class-transformer: fix: ExposeAll does not work with excludeExtraneousValues

Description

Strategy ‘exposeAll’ does not work as expected with true excludeExtraneousValues flag. Actual behaviour is as all properties were not exposed.

Minimal code-snippet showcasing the problem

class Dog {
  name: string;
}
const plainDoggie = {
      name: 'Azor',
      surname: 'dogs does not have surnames :('
};
const doggie = plainToClass(Dog, plainDoggie, {
      strategy: 'exposeAll',
      excludeExtraneousValues: true
});
console.log('doggie', doggie);
// should be {name:'Azor'}, but is {} instead

StackBlitz example

Expected behavior

All properties are exposed. In above example doggie = {name: ‘Azor’}

Actual behavior

Properties are not exposed. In above example doggie = {}

About this issue

Original URL
State: open
Created 3 years ago
Reactions: 57
Comments: 28

Most upvoted comments

strategy: 'exposeAll' is a strategy: it should mean that by default, everything is exposed. excludeExtraneousValues: true means if something outside the class is in the object, then remove it. The combination of these two options should logically be that you don’t need to decorate anything in the class with @Expose because everything will be exposed, but extraneous values should be removed.

Thus, this is a bug.

+52

xaphod on Dec 1, 2021

strategy: 'exposeAll' is a strategy: it should mean that by default, everything is exposed.

excludeExtraneousValues: true means if something outside the class is in the object, then remove it.

The combination of these two options should logically be that you don’t need to decorate anything in the class with @Expose because everything will be exposed, but extraneous values should be removed.

Thus, this is a bug.

Yes! 👍

+26

TheCoordinator on Dec 1, 2021

Same here, is there any solutions for this yet?

you can use @Expose for each property that you wanna expose it

minhduc-1999 on Nov 19, 2021

I faced the same issue so I created an extension method to achieve the wanted behavior:

Create a new TypeScript file ‘transform.dto.ts’

import { plainToInstance } from 'class-transformer';
import { getMetadataStorage } from 'class-validator';

export function transformToDto<T>(DtoClass: new () => T, data: any): T {

    const metadataStorage = getMetadataStorage();
    const dtoMetadata = metadataStorage.getTargetValidationMetadatas(DtoClass, '', true, true);

    const dtoInstance = plainToInstance(DtoClass, data);

    // Extract the keys from the DTO class metadata
    const dtoKeys = dtoMetadata.map(meta => meta.propertyName);

    // Filter out fields not in the DTO
    return dtoKeys.reduce((filtered, key) => {
        filtered[key] = dtoInstance[key];
        return filtered;
    }, {} as T);
}

Use it like this:

const myInstance = transformToDto(myDTO, myData);

tapava on Aug 27, 2023

It has been 2 years and this has yet to be resolved… Why?

Hareloo on Feb 22, 2024

Any news on this issue?

mwanago on Nov 16, 2023

Any news on this issue? This simple change could be very beneficial for a lot of users.

gterras on Aug 9, 2022

Sorry for disturbing. @NoNameProvided Could you plz have a look at this issue?

Option strategy: 'excludeAll' behave allmost the same as excludeExtraneousValues: true, is that by design?

It seems like that keys are the same except isMap and ignoreDecorators

ImJoeHs on Jul 23, 2021