Preserve existing persistence context property value during AOT processing

[christophstrobl]

The generated CodeBlock that takes care of injecting the PersistenceContext may override an existing property value. This PR checks existing values and potentially omits creating the code block.

Related to: spring-projects/spring-data-jpa#2753 & spring-projects/spring-data-commons#2760

[sdeleuze]

Worth to review with @snicoll when he is back from PTO.

@christophstrobl Is this PR ready for review for potential merge or do you plan further refinement?

[christophstrobl]

@sdeleuze you can review it already. Happy to modify if necessary.

[snicoll]

So it looks like something has post-processed the persistence context already and the core goes in the way. I think we need to fix this differently.

If I understand correctly, Spring Data has knowledge of something that we don't. Why isn't that reflected in the BeanDefinition. If it is, why is the skip necessary?

[christophstrobl]

There's an EntityManagerBeanDefinitionRegistrarPostProcessor in data-jpa that post processes EntityManagerFactory. @odrotbohm can you please help us find the right point for the changes.

[mp911de]

Spring Data is setting the property value for entityManager within the BeanDefinition. In JVM mode, the container skips @PersistenceContext post-processing for the property while AOT mode works differently.

[snicoll]

InjectionMetadata#inject has a checkPropertySkipping that is meant to determine if injection should take place. I missed that while building the AOT contribution for the persistence context. It should attempt to run the same code so that no contribution takes place if it should be skipped.

[snicoll]

Thanks for the PR @christophstrobl but I think we should tackle this one differently. I've created #30476