no stack trace for App Promise Reject with non-Error reasons

[samijaber]

Link to the code that reproduces this issue

https://github.com/samijaber/nextjs-reject-bug-repro/

To Reproduce

1. https://github.com/samijaber/nextjs-reject-bug-repro/
2. npm run dev
3. open / and see error message
4. toggle the two different promises to compare stack traces https://github.com/samijaber/nextjs-reject-bug-repro/blob/ea125b442fbb275efcb3341fa70a4f2199395708/src/app/page.tsx#L112-L117

Current vs. Expected behavior

When a Promise reject has an Error reason:

When a Promise reject has a non-Error reason (an arbitrary object):

note how we lose information on where the rejection is coming from.

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 24.2.0: Fri Dec  6 19:01:59 PST 2024; root:xnu-11215.61.5~2/RELEASE_ARM64_T6000
  Available memory (MB): 32768
  Available CPU cores: 10
Binaries:
  Node: 20.11.0
  npm: 10.2.4
  Yarn: 1.22.19
  pnpm: 8.10.2
Relevant Packages:
  next: 15.2.3 // Latest available version is detected (15.2.3).
  eslint-config-next: N/A
  react: 19.0.0
  react-dom: 19.0.0
  typescript: 5.8.2
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Error Handling

Which stage(s) are affected? (Select all that apply)

next dev (local)

Additional context

No response

[samijaber]

Bug repro commit samijaber/nextjs-reject-bug-repro@ea125b4

[milkbottle0305]

In Next.js, when you reject a Promise with a non-Error object, the stack trace is not provided, making debugging harder. This is because JavaScript only includes a stack trace for Error objects. The solution is to reject the Promise with an Error object.

Example:

// Incorrect approach
return Promise.reject({ message: 'Something went wrong' });

// Correct approach
return Promise.reject(new Error('Something went wrong'));

This way, the stack trace will be included, making error tracking possible.
Reference: https://nextjs.org/docs/messages/threw-undefined