next-auth: Type error in session callback for `user` and `token` properties

Environment

npmPackages: @auth/core: ^0.* => 0.20.0 @auth/drizzle-adapter: ^0.* => 0.3.14 @auth/sveltekit: ^0.* => 0.5.2 Node: 20.3.1 - /opt/homebrew/bin/node

Reproduction URL

https://github.com/thomasmol/authjsbugs

Describe the issue

related to #9437

i get a type error in the session callback for the user or token property:

Property 'user' does not exist on type '({ session: Session; user: AdapterUser; } | { session: Session; token: JWT; }) & { newSession: any; trigger?: "update" | undefined; }'.

error claims user does not exist, while it does, although it depends on the database strategy used.

error located here on the user property in hooks.server.ts:

callbacks: {
  session: async ({ session, user }) => {
    if(session.user){
      session.user.id = user.id;
      }
    return session;
  }
},

not sure if useful but this is copilot explaining: "The error message you’re seeing is due to TypeScript not being able to determine the exact type of the object that’s being passed to the session callback. The type of the object is a union type, which means it could be one of several types. In this case, it could be { session: Session; user: AdapterUser; } or { session: Session; token: JWT; }.

The user property exists on the first type, but not on the second. When you try to access user.id, TypeScript can’t guarantee that user will always be present, hence the error."

How to reproduce

install auth core + auth sveltekit, create hooks.server.ts and add a the session callback. type error occurs on user and token, but not the session property.

Expected behavior

no type errors

About this issue

Original URL
State: closed
Created 6 months ago
Reactions: 12
Comments: 16 (1 by maintainers)

Commits related to this issue

fix(types): For Property 'user' or 'token' does not exist on types (#9633) — committed to ajstars1/next-auth by ajstars1 5 months ago
Fixed user session type mismatch in the latest Next Auth update https://github.com/nextauthjs/next-auth/issues/9633#issuecomment-1899645783 — committed to FlorianLeChat/Simple-File-Storage by FlorianLeChat 5 months ago

Most upvoted comments

Can confirm this on the latest next-auth: 5.0.0-beta.5

+26

Kinbaum on Jan 18, 2024

FYI for a quick fix, just manually set the types while setting user as optional, e.g.

import NextAuth, { type Session, type User } from "next-auth";

export const auth = NextAuth({
  callbacks: {
    async session({ session, user }: { session: Session; user?: User }) {
      if (user) {
        // do whatever here
      }
      return session;
    },
  },
});

+12

jeremy-code on Jan 19, 2024

Downgrading to beta.4 was the easiest and least hacky fix that worked for me. Make sure to delete the ^ symbol.

Before: CleanShot 2024-01-23 at 22 26 04@2x

After: CleanShot 2024-01-23 at 22 26 32@2x

travistylervii on Jan 24, 2024

Same here, when trying to access the token in the session callback using the jwt strategy, it wont let me access the second part of the params which included the token. Only present in authjs 5 beta 5, not in authjs 5 beta 4.

async session({ session, token}: {session: Session, token?: any}) { this is what worked for me you can also try as far i understood this is a typescript error .

sahilq312 on Jan 20, 2024

I was able to pass the error putting ‘?’ on the token. I’m in Next Auth Beta 5.

Ealanisln on Jan 22, 2024

This seems to be related to https://github.com/Microsoft/TypeScript/issues/14094.

Minimum code:

type Obj1 = { a: string, b: string }
type Obj2 = { a: string, c: string }

const func = (args: Obj1 | Obj2) => {
    args.b = ""
         ^
         Property 'b' does not exist on type 'Obj1 | Obj2'.
           Property 'b' does not exist on type 'Obj2'.
}

https://www.typescriptlang.org/play?#code/C4TwDgpgBA8gRgKwIxQLxQN5QIYC4oDOwATgJYB2A5gDRRz5FlVQC+AUKJLIgExqY4GJCjSgBjIU0qs2bMQHtyRKADMAruTH8AFNmKUC+eMigAfbgh4BKNAD5MbKE5z6CAOjj8ARF7bsgA

Using { session, user?, token? } instead of { session, user } | { session, token } seems to fix this.

nbifrye on Jan 15, 2024

i think #9646 is the solution to this as proposed by @nbifrye. It is more due to a limitation in typescript rather than authjs

thomasmol on Jan 18, 2024