refactor: Improve `returning` and `with`. #551

michael-simons · 2023-01-09T12:30:31Z

This addresses and fixes #547 to some extend. The goal was to allow compilation of

var cypher = Cypher.match(person)
    .returning(
        person,
        Expressions.count(person.relationshipTo(person, "ACTED_IN")).as("acted_in_rel_count")
    ).build();

without aliasing the person node with as.

This could be achieved by allowing IdentifiableElement on the returning methods the same way this PR does with the with methods. However, in contrast to with, return does allow non-aliased expressions, so the overload taking in Expression must continue to exists. That will rule out to add another overload with a Collection<SomethingElse>, as they will have the same type erasure as existing methods. Adding a varg of IdentifiableElement will break a gazillion lines of code, even in our tests, as the method will then be ambiguous.

I think the original sin was having Node and Relationship indirectly implement Named through PropertyContainer. If that wasn't the case, Named could become an expression and things will resolve nicely without additional overloads.

That change however would take several engineering weeks and turn the DSL inside out and can't be part of this change.

We created #550 for the next major release after 2023.0.0 to track this issue.

This change here will require some changes to calling code of with, but getting rid of about 250 LoC is worth the change, in addition, with will actually be nicer.