How to validate child DTO conditionally with class-validator? - class-validator

Question

I am trying to conditionally validate nested DTO with class validator, but #ValidateIf seems to be not applying correctly and always validating the nested class.
I have the following DTO:
export class SuperAdminStoreDto extends StoreDto {
#IsOptional()
#IsBoolean()
readonly payments: boolean;
#ValidateIf(object => object.payments)
#ValidateNested({ each: true })
#Type(() => PaymentDetails)
readonly payment_details: PaymentDetails[];
}
class PaymentDetails {
#IsNumberString()
#IsNotEmpty()
readonly min: string;
#IsNumberString()
#IsNotEmpty()
readonly max: string;
#IsNumberString()
#IsNotEmpty()
readonly percentage: string;
}
Let's say the object being validated is:
{
"payments": false,
"payment_details": {
"min": "1"
}
}
I get no errors although I should because I have set the validator with following flags:
{
whitelist: true,
forbidNonWhitelisted: true,
forbidUnknownValues: true,
validationError: {
target: false,
}
}
I am expecting the validator to not allow the child object to be present and throw an error.

Answer 1

One option I've used is to create a custom decorator to validate the nested object since custom decorators work with #ValidateIf()
type Class<T> = { new (...args: any[]): T };
export function ValidateDtoArray(dto: Class<any>, validationOptions?: ValidationOptions) {
return function (object: unknown, propertyName: string) {
registerDecorator({
name: 'validateDto',
target: (object as any).constructor,
propertyName: propertyName,
options: validationOptions,
validator: {
async validate(value: unknown, args: ValidationArguments) {
if (!isArray(value)) return false;
for (let i = 0; i < (value as any[]).length; i++) {
const array_value = (value as any[])[i];
if(typeof array_value !== 'object') return false;
const validation_errors = await validate(plainToClass(dto, array_value as Record<string, unknown>);
if (validation_errors.length > 0) return false;
}
return true;
},
defaultMessage(validationArguments?: ValidationArguments) {
return `Can only be of type ${dto.name}[]`;
},
},
});
};
}
Your code then becomes
export class SuperAdminStoreDto extends StoreDto {
#IsOptional()
#IsBoolean()
readonly payments: boolean;
#ValidateIf(object => object.payments)
#ValidateDtoArray(PaymentDetails)
#Type(() => PaymentDetails)
readonly payment_details: PaymentDetails[];
}