The ActiveModel::Lint in rails edge requires persisted? and drops requirement for new_record? and destroyed? as they're no longer called in used in ActionPack.

The active_model plugin targets the latest gem release, which is 3.0.0-beta, and still uses new_record? and destroyed? (previously, it targeted 3.0-pre). Depending on changes in other projects' code not yet released as a gem is not something Sequel does.

I don't want to track other projects' edges, as I don't feel it's a good use of my time. Also, when I release Sequel 3.9.0 in a couple of weeks, people that just install available gems would not be able to use Sequel's active_model plugin, since it would depend on an API that isn't used in the latest available active_model gem.

Please open a new ticket when a gem with the new ActiveModel API is officially released (3.0.0-rc1?). Until then, I recommend setting up your own Github fork for Sequel with the necessary AMo changes. Then, when a new AMo gem is released, you can just point me to your repository, and I can easily merge the changes.