[9.5.6-canary.17][notFound][Vercel] incorrect props in custom 404-page when using blocking fallback

[rokinsky]

Bug report

Describe the bug

I use the notFound feature on SSG pages with enabled blocking fallback. The custom 404-page gets incorrect props from getStaticProps when notFound occurs. This happens only when an app is deployed to Vercel.

To Reproduce

Repository: next.js-bug-not-found-props
Steps to reproduce the behavior:

1. Deploy the app to Vercel
2. Go to the website, e.g. https://next-js-bug-not-found-props.vercel.app
3. See

{
  "url": {
    "query": {},
    "pathname": "/404",
    "asPath": "/[[...slug]]"
  }
}

first and see

{
  "url": {
    "query": {},
    "pathname": "/404",
    "asPath": "/"
  }
}

after hydration

Expected behavior

Displaying

{
  "is404": true
}

Screenshots

N/A

System information

• OS:macOS
• Browser (if applies): chrome
• Version of Next.js: 9.5.6-canary.17
• Version of Node.js: v10.22.1

Additional context

Works great locally in dev and prod modes.

[ijjk]

Good catch, thanks for testing these features out and reporting!

[rokinsky]

Thanks for all the fixes, @ijjk! 😊

[balazsorban44]

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