Improve useVitePreprocess

[bluwy]

When enabling useVitePreprocess, importsNotUsedAsValues: "preserve" won't be forced on the entire codebase, only in Svelte files.

[dummdidumm]

What is the use case for this? Getting rid of the need to use svelte-preprocess when you use TypeScript and nothing else?

[bluwy]

Yes, and also when using css preprocessors like scss and stylus. Typescript would be handled with Vite's own esbuild instance so it would replace the need for svelte-preprocess-esbuild. Css preprocessors config can be shared via the Vite config too.

There is still use cases for svelte-preprocess though, like the recent TypeScript improvements, or it's more advanced preprocessing for style tags.