There is related PR in Symfony annotations class reader. I share it here, because it might bring some inspiration or path to find united way with parsing and working with attributes for both Symfony and Dotrine.

I have modified the existing AnnotationClassLoader so that it merges attributes and annotations. This way, an application could transparently switch from annotations to attributes. Moreover, the AnnotationClassLoader does not require an annotation reader anymore.

The file https://github.com/symfony/symfony/pull/37474/files#diff-90cbecfd4505e6e8af5842db11add3b5

@TomasVotruba i don't believe it makes sense to integrate AnnotationClassLoader with attributes for more than a few simple cases, because attributes will not be 100% compatible with annotations. Tieing them together makes everything complicated instead.

@beberlei Thanks for sharing. I haven't really digged into it, as the migration path is my only focus here. It would be better to comment to the author there, if you find it useful.

Good luck guys ! You rock !

Great work on getting native attribute support into doctrine! @beberlei we (neos/flow framework) however now suffer from a slight change in expectations for some annotation classes - namely the ManyToOne, ManyToMany and Embedded now have a required first constructor argument. While those arguments were always considered "required" in a pure doctrine environment, we partially enhanced the DX by extracting some information for the annotations from other reflection data (like the targetEntity/class the annotation targets). Hence we have usage of doctrine annotations like:

@var SomeEntity
@ORM\ManyToMany

which now breaks, because the ManyToMany is attempted to be constructed with null as targetEntity in the DocParser. Until now we solved the "missing" targetEntity (and other things) via a custom AnnotationDriver and that worked out quite nicely. With this change we are at a loss though, because we'd need to hook into the DocParser now, which happens way too early.

See neos/flow-development-collection#2487 (comment)

While we can "solve" this by restricting doctrine/orm to <2.9, we would also like to move towards PHP8 support and attributes. For us the best solution would be if those three constructors would allow null for their first argument, but I understand that would mean you'd need to check for that null at runtime which is a step backward. Optimally the Annotation would not be instanciated until it is used for mapping, but that would be too great a change.
Are there any other possible ways to "enhance" the annotations and hook into the instanciation process?