I want to use Pick<Type, Keys> generically, so I could retrieve keys dynamically ONLY if those exist on the provided Type.

I tried creating a type GenericPick<T extends Partial<PropertyType>> = Pick<Type, Keys> but, probably due to the Partial<Type> type, it returns Keys specified in Pick<Type, Keys> even if they do not exist on the provided Type.

The only way I’ve been able to make this work was by using Conditional Types where I have to validate every possible property with Type extends Pick<Type, Keys> which make the creation of the type seems very boilerplate.

My question is, is there a better way to use generic Pick<Type, Keys> to avoid using Conditional Types?

Here is an example to reproduce what I’m trying to do…

interface Properties {
  name: string;
  animal: true;
  plant: true;
  fly: boolean;
  swim: boolean;
  walk: boolean;
}

type Bird = Pick<Properties, 'name' | 'animal' | 'fly'>;
type Fish = Pick<Properties, 'name' | 'animal' | 'swim'>;
type Dog = Pick<Properties, 'name' | 'animal' | 'walk'>;
type Plant = Pick<Properties, never>;

// this works
export type ConditionalPick<T extends Partial<Properties>> =
  T extends Pick<Properties, 'name' | 'animal' | 'fly'>
    ? Pick<Properties, 'name' | 'animal' | 'fly'>
    : T extends Pick<Properties, 'name' | 'animal' | 'swim'>
      ? Pick<Properties, 'name' | 'animal' | 'swim'>
      : T extends Pick<Properties, 'name' | 'animal' | 'walk'>
        ? Pick<Properties, 'name' | 'animal' | 'walk'>
        : undefined

const bird: ConditionalPick<Bird> = {
  name: 'coco',
  animal: true,
  fly: true,
};

const fish: ConditionalPick<Fish> = {
  name: 'nemo',
  animal: true,
  swim: true,
};

const dog: ConditionalPick<Dog> = {
  name: 'rex',
  animal: true,
  walk: true,
};

// Good: we cannot assign 'animal' property
const plant: ConditionalPick<Plant> = undefined; 

// this doesn't work
export type GenericPick<T extends Partial<Properties>> = Pick<T, 'name' | 'animal' | 'fly' | 'swim' | 'walk'>

// bad: those properties don't exist on type Plant
const plantTwo: GenericPick<Plant> = {
  name: 'some plant',
  animal: false, 
  fly: false,
  swim: false,
  walk: false,
}

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