Absent nested optional shennanigans

[Tillerino]

Uh... so this is partially for science, I guess. It's obscure enough to not matter, but I'd like to understand the reasoning. I stumbled upon this because I am working on a smaller databind library myself and of course I'm always comparing to Jackson for sensible defaults. Observe the following:

record R(Optional<Optional<String>> s) { }

R r = new ObjectMapper()
	.registerModule(new Jdk8Module())
	.readValue("{}", new TypeReference<>() {});

assertFalse(r.s.isPresent());

Here, an Optional<Optional<String>> property is absent from the JSON to deserialize. Naively, I expected the property to be set to an empty optional, but actually it's Optional.of(Optional.empty()), so the snippet above crashes.

I didn't find any tests which explicitly cover this here, so I guess it wasn't really considered a worthwhile edge case. But I think following through with these weird cases helps in figuring out consistent behaviour in general. Do you think that the current behaviour (Optional.of(Optional.empty())) is correct or do you think Optional.empty() would be correct?