defineModel behavior without parent passing v-model different between strings and arrays

[danielkellyio]

Vue version

3.4.38

Link to minimal reproduction

https://stackblitz.com/edit/vitejs-vite-9pbycg?file=src%2FApp.vue,src%2Fcomponents%2FMyArrayComponent.vue,src%2Fcomponents%2FMyStringComponent.vue&terminal=dev

Steps to reproduce

1. use defineModel in a child component to define some array data (call it model)
2. alter model by pushing a new array item to it

What is expected?

Template to re-render with new item in the array

What is actually happening?

template does not re-render

System Info

No response

Any additional comments?

Replacing the entire array works as expected but pushing does not. Maybe this is intended (not deep)?
If so, perhaps the docs should include a note about this.

Thanks!

[edison1105]

This is the intended behavior. The model is a custom ref and only triggers when .value is replaced.

[dabernathy89]

I don't understand where the "intended behavior" is defined, as the original RFC didn't mention the limitation that only primitives would be supported. This feels more like a bug to me; if defineModel creates a ref why shouldn't it behave like a standard ref? And why would the behavior be different when v-model is provided vs not provided?