fix(vue): handle undefined on import.meta.hot.accept (fixes #8625)

[sapphi-red]

Description

fixes #8625

refs #8626

Additional context

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[patak-dev]

So with an undefined mod we still calls .acept to give users a way to react to errors? Do we have special handling for this somewhere? Or we always bail out?

[bluwy]

I had also wondered about how errors are reported with import.meta.hot, and I found FredKSchott/esm-hmr#3 (though the convo sort-of derailed to client errors instead of build errors). I'm not sure what's the correct way here, but if Vite proceeds with undefined module being an error happened, it may soon become a standard by itself.

[sapphi-red]

We still call .accept with undefined mod for that reason (I'm not sure if it is useful).
There isn't a special handling nor a comment about this, so it could be a non-intended behavior.

Here, when there is an error at import, moduleMap.set(dep, newMod) won't be called.

vite/packages/vite/src/client/client.ts

Lines 411 to 421 in ce790c4

	try {
	const newMod: ModuleNamespace = await import(
	/* @vite-ignore */
	base +
	path.slice(1) +
	`?import&t=${timestamp}${query ? `&${query}` : ''}`
	)
	moduleMap.set(dep, newMod)
	} catch (e) {
	warnFailedFetch(e, dep)
	}

So this moduleMap.get(dep) will be undefined.

vite/packages/vite/src/client/client.ts

Lines 426 to 428 in ce790c4

	for (const { deps, fn } of qualifiedCallbacks) {
	fn(deps.map((dep) => moduleMap.get(dep)))
	}

[patak-dev]

I think that maybe an API specific to communicating errors could be better here. But maybe I'm missing some context. We can merge this, and in any case, count it as a temporal guard and discuss this in the next team meeting.