Class-Validator node.js provide custom error

I have a custom validator constraint and annotation created for checking whether entity with given property already exists or not, here is the code

import { Inject, Injectable } from '@nestjs/common';
import { registerDecorator, ValidationArguments, ValidationOptions, ValidatorConstraint } from 'class-validator';
import { ValidatorConstraintInterface } from 'class-validator/types/validation/ValidatorConstraintInterface';
import { Connection } from 'typeorm';
import { InjectConnection } from '@nestjs/typeorm';

@ValidatorConstraint({ async: true })
@Injectable()
export class EntityExistsConstraint implements ValidatorConstraintInterface {

  constructor(@InjectConnection() private dbConnection: Connection) {
  }

  defaultMessage(validationArguments?: ValidationArguments): string {
    return `${validationArguments.constraints[0].name} with ${validationArguments.property} already exists`;
  }

  validate(value: any, validationArguments?: ValidationArguments): Promise<boolean> | boolean {
    const repoName = validationArguments.constraints[0];
    const property = validationArguments.property;
    const repository = this.dbConnection.getRepository(repoName);
    return repository.findOne({ [property]: value }).then(result => {
      return !result;
    });
  }

}

export function EntityExists(repoName, validationOptions?: ValidationOptions) {
  return function(object: any, propertyName: string) {
    registerDecorator({
      target: object.constructor,
      propertyName: propertyName,
      options: validationOptions,
      constraints: [repoName],
      validator: EntityExistsConstraint,
    });
  };
}

Everything works fine, but I receive this response when the validation fails

{
    "statusCode": 400,
    "message": [
        "User with email already exists"
    ],
    "error": "Bad Request"
}

I want the error be Conflict Exception=> statusCode 409, how can I achieve this?

class-validator doesn't do anything with the http codes. It only validates and returns a list of errors or an empty array.

What you need to do is to check framework you use, I assume it's nestjs or routing-controllers.

In the case of routing-controllers you need to write own after middleware and disable default middleware (it converts validation errors to 400 bad requests). More info is here: https://github.com/typestack/routing-controllers#error-handlers

In the case of nestjs - the same steps. More info you can find here: https://docs.nestjs.com/exception-filters#catch-everything