v-once and "unmount callbacks", possible memory leak?

[CamilleDrapier]

Version

3.2.26

Reproduction link

codesandbox.io

Steps to reproduce

• click on the "toggle" button at least twice

What is expected?

Console statements saying that the "OtherCmponent" is unmounted/destroyed are shown along with the "mounted" statements.

What is actually happening?

Only the mount statements are shown

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This was behaving differently in vue2, as the "destroy callbacks" were called, see: https://codesandbox.io/s/lingering-water-j7g43

This might also be related to this external issue: intlify/vue-i18n#844 (I think I can see evidence of something similar with vue-router) and generally, it might introduce memory leaks when using Components that were not specifically written to account for the beforeUnmount/unmounted not being called.

Please do let me know if this is not an issue but just a documentation miss (is it specified somewhere or should it be?), or if this is just my misunderstanding.

[shining-mind]

The v-memo=[] can be used as workaround, the Vue will call unmount for the components in the cached subtree.

UPD: a more obvious example of the bug. The unmount is not called as the result the global click listener is not removed.