This is a bug, it should not be never. However, something like string | `${string}.a` | `${string}.b` would get eagerly simplified down to just string.

type T = `${string}` | `${string}.a` | `${string}.b`
//   ^? type T = string

So, Paths<Record<string, { a: number; b: number; }>> would result in just string. Maybe we could return an uncollapsed union like (string & {}) | `${string}.a` | `${string}.b` , but we’d have to decide in what situations we should return an uncollapsed union.

I'll put a PR to at least return string instead of never, and then options like depth and leavesOnly can be used to control the output, like:

type T1 = Paths<{[x: string]: {a: string; b: string}}, {leavesOnly: true}>;
//   ^? type T1 = `${string}.a` | `${string}.b`

type T2 = Paths<{[x: string]: {a: string; b: string}}, {depth: 1}>;
//   ^? type T1 = `${string}.a` | `${string}.b`

type T3 = Paths<{[x: string]: {a: string; b: {c: string}}}, {depth: 1 | 2}>;
//   ^? type T1 = `${string}.a` | `${string}.b` | `${string}.b.c`

@rhyek This is likely going to take some time to get fixed because we're working on a major release. In the meantime, if this is urgent, you can try this hack:

import { Paths } from 'type-fest';

type Type = Record<string, { a: number; b: number }>;

declare const ignore: unique symbol;

type Test1 = Paths<Type & { [ignore]: never }>;
//   ^? type Test1 = string

type Test2 = Paths<Type & { [ignore]: never }, { leavesOnly: true }>;
//   ^? type Test2 = `${string}.a` | `${string}.b`

type Test3 = Paths<Type & { [ignore]: never }, { depth: 1 }>;
//   ^? type Test3 = `${string}.a` | `${string}.b`

Playground

Uh oh!

Paths should handle Record types with arbitrary string keys #1190

Description

Metadata

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

Issue actions