rallly/pages/_error.tsx

import * as Sentry from "@sentry/nextjs";
import { NextPage, NextPageContext } from "next";
import NextErrorComponent, { ErrorProps as NextErrorProps } from "next/error";

interface ErrorProps extends NextErrorProps {
  hasGetInitialPropsRun?: boolean;
  err: Error;
}

/**
 * This custom error page is based on the Sentry example, with added TypeScript
 * @see https://docs.sentry.io/platforms/javascript/guides/nextjs/manual-setup/
 */
const Page: NextPage<ErrorProps> = ({
  statusCode,
  hasGetInitialPropsRun,
  err,
}) => {
  if (!hasGetInitialPropsRun && err) {
    // getInitialProps is not called in case of
    // https://github.com/vercel/next.js/issues/8592. As a workaround, we pass
    // err via _app.js so it can be captured
    Sentry.captureException(err);
    // Flushing is not required in this case as it only happens on the client
  }

  return <NextErrorComponent statusCode={statusCode} />;
};

Page.getInitialProps = async ({
  res,
  err,
  asPath,
}: NextPageContext): Promise<ErrorProps> => {
  const errorInitialProps = (await NextErrorComponent.getInitialProps({
    res,
    err,
  } as NextPageContext)) as ErrorProps;

  // Workaround for https://github.com/vercel/next.js/issues/8592, mark when
  // getInitialProps has run
  errorInitialProps.hasGetInitialPropsRun = true;

  // Running on the server, the response object (`res`) is available.
  //
  // Next.js will pass an err on the server if a page's data fetching methods
  // threw or returned a Promise that rejected
  //
  // Running on the client (browser), Next.js will provide an err if:
  //
  //  - a page's `getInitialProps` threw or returned a Promise that rejected
  //  - an exception was thrown somewhere in the React lifecycle (render,
  //    componentDidMount, etc) that was caught by Next.js's React Error
  //    Boundary. Read more about what types of exceptions are caught by Error
  //    Boundaries: https://reactjs.org/docs/error-boundaries.html

  if (err) {
    Sentry.captureException(err);

    // Flushing before returning is necessary if deploying to Vercel, see
    // https://vercel.com/docs/platform/limits#streaming-responses
    await Sentry.flush(2000);

    return errorInitialProps;
  }

  // If this point is reached, getInitialProps was called without any
  // information about what the error might be. This is unexpected and may
  // indicate a bug introduced in Next.js, so record it in Sentry
  Sentry.captureException(
    new Error(`_error.js getInitialProps missing data at path: ${asPath}`),
  );
  await Sentry.flush(2000);

  return errorInitialProps;
};

export default Page;