triggerRef does not activate watch callbacks on shallow refs

[danielh57]

Version

3.0.0-rc.5

Reproduction link

https://github.com/hd721/vue3-triggerref/blob/master/src/App.vue#L12

Steps to reproduce

1. Create a shallow ref.
2. Use watch (not watchEffect) to add a side effect when the ref changes.
3. Update a nested property of the ref's inner value.
4. Use triggerRef to notify Vue that the ref has been modified.

What is expected?

The watch callback is called.

What is actually happening?

The watch callback is not called.

---

This code is adapted from the Vue 3 documentation, which uses watchEffect and works correctly. I couldn't find any mention of the behavior being different for watch.