Prerendering causing build error in SvelteKit

[WhyAsh5114]

Environment

  System:
    OS: Windows 11 10.0.22621
    CPU: (12) x64 AMD Ryzen 5 3600 6-Core Processor
    Memory: 6.26 GB / 15.91 GB
  Binaries:
    Node: 18.18.2 - C:\Program Files\nodejs\node.EXE
    npm: 10.2.3 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Edge: Chromium (120.0.2210.144)
    Internet Explorer: 11.0.22621.1
  npmPackages:
    @auth/core: ^0.23.0 => 0.23.0
    @auth/sveltekit: ^0.9.0 => 0.9.0

Reproduction URL

https://github.com/WhyAsh5114/authjs-sveltekit-prerender

Describe the issue

Marking a route as prenderable with export const prerender = true creates a build error, usable in dev though. Removing the prerender line fixes it.

TypeError: Cannot read properties of undefined (reading 'length')
    at Object.handle (file:///D:/Programming/Web/authjs-sveltekit-prerender/.svelte-kit/output/server/chunks/hooks.server.js:49:24)
    at respond (file:///D:/Programming/Web/authjs-sveltekit-prerender/.svelte-kit/output/server/index.js:2650:43)
    at async visit (file:///D:/Programming/Web/authjs-sveltekit-prerender/node_modules/@sveltejs/kit/src/core/postbuild/prerender.js:202:20)

node:internal/event_target:1033
  process.nextTick(() => { throw err; });
                           ^
Error: 500 /prerender
To suppress or handle this error, implement `handleHttpError` in https://kit.svelte.dev/docs/configuration#prerender
    at file:///D:/Programming/Web/authjs-sveltekit-prerender/node_modules/@sveltejs/kit/src/core/config/options.js:202:13
    at file:///D:/Programming/Web/authjs-sveltekit-prerender/node_modules/@sveltejs/kit/src/core/postbuild/prerender.js:65:25
    at save (file:///D:/Programming/Web/authjs-sveltekit-prerender/node_modules/@sveltejs/kit/src/core/postbuild/prerender.js:403:4)
    at visit (file:///D:/Programming/Web/authjs-sveltekit-prerender/node_modules/@sveltejs/kit/src/core/postbuild/prerender.js:236:3)
Emitted 'error' event on Worker instance at:
    at [kOnErrorMessage] (node:internal/worker:300:10)
    at [kOnMessage] (node:internal/worker:311:37)
    at MessagePort.<anonymous> (node:internal/worker:212:57)
    at [nodejs.internal.kHybridDispatch] (node:internal/event_target:757:20)
    at exports.emitMessage (node:internal/per_context/messageport:23:28)

Node.js v18.18.2

How to reproduce

1. Initialize new SvelteKit project, install @auth/sveltekit and @auth/core.
2. Setup the handle hook with SvelteKitAuth()
3. Create a prerenderable route, exclude it from validation in the root layout so it's accessible even if not logged in.
4. Try building with npm run build.

Expected behavior

Build should succeed.

[elron]

I have the same issue with netlify build.

