`beforeUpdate` is not called if we explicitly state `v-slot:default`

Version

2.6.11

Reproduction link

https://jsfiddle.net/WofWca/da0v8nqc/23/

Steps to reproduce

Click on the gray box under “With `v-slot:default`:”

What is expected?

beforeUpdate of WithVSlot component is called.

What is actually happening?

It is NOT called.

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Under “No `v-slot`:” there is an identical component, except it lacks v-slot:default. It works as I expect it.

[despreston]

i looked into this a little more none of the lifecycle hooks get triggered in that first failing component e. g ‘updated’ is also not triggered

Edit

It looks like the Dep being created for beforeUpdateCallCount is not being set correctly with the ‘with-v-slot’ component.

‘my-component-with-slot’ is being added as a sub to the Dep for that variable but ‘with-v-slot’ is not. i.e, the update to that value is not going beyond ‘my-component-with-slot’

there are two separate Dep’s being created for that beforeUpdateCallCount variable. so I can see it adding ‘with-v-slot’ as a sub, but when the actual click handler happens and the value changes, the wrong Dep is sending notifications. i can tell because this.uid in the Dep does not match the Dep that ‘with-v-slot’ is subscribed to

[posva]

It’s because the implementation is different, like @KaelWD said, the point of https://github.com/vuejs/vue/issues/9756 is to make it consistent by making it both lazily invoked, which is more performant but also does not trigger the beforeUptade. And that aligns with how slots work in Vue 3