$subscribe misses event when several mutations happen synchronously one after another

[dmytro-grablov]

Reproduction

https://play.pinia.vuejs.org/#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

Steps to reproduce the bug

The store defines 2 properties on state. The click handler increments both of them simultaneously.
The $subscribe callback prints to the console the resulting mutation

Open the playground and open the browser console.
Click on the button

Expected behavior

either 2 log statements in the console with respective mutations
or 1 event in the console with 1 mutation, but 2 events inside, one for each changed property

Actual behavior

there is only one entry with one mutation event, for prop1.
prop2 is unreported

Additional information

If the change happened on different ticks, as shown here , both events will be reported.

This is probably similar to #992 , but I find the problem more generic.

Basically it means if I have an action that alters several state elements as shown here, my subscribers will miss some of the mutations.

[posva]

This is because $subscribe are watchers under the hood. You can get the behavior you want by using flush: 'sync'. It's slightly less performant but that won't matter in 99% of the cases.

[dmytro-grablov]

thank you for the hint