Fix MoneySerializer not registered on Rails 8.1.0+

[yukideluxe]

Fixes #779

Passing a Money as an Active Job argument can fail with ActiveJob::SerializationError because MoneyRails::ActiveJob::MoneySerializer never gets registered. This happens on Rails 8.1, and also on Rails ≤ 8.0 when ActiveJob::Base is loaded after boot (for example with config.eager_load = false). With this change the serializer is registered on every boot, on Rails 7.0 through 8.1, however Active Job is loaded.

Root cause

money-rails registered its serializer by appending to config.active_job.custom_serializers inside an ActiveSupport.on_load(:active_job) block. Rails reads that list once, and when it reads it depends on the version:

Rails	Rails reads custom_serializers in	What went wrong
≤ 8.0	config.after_initialize	If ActiveJob::Base loads after boot (e.g. eager_load = false), money-rails appends after Rails has already read the list
8.1.0 / 8.1.1 (rails/rails@b7cd3018ef)	on_load(:active_job)	Same hook as money-rails. Rails registers its callback first, so it always reads the list before money-rails appends
8.1.2+ (rails/rails@c0dc92e9e9)	on_load(:active_job_arguments)	Works only if the :active_job hook happens to fire before the :active_job_arguments one

Switching money-rails to on_load(:active_job_arguments) would not help: that hook does not exist before 8.1.2, and it still depends on callback order.

Fix

MoneyRails::Hooks.init (called from the railtie initializer) now registers the serializer directly:

if defined?(::ActiveJob::Serializers)
  require "money-rails/active_job/money_serializer"
  ::ActiveJob::Serializers.add_serializers(MoneyRails::ActiveJob::MoneySerializer)
end

This skips config.active_job.custom_serializers entirely, so it no longer matters when Rails reads it. It's safe because on every supported version Rails only adds the config list to ActiveJob::Serializers (add_serializers) and never replaces it, so a serializer registered earlier stays registered. It also no longer references Rails.application, so the Hooks.init call documented in the README for non-Rails apps registers the serializer too.

Tests

• New example in spec/active_job/money_serializer_spec.rb round-trips a Money through ActiveJob::Arguments.serialize / deserialize.
• The dummy app now requires active_job/railtie (inside a rescue LoadError, because the Mongoid gemfiles don't include Active Job) so these specs actually run.
• The full suite passes on the active_record7.0 through active_record8.1 gemfiles.

The new example fails without the fix on Rails 7.0 and 8.0. On Rails 8.1.2 it passes even without the fix, because the dummy app happens to fire the hooks in the working order. CI deletes the lockfiles and installs the newest 8.1 patch (8.1.4 in the latest run), and I haven't checked whether the example fails there without the fix. So we can't count on CI to catch an 8.1 regression, and 8.1.0/8.1.1 aren't tested at all.

@jaredmoody would you mind checking whether this fixes what you are seeing? Thanks!

🤖 Generated with Claude Code

[yukideluxe]

@jaredmoody reported my original fix did not solve the problem and @sk- said the current code doesn't work when config.eager_mode = false, so I've been drilling Claude to test all the combos 😳

I must admit this is going a bit over my head and my main goal is to simplify the code and avoid Rails version checks at all costs, so after a bunch of back and forth I think the whole thing can be simplified by just adding the MoneySerializer directly into ::ActiveJob::Serializers and stop using the custom_serializers config that is consumed at different moments of boot time depending on the Rails version used... I think this also addresses @wwahammy's concern 🤔

Could somebody help me confirm?! 🙏🏻

Ping @sunny

PS: CI failures seem unrelated, I will fix in main before merging

[wwahammy]

@yukideluxe I think this all makes sense to me. I think it looks good.

One concern I do have is that the the CI only appeared to test on MongoDB so I'd be worried about whether the tests are missing anything due to that.

[yukideluxe]

@wwahammy sorry the delay!

One concern I do have is that the the CI only appeared to test on MongoDB so I'd be worried about whether the tests are missing anything due to that.

The name is misleading! CI runs the whole AR test suite 🙏🏻