5:50:48 AM: ✓ built in 3.52s
5:50:49 AM: node:internal/event_target:1011
5:50:49 AM:   process.nextTick(() => { throw err; });
5:50:49 AM:                            ^
5:50:49 AM: ReferenceError [Error]: Request is not defined
5:50:49 AM:     at visit (file:///opt/build/repo/node_modules/@sveltejs/kit/src/core/postbuild/prerender.js:202:45)
5:50:49 AM:     at Object.fn (file:///opt/build/repo/node_modules/@sveltejs/kit/src/core/postbuild/prerender.js:184:22)
5:50:49 AM:     at dequeue (file:///opt/build/repo/node_modules/@sveltejs/kit/src/core/postbuild/queue.js:40:42)
5:50:49 AM:     at Object.add (file:///opt/build/repo/node_modules/@sveltejs/kit/src/core/postbuild/queue.js:67:4)
5:50:49 AM:     at enqueue (file:///opt/build/repo/node_modules/@sveltejs/kit/src/core/postbuild/prerender.js:184:12)
5:50:49 AM:     at prerender (file:///opt/build/repo/node_modules/@sveltejs/kit/src/core/postbuild/prerender.js:452:6)
5:50:49 AM:     at async MessagePort.<anonymous> (file:///opt/build/repo/node_modules/@sveltejs/kit/src/utils/fork.js:22:16)
5:50:49 AM: Emitted "error" event on Worker instance at:
5:50:49 AM:     at Worker.[kOnErrorMessage] (node:internal/worker:298:10)
5:50:49 AM:     at Worker.[kOnMessage] (node:internal/worker:309:37)
5:50:49 AM:     at MessagePort.<anonymous> (node:internal/worker:205:57)
5:50:49 AM:     at MessagePort.[nodejs.internal.kHybridDispatch] (node:internal/event_target:736:20)
5:50:49 AM:     at MessagePort.exports.emitMessage (node:internal/per_context/messageport:23:28)
5:50:49 AM: ​
5:50:49 AM: "build.command" failed                                        
5:50:49 AM: ────────────────────────────────────────────────────────────────
5:50:49 AM: ​
5:50:49 AM:   Error message
5:50:49 AM:   Command failed with exit code 1: npm run build (https://ntl.fyi/exit-code-1)
5:50:49 AM: ​
5:50:49 AM:   Error location
5:50:49 AM:   In Build command from Netlify app:
5:50:49 AM:   npm run build
5:50:49 AM: ​
5:50:49 AM:   Resolved config
5:50:49 AM:   build:
5:50:49 AM:     command: npm run build
5:50:49 AM:     commandOrigin: ui
5:50:49 AM:     environment:
5:50:49 AM:       - VITE_PUBLIC_WORDPRESS_API_URL
5:50:49 AM:     publish: /opt/build/repo/build
5:50:49 AM:     publishOrigin: ui
5:50:49 AM: Build failed due to a user error: Build script returned non-zero exit code: 2
5:50:49 AM: Failing build: Failed to build site
5:50:49 AM: Failed during stage "building site": Build script returned non-zero exit code: 2
5:50:49 AM: Finished processing build request in 23.884s

EDITED: Turns out I had Node version 16 in Netlify. I set Node version 20 and problem solved. Sharing this in case anyone encounters the same problem as I did...

[Tom-Nudell]

I'm getting the same error as @WhyAsh5114 when trying to build my project with sveltekit's static adapter. Error persists in Node.js v21.5.0, but I had the same error in Node.js v18.16.0.

Reproduce the bug by cloning sveltekit-auth-example and configure svelte.config.js the the static adapter default from https://kit.svelte.dev/docs/adapter-static

TypeError: Cannot read properties of undefined (reading 'length')
    at Object.handle (file:///sveltekit-auth-example/.svelte-kit/output/server/chunks/hooks.server.js:56:24)
    at respond (file:///sveltekit-auth-example/.svelte-kit/output/server/index.js:2713:43)
    at Server.respond (file:///Git/sveltekit-auth-example/.svelte-kit/output/server/index.js:2976:12)
    at generate_fallback (file:///Git/sveltekit-auth-example/node_modules/@sveltejs/kit/src/core/postbuild/fallback.js:38:32)
    at async MessagePort.<anonymous> (file://sveltekit-auth-example/node_modules/@sveltejs/kit/src/utils/fork.js:22:16)

node:internal/event_target:1096
  process.nextTick(() => { throw err; });
                           ^
Error: Could not create a fallback page — failed with status 500
    at generate_fallback (file:///sveltekit-auth-example/node_modules/@sveltejs/kit/src/core/postbuild/fallback.js:53:8)
    at async MessagePort.<anonymous> (file://sveltekit-auth-example/node_modules/@sveltejs/kit/src/utils/fork.js:22:16)

Node.js v21.5.0
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

[ndom91]

Hey folks, sorry about this, we've just shipped a little fix in @auth/sveltekit@0.11.1 which takes the sveltekit exported base path into account.

