RFC: allow throwing PublicError instances inside server actions

[remorses]

Goals

Make error handling in server actions simpler by throwing instances of a PublicError class (exported from next)

Currently error messages get stripped away from server actions errors: https://x.com/asidorenko_/status/1702684047879626792?s=20

Non-Goals

No response

Background

Currently error messages get stripped away from server actions errors: https://x.com/asidorenko_/status/1702684047879626792?s=20

The alternative to this proposal would be to return an object with an error field, but this is not idiomatic in JavaScript and most existing code use exceptions instead

Migrating user code to server actions with this RFC would mean replacing some throw new Error with throw new PublicError

Without this proposal you would need to wrap all server actions with a try catch block and manually handle each error type, which would mean implementing this RFC in user code (or worse, passing all errors down to the client, possibly exposing secret data)

Proposal

Add a PublicError error class (or a different name, see x poll) that retains its error message and properties when thrown inside a server action

The client code can then handle these errors, in case the server action is called directly by using a catch block or using the useFormStatus hook when using the action prop

To make error handling easier i would also suggest turning any non PublicError into a PublicError('Unexpected error') so that the user will never see cryptic error messages like The specific error message is omitted ...

Example

import { PublicError } from 'next'
import toast from 'react-hot-toast'

export default function ServerComponent() {

  async function myAction(userId) {
    'use server'
    const isLoggedIn = await authenticate(userId)
    if (!isLoggedIn) throw new PublicError(`forbidden`)
    // ...
  }
  return <button onClick={() => myAction(userId).catch(e => toast.error(e.message))} />
}

[gerynugrh]

Perfectly solve a problem that we have in mind, would love to see a way to configure error obfuscation behavior