fix: plainToClass overwrites ObjectIds

[mikison9]

Description

Hi, I'm trying to use plainToClass to remove sensitive data from objects in my API, but the plainToClass function overwrites the ObjectIds with new values. Below is a minimal code snippet that demonstrates it.

Minimal code-snippet showcasing the problem

import { Expose, plainToClass } from "class-transformer";
import { ObjectId } from "mongodb";
import "reflect-metadata";

class Obj {
  @Expose()
  field1: ObjectId;
  @Expose()
  field2: ObjectId;
  @Expose()
  field3: ObjectId;
}

let objects = [];

let fieldCount = 3;

let fields = ["field1", "field2", "field3"];

let objectCount = 10;

// gen objects with random objectIds

for (let x = 0; x < objectCount; x++) {
  let obj: any = {};

  for (const field of fields) {
    obj[field] = new ObjectId();
  }

  objects.push(obj);
}

console.log(objects.length);

// let classObjects = []

let mismatchedCount = 0;

for (const obj of objects) {
  let clsObj = plainToClass(Obj, obj, { excludeExtraneousValues: true });

  for (const field of fields) {
    if (clsObj[field].toString() != obj[field].toString()) {
      console.log(
        `mismatched: \nafter: ${JSON.stringify(
          clsObj
        )} \nbefore:${JSON.stringify(obj)}`
      );

      mismatchedCount += 1;

      break;
    }
  }
}

console.log(`mismatched count: ${mismatchedCount}`);

Output:

10
mismatched: 
after: {"field1":"622e0f388601f22386f635fb","field2":"622e0f388601f22386f635fc","field3":"622e0f388601f22386f635fd"} 
before:{"field1":"622e0f388601f22386f635dd","field2":"622e0f388601f22386f635de","field3":"622e0f388601f22386f635df"}
mismatched: 
after: {"field1":"622e0f388601f22386f635fe","field2":"622e0f388601f22386f635ff","field3":"622e0f388601f22386f63600"} 
before:{"field1":"622e0f388601f22386f635e0","field2":"622e0f388601f22386f635e1","field3":"622e0f388601f22386f635e2"}
mismatched: 
after: {"field1":"622e0f388601f22386f63601","field2":"622e0f388601f22386f63602","field3":"622e0f388601f22386f63603"} 
before:{"field1":"622e0f388601f22386f635e3","field2":"622e0f388601f22386f635e4","field3":"622e0f388601f22386f635e5"}
mismatched: 
after: {"field1":"622e0f388601f22386f63604","field2":"622e0f388601f22386f63605","field3":"622e0f388601f22386f63606"} 
before:{"field1":"622e0f388601f22386f635e6","field2":"622e0f388601f22386f635e7","field3":"622e0f388601f22386f635e8"}
mismatched: 
after: {"field1":"622e0f388601f22386f63607","field2":"622e0f388601f22386f63608","field3":"622e0f388601f22386f63609"} 
before:{"field1":"622e0f388601f22386f635e9","field2":"622e0f388601f22386f635ea","field3":"622e0f388601f22386f635eb"}
mismatched: 
after: {"field1":"622e0f388601f22386f6360a","field2":"622e0f388601f22386f6360b","field3":"622e0f388601f22386f6360c"} 
before:{"field1":"622e0f388601f22386f635ec","field2":"622e0f388601f22386f635ed","field3":"622e0f388601f22386f635ee"}
mismatched: 
after: {"field1":"622e0f388601f22386f6360d","field2":"622e0f388601f22386f6360e","field3":"622e0f388601f22386f6360f"} 
before:{"field1":"622e0f388601f22386f635ef","field2":"622e0f388601f22386f635f0","field3":"622e0f388601f22386f635f1"}
mismatched: 
after: {"field1":"622e0f388601f22386f63610","field2":"622e0f388601f22386f63611","field3":"622e0f388601f22386f63612"} 
before:{"field1":"622e0f388601f22386f635f2","field2":"622e0f388601f22386f635f3","field3":"622e0f388601f22386f635f4"}
mismatched: 
after: {"field1":"622e0f388601f22386f63613","field2":"622e0f388601f22386f63614","field3":"622e0f388601f22386f63615"} 
before:{"field1":"622e0f388601f22386f635f5","field2":"622e0f388601f22386f635f6","field3":"622e0f388601f22386f635f7"}
mismatched: 
after: {"field1":"622e0f388601f22386f63616","field2":"622e0f388601f22386f63617","field3":"622e0f388601f22386f63618"} 
before:{"field1":"622e0f388601f22386f635f8","field2":"622e0f388601f22386f635f9","field3":"622e0f388601f22386f635fa"}
mismatched count: 10

[SahilMahadwar]

am using this workaround. i hope they fix this soon

export class AuthResDto {
  @Expose()
  @Transform((value) => value.obj._id.toString())
  _id: ObjectId;

  @Expose()
  email: string;
}