Vitest equality checks fail when comparing arrays of dates and times

[tomgodber]

Hi,

I love what you've done polyfilling Temporal - I'm working on a new project and have no desire to keep using Dates for it. However I have encountered an odd bug when checking equality of arrays of Temporal objects (recreated in the attached test) which has shaken my confidence a bit...

If I do straight equality checks for two PlainDates, or PlainTimes, or ZonedDateTimes then it all works as expected - if A and B are equal then vitest's expect(a).toEqual(b) passes, if they are different it fails.

However if instead I run expect([a,b]).toEqual([b,a]) it always passes, regardless of whether a and b are the same or different. Not ideal!

temporal.test.txt

This is on node 23.5.0, vitest 3.1.1, temporal 0.30.0, typescript 5.8.2.

Any ideas? I'm not sure if the problem sits inside the library, vitest or somewhere in-between but it certainly isn't the outcome I'd expect!

Thanks,

Tom

[glsignal]

I encountered something similar along my travels recently as well, and included a minimal reproduction here: https://github.com/glsignal/fullcalendar-temporal-repro

From what I can tell poking around in the vitest source code, it seems as though the polyfill objects appear equal when it gets to the object deep equality checks. When vitest tries to enumerate the instance's keys to check that they match, it only receives an empty list (at least when I do the same in the node repl).

I'm not 100% certain about whether this is the cause, but it seems relevant/interesting for the described problem. I'd take some time to familiarise with the way everything's set up in the polyfill and see if something stands out

Thanks for the efforts on the project!

Edit: since this is also the case for other objects (e.g. Date), it might be a case of waiting for upstream tools to add special handling for Temporal.* objects as they do with other data types.

In the mean time perhaps using custom equality testers is the way to go (not-fully-correct example)

[arshaw]

Looks like Vitest released this
vitest-dev/vitest#8007
https://github.com/vitest-dev/vitest/releases/tag/v3.2.0