perf: stricter dynamicImportVars transform filter

[patak-dev]

Description

The @react-refresh virtual module has:

const __hmr_import = (module)=>import(/* @vite-ignore */
__vite__injectQuery(module, 'import'));

This is the only dynamic import and should be ignored, but the fast short-circuit regex in the dynamic import vars plugin fails to discard this case. This PR makes the guard stricter so @react-refresh and other similar modules won't need to be parsed.

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[bluwy]

Maybe it's worth benchmarking how long it'll take the regex to run with this PR 🤔 In the past I've found that longer regexes slows down it's matching, so this PR could create a fast-path for @react-refresh, but slows down matching for all other modules.

[patak-dev]

To be honest, I don't know how to properly measure the impact. Checking with perf.link, I see it is a bit slower but it is quite noisy when I try to compared against another base.

[bluwy]

I think according to the perf link, it might not be worth optimizing this case 🤔 It does show an overall slow down especially that the pattern won't exist in most files.

[patak-dev]

Ok, let's close this one. @ArnaudBarre you could add @react-refresh to build.dynamicImportVarsOptions and it seems that it is also going to get then filtered during dev... I don't think we should support this config option as is though 🤔
I think somehow it will be nice that @react-refresh isn't parsed by acorn every time.

[ArnaudBarre]

This import was moved to the shared utils for perf reason already in vitejs/vite-plugin-react#143
So this should be parsed only once, I think this is fine