Next-auth: ReferenceError: window is not defined

[alephart]

Your question

getSession() can be used on server-side, requires next-auth/client. Into client.js of next-auth window object is checked. However window only exists in the Browser, so I get the error, ReferenceError: window is not defined .... and this is absolutely right.

This response is obtained by the server at build time (in dev and prod):

error:

UnhandledPromiseRejectionWarning: ReferenceError: window is not defined
    at /.../node_modules/next-auth/dist/client/index.js:279:69
    at Generator.next (<anonymous>)
    at asyncGeneratorStep (/.../node_modules/next-auth/dist/client/index.js:22:103)
    at _next (/.../node_modules/next-auth/dist/client/index.js:24:194)
    at /.../node_modules/next-auth/dist/client/index.js:24:364
    at new Promise (<anonymous>)
    at /.../node_modules/next-auth/dist/client/index.js:24:97
    at signIn (/.../node_modules/next-auth/dist/client/index.js:304:18) ...

What are you trying to do
I want to be able to get the session of a user from the server side, with the aim of returning data from a database.

Feedback
*Documentation getSession() Example:

import { getSession } from 'next-auth/client'

export default async (req, res) => {
  const session = await getSession({ req })
  if (session) {
    // Signed in
    console.log('Session', JSON.stringify(session, null, 2))
  } else {
    // Not Signed in
    res.status(401)
  }
  res.end()
}

• [*] Found the documentation helpful
• [*] Found documentation but was incomplete

Quite possibly the context I want to apply is not correct, I don't know, however using the code according to the example is the error that is obtained.

Any guide on how to correct this?

[iaincollins]

Hi there! I'm not sure how you are getting this error, we'd need to have a repo to look at to see what's going on.

The example repo has examples for using getSession in an API route and on a server side rendered page:
https://github.com/nextauthjs/next-auth-example/blob/main/pages/api/examples/session.js
https://github.com/nextauthjs/next-auth-example/blob/main/pages/protected-ssr.js

If signed in to the example site, you can confirm they both work:
https://next-auth-example.now.sh/api/examples/session
https://next-auth-example.now.sh/protected-ssr

I'm not sure what would cause the error you are seeing, perhaps something about the build process.

[alephart]

Hi Iain, this examples work perfect! no problem.

I was looking to perform a page redirect, using SignIn() without user action:

if (!session) {
     signIn();
     return null;
   }

This was calling window from the Server ... my mistake, sorry!.

This is more correct:

...
if (!session) {return <AccessDenied />}
...

And into AccessDenied click action to SignIn():

...
<button onClick={() => signIn()}>Sign In</button>
...

Regards,

[iaincollins]

@alephart Thank you for the followup!

There are quite a few situations where this sort of thing trips folks up - it's a tricky area with a library designed to support client and server side rendering with both browser and server based imports - and I really appreciate the detail as it helps us design behaviour that can help reduce confusing situations like this (e.g. via console warnings or additional conditional checks).