feat(typescript-types): Add KeyPaths<T, F, O>

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

@@ -0,0 +1,32 @@
+import type { KeyPaths } from '@/key-paths.js'
+import { expect } from 'tstyche'
+
+interface ExampleObject {
+	nullvalue: null
+	simplevalue: string
+	config: {
+		nullvalue: null
+		simplevalue: string
+	}
+}
+
+expect<KeyPaths<ExampleObject>>().type.toBe<'simplevalue' | 'config.simplevalue'>()
+expect<KeyPaths<ExampleObject, never>>().type.toBe<
+	'nullvalue' | 'simplevalue' | 'config.nullvalue' | 'config.simplevalue'
+>()
+expect<KeyPaths<ExampleObject, null>>().type.toBe<'simplevalue' | 'config.simplevalue'>()
+expect<KeyPaths<ExampleObject, string>>().type.toBe<'nullvalue' | 'config.nullvalue'>()
+
+expect<KeyPaths<ExampleObject, null, { separator: '-' }>>().type.toBe<'simplevalue' | 'config-simplevalue'>()
+expect<KeyPaths<ExampleObject, null, { leavesOnly: false }>>().type.toBe<
+	'simplevalue' | 'config' | 'config.simplevalue'
+>()
+
+expect<KeyPaths<any, string>>().type.toBe<unknown>()
+expect<KeyPaths<any, never>>().type.toBe<unknown>()
+
+expect<KeyPaths<ExampleObject, any>>().type.toBeAssignableTo<never>()
+expect<KeyPaths<ExampleObject, unknown>>().type.toBeAssignableTo<never>()
+expect<KeyPaths<any, any>>().type.toBeAssignableTo<never>()
+expect<KeyPaths<never, any>>().type.toBeAssignableTo<never>()
+expect<KeyPaths<never, never>>().type.toBeAssignableTo<never>()