fix: referential equalities should ignore child nodes

[KATT]

Closes #245

• Short-circuit result of the walker on already-seen objects
• Will make outputs less noisy
• Should make superjson faster too

---

yarn test --watch --testNamePattern "#245" --testPathPattern index

[KATT]

I actually would prefer to return the same here as when we hit circular references here ({ transformedValue: null }) as it would make the output a lot smaller, but that would likely be a breaking change

[KATT]

@Skn0tt:
would it be OK to return null here under some sort of options flag? it would make big outputs a lot smaller

[Skn0tt]

I like that idea conceptually - less duplicated data is always better - but I agree it's both a breaking change (the output JSON wouldn't have the same structure anymore), and it makes SuperJSON output harder to understand.

I'm assuming you'd like to reduce the output size to save bandwidth, right? Maybe we could perform some kind of benchmark on the difference this would make in practice - I could imagine that with Gzip / Brotli, the difference isn't that big. If we find that the difference is significant even with compression, then I agree we should add a flag for this behaviour! (not in this PR though)

[KATT]

Will do a follow-up PR! 👀

[Skn0tt]

This looks really good! My half-baked attempt at solving the test is here: #246 But I wholly prefer your approach.

[Skn0tt]

I like that idea conceptually - less duplicated data is always better - but I agree it's both a breaking change (the output JSON wouldn't have the same structure anymore), and it makes SuperJSON output harder to understand.

I'm assuming you'd like to reduce the output size to save bandwidth, right? Maybe we could perform some kind of benchmark on the difference this would make in practice - I could imagine that with Gzip / Brotli, the difference isn't that big. If we find that the difference is significant even with compression, then I agree we should add a flag for this behaviour! (not in this PR though)

[Skn0tt]

Published as part of https://github.com/blitz-js/superjson/releases/tag/v1.13.0