fix: `Type 'undefined' is not assignable to type 'ValidationOptions'.` when creating validation decorators

[ashuvssut]

I am creating a custom class validator using class-validator package.
https://github.com/typestack/class-validator#custom-validation-classes

import {
  registerDecorator,
  ValidationOptions,
  ValidatorConstraint,
  ValidatorConstraintInterface,
} from "class-validator";

import { User } from "../../../entity/User";

@ValidatorConstraint({ async: true })
export class IsEmailAlreadyExistConstraint implements ValidatorConstraintInterface{
  validate(email: string) {
    return User.findOne({ where: { email } }).then(user => {
      if (user) return false;
      return true;
    });
  }
}

export function IsEmailAlreadyExist(validationOptions?: ValidationOptions) {
  return function (object: Object, propertyName: string) {
    registerDecorator({
      target: object.constructor,
      propertyName: propertyName,
      options: validationOptions,
      constraints: [],
      validator: IsEmailAlreadyExistConstraint,
    });
  };
}

I am getting this error

(property) ValidationDecoratorOptions.propertyName: string
Target object's property name to be validated.

Argument of type '{ target: Function; propertyName: string; options: ValidationOptions | undefined; constraints: never[]; validator: typeof IsEmailAlreadyExistConstraint; }' is not assignable to parameter of type 'ValidationDecoratorOptions' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
  Types of property 'options' are incompatible.
    Type 'ValidationOptions | undefined' is not assignable to type 'ValidationOptions'.
      Type 'undefined' is not assignable to type 'ValidationOptions'.

Solution
when creating custom class validators, validationOptions can not be undefined.
It gives off this error: Type 'undefined' is not assignable to type 'ValidationOptions'.

so the validationOption argument from custom validation decorator functions should not allowed to be optional.

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