set value for given object path with TypeScript

setPathRequired.ts

import { CamelCasedPropertiesDeep, Merge } from 'type-fest'
import { DeepRequired, MarkRequired } from 'ts-essentials'


// https://www.typescriptlang.org/play?ts=4.1.0-pr-40336-88&ssl=25&ssc=78&pln=1&pc=1#code/FAFwngDgpgBACgQxACwJIFsIBsA8AVAGhgGkowYoAPEKAOwBMBnGAazIHsAzGPAPhgC8wGCTIVqdJjEYgATgEtaAc2EwA-DwDapMAF1xNBswBKUAMbtZ9HDIXKiCWmF6qRGgD4wABgBIA3joAvgB0-ogoGNj42mS6RACilGZYAK70UDhsYFxaOnGsHNyOYJq6vPwAZNJyikqBXq4iMJ6+AWQh-onJaRlZOXgxekR9RU6lldV2dQ1NMABcMLRQAG5QsqoLS6uyANzAoJCw4WiYWABM+PwC8EgnUYQF2dx8zY-9ewfQNyiXgt9351+VEMUlstVeIx46n+kUBLwWkLwH3AX2OADUEKkMg84AZJMxjpcrqpccD8d5-IpOGtRGAOn4qTTTDJ6qoNDo8UY3s9GhpmSBOVJCQM8i5Zm5-hisdE8kR+WLxZsVmtGkrtht4ILmIjeVo4LpVYtlbt9ulkghZLBOClaGYQPJ2LQYEooCB8ERSRIucLygAKdgAIwAVgsHhBbgs4ABKSO3KUpbEe3gfCy0GQwQNB8wC65+VSceSyGQAOQQ6CgCwARAAReRQJTsSsEVRYBAlssVmCVgASCAAXk3VAgXQsAMwABmbIggsnYWbtjAWmkafkWHarpgQLHkICbMFTNQDKRAlkXMAAbAAOGCBKdNVe0dddgDCjpkSCge4PCiPJ6LCwARjOG87wNQIYDbfc3xAD4XRAf1g2zIhKxnOdzErKMdiAA

type PathImpl<T, Key extends keyof T> = Key extends string
  ? T[Key] extends Record<string, unknown>
    ?
        | `${Key}.${PathImpl<T[Key], Exclude<keyof T[Key], keyof unknown[]>> &
            string}`
        | `${Key}.${Exclude<keyof T[Key], keyof unknown[]> & string}`
    : never
  : never

type PathImpl2<T> = PathImpl<T, keyof T> | keyof T

type Path<T> = PathImpl2<T> extends string | keyof T ? PathImpl2<T> : keyof T

type PathValue<T, P extends Path<T>> = P extends `${infer Key}.${infer Rest}`
  ? Key extends keyof T
    ? Rest extends Path<T[Key]>
      ? PathValue<T[Key], Rest>
      : never
    : never
  : P extends keyof T
  ? T[P]
  : never

type SetPathRequiredImpl1<T, P extends string> = P extends keyof T
  ? MarkRequired<T, P>
  : P extends `${infer A}.${infer B}`
  ? A extends keyof T
    ? Merge<
        MarkRequired<T, A>,
        {
          [K in A]: SetPathRequiredImpl1<MarkRequired<T, A>[K], B>
        }
      >
    : never
  : never

type SetPathRequired<
  T,
  P extends Path<DeepRequired<T>> & string
> = SetPathRequiredImpl1<T, P>

declare function set<
  T,
  P extends Path<DeepRequired<T>> & string,
  V extends PathValue<DeepRequired<T>, P>
>(obj: T, path: P, value: V): SetPathRequired<T, P>