SignIn callback returning a relative path fails

[nhuethmayr]

Hi guys,

I'm having the following piece of code in my project

signIn: async ({ user }) => {
  //signing in -> email must exist...
  const unknownUser = user.emailVerified === null

  if (unknownUser) {
    return new URL(
      '/sign-in?error=UnknownUser',
      process.env.NEXTAUTH_URL
    ).toString()
  }

  return true
}

As you can see, instead of returning a relative URL - I'm returning an absolute one.

This is due to an error I get when doing otherwise.

From the browser

and here the source

next-auth/packages/next-auth/src/react/index.tsx

Line 277 in 1e886b9

const error = new URL(data.url).searchParams.get("error")

The error above can be avoided by returning an absolute URL which then causes problems on Vercel because the environment variable NEXTAUTH_URL does not exist.

https://next-auth.js.org/configuration/callbacks#sign-in-callback
The documentation clearly states that I should be able to return a relative path so I'm wondering what I need to do for this to work properly. I'd most certainly prefer a solution that does not require me to do string-concat magic

[nicoladj77]

@nhuethmayr did you ever fix this?

[nhuethmayr]

Let me see