Add Support for Bun Runtime

[jdgamble555]

Describe the problem

It would be awesome to have support for the new Public Bun Runtime on Vercel!

https://vercel.com/blog/bun-runtime-on-vercel-functions
https://vercel.com/docs/functions/runtimes/bun

Describe the proposed solution

Add a bun runtime for Vercel deployments adapter!

Alternatives considered

Add a bun specific runtime and deno specific runtime?

adapter({
	runtime: 'bun'
}),

Importance

nice to have

Additional Information

Not sure if there could just be instructions for deployment instead of an adapter.

[bretth18]

the latest version of @sveltejs/adapter-vercel (v6.1.1) supports experimental_bun1.x as a runtime type:

adapter({
    runtime: "experimental_bun1.x",
})

but fwiw, I have not been able to get this to actually deploy correctly on vercel, even with the default template from sv create. the app builds fine, but once deployed the vercel functions seem to crash with the following error:

ReferenceError: Cannot access 'default' before initialization.
    at d (/opt/rust/nodejs.js:16:21862)
    at processTicksAndRejections (native:7:39)
Bun process exited with exit status: 1. The logs above can help with debugging the issue.

i tried this with and without adding a vercel.json indicated in the vercel docs like this:

{
	"$schema": "https://openapi.vercel.sh/vercel.json",
	"bunVersion": "1.x"
}

[elliott-with-the-longest-name-on-github]

To be clear, the Vercel adapter does support deploying using the Bun runtime -- what @bretth18 describes is the correct way to do it. You can set the runtime globally through adapter config or through export const config = { runtime: 'experimental_bun1.x' } from a +page or +layout file.

The bug he's running into appears to be a Vercel issue, though. I'm keeping this issue open for tracking but I'm not sure there's anything we can do on this end yet.

[elliott-with-the-longest-name-on-github]

https://github.com/elliott-with-the-longest-name-on-github/buntime-svelte-test

Created a repro

[elliott-with-the-longest-name-on-github]

Worked with the Bun team, should be fixed when this is merged: oven-sh/bun#24389

After that's merged, it'll start working whenever Vercel upgrades the bun runtime version (should be shortly after).

[jdgamble555]

@elliott-with-the-longest-name-on-github - Thanks Elliott! Excited to try it!

Side note... it says Vercel Edge will be depreciated soon for SvelteKit, is Vercel getting rid of the Edge Runtime too (they moved it to functions recently)?

I assume the plan is for Bun Runtime to replace it?

J

[elliott-with-the-longest-name-on-github]

The edge runtime is effectively deprecated at Vercel. It still works but it actually just runs Node.js now. There really aren't any benefits to it over the default Node.js on fluid compute.

[jdgamble555]

They moved it under the functions umbrella, but SvelteKit and Nitro docs say it is soon depreciated completely.

I don't see any official Vercel or NextJS docs that confirm that the runtime itself is depreciated (or will be)...

[elliott-with-the-longest-name-on-github]

I have spoken with the compute team (for context, I work at Vercel). I'm not sure if we'll ever actually sunset the edge runtime in the sense that it'll stop working, but active development on it has ceased and it's in maintenance mode. We never recommend deploying to it as there are really no benefits to it over the "regular" node runtime -- hence the "please migrate away from it" banners at the top of the edge runtime documentation.

[elliott-with-the-longest-name-on-github]

This should be fixed now!