[BUG] [with-firebase-authentication] getServerSideProps issues

Bug report

Describe the bug

I just cloned the example project with-firebase-authentication and followed the instructions within the README.md to setup. After running the command npm run dev and went to my browser on localhost:3000, I received an error within my terminal.

Error: Error serializing `.user` returned from `getServerSideProps` in "/".
Reason: `undefined` cannot be serialized as JSON. Please use `null` or omit this value all together.

To Reproduce

1. Go to https://github.com/zeit/next.js/tree/canary/examples/with-firebase-authentication
2. Followed the setup guide exactly.
3. Go to localhost:3000 to see the webpage
4. See error within page and terminal

Expected behavior

Expected to see the the login button within the page.

Screenshots

If applicable, add screenshots to help explain your problem.

System information

• OS: macOS
• Browser: Chrome
• Version of Next.js: ^9.3.3
• Version of Node.js: v10.16.3

[timneutkens]

Sure!

[kohchihao]

I may have found a fix for the problem.

Changing within getServerSideProps

const user = req && req.session ? req.session.decodedToken : null

to

const user = req.session && req.session.decodedToken ? req.session.decodedToken : null

seems to fix the issue for me.