fix(vModel): skip value update in mounted hook if value was previously updated

[edison1105]

close #12460

The root cause is that the component's mounted hook is executed asynchronously, while the beforeUpdate hook is executed synchronously. If an update occurs during the component's mounting, the beforeUpdate hook will execute before mounted. This also causes vModelText's beforeUpdate to execute before mounted, resulting in the value set in the beforeUpdate hook being updated again in the mounted hook.

• playground 1 onBeforeUpdate of the component is executed before onMounted
• playground 2 beforeUpdate of the directive is executed before mounted

I'm not sure if this is the correct solution, but the impact should be minimal. Perhaps the correct approach is to ensure that the mounted hook always executes before the beforeUpdate hook.

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	100 kB (+123 B)	38 kB (+34 B)	34.3 kB (+62 B)
vue.global.prod.js	158 kB (+123 B)	57.8 kB (+28 B)	51.4 kB (+4 B)

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	47.2 kB	18.3 kB	16.8 kB
createApp	55.2 kB	21.3 kB	19.5 kB
createSSRApp	59.3 kB	23.1 kB	21 kB
defineCustomElement	60.1 kB	22.9 kB	20.8 kB
overall	69.1 kB	26.5 kB	24.1 kB

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commit: 90daa5c

[edison1105]

/ecosystem-ci run

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[jods4]

To be honest I don't know what the best resolution is.

This feels a bit like a hack/work-around: vModelText is modified so that out-of-order hooks do not impact the <input> value, but the root cause of problem is still there and may affect other directives or components.

I think the intuition / expectation of Vue developers are:

1. mounted is called after component is inserted in DOM.
2. beforeUpdate is never called before mounted.

Based on this, I'd say that if an update happens while the component is being mounted, then maybe one solution may be this: no beforeUpdate or updated hooks are called; and when mounted is invoked it contains the current values, not a snapshot of values when it was enqueued?

[edison1105]

then maybe one solution may be this: no beforeUpdate or updated hooks are called; and when mounted is invoked it contains the current values, not a snapshot of values when it was enqueued?

If beforeUpdate or updated is not called, it might cause some edge cases, I think it should put the beforeUpdate and updated hooks into pendingPostFlushCbs to ensure they are called.

[jods4]

@edison1105 Maybe that would be a solution, too.
It's an important change because what was a sync hook would become async/delayed but I can't tell if this is an issue or not.
To mitigate this, one approach could be to queue beforeUpdate and updated only when mounted hasn't been called yet?

[edison1105]

@jods4

one approach could be to queue beforeUpdate and updated only when mounted hasn't been called yet?

Yes, that's what I meant above.