Bug ConditionalPick

[salisbury-espinosa]

Bug description

import type { ConditionalPick } from 'type-fest';

interface TestInterface {
  a: string;
}

// TS validates that everything is ok - WHY ? 
// ConditionalPick<TestInterface, number> === {} .....

const test123123123: ConditionalPick<TestInterface, number> = {
  sdfsdfsdf: 'asdasd',
};

[som-sm]

This happens because ConditionalPick currently returns the {} type when no matching key is found.

type TestKeys = ConditionalPick<{a: string}, number>;
//   ^? type TestKeys = {}

In cases like these, the output should probably be never.

[benzaria]

@salisbury-espinosa u can use a wrapper at the moment if urgent!

import type {ConditionalKeys, EmptyObject} from 'type-fest'

type ConditionalPick<T, V> = Pick<T, ConditionalKeys<T, V>> extends infer Result
	? Result extends EmptyObject
		? never
		: Result
	: never;

or an IsEqual can do as well:

type ConditionalPick<T, V> = Pick<T, ConditionalKeys<T, V>> extends infer Result
	? IsEqual<{}, Result> extends true
		? never
		: Result
	: never;

Also I think this can settle the issue?