Hidden error with await rejected promise inside getStaticPaths

[urffin]

What version of Next.js are you using?

12.0.0

What version of Node.js are you using?

14.16.0, 15.9.0

What browser are you using?

any browser

What operating system are you using?

macOS

How are you deploying your application?

next build

Describe the Bug

if in async function getStaticPaths error raised in some nested async function, called with await, like this

export const getStaticPaths = async () => {
  await Promise.reject('Error hidden');
  // throw new Error('Raised error');
};

then when execute next build in console would be output just

 Build optimization failed: found page without a React Component as default export in pages/dyn/[num]

instead normal error message. If throw error directly - then log is fine

Expected Behavior

output concrete error message

To Reproduce

https://stackblitz.com/edit/nextjs-pnhrbs?file=pages/dyn/[num].jsx

To reproduce run: next build

enough

export const getStaticPaths = async () => {
  await Promise.reject('Error hidden'); // any rejected promise with message
  // throw new Error('Raised error');
};

[balazsorban44]

It is generally a good idea to reject with an Error if you have control over that.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/reject#description

Currently, this is why you are getting that message. Next.js checks if the thrown error is an instance of Error:

next.js/packages/next/build/index.ts

Line 1027 in cffd209

if (isError(err) && err.message !== 'INVALID_DEFAULT_EXPORT')

[urffin]

Hmmmm. interesting... But anyway this seems not an obviously: we have exception, but can't take reason and error message related to page without a React Component

[urffin]

@balazsorban44 is it possibly do more relevant error message? without changing nested promise

as workaround, of course i can

await promise.catch(e => Promise.reject(new Error(e)))

but this looks ugly

[balazsorban44]

await promise in that case would be enough I think. If the promise fails, it will just throw its error, which is caught by Next.js

[urffin]

await promise in that case would be enough I think. If the promise fails, it will just throw its error, which is caught by Next.js

No, this work only if promise rejected with new Error, if reject reason any other value, for example string - output just message about Build optimization failed: found page without a React Component as default export in ...

This is a problem to detect real error reason.

[ijjk]

Hi, this should be fixed in the latest version of Next.js v12.0.10, please update and give it a try.

Related fix: #33753

[github-actions]

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