feat(typescript-types): Add KeyPath<T, Separator = '.'>

packages/typescript-types/README.md

@@ -34,6 +34,12 @@ The types included in this library are categorized by their purpose.
 
 [`OptionalKeysOf<T>`]: src/optional-keys-of.ts
 
+#### Conversion Types
+
+| Type                              | Description                                                        |
+| --------------------------------- | ------------------------------------------------------------------ |
+| [`KeyPath<T, Separator = '.'>`][] | Converts a `Separator` separated string into a tuple of its parts. |
+
 #### Combination Types
 
 | Type                               | Description                                                                                                             |

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

@@ -0,0 +1,9 @@
+import type { If } from './if.js'
+import type { IsEmptyString } from './is-empty-string.js'
+
+export type KeyPath<
+	P extends string,
+	Separator extends string = '.'
+> = P extends `${infer Key}${Separator}${infer Rest}`
+	? [Key, ...KeyPath<Rest, Separator>]
+	: If<IsEmptyString<P>, [], [P]>

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

@@ -0,0 +1,11 @@
+import type { KeyPath } from '@/key-path.js'
+import { expect } from 'tstyche'
+
+expect<KeyPath<''>>().type.toBe<[]>()
+expect<KeyPath<'Key'>>().type.toBe<['Key']>()
+expect<KeyPath<'Key.Path'>>().type.toBe<['Key', 'Path']>()
+expect<KeyPath<'Key.Path', '-'>>().type.toBe<['Key.Path']>()
+expect<KeyPath<'Key.Path-One', '-'>>().type.toBe<['Key.Path', 'One']>()
+
+expect<KeyPath<any>>().type.toBe<[] | [string]>()
+expect<KeyPath<never>>().type.toBeAssignableWith<never>()