"Unexpected fiber popped" / "An unexpected error has occurred"

Bug report

Describe the bug

At least two of the NextJS examples do not work when run “out of the box”.

To Reproduce

1. Follow the steps in either of these two READMEs:
   • nextjs-with-typescript
   • hello-world
2. Run npm install && npm run dev.
   • React will report “Unexpected fiber popped” and “Unexpected pop” in the console.
   • In the Material UI example, buttons will not demonstrate the ripple effect when clicked. In my application, the effects are more severe, leading to loss of interactivity.
3. Deploy using npx now. Resulting application will report errors.
   • nextjs-with-typescript deployment
   • hello-world deployment

Expected behavior

Given examples work when deployed and run.

Screenshots

If applicable, add screenshots to help explain your problem.

System information

• OS
  • Development: Ubuntu 18.04 LTS
  • Deployment: Zeit Now platform
• Browser: Reproducible in Chrome and Firefox
• Version of Next.js: 9.0.6 (current latest)

[acdlite]

This is now fixed in v16.10.1.

However, it’s more like a workaround to fail gracefully because the behavior is not supported. It only accidentally worked in 16.9. We will warn in a future minor.

So we need to figure out how to address this in Next.

More context here: https://github.com/facebook/react/issues/16938#issuecomment-536207871

[Timer]

Hi everyone! Like the error message suggests, this may be a bug with React 16.10. I’ve opened an issue in the React project to track this: https://github.com/facebook/react/issues/16938.

Please downgrade to react@16.9.0 and react-dom@16.9.0 for the time being.

Thanks!