unexpected full reloads for modules that are not referenced

[mmmmmmmgo]

Describe the bug

1. First, App.tsx import the Foo method of a.ts
2. Then I removed the Foo method, and now a.ts is not imported by any file
3. Modify the a.ts file at this time. After saving, vite reload the entire page, HMR does not work.

Area.mp4

Reproduction

https://stackblitz.com/edit/vitejs-vite-d4lgyd?file=src%2Fa.ts,src%2FApp.tsx&terminal=dev

Steps to reproduce

No response

System Info

...

Used Package Manager

pnpm

Logs

No response

Validations

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• Read the Contributing Guidelines.
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• The provided reproduction is a minimal reproducible example of the bug.

[stackblitz]

Start a new pull request in StackBlitz Codeflow.

• vitejs-vite-d4lgyd (Open reproduction)

[mmmmmmmgo]

This may be the key code

vite/packages/vite/src/node/server/hmr.ts

Lines 399 to 401 in 720447e

	if (!node.importers.size) {
	return true
	}

[hi-ogawa]

The behavior might not be entirely ideal, but it doesn't look so bothering either. Can you maybe explain if you have any concrete use cases where this scenario shouldn't full reload?

[bluwy]

Yeah this may be hard to fix because the no-importers check is used to assume a module is a root, e.g. if you ssrLoadModule a .js file, that file would be the root so it assumes a full reload.

If we want to fix this, we need an alternate way to track the root, which is similar to #16664 that is the inverse of the problem, where a circular dep causes the root to not be detected and miss a reload.