question: Is it possible to skip transformation without excluding the property

[Eyal-Benari]

I have a class that has three properties: "type", "data" and "metadata". Based on the value of "type" I am transforming "data" and "metadata" to different classes. I am using the @Type decorator with a function that returns different classes with a switch-case on "type" (I don't think I can use a normal discriminator because the "type" property is not inside "data" or "metadata", and I can't use @type on the whole class). I want to skip transformation on "data" or "metadata" when "type" is equal to some value. I want the property to be in the transformed class as a plain object (mostly for logging purposes, I'll just dump the value into the log).

import { Type } from "class-transformer";

class AMetadata {
	foo!: string;
}
class BMetadata {
	bar!: number;
}
class AData {
	foobar!: string;
}
class CData {
	banana!: string;
}

const TYPES = ["a", "b", "c"] as const;
type TType = typeof TYPES[number];

export class EventSchema {
	type!: TType;

	@Type(options => {
		if (!options || !options.object) return unknown;
		switch (options.object.type as TType) {
			case "a":
				return AMetadata;
			case "b":
				return BMetadata;
			case "c":
				return unknown;
		}
	})
	metadata!: AMetadata | BMetadata | unknown;

	@Type(options => {
		if (!options || !options.object) return unknown;
		switch (options.object.type as TType) {
			case "a":
				return AData;
			case "b":
				return unknown;
			case "c":
				return CData;
		}
	})
	data!: AData | CData | unknown;
}

The problem:
I don't know of a way to return an "unknown" value in the @Type decorator callback. The callback only returns a Function and when trying to return something like (value: unknown) => value I got the error "Cannot read properties of undefined (reading 'constructor')", which probably means it only accepts classes. I want to support any value (string, boolean, number, Record<string, unknown>), but I could not find a way to achieve this.