@getanthill/datastore/src/api/middleware/errorHandler.ts

Event-Sourced Datastore

import type {
  ErrorRequestHandler,
  NextFunction,
  Request,
  Response,
} from 'express';
import type { ResponseError, Services } from '../../typings';

import statusCodes from 'http-status-codes';

export function errorHandler(services: Services): ErrorRequestHandler {
  /**
   * Note: the last argument `next` is important because if its not present, the function
   * will not be called at all.
   */
  return (
    err: ResponseError,
    _req: Request,
    res: Response,
    _next: NextFunction,
  ): void => {
    if (typeof err !== 'object') {
      // If the object is not an Error, create a representation that appears to be
      err = {
        name: 'Internal Server Error',
        // eslint-disable-line no-param-reassign
        status: statusCodes.INTERNAL_SERVER_ERROR,
        message: String(err), // Coerce to string
      };
    } else {
      // Ensure that err.message is enumerable (It is not by default)
      Object.defineProperty(err, 'message', { enumerable: true });
      Object.defineProperty(err, 'status', {
        enumerable: true,
        value: err.status || statusCodes.INTERNAL_SERVER_ERROR,
      });
    }

    if (err.status === statusCodes.INTERNAL_SERVER_ERROR) {
      services.telemetry.logger.error(
        '[Express#ErrorHandler] Internal server error',
        err,
      );
    }

    const errorBody = {
      message: err.message,
      status: err.status,
      details: err.details ?? [],
    };

    // If we have a server error, then we need to obfuscate its details in the
    // response.
    if (err.status === statusCodes.INTERNAL_SERVER_ERROR) {
      services.telemetry.logger.error(
        '[Express#ErrorHandler] Internal Server Error',
        { err },
      );
      errorBody.message = 'Internal Server Error';
    }

    services.telemetry.logger.debug('[Express#ErrorHandler] Error response', {
      errorBody,
    });

    res.locals.meter &&
      res.locals.meter({ state: err.status, ...res.locals.attributes });

    res.status(err.status!).json(errorBody);
  };
}