Event number validation fails for zero which is inconistent with props

[lukedrive]

Version

3.5.13

Reproduction link

play.vuejs.org/

Steps to reproduce

1. Define an event with type Number.
2. Emit that event with the argument as numeric value zero.
3. Vue shows an error saying that the event validation failed.

What is expected?

Numeric events should succeed for zero.

What is actually happening?

Event validation fails and a warning is displayed.

---

I am aware you can get around this by setting the event to "required: false" but means any falsey value can be emitted without an warning.
As stated in the title and demonstrated in the example this functionality is different to props since props allow zero when set to number type even if required is explicitly set to true for them.
This are many case were my expected functionality would work better e.g. custom checkboxes what emit either 1 or 0 for checked and unchecked.

[KazariEX]

Please refer to the runtime syntax of defineEmits https://vuejs.org/guide/components/events.html#declaring-emitted-events

[lukedrive]

I see, so that syntax isn't correct. Is there no way validate emit types without typescript or writing a custom function for it?

[KazariEX]

Your use case is half correct. When passing in a validate function (zeroEvent: Number), its return value will be used as the validation condition, and any falsy value will be considered as validation failure. You happened to pass in 0.

[lukedrive]

Thanks for explaining. I was wondering why it worked at all