• You'll have to install that version of @auth/sveltekit
• Add basePath: '/auth' to your hooks.server.ts or wherever you have your auth.js config. It is the default, but there still seems to be an issue there - I'll continue to investigate it, but adding the basepath manually to the config fixes it for now.
• In addition, don't forget to add a secret value to your auth.js config (unrelated to this, but strongly suggested - I see that the repro you linked was missing it).

Also on an unrelated note, you no longer need to explicitly install @auth/core. You can import the providers from @auth/sveltekit. For example:

import Google from "@auth/sveltekit/providers/google";

Working config

// /src/auth.ts
import { SvelteKitAuth } from "@auth/sveltekit";
import Google from "@auth/sveltekit/providers/google";
import { AUTH_GOOGLE_ID, AUTH_GOOGLE_SECRET } from "$env/static/private";

export const { handle } = SvelteKitAuth({
  basePath: "/auth",
  secret: "abc", // Replace with output of `openssl rand -hex 32 | xc` from termianl
  providers: [
    Google({ clientId: AUTH_GOOGLE_ID, clientSecret: AUTH_GOOGLE_SECRET }),
  ],
});

// /src/hooks.server.ts
export { handle } from "./auth"

Making the above changes got your project (WhyAsh5114/authjs-sveltekit-prerender) to build successfully, including with the one route marked as prerender.

[WhyAsh5114]

When using this new hooks.server.ts file with the latest @auth/sveltekit package:

import { SvelteKitAuth } from "@auth/sveltekit";
import Google from "@auth/sveltekit/providers/google";

export const { handle, signIn, signOut } = SvelteKitAuth({
  basePath: "/auth",
  providers: [Google],
  trustHost: true
});

I get this new error during build:

Error: Cannot read values from $env/dynamic/private while prerendering (attempted to read env.AUTH_URL). Use $env/static/private instead

What should I do to fix this?

[ndom91]

When using this new hooks.server.ts file with the latest @auth/sveltekit package:

import { SvelteKitAuth } from "@auth/sveltekit";
import Google from "@auth/sveltekit/providers/google";

export const { handle, signIn, signOut } = SvelteKitAuth({
  basePath: "/auth",
  providers: [Google],
  trustHost: true
});

This is your hooks.server.ts? Using the latest @auth/sveltekit the config should be in a /src/auth.ts and the src/hooks.server.ts should just import and use the handle return value from SvelteKitAuth in /src/auth.ts.

Something like this:

Sorry for the confusion, new docs coming soon.

[cdellinger]

There still seems to be an issue here. If I create a latest sveltekit project and use @auth/sveltekit 0.13.0 I get the same error message when building as @WhyAsh5114 with the following code in auth.ts

export const { handle } = SvelteKitAuth({
    providers: [Google],
    callbacks: {
        async session({ session, user }) {
            session.user = {
                id: user.id, 
                name: user.name,
                email: user.email,
                image: user.image,
                emailVerified: user.emailVerified
            };
            return session;
        }
    },
    basePath: '/auth', 
    secret: AUTH_SECRET
});

and hooks.server.ts as follows:
export { handle } from "./auth"
As recommended at https://authjs.dev/reference/sveltekit#managing-the-session, I have a +layout.server.ts file as follows:

import type { LayoutServerLoad } from './$types';

export const load: LayoutServerLoad = async (event) => {
  return {
    session: await event.locals.getSession()
  };
};

If I comment out the line that sets the session, the error message disappears.

//session: await event.locals.getSession()
Is the example at https://authjs.dev/reference/sveltekit#managing-the-session not to be followed any longer?

[WhyAsh5114]

issue still persists, even after separating the auth.ts and hooks.server.ts, only occurs when prerendering
Error: Cannot read values from $env/dynamic/private while prerendering (attempted to read env.AUTH_URL). Use $env/static/private instead

[ndom91]

We're looking into it in #10117 if anyone wants to participate there atm