TypeScript and JWT Decode

[mertturkmenoglu]

Hello everyone,

I am trying to use JWT and I got a problem.

import NextAuth, { User } from 'next-auth';
import Providers from 'next-auth/providers';
import jwt from 'jsonwebtoken';

export default NextAuth({
  providers: [
    Providers.Credentials({
      // Providers code
    }),
  ],
  session: {
    jwt: true,
  },
  jwt: {
    // !!! Type problem !!!
    // Type 'Promise<string | JwtPayload>' is not assignable to type 'Promise<JWT>'. 
    decode: async (params: JWTDecodeParams | undefined) => {
      const token = params?.token ?? '';
      const secret = params?.secret ?? '';
      const decodedToken = jwt.verify(token, secret, { algorithms: ['HS256'] });
      return decodedToken;
    },
  },
});

When I ignore the TS error and run the code, it works and decodes.

I tried to change the code:

// Other code
decode: async (params: JWTDecodeParams | undefined) => {
    const token = params?.token ?? '';
    const decodedToken = jwt.decode(token);
  
    if (decodedToken === null || typeof decodedToken === 'string') {
      return Promise.reject();
    }
  
    return decodedToken;
},

This time TS error is gone but the code doesn't work.

What am I missing?

Thank you so much.

Edit: We are doing custom encode / decode operations because we need to add some Hasura specific values to data.