msw/src/core/typeUtils.ts

Seamless REST/GraphQL API mocking library for browser and Node.js.

type Fn = (...arg: any[]) => any

export type MaybePromise<T> = T | Promise<T>

export type RequiredDeep<
  Type,
  U extends Record<string, unknown> | Fn | undefined = undefined,
> = Type extends Fn
  ? Type
  : /**
     * @note The "Fn" type satisfies the predicate below.
     * It must always come first, before the Record check.
     */
    Type extends Record<string, any>
    ? {
        [Key in keyof Type]-?: NonNullable<Type[Key]> extends NonNullable<U>
          ? NonNullable<Type[Key]>
          : RequiredDeep<NonNullable<Type[Key]>, U>
      }
    : Type

/**
 * @fixme Remove this once TS 5.4 is the lowest supported version.
 * Because "NoInfer" is a built-in type utility there.
 */
export type NoInfer<T> = [T][T extends any ? 0 : never]