Cleanup prebundleSvelteLibraries

[bluwy]

Describe the problem

Fix the remaining issues for prebundleSvelteLibraries, which should be the correct way forward for Vite prebundling of Svelte libraries. Namely:

• Automatic re-prebundle when svelte config change.
• Allow deep importing Svelte components.
• Allow importing libraries with a Svelte component entrypoint.
• Make sure Vite 2.9 prebundling changes works

Some fixes may need to be in Vite core. Collecting these issue here so I don't forget, or if someone likes to tackle them.

Describe the proposed solution

Goal is to fix them by year end.

Alternatives considered

Not fix them by year end

Importance

would make my life easier

[bluwy]

Update: no2 and no3 are being dealt at vitejs/vite#6801

[josdejong]

Short question: what will be the default behavior after this is finished? Will that be prebundleSvelteLibraries: true?

Background: I'm creating a sveltekit library (see here), but in order to be able to use it right now, every client has to configure kit.vit.optimizeDeps.include: [...list with commonjs deps...]. I noticed that this is not needed anymore when setting experimental.prebundleSvelteLibraries: true, which is great! So I hope this will become the default in the end: that will make using my library a breeze (just install and use, no extra config needed).

[bluwy]

Hi. Ideally this will be the new default behaviour, but I would put it in a short experimental phase first just in case there are edge cases.

I'm creating a sveltekit library (see here), but in order to be able to use it right now, every client has to configure kit.vit.optimizeDeps.include: [...list with commonjs deps...]

This should be handled by default by vite-plugin-svelte already (nested/transitive dependency inclusion), so it's weird that that's needed for your library. I think the optimizeDeps.include can be removed now and it will work, but feel free to open an issue if it doesn't.

[josdejong]

Awesome!

Good to know that this is supposed to "just" work. I'll double check whether I'm using all the latest versions of svelte/kit/vite and verify whether optimizeDeps.include is still needed, if so I'll open a new issue, thanks Bjorn.

UPDATE: managed to get it working 🎉 . There where only two troublesome dependencies left, I could replace one and create a workaround for the other.