From d1c4b82e0b69678d6883f9be3eec950c9a1c7433 Mon Sep 17 00:00:00 2001
From: Homa Wong <homawong@gmail.com>
Date: Fri, 4 Jan 2019 16:27:09 -0800
Subject: [PATCH] feat: add RequiredPick and RequiredExcept (#9)

---
 README.md            |  8 ++++++++
 src/Required.spec.ts |  8 +++-----
 src/Required.ts      | 10 ++++++----
 src/index.ts         |  2 ++
 4 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/README.md b/README.md
index 055dd6d483..03b4b5f40d 100644
--- a/README.md
+++ b/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.
diff --git a/src/Required.spec.ts b/src/Required.spec.ts
index a4ade2c187..a1e36d06a1 100644
--- a/src/Required.spec.ts
+++ b/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)
 })
diff --git a/src/Required.ts b/src/Required.ts
index 187d29d2a3..e07105fcef 100644
--- a/src/Required.ts
+++ b/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>
diff --git a/src/index.ts b/src/index.ts
index feadcfa608..b2df7d10c8 100644
--- a/src/index.ts
+++ b/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'