Bug: putting promise into JSX will cause hydration issue

[himself65]

React version: 18.3.0-canary-5dd35968b-20231201

Steps To Reproduce

1. clone https://github.com/himself65/react-hydration-error
2. pnpm install && pnpm run dev

Link to code example:

import { Component } from '@/components/component'

export default function Home () {
  const delayedMessage = new Promise((resolve) => {
    setTimeout(() => resolve('Hello from server!'), 2000)
  })
  return (
    <main>
      <div>
        <Component delayedMessage={delayedMessage}/>
      </div>
    </main>
  )
}

"use client"
export function Component ({
  delayedMessage
}) {
  return (
    <div>
      {delayedMessage}
    </div>
  )
}

The current behavior

The expected behavior

Won't have hydration error

[himself65]

Related downstream repo: https://github.com/dai-shi/waku/pull/203

[himself65]

https://github.com/dai-shi/waku/issues/202

[himself65]

I think this is a React issue, not next.js. Since our customized react framework has the same error

[NakZMichael]

Prop values passed from a Server Component to Client Component must be serializable.

https://react.dev/reference/react/use-client

I think using async/await works well.

Sorry, Promise is serealizable. I misunderstood.

[NakZMichael]

Values of serialized promises are different between client side and server side.

[godspeed-03]

The issue can be resolved by using useEffect hook .
Head to next js documentation.

• https://nextjs.org/docs/messages/react-hydration-error

[NakZMichael]

I found a workaround for this matter. It is to use use to Promises.
https://github.com/NakZMichael/react-hydration-error

However, looking at the following PR, it appears that this workaround is not supposed to be necessary.
#25634

And it seems to be related to the following Issue discussed in the Next.js repository.
vercel/next.js#56470

[himself65]

Since promise is a valid jsx element, I think it should not cause ssr issues or otherwise should be documented

[MadhuSaini22]

@himself65 , Thanks for reporting the hydration issue with promises in JSX. Putting promises directly in JSX can be tricky in React 18.
Here's a quick fix:

Render a placeholder on the server while the promise resolves on the client (e.g., a loading spinner). Update the DOM with the resolved value once it's available.
Remember to update the server-side HTML with the resolved value for optimal performance.

For more advanced handling, consider Suspense or data fetching libraries like react-query or SWR.

Happy coding!

[github-actions]

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[himself65]

bump