NestJS: DTO transform default values not working if parameter is not passed in the payload

I’ve created a controller that receives a POST/ ... request.
one of the parameters is optional and it’s for example called contentType.
in the service i check if the contentType is equal to something and regarding to the result it does something.
because the parameter is not mandatory, I want to set it a default value.
in that case I used @Transform() decorator in the DTO.
When I do the call I don’t see the default values I defined in the decorator it in the service.

Expected:

sort = {date: -1}

contentType = ‘json’

Result in Service:

sort = undefined

contentType = undefined

My NestJS Config:
Using nestJS V10
reflect-metadata version: ^0.2.2″

  1. Main.ts:

    const app = await NestFactory.create(AppModule);
    ...
    app.useGlobalPipes(
    new ValidationPipe({
      transform: true,
      transformOptions: { enableImplicitConversion: true },
      whitelist: true,
      }),
    );
  1. DTO:

    export class ListDto {
    ... more...
        
    @IsObject()
    @IsOptional()
    @Transform(({ value }) => value ?? { date: -1 })
    sort?: Record<string, SortOrder>;  // Types Defined above I just don't want to pollute the example.
            
    @IsString()
    @IsOptional()
    @IsIn(['json', 'xlsx', 'csv'], {
    message: 'contentType must be one of: json, xlsx, csv',
    })
    @Transform(({ value }) => value ?? 'json')
    contentType?: Extension;
    }
  1. Controller:

 @Post('list')
 async list(@Body() list: ListDto): Promise<any> {
   try {
     console.log(list.sort) // <-- Expected default value defined in decorator, but undefined
     console.log(list.contentType) // <-- Expected default value defined in decorator, but undefined
     return await this.someService.list(list);
   } catch (error) {
    ....
   }
 }
  1. request body:

    {
      "param1" : "Some value",
      "param2" : "Some other"
      //NOT Passing sort or contentType
    }
  1. Service method declaration:

async list({
...more...
sort,
contentType,
}: ListeDto): Promise<List> {
console.log(contentType) <-- Expect to see the default value from the decorator, but undefined
console.log(sort)  <-- Expect to see the default value from the decorator, but undefined
...some implementation...
}

Where did I do wrong?
Or what am I missing?