I’m developing a REST API with express that relies on a custom ApiError class and a custom errorHandler function for handling async errors in a scalable way.

As a refernce:

ApiError:

export class ApiError extends Error {
  statusCode;

  constructor(message: string, status = 500) {
    super(message);
    Error.captureStackTrace(this, this.constructor);
    this.statusCode = status;
  }
}

errorHandler:

type CustomError = Error | (new (...args: any[]) => Error);

export const errorHandler = (
  err: CustomError,
  req: Request,
  res: Response,
  next: NextFunction
) => {
  console.log(`Error middleware: ${err}`);

  if (err instanceof ApiError) {
    return res.status(err.statusCode).json(err.message);
  }

  return res.status(500).json('Internal server error');
};

And at this point, in app.ts – after importing express-async-errors – errorHandler is used as the last middleware in order to handle all the ApiError instances thrown by controllers:

app.ts:

/*
 * Imports
 */

import 'express-async-errors';

/*
 * Other middlewares and logic
 */

app.use('/api', router());
app.use(errorHandler);

The issue is that ts-node-dev won’t handle ApiError instances as such – this means that if at any point in the code there was an ApiError thrown, the server would respond with the default handler provided in errorHandler:

controller.ts:

/*
 * After some logic
 */

throw new ApiError("This won't run", 400);

server response:

"Internal server error" //StatusCode: 500

In other words, the following condition would not evaluate to true:

if(new ApiError('...',400) instance of ApiError){
 /*
  * This won't run
  */
}

I can tell that the issue is related to ts-node-dev and not the code itself as if I were to run the transpiled code inside dist with nodemon the server would respond as expected.