Use req.originalUrl for better Vite compatibility

[benmccann]

This gets us pretty darn close to being able to set the base option in Vite correctly. Right now we hardcode it to ./, which isn't correct and I suspect is one of the reasons the highly upvoted #2958 doesn't work. There's one more thing we'll need to fix it which is vitejs/vite#9236 and I'm working on getting that in as part of Vite 4

The reason we need this is that Vite rewrites the url to strip out the base path, which makes the url not what we might expect. I looked into changing that in Vite and discussed with the Vite team. While there's the possibility we might be able to do it, it's not easy and would affect the entire Vite ecosystem, so we'd need to get buy in from all the other frameworks. And actually, what Vite is doing is how the Express ecosystem works and is explicitly what originalUrl was provided for, so there's a good argument they shouldn't change anything on their side

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[Rich-Harris]

Could we do something like req.url = req.originalUrl in the middleware? This change makes me nervous, it feels like a workaround rather than a fix

[benmccann]

Yeah, that works too and is even easier. Done.

[Conduitry]

Was there something else with vite preview that you wanted to address that isn't covered by this?

[benmccann]

I don't think we'd have to do it in preview because I don't think Vite's base middleware will be invoked there. E.g. we're responsible for serving static assets in preview and that will remain the case even with Vite 4:

kit/packages/kit/src/exports/vite/preview/index.js

Line 57 in be01da3

sirv(join(svelte_config.kit.outDir, 'output/client'), {