How to report a different error in beforeSend

[francescov1]

Im running Sentry in a Nodejs Express server. Currently, I have the following error middleware:

export const errorHandlers = [
  errorRouter,
    Sentry.Handlers.errorHandler({
      shouldHandleError(err: any) {
        if (
          err.status < 500 &&
          err instanceof AppError &&
          !(err instanceof UnknownError) &&
          !(err instanceof InvalidArgumentError)
        ) {
          return false;
        }

        return true;
      }
  }),
  errorResponse
];

The idea is to do some error reformatting for clients in errorRouter, then report the error to Sentry if its not something we're expecting, and finally return the error to the client with errorResponse.

As part of the errorRouter middleware, I return a new error to next(error) which is of instance AppError (this is an internal error class we use). On this error, we have a field called originalError which contains the originally caught error. I would like to report the appError.originalError to Sentry, rather than the app error, since app errors can sometimes be simple user-facing error messages without anything too useful. How can I do this? I was thinking of overwriting or pushing to the event.exception.values array in beforeSend, but haven't found docs on how to format this properly. The stacktrace field specifically im unsure about how to set.

Would love any feedback on the implementation and suggestions for a solution

[AbhiPrasad]

Would linking the errors with error.cause work here? https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error/cause

See a sentry blog post: https://blog.sentry.io/making-your-javascript-projects-less-noisy/#pass-the-original-error-cause

[francescov1]

This looks perfect, I can't believe I've never heard of it before. Will try it out, thanks!