feat: allow import.meta.hot define override

[doman412]

Description

Fix #8921

This allows users to preserve import.meta.hot in the build by using define: { 'import.meta.hot': 'import.meta.hot' } in the config. Being able to preserve these keywords in the final build is useful for library development builds that want to include HMR code directly in the library.

Additional context

Not sure if this requires more tests than what I've provided, but if so, let me know where and I can add them.

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[antfu]

Vite usually does not transform libraries under node_modules, so having import.meta.hot in your lib might not always work. I'd suggest using https://github.com/antfu/vite-hot-client

[bluwy]

Oh I didn't know that. Could it be because in Vite 2, esbuild was incorrectly transforming import.meta.hot to ({}).hot? I think this is fixed in Vite 3 now, and it looks like importAnalysis work in node_modules too.

[antfu]

If the dep get optimized would that still work?

[bluwy]

I guess it would because import.meta.hot is preserved in the optimized bundle, and importAnalysis would detect and inject the hot context. I also did a quick test and it seems to work.

[patak-dev]

One thing we changed in Vite 3 is that optimized deps are going now through the vite plugin pipeline, as we need to replicate what the build did in v2 with plugin commonjs