PickType ignore parent's @Transform when grandparent use @Transform

[KuanWenChen]

Is there an existing issue for this?

• I have searched the existing issues

Current behavior

My ValidationPipe setting is

app.useGlobalPipes(new ValidationPipe({ transform: true }));

My Dto is

import { PickType } from '@nestjs/swagger';
import { Expose, Transform } from 'class-transformer';

export class TestDto1 {
  @Expose()
  @Transform(() => {
    console.log('TestDto1 Transform');
    return 1;
  })
  version!: number;
}

export class TestDto2 extends PickType(TestDto1, ['version']) {
  @Transform(() => {
    console.log('TestDto2 Transform');
    return 2;
  })
  version!: number;
}

export class TestDto3PickTypeVersion extends PickType(TestDto2, ['version']) {
  @Transform(() => {
    console.log('TestDto3 Transform');
    return 3;
  })
  version!: number;
}

export class TestDto3ExtendVersion extends TestDto2 {
  @Transform(() => {
    console.log('TestDto3 Transform');
    return 3;
  })
  version!: number;
}

My Controller is

@Controller('test')
export class TestController {
  @Post('/pick-type-version')
  test1(@Body() testDto3PickTypeVersion: TestDto3PickTypeVersion) {
    return testDto3PickTypeVersion;
  }

  @Post('/extend-version')
  test2(@Body() testDto3ExtendVersion: TestDto3ExtendVersion) {
    return testDto3ExtendVersion;
  }
}

When I call 「http://localhost:3000/pick-type-version」

TestDto3PickTypeVersion ignore TestDto2's @Transform.

When I call 「http://localhost:3000/extend-version」

TestDto2's @Transform would work.

If I change TestDto1 as

export class TestDto1 {
  @Expose()
  version!: number;
}

TestDto2's @Transform would be work too.

Minimum reproduction code

https://github.com/KuanWenChen/swagger-issue

Steps to reproduce

npm install
npm run start:dev

goto website http://localhost:3000/swagger

Call Api and See log.

Expected behavior

When I call「http://localhost:3000/pick-type-version」, I need to see 「TestDto2 Transform」

TestDto3PickTypeVersion should not ignore TestDto2's @Transform.

Package version

^7.1.13

NestJS version

10.2.7

Node.js version

v18.16.0

In which operating systems have you tested?

• macOS
• Windows
• Linux

Other

No response

[Kamil Mysliwiec]

Would you like to create a PR for this issue?

[KuanWenChen]

OK, I has found the problem is happen at mapped-types function inheritTransformationMetadata

The problem is occurring at existingRules, and targetMetadataEntries are overwriting values taht with the same key ; they should merge.

I have created another issue for this problem.

[Kamil Mysliwiec]

nestjs/mapped-types#1212