thanks for opening the JIRA issue. I'll make sure that the validation rule will honar every instance of type RequiredAnnotationBeanPostProcessor because if this works with Spring it should work with Spring IDE as well.
Since the validation API is considered as open extension point of Spring IDE that could be used by clients to implement custom validation logic, I think you are right that the usage of internal classes is a little unsatisfying (please note that one can implement a validation rule with only the use of non-internal classes).Yes because of the internal packages.
Would moving the BeansValidationContext (hmm why not adding a public IBeansValidationContext interface?), AbstractBeanValidationRule and AbstractNonInfrastructureBeanValidationRule into the package org.springframework.ide.eclipse.beans.core.model.v alidation solve your problem? I think we could go ahead and consider these classes 'public API'.