Vue infinite loop detection should throw a real error in dev, not just log a warning to console

[Inori-Lover]

Vue version

3.2.45

Link to minimal reproduction

github repo

Steps to reproduce

1. pnpm dev, open chrome dev tool
2. click the button
3. pnpm dev && pnpm preview, click button again
4. compare both console log

What is expected?

both dev and prod mode should work in same way; or the code did not cause recursively update

What is actually happening?

in dev mode, recursive update will stop auto;
in prod mode, it just continue run

System Info

System:
    OS: Windows 10 10.0.22621
    CPU: (12) x64 Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz
    Memory: 21.69 GB / 31.92 GB
  Binaries:
    Node: 16.17.1 - ~\AppData\Local\fnm_multishells\17284_1672413295400\node.EXE
    npm: 8.15.0 - ~\AppData\Local\fnm_multishells\17284_1672413295400\npm.CMD
  Browsers:
    Edge: Spartan (44.22621.963.0), Chromium (108.0.1462.54)
    Internet Explorer: 11.0.22621.1
  npmPackages:
    vue: ^3.2.45 => 3.2.45

Any additional comments?

sfc.vuejs.org even in PROD mode, it still use dev vue file so i upload a github repo.

the key code

watch(() => [state.value.deep], () => {
  state.value = { deep: false }
  // console.log('watch', ++count)
})

====

english is not my first lang, so i write a chinese version desc here too.

复现：

1. clone repo后，跑dev，尝试点击button
2. 观察控制台输出
3. pnpm dev && pnpm preview, 再次点击button
4. 再次观察控制台输出

期望：
dev与prod mode两边的行为一致，或者这段代码根本不会产生死循环更新

实际：
dev会在安全范围内停掉这个watch
prod则会跑到死

[sxzz]

+++ watch(() => state.value.deep, () => {
--- watch(() => [state.value.deep], () => {

or check the new value and old value yourself

It will avoid recursive updates.

[sxzz]

in dev mode, recursive update will stop auto; in prod mode, it just continue run

The behaviors of dev and prod are expected since Vue emitted a warning when dev mode. The developers should fix this.

core/packages/runtime-core/src/scheduler.ts

Lines 262 to 277 in 76b8573

	if (count > RECURSION_LIMIT) {
	const instance = fn.ownerInstance
	const componentName = instance && getComponentName(instance.type)
	warn(
	`Maximum recursive updates exceeded${
	componentName ? ` in component <${componentName}>` : ``
	}. ` +
	`This means you have a reactive effect that is mutating its own ` +
	`dependencies and thus recursively triggering itself. Possible sources ` +
	`include component template, render function, updated hook or ` +
	`watcher source function.`
	)
	return true
	} else {
	seen.set(fn, count + 1)
	}

[Vue warn]: Maximum recursive updates exceeded. This means you have a reactive effect that is mutating its own dependencies and thus recursively triggering itself. Possible sources include component template, render function, updated hook or watcher source function.

[Inori-Lover]

+++ watch(() => state.value.deep, () => {
--- watch(() => [state.value.deep], () => {

or check the new value and old value yourself

It will avoid recursive updates.

i am not interested in how to fix this code; if i write the logic, data update will not appera in watch cb but in event cb.
i think it is important than a framework have same behavior in both mode, both stop the browser or both stop in max count

[sxzz]

I think it is an intentionally optimized behavior of Vue. There are some small differences in behavior between production and development modes, but they are aimed to improve the developing experience.

In this case, the browser will be stuck by infinite looping. So that's why Vue will stop it and emit a warning in dev mode. Relate PR: #456

If you insist that the behavior can be improved or removed, I'm also happy to reopen the issue for a more in-depth discussion.

/cc @LinusBorg @yyx990803

[Inori-Lover]

@sxzz tks

[LinusBorg]

i think it is important than a framework have same behavior in both mode, both stop the browser or both stop in max count

• the max count check has a negative performance impact, so it's active only in dev.
• and it's in dev because the warning we can give this way is much more helpful than a context-free max stack size exceeded.

So it's a compromise to get both better dev experience and better prod performance.

What specific problem does the current behavior pose for you that would be worth giving that up? Both will effectively stop the app and throw an error?

[Inori-Lover]

@LinusBorg problem is same wrong code, vue "work" in dev mode but not in prod mode.

may be vue team can consider thrown error in dev mode too?

[sxzz]

Actually, warnings are not to be ignored in Vue.

[Inori-Lover]

@sxzz i know vue team has warning me/us in console to friendly reminder me modify my code, but catch an error then change it to a warn is not a good practice, right? it make wrong code "work".
and we can not expect all dever open dev tool all the time

[sxzz]

@Inori-Lover 🤔 Hmmm it makes sense.

I think we should change the warning to an error too and it's a serious error to be fixed by developers.

[LinusBorg]

Agreed.