feat(typescript-types): Remove optionality of keys in Assign

packages/typescript-types/src/assign.ts

@@ -1,9 +1,15 @@
 import type { OptionalKeysOf } from './optional-keys-of.js'
 
+type GetNonOptionalValueAt<Obj, Key, Default> = Key extends keyof Obj
+	? undefined extends Obj[Key]
+		? Default
+		: Obj[Key]
+	: Default
+
 export type Assign<
 	Shape extends object,
 	Defaults extends Pick<Required<Shape>, OptionalKeysOf<Shape>>,
 	Obj extends Shape
 > = {
-	[K in keyof Shape]: K extends keyof Obj ? Obj[K] : K extends keyof Defaults ? Defaults[K] : never
+	[K in keyof Shape]-?: GetNonOptionalValueAt<Obj, K, K extends keyof Defaults ? Defaults[K] : never>
 }

packages/typescript-types/test/assign.tst.ts

@@ -1,29 +1,46 @@
 import type { Assign } from '@/assign.js'
 import { expect } from 'tstyche'
 
-interface Person {
+interface OptionsWithRequired {
 	name: string
+	tag?: string
 	age?: number
-}
-
-interface Options extends Person {
-	relations?: Array<Person>
+	relations?: Array<OptionsWithRequired>
 }
 
 interface DefaultValues {
-	name: 'Max Mustermann'
+	tag: 'Max Mustermann'
 	age: 17
 	relations: []
 }
 
-expect<Assign<Options, DefaultValues, { name: 'Another Name' }>>().type.toBe<{
+expect<Assign<OptionsWithRequired, DefaultValues, { name: 'Another Name' }>>().type.toBe<{
 	name: 'Another Name'
-	age?: 17
-	relations?: []
+	tag: 'Max Mustermann'
+	age: 17
+	relations: []
 }>()
 
-expect<Assign<Options, DefaultValues, { name: 'Another Name'; age: 18 }>>().type.toBe<{
+expect<Assign<OptionsWithRequired, DefaultValues, { name: 'Another Name'; age: 18 }>>().type.toBe<{
 	name: 'Another Name'
-	age?: 18
-	relations?: []
+	tag: 'Max Mustermann'
+	age: 18
+	relations: []
+}>()
+
+interface Options {
+	tag?: string
+	age?: number
+}
+
+expect<Assign<Options, DefaultValues, {}>>().type.toBe<{
+	tag: 'Max Mustermann'
+	age: 17
+}>()
+
+interface SpecifiedOptions extends Options {}
+
+expect<Assign<Options, DefaultValues, SpecifiedOptions>>().type.toBe<{
+	tag: 'Max Mustermann'
+	age: 17
 }>()