[Typescript] 125. Extreme - Object Key Paths

Get all possible paths that could be called by _.get (a lodash function) to get the value of an object

type T1 = ObjectKeyPaths<{ name: string; age: number }>; // expected to be 'name' | 'age'
type T2 = ObjectKeyPaths<{
  refCount: number;
  person: { name: string; age: number };
}>; // expected to be 'refCount' | 'person' | 'person.name' | 'person.age'
type T3 = ObjectKeyPaths<{ books: [{ name: string; price: number }] }>; // expected to be the superset of 'books' | 'books.0' | 'books[0]' | 'books.[0]' | 'books.0.name' | 'books.0.price' | 'books.length' | 'books.find'

 

/* _____________ Your Code Here _____________ */

type GenNode<K extends string | number, IsRoot extends boolean> = IsRoot extends true? `${K}`: `.${K}` | (K extends number? `[${K}]` | `.[${K}]`:never)

type ObjectKeyPaths<
  T extends object,
  IsRoot extends boolean = true,
  K extends keyof T = keyof T
> = 
K extends string | number ?
  GenNode<K,IsRoot> | (T[K] extends object? `${GenNode<K,IsRoot>}${ObjectKeyPaths<T[K],false>}`:never)
  :never;


/* _____________ Test Cases _____________ */
import type { Equal, Expect, ExpectExtends } from '@type-challenges/utils'

const ref = {
  count: 1,
  person: {
    name: 'cattchen',
    age: 22,
    books: ['book1', 'book2'],
    pets: [
      {
        type: 'cat',
      },
    ],
  },
}

type cases = [
  Expect<Equal<ObjectKeyPaths<{ name: string; age: number }>, 'name' | 'age'>>,
  Expect<
  Equal<
  ObjectKeyPaths<{
    refCount: number
    person: { name: string; age: number }
  }>,
  'refCount' | 'person' | 'person.name' | 'person.age'
  >
  >,
  Expect<ExpectExtends<ObjectKeyPaths<typeof ref>, 'count'>>,
  Expect<ExpectExtends<ObjectKeyPaths<typeof ref>, 'person'>>,
  Expect<ExpectExtends<ObjectKeyPaths<typeof ref>, 'person.name'>>,
  Expect<ExpectExtends<ObjectKeyPaths<typeof ref>, 'person.age'>>,
  Expect<ExpectExtends<ObjectKeyPaths<typeof ref>, 'person.books'>>,
  Expect<ExpectExtends<ObjectKeyPaths<typeof ref>, 'person.pets'>>,
  Expect<ExpectExtends<ObjectKeyPaths<typeof ref>, 'person.books.0'>>,
  Expect<ExpectExtends<ObjectKeyPaths<typeof ref>, 'person.books.1'>>,
  Expect<ExpectExtends<ObjectKeyPaths<typeof ref>, 'person.books[0]'>>,
  Expect<ExpectExtends<ObjectKeyPaths<typeof ref>, 'person.books.[0]'>>,
  Expect<ExpectExtends<ObjectKeyPaths<typeof ref>, 'person.pets.0.type'>>,
  Expect<Equal<ExpectExtends<ObjectKeyPaths<typeof ref>, 'notExist'>, false>>,
  Expect<Equal<ExpectExtends<ObjectKeyPaths<typeof ref>, 'person.notExist'>, false>>,
  Expect<Equal<ExpectExtends<ObjectKeyPaths<typeof ref>, 'person.name.'>, false>>,
  Expect<Equal<ExpectExtends<ObjectKeyPaths<typeof ref>, '.person.name'>, false>>,
  Expect<Equal<ExpectExtends<ObjectKeyPaths<typeof ref>, 'person.pets.[0]type'>, false>>,
]