typescript pure type define in [defineProps] with custom type lead to error

[TrungRueta]

Hi!

To day i tried implement plugin (v.0.5.4) into my nuxt project. i found a bug:

Follow plugin's readme instruction we had support defineProps.

Follow Vue 3 script setup frc about typescript user, we can define props in component like:

const props = defineProps<{
  foo: string
  bar?: number
}>()

This example work with plugin , but when i try define prop with custom type:

// custom type
export interface DocVersion {
  version: number
}

// component

<script lang="ts" setup>
import { DocVersion } from '~/lib/doc/Doc'

const props = defineProps<{ version?: DocVersion }>()
</script>

<template>
  <div>
    {{ version }}
  </div>
</template>

i got error message on runtime:

[Vue warn]: Invalid prop type: "null" is not a constructor

After research vue3 rfc's document above i found that:

"In dev mode, the compiler will try to infer corresponding runtime validation from the types. For example here foo: String is inferred from the foo: string type. If the type is a reference to an imported type, the inferred result will be foo: null (equal to any type) since the compiler does not have information of external files."

In vue 2 env, { typeName: { type: null } } is not a valid format. Component still working on runtime but error thown out.

Can we have any workaround for now?

Many thank for your plugin!
Trung.

---

Update:

I think for now, before smart authors update a fix, we can workaround by:

set Vue.config.silent = true to disable all warning. This will disable warning about type:null is not a constructor. Component still working ok in runtime.

My suggest to fix plugin is:
Plugin should compile defienProps + custom type to type:Null or type: Object. this will more correct and avoid mismatch.

---

update 2

Look like we also can bypass error like this:

const props = defineProps<{ version?: {} & DocVersion }>()

Thankyou!

[antfu]

From the Vue 3 doc:

As of now, the type declaration argument must be one of the following to ensure correct static analysis:

• A type literal
• A reference to an interface or a type literal in the same file

I agree we could have type: Null for that