Save HTTP exception description as a property of HttpException

[egormkn]

Feature Request

Is your feature request related to a problem? Please describe.

I have an issue when implementing a custom ExceptionFilter for an MVC application. When the exception filter catches a HttpException, I want to render a template with HTTP error code, description, and message (e.g. 401 Unauthorized: Wrong username or password). While I can easily get error code and message, getting the HTTP error description (Unauthorized in this case) is harder than it should be: it is stored in the error property of JSON response. At the same time HttpException has a name property, that is always initialized to 'Error'.

Describe the solution you'd like

I'd like the name property of HttpException to be initialized with HTTP error description.

Teachability, Documentation, Adoption, Migration Strategy

Here is how it can be used:

import { Catch, ArgumentsHost, HttpStatus, Logger, ExceptionFilter, HttpException } from '@nestjs/common';
import { Request, Response } from 'express';

@Catch()
export class DefaultExceptionFilter implements ExceptionFilter<any> {
  private readonly logger = new Logger('ExceptionHandler');

  catch(exception: any, host: ArgumentsHost) {
    const ctx = host.switchToHttp();
    const req = ctx.getRequest<Request>();
    const res = ctx.getResponse<Response>();
                         // now it is always equal to 'Error' ---v
    const name = exception instanceof HttpException ? exception.name : 'Internal Server Error';
    const message = exception instanceof HttpException ? exception.message : '';
    const status =
      exception instanceof HttpException ? exception.getStatus() : HttpStatus.INTERNAL_SERVER_ERROR;

    res.status(status).render('error', { name, message, status });
    if (!(exception instanceof HttpException)) {
      return 'message' in exception
        ? this.logger.error(exception.message, exception.stack)
        : this.logger.error(exception);
    }
  }
}

[kamilmysliwiec]

I'd like the name property of HttpException to be initialized with HTTP error description.

name property should be equal to the name of the class. Currently it's always Error (which is incorrect). I'll fix it shortly.

In the meantime, you can use this:

Object.getPrototypeOf(exception).constructor.name

as w workaround

[egormkn]

I think that it would be nice to be able to get a human-readable description of an error (Not Found instead of NotFoundException). While I can get it from the error property of a JSON response (that might not even be there) or derive by myself from status code, this doesn't seem to be the right way.
I thought about adding an optional description argument to the HttpException constructor, that will save description from its subclasses.

[kamilmysliwiec]

You could always generate a human-readable description based on the serialized class names (e.g., by adding spaces between uppercased characters). Let's track this here #5859

[JaapWeijland]

Hi there, sorry to resurrect this issue, but I think I experience something that is related and thus not yet fixed.

I have two files, a service and a controller. In the service, I perform an API call. When this API call returns a response indicating that I am unauthorized, I throw a new UnauthorizedException(). The controller catches all errors thrown by the service, checks them and if needed, complements them. An UnauthorizedException may be rethrown as is, so I do the following to check whether the error is an UnauthorizedException:

try {
...
} catch (error) {
    if (error instanceof UnauthorizedException) throw error;
    throw new InternalServerErrorException(error);
}

However, error instanceof UnauthorizedException always returns false. I did some research and stumbled upon the following FAQ about Typescript: https://github.com/Microsoft/TypeScript/wiki/Breaking-Changes#extending-built-ins-like-error-array-and-map-may-no-longer-work:

As part of substituting the value of this with the value returned by a super(...) call, subclassing Error, Array, and others may no longer work as expected.

...and:

instanceof will be broken between instances of the subclass and their instances, so (new FooError()) instanceof FooError will return false.

Since UnauthorizedException is an indirect subclass of Error, I think we're dealing with the same kind of issue here, namely that the prototype of the error is incorrectly set. Is this correct?

[kamilmysliwiec]

Please, use our Discord channel (support) for such questions. We are using GitHub to track bugs, feature requests, and potential improvements.