We should add a CI job in Hibernate ORM for Hibernate Reactive, so that people can notice when their change breaks Hibernate Reactive, and solve problems early.

It would run in particular on each pull request to Hibernate ORM. At minimum it should cover PRs to main, but covering PRs to maintenance branches could be useful too.

It would build Hibernate ORM (without tests), then clone Hibernate Reactive and build it against the version of Hibernate ORM we just built.

The bare minimum would be to compile Hibernate Reactive, and it would already be helpful. If it’s easy, we could test against DBs, starting with PostgreSQL, but that can be a follow-up.

The selection of the Hibernate Reactive branch to test against is TBD. We probably want something relatively dynamic that would pick a wip/* branch from Hibernate Reactive if there is one: those are branches where we put patches that provide compatibility with the latest snapshot of Hibernate ORM, when these patches cannot be merged to main yet due to the corresponding ORM version not being released yet.

This is likely easier to implement on GitHub actions, since Hibernate Reactive jobs use GitHub actions.