Route update unexpectedly triggers watchers

[lwansbrough]

Reproduction

https://jsfiddle.net/sj1chxmd/2/

Steps to reproduce the bug

Observe behaviour in this repro (Vue 2.7): https://jsfiddle.net/sj1chxmd/2/
Then compare the behaviour in this repro (Vue 3): https://jsfiddle.net/sf2gutkr/1/

Expected behavior

The behaviour should be the same between the two examples.

Actual behavior

The presence of a reactive variable on the <router-view> in the Vue 3 version forces its descendants' watchers to update. I believe the correct behaviour should be the Vue 2.7 behaviour.

Additional information

Related:

• route change should not be changing state until the previous component has been unmounted vue-router#3393
• Please reopen #3393 #1590

[posva]

Duplicate of vuejs/core#7030