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sveltejs / vite-plugin-svelte

Svelte plugin for http://vitejs.dev/
MIT License
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experiment: try to declare virtual css modules sideeffect free #760

Closed dominikg closed 1 year ago

dominikg commented 1 year ago

unfortunately the only thing that seems to work is using the sideEffects field in package.json.

using annotation comments isn't working for import/export and both returning moduleSideEffects: false from the load hook or a custom rollup.treeshake function does not lead to the magenta css being omitted in the testcase :(

bluwy commented 1 year ago

Looks like it's being overridden at https://github.com/vitejs/vite/blob/22bd67d70a1390daae19ca33d7de162140d533d6/packages/vite/src/node/plugins/css.ts#L515

If I add a post Vite plugin to force it to moduleSideEffects: false, the CSS are all gone as Vite is unable to retrieve them in renderChunk (as the linked code comment showed). The package.json sideEffects trick worked because it sets *.svelte files as no side-effects instead, which covers the CSS treeshaking one level higher, so it doesn't hit the Vite caveat.

This seems a little tricky. Maybe Vite needs to handle CSS moduleSideEffects: false specifically.