Error Handling

Intent utilises ExceptionFilter by NestJS. When you create a new app, it comes with an HTTP Exception Filter which you can customise as per your need. You can make changes to the handleHttp method as per your need.

When you start a new Intent application, it comes pre-configured with an ApplicationExceptionFilter located inside app/errors/filter.ts directory.

Your application comes with out-of-the-box Sentry integration, making it easier for you to report your errors directly to Sentry. We will see how we can do it.

Configuration

You can configure your exception filter by changing settings inside the config/app.ts file. It comes with a few default configuration which provides elegant error handlings in your application.


import { registerAs, toBoolean, AppConfig, ValidationErrorSerializer } from '@libs/intent';
export default registerAs(
  'app',
  () =>
    ({
      name: process.env.APP_NAME || 'NestJS App',
      env: process.env.APP_ENV || 'local',
      debug: toBoolean(process.env.APP_DEBUG || true),
      url: process.env.APP_URL || 'localhost',
      port: +process.env.APP_PORT || 5000,
      cors: { origin: true },
      locale: 'en',
      currency: 'INR',
      error: {
        validationErrorSerializer: ValidationErrorSerializer,
      },
      sentry: {
        dsn: process.env.SENTRY_DSN,
        tracesSampleRate: 1.0,
        profilesSampleRate: 1.0,
        integrateNodeProfile: true,
      },
    }) as AppConfig,
);

Debug Mode

The debug option in config/app.ts file determines how much information shall be exposed in the response. By default, this settings is based on APP_DEBUG environment variable.

Validation Error Serializer

Using the validationErrorSerializer config you can customise the validation error object which is passed to the client whenever there is a 422 exception.

Intent comes with a default serializer ValidationErrorSerializer which should be good enough, however you can change it by providing your own custom class.


import { ValidationError } from 'class-validator';
import { isEmpty, Str } from '@intentjs/core';
export class CustomValidationErrorSerializer {
  async handle(errors: ValidationError[]): Promise<Record<string, any>> {
    // add your custom logic here.
    return '';
  }
}

Handling Exceptions

To handle HttpException inside your application, the ApplicationExceptionFilter comes with a handleHttp method, where you can write your own logic for handling a custom exception.

Let's say you want to handle ValidationFailed exception, you can do it like below


handleHttp(exception: any, req: Request, res: Response) {
    if (exception instanceof ValidationFailed) {
        return res.send(422).send({ error: 'validation failed' });
    }
    return res.status(this.getStatus(exception)).send(exception);
}

Reporting Exceptions

There can be situations when you don't to report an exception to other tools like Sentry or some custom error listener, in such cases, you can add your exception to the doNotReport method in your ApplicationExceptionFilter.

Let's say we don't want to report the ValidationFailed exceptions to Sentry, you can simply add it in the doNotReport array, and it will never be reported.


doNotReport(): Array<Type<HttpException>> {
    return [
        ValidationFailed
    ];
}

Sentry Integration

We have added support for Sentry in Intent, so that you don't have to set it up manually. To start reporting your errors to Sentry, we first need to follow a few steps


npm i @sentry/node --save

If you would also like to enable Sentry Node Profiling in your application, you can also install


npm i @sentry/profiling-node --save

Now that the essential packages are installed, we just need to configure the SENTRY_DSN attribute in the .env file. You can get this value from the Sentry console.

Intent will only report errors which are not added in the doNotReport array.

Validation Console