feat: add RequiredPick and RequiredExcept (#9)

README.md

@@ -59,6 +59,14 @@ Make type T optional recursively.
 
 Make type T required recursively.
 
+### `RequiredPick<T, U>`
+
+Makes the properties specified in `U` becomes required.
+
+### `RequiredExcept<T, U>`
+
+Makes the properties not specified in `U` becomes required.
+
 ### `ValueOf<T>`
 
 Type of the value of the properties of T.

src/Required.spec.ts

@@ -1,5 +1,5 @@
 import { RequiredExcept, RequiredPick } from './Required';
-import { excludeUndefined } from './test-util';
+import { excludeUndefined, acceptNoUndefined } from './test-util';
 
 test('make picked properties optional', () => {
   type Foo = {
@@ -10,8 +10,7 @@ test('make picked properties optional', () => {
 
   let y: RequiredPick<Foo, 'a'> = {} as any
 
-  // https://github.com/Microsoft/TypeScript/issues/29269
-  // acceptNoUndefined(y.a)
+  acceptNoUndefined(y.a)
   y.b = undefined
   y.c = excludeUndefined(y.c)
 })
@@ -26,7 +25,6 @@ test('make not picked properties optional', () => {
   let y: RequiredExcept<Foo, 'a'> = {} as any
 
   y.a = undefined
-  // https://github.com/Microsoft/TypeScript/issues/29269
-  // acceptNoUndefined(y.b)
+  acceptNoUndefined(y.b)
   y.c = excludeUndefined(y.c)
 })

src/Required.ts

@@ -1,7 +1,9 @@
+// Thanks [jack-williams](https://github.com/jack-williams) for the [solution](https://github.com/Microsoft/TypeScript/issues/29269#issuecomment-451602962)
+
 export type RequiredPick<T, U extends keyof T> = {
-  [P in keyof T]: T[P] extends undefined ? never : T[P]
-}
+  [P in U]-?: Exclude<T[P], undefined>
+} & Pick<T, Exclude<keyof T, U>>
 
 export type RequiredExcept<T, U extends keyof T> = {
-  [P in keyof T]: P extends U ? T[P] : Exclude<T[P], undefined>
-}
+  [P in Exclude<keyof T, U>]-?: Exclude<T[P], undefined>
+} & Pick<T, U>

src/index.ts

@@ -7,3 +7,5 @@ export * from './RecursiveIntersect';
 export * from './RecursivePartial';
 export * from './RecursiveRequired';
 export * from './reduceKey';
+export * from './Required';
+export * from './ValueOf'