NestJS ValidationPipe with ValidateIf not preventing conditional field validation

Question

I'm building an accounting application using NestJS. I have a DTO called CreateTransactionDto, and I want certain fields to be required or forbidden based on the value of transactionType. For example:

If transactionType = SALE, then fields like quantity and unitPrice must be provided, but receivedAmount must not be included.

If transactionType = PAYMENT, then receivedAmount is required, and quantity and similar fields must not be included.

Here’s how I’ve defined validation for the receivedAmount field:

// dto
@ApiProperty({
  description: 'Type of the transaction',
  enum: TransactionType,
})
@IsNotEmpty()
@IsEnum(TransactionType)
transactionType: TransactionType;

@ValidateIf((o: CreateTransactionDto) => o.transactionType === TransactionType.PAYMENT)
@IsNotEmpty({
  message: 'Received amount is required for PAYMENT transactions',
})
@IsNumber()
@ValidateIf((o: CreateTransactionDto) => o.transactionType === TransactionType.SALE)
@IsEmpty({
  message: 'Received amount should not be provided for SALE transactions',
})
receivedAmount?: number;

I'm also using the global ValidationPipe with the following configuration:

// main.ts
app.useGlobalPipes(
  new ValidationPipe({
    transform: true,
    whitelist: true,
    forbidNonWhitelisted: true,
    forbidUnknownValues: true,
    stopAtFirstError: false,
  }),
);

However, when I send the following JSON payload, no validation error occurs:

{
  "customerId": 1,
  "transactionType": "SALE",
  "transactionDate": "2023-10-01",
  "description": "Sale of goods",
  "quantity": 10,
  "quantityUnit": "pcs",
  "unitPrice": 50,
  "receivedAmount": 500
}

Even though transactionType is SALE, and receivedAmount should not be included, the request goes through without validation errors.

My question is: How can I correctly use ValidateIf to conditionally validate or reject fields based on other field values? Is there something I'm missing or doing wrong?

Abie.exe · Accepted Answer · 2025-04-25 16:40:47Z

`@ValidateIf` and Inside It Handle the Logic

Instead of layering multiple @ValidateIfs and validators, consolidate validation using a single custom @ValidateIf() for each conditional branch.

@ValidateIf((o) => o.transactionType === TransactionType.PAYMENT)

@IsNotEmpty({ message: 'Received amount is required for PAYMENT transactions' })

@IsNumber()

receivedAmount?: number;

@ValidateIf((o) => o.transactionType === TransactionType.SALE && o.receivedAmount !== undefined)

@IsEmpty({ message: 'Received amount should not be provided for SALE transactions' })

receivedAmount?: number;

Create a custom validator for receivedAmount:

import {
  registerDecorator,
  ValidationOptions,
  ValidationArguments,
} from 'class-validator';

export function IsValidReceivedAmount(validationOptions?: ValidationOptions) {
  return function (object: any, propertyName: string) {
    registerDecorator({
      name: 'isValidReceivedAmount',
      target: object.constructor,
      propertyName: propertyName,
      options: validationOptions,
      validator: {
        validate(value: any, args: ValidationArguments) {
          const obj = args.object as any;
          if (obj.transactionType === 'PAYMENT') {
            return typeof value === 'number' && value !== null;
          } else if (obj.transactionType === 'SALE') {
            return value === undefined || value === null;
          }
          return true;
        },
        defaultMessage(args: ValidationArguments) {
          const obj = args.object as any;
          if (obj.transactionType === 'SALE') {
            return 'receivedAmount should not be provided for SALE transactions';
          }
          if (obj.transactionType === 'PAYMENT') {
            return 'receivedAmount is required for PAYMENT transactions';
          }
          return 'Invalid value for receivedAmount';
        },
      },
    });
  };
}

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`@ValidateIf` and Inside It Handle the Logic