@auth/sveltekit does not work with SvelteKit 3

[LucidityDesign]

See #13502

[kgeminicdev]

Until there's a release with SvelteKit 3 support, you can patch @auth/sveltekit 1.11.3 locally. Only two changes are needed. I reproduced both failures from #13502 in a minimal SvelteKit 3.0.1 app with adapter-node 6.0.0 and the GitHub provider, and with these edits it builds, sign-in redirects to GitHub, sign-out redirects back, and /auth/providers responds.

With pnpm:

pnpm patch @auth/sveltekit@1.11.3
# edit the files below in the folder it prints, then:
pnpm patch-commit <that folder>

1. base (build error). In dist/env.js, dist/client.js and dist/webauthn.js, replace

import { base } from "$app/paths";

with

const base = "";

SvelteKit 3 no longer exports base, and resolve("/") isn't a drop-in replacement: on the server it returns a relative path (./) by default, which would break basePath. If you set a base path in your kit config, put that string (for example "/app") instead of "".

2. External redirects (runtime error redirect_external_not_allowed). In dist/actions.js, add { external: true } to the redirects. That's three different lines, and the last one appears twice (in signIn and signOut):

redirect(302, signInURL.toString(), { external: true });
redirect(302, url, { external: true });
redirect(302, res.redirect, { external: true });

Before this change the sign-in action failed with redirect_external_not_allowed. After it, the action returned a redirect to https://github.com/login/oauth/authorize?....

$app/environment and $env/dynamic/private are deprecated in SvelteKit 3 but still work, so they can stay for now.

My test was a production build (vite build + node build) with npm, where I edited the files in node_modules directly. I didn't run a real OAuth login, since the client ID was a dummy.

[LucidityDesign]

Thank you ChatGPT, that works