toRefs type is wrong when using defineProps with optional boolean props

[extrem7]

Version

3.2.26

Reproduction link

stackblitz.com

Steps to reproduce

import { toRefs } from 'vue'

const props = defineProps<{
  isLive?: boolean
}>()

const { isLive } = toRefs(props)

What is expected?

According to fix(runtime-core): ensure declare prop keys are always present type of isLive should be:

Ref<boolean>

What is actually happening?

The type of isLive actually is:

Ref<boolean | undefined> | undefined

---

isLive couldn't be undefined in no case

[liulinboyi]

In this test case if the props type is Boolean, absent should cast to false.

[StephenChips]

Interesting, I tend to think this is a bug, since other primitive type's default value is undefined.

[liulinboyi]

Interesting, I tend to think this is a bug, since other primitive type's default value is undefined.

If it's a bug,it's easy to fix,change the handling of this situation

    // boolean casting
    if (opt[BooleanFlags.shouldCast]) {
      if (isAbsent && !hasDefault) {
        value = false
      } else if (
        opt[BooleanFlags.shouldCastTrue] &&
        (value === '' || value === hyphenate(key))
      ) {
        value = true
      }
    }

to

    // boolean casting
    if (opt[BooleanFlags.shouldCast]) {
      if (isAbsent && !hasDefault) {
        value = undefined
      } else if (
        opt[BooleanFlags.shouldCastTrue] &&
        (value === '' || value === hyphenate(key))
      ) {
        value = true
      }
    }

but in this test case if the props type is Boolean, absent should cast to false.

[StephenChips]

@liulinboyi

If is a not a bug, why we need this behaviour, what is the motivation of this design? It is kind of odd and inconsistent to other types. IMO, absent value should always be undefined.

I noticed that only boolean props will do the casting, other types will just remain undefined (e.g. number, string).

[extrem7]

@StephenChips I think there are two different moments: Ref<boolean | undefined> and Ref<> | undefined. Seems like the second has no sense (because keys are always present in props). The first case may be consistent behavior.

[ig1na]

Even when using withDefaults setting the prop to undefined, the type becomes Ref<boolean> but should be Ref<boolean | undefined>

Is there any workaround to use watchers on props without using toRefs ?

[Guebbit]

The problem is still there, I thought it was a little ugly to put an additional check, hope it will be fixed soon