Thanks for the PR @Zegveld.

I like the idea. However, I am not to happy with the fact that we have to expose this on the FormattingMessager itself. I would propose an alternative solution. Instead of doing this on the caller side we could do it by creating a new instance of the FormattingMessage. This can be done in the MapperCreationProcessor by creating a new instance using the mapperTypeElement which is actually the @Mapper for which an implementation is being created at the moment and I guess is the one in the sourceMethod for you.

Regarding

when trying to add the message I get different results depending on the compiler:
jdk: Occured at 'map(SOURCE)' in 'AbstractMapper'.
eclipse: Occured at 'public abstract TARGET map(SOURCE) ' in 'AbstractMapper'.

Instead of testing it like that I would rather cast to Executable element (if the element is a method) and provide a consistent message from our side.

I agree with that the current solutions isn't the best one, I've been thinking about another way for a while including what you mentioned but so far I haven't been able to get that route working without duplicating a lot of code. Seeing as I'm not a fan of code duplication I'm not willing to put that solution forward.

My new idea is to use a decorator pattern on the Message object as well as on the FormattingMessager.
This would basically mean that the Message object gets an interface which will be implemented by both the current enum, and the decorator. The decorator is constructed by putting an object matching the interface in it, and most of the functionality will be passed through, except for the bits that we want to adjust. These bits are the message location (Edit: at the FormattingMessager) and an extension to the message text (Edit: at the Message).

Originally I tried to use the decorator pattern purely on the FormattingMessager itself, but that didn't work out that well. But if I combine a decorator on the FormattingMessager with a decorator on the Message object, then I should be able to get it working nicely. Also this will allow a bit more flexibility with messages enhancement in the future.

Going to work on this idea during the coming weekend, if I have time.

(Edit: This PR got automatically closed because I forced the changes away. 😸 )