https://blog.boopathi.in/typescript-typing-object-paths/

typescript-typing-object-paths.ts

type ObjectPathNormalize = T extends Array<infer U>
  ? U extends object
    ? Required<U>
    : never
  : T extends object
  ? Required<T>
  : never;

type Normalize<T> = ObjectPathNormalize<T>;
type Normalize1<T, Key1 extends keyof Normalize<T>> = ObjectPathNormalize<
  Normalize<T>[Key1]
>;
type Normalize2<
  T,
  Key1 extends keyof Normalize<T>,
  Key2 extends keyof Normalize1<T, Key1>
> = ObjectPathNormalize<Normalize1<T, Key1>[Key2]>;
type Normalize3<
  T,
  Key1 extends keyof Normalize<T>,
  Key2 extends keyof Normalize1<T, Key1>,
  Key3 extends keyof Normalize2<T, Key1, Key2>
> = ObjectPathNormalize<Normalize2<T, Key1, Key2>[Key3]>;

function createObjectPath<T>(_: T) {
  return function field<
    Key1 extends keyof Normalize<T>,
    Key2 extends keyof Normalize1<T, Key1>,
    Key3 extends keyof Normalize2<T, Key1, Key2>,
    Key4 extends keyof Normalize3<T, Key1, Key2, Key3>
  >(k1: Key1, k2?: Key2, k3?: Key3, k4?: Key4) {
    if (k2) {
      if (k3) {
        if (k4) {
          return [k1, k2, k3, k4];
        }
        return [k1, k2, k3];
      }
      return [k1, k2];
    }
    return [k1];
  };
}