ApiProperty with enum undefined changes type

[nxht]

Is there an existing issue for this?

• I have searched the existing issues

Current behavior

Query parameter name shown as number despite the dto type says string

Minimum reproduction code

https://github.com/nxht/test-nestjs

Steps to reproduce

1. pnpm install
2. pnpm start:dev
3. Open http://localhost:3000/docs#/App/AppController_getHello

Expected behavior

Query parameter name should be string

Package version

8.1.0

NestJS version

10.4.15

Node.js version

20.9.0

In which operating systems have you tested?

• macOS
• Windows
• Linux

Other

DTO tested:

export class TestDto {
  @ApiProperty({
    type: 'string',
    enum: undefined,
  })
  name: string;
}

When the enum: undefined is removed, it works normally.

[kamilmysliwiec]

What's the point of setting enum to undefined?

[nxht]

What's the point of setting enum to undefined?

Currently using custom decorator to wrap the ApiProperty.
During the step there's change on the key name from enumType => enum.
I didn't explicitly set the enum to be undefined. But if the enumType is missing, it'll pass undefined to the enum, causing the issue.

Simple example would be like

import { ApiProperty } from '@nestjs/swagger';

const CustomDecorator = ({ enumType }: { enumType?: object } = {}) => {
  return (object: object, propertyName: string): void =>
    ApiProperty({ type: 'string', enum: enumType })(object, propertyName);
};

export class TestDto {
  @CustomDecorator()
  name: string;
}

I do know this can be solved by checking enumType before setting it to ApiProperty and I fixed my case this way. But I don't think it's an expected behaviour.

[kamilmysliwiec]

Got it. Sounds like this could be easily fixed by adding another condition to the if statement here https://github.dev/nestjs/swagger/blob/e19d30ce2d807001519c29f30030a88c04d7e5c3/lib/decorators/api-property.decorator.ts#L67 Would you like to create a PR for this?