Tijms Thanks for the very detailed report, very helpful.

I applied the suggested changes here: https://github.com/hibernate/hibernate-validator/pull/846

Do you think you could contribute an integration test so that we prevent regression on this? We have an osgi/ module with an integrationtest/ module. If not convenient, we can create another module in osgi/cdi/.

Some comments/questions:

1. Name host bundle referenced is the wrong one

I changed the names to org.hibernate.validator and org.hibernate.validator.cdi to be consistent with the Java 9 module names.

2. Export for CDI extension package missing: org.hibernate.validator.cdi.internal

The idea of the internal package is that it shouldn't be exported. I moved ValidationExtension to the root package but I'm not sure it's the only class you need. It would be nice if you could check that using the code in my PR.