defineModel has wrong type when used with `@update:model-value` event

[thomasaull]

Vue version

3.5.13

Link to minimal reproduction

https://play.vuejs.org/#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

Steps to reproduce

• Run the playground
• Check the console
• The onUpdateDate method is called twice, the first time with a Date the second time with undefined. The typescript types don’t reflect this behaviour

What is expected?

The types should indicate that the event payload can be Date | undefined

What is actually happening?

The event payload is typed as Date

System Info

Any additional comments?

Types as they show up in my IDE (VS Code):

• const modelDate: ModelRef<Date | undefined, string, Date | undefined, Date | undefined>
• (property) "onUpdate:date"?: ((date: Date) => any) | undefined

Please note that the SFC Playground (at least for me) doese not show the types correctly for some reason

[jh-leong]

As a workaround:

- const modelDate = defineModel<Date>('date', {
+ const modelDate = defineModel<Date | undefined>('date', {
    required: false
  })

[RylanBueckert-Broadsign]

The @update:model-value event should only be able to be undefined if it is not required and there is not a default. The fix made to vue-tsc v2.2.2 does not check if a default value was given.

[KazariEX]

It has been fixed by vuejs/language-tools@1e84c6a.

[RylanBueckert-Broadsign]

It has been fixed by vuejs/language-tools@1e84c6a.

@KazariEX Looking at the change, I am not sure it will always work. What if the default value is a falsy value like 0 or an empty string? Shouldn't the check be more like:
if (!defineModel.required && !('defaultValue' in defineModel)) {
or
if (!defineModel.required && defineModel.defaultValue !== undefined) {

[KazariEX]

My mistake. Could you please open a PR for it?

[thomasaull]

The @update:model-value event should only be able to be undefined if it is not required and there is not a default. The fix made to vue-tsc v2.2.2 does not check if a default value was given.

@RylanBueckert-Broadsign I think this is not correct for non-required models with a default value, since nothing is stopping you from doing myModel.value = undefined at a later stage, right?

[RylanBueckert-Broadsign]

The @update:model-value event should only be able to be undefined if it is not required and there is not a default. The fix made to vue-tsc v2.2.2 does not check if a default value was given.

@RylanBueckert-Broadsign I think this is not correct for non-required models with a default value, since nothing is stopping you from doing myModel.value = undefined at a later stage, right?

@thomasaull vue-tsc does show me an error if I try to set a model with a default value to undefined (both in my IDE and if I build).

const model = defineModel<number | null>({ default: null });

model.value = undefined; // Error here: Type 'undefined' is not assignable to type 'number | null'

[thomasaull]

@RylanBueckert-Broadsign Yes you’re right, the type changes from string | undefined to string when a default value is set:

const model = defineModel<string>() // ModelRef<string | undefined, string>
const model = defineModel<string>({ default: 'test' }) // ModelRef<string, string>