2759-requiredbykeys.ts

/**
 * 2759 - RequiredByKeys
 *
 * Implement a generic `RequiredByKeys<T,  K>` which takes two type argument `T` and `K`.
 *
 * `K` specify the set of properties of `T` that should set to be required. When `K` is not provided, it should make all properties required just like the normal `Required<T>`.
 *
 * For example
 *
 * ```typescript
 * interface User {
 *   name?: string
 *   age?: number
 *   address?: string
 * }
 *
 * type UserRequiredName = RequiredByKeys<User, 'name'> // { name: string; age?: number; address?: string }
 *
 * ```
 */

/* _____________ Your Code Here _____________ */

type RequiredByKeys<T extends object, K extends keyof T = keyof T> =
  Omit<Omit<T, K> & { [Key in K]-?: T[Key] }, never>

/* _____________ Test Cases _____________ */
import type { Equal, Expect } from '@type-challenges/utils'

interface User {
  name?: string
  age?: number
  address?: string
}

interface UserRequiredName {
  name: string
  age?: number
  address?: string
}

interface UserRequiredNameAndAge {
  name: string
  age: number
  address?: string
}

type cases = [
  Expect<Equal<RequiredByKeys<User, 'name'>, UserRequiredName>>,
  Expect<Equal<RequiredByKeys<User, 'name' | 'age'>, UserRequiredNameAndAge>>,
  Expect<Equal<RequiredByKeys<User>, Required<User>>>,
  // @ts-expect-error
  Expect<Equal<RequiredByKeys<User, 'name' | 'unknown'>, UserRequiredName>>,
]