificationSubscriptionTest#test_record_and_set_subscriptions_when_using_a_regexp:
Ractor::Error: can not copy Hash object.
    lib/active_support/ractors.rb:117:in 'Ractor.make_shareable'
    lib/active_support/ractors.rb:117:in 'ActiveSupport::Ractors.make_shareable'
    lib/active_support/ractors.rb:79:in 'ActiveSupport::Ractors.try_make_shareable'
    lib/active_support/notifications.rb:359:in 'ActiveSupport::Notifications.record_subscriptions'
    lib/active_support/notifications.rb:314:in 'ActiveSupport::Notifications.subscribe'
    test/notifications_test.rb:604:in 'block in <class:NotificationSubscriptionTest>'

1 runs, 0 assertions, 0 failures, 1 errors, 0 skips
$