feat(typescript-types): Allow inversion of filter in KeyPaths<T, O, F>

packages/typescript-types/src/key-paths.ts

@@ -7,11 +7,13 @@ import type { Assign } from './assign.js'
 interface KeyPaths_Options {
 	separator?: string
 	leavesOnly?: boolean
+	invertFilter?: boolean
 }
 
 interface KeyPaths_DefaultOptions {
 	separator: '.'
 	leavesOnly: true
+	invertFilter: false
 }
 
 type GetPrefixedKey<
@@ -34,8 +36,16 @@ type KeyPathsOfStringKeys<
 	Parent extends string = ''
 > = {
 	[Key in keyof Obj & string]: Obj[Key] extends Filter
-		? never
-		: KeyPathOf<Obj[Key], Options, GetPrefixedKey<Parent, Key, Options['separator']>, Filter>
+		? If<
+				Options['invertFilter'],
+				KeyPathOf<Obj[Key], Options, GetPrefixedKey<Parent, Key, Options['separator']>, Filter>,
+				never
+			>
+		: If<
+				Options['invertFilter'],
+				never,
+				KeyPathOf<Obj[Key], Options, GetPrefixedKey<Parent, Key, Options['separator']>, Filter>
+			>
 }[keyof Obj & string]
 
 export type KeyPaths<

packages/typescript-types/test/key-paths.tst.ts

@@ -16,12 +16,7 @@ interface ExampleObject {
 	}
 }
 
-expect<KeyPaths<ExampleObject>>().type.toBe<
-	'simplevalue' | 'optionalKey.simplevalue' | 'unknownKey' | 'config.simplevalue'
->()
-expect<KeyPaths<ExampleObject, {}, any>>().type.toBeAssignableTo<never>()
-expect<KeyPaths<ExampleObject, {}, unknown>>().type.toBeAssignableTo<never>()
-expect<KeyPaths<ExampleObject, {}, never>>().type.toBe<
+type AllKeys =
 	| 'nullvalue'
 	| 'simplevalue'
 	| 'optionalKey.nullvalue'
@@ -29,7 +24,14 @@ expect<KeyPaths<ExampleObject, {}, never>>().type.toBe<
 	| 'unknownKey'
 	| 'config.nullvalue'
 	| 'config.simplevalue'
+
+expect<KeyPaths<ExampleObject>>().type.toBe<
+	'simplevalue' | 'optionalKey.simplevalue' | 'unknownKey' | 'config.simplevalue'
 >()
+expect<KeyPaths<ExampleObject, {}, any>>().type.toBeAssignableTo<never>()
+expect<KeyPaths<ExampleObject, {}, unknown>>().type.toBeAssignableTo<never>()
+expect<KeyPaths<ExampleObject, {}, never>>().type.toBe<AllKeys>()
+expect<KeyPaths<ExampleObject, { invertFilter: true }, any>>().type.toBe<AllKeys>()
 expect<KeyPaths<ExampleObject, {}, null>>().type.toBe<
 	'simplevalue' | 'optionalKey.simplevalue' | 'unknownKey' | 'config.simplevalue'
 >()