AllPaths

allPaths.ts

// https://mobile.twitter.com/AndaristRake/status/1625130160277028864
// https://twitter.com/GabrielVergnaud/status/1623814585445675008?s=20&t=iG8sUzPLNZNgog-tAttHiw

type AllPaths<T> =
    // if `T` is an object with string keys
    T extends Record<string, unknown>
      // Assign the union `keyof T` to a variable `K`
      ? keyof T extends infer K
        // We distribute K.
        // For each member in `K`:
        ? K extends string
          // Concat `K` with the rest of the path
          ? K | `${K}.${AllPaths<T[K]>}`
          // unreachable branch (`K` is always a string)
          : never
        // unreachable branch (`extends infer` is always truthy)
        : never
      // if `T` isn't a record, we return the empty type
      : never;

type Result = AllPaths<{
  idle: unknown;
  loading: unknown;
  other: {
    awesome: {
      foo: unknown;
    };
  };
  yet: {
    another: {};
  };
}>;

type Display = Result;
//    ^?

// alternative

const hugeObj = { a0: { a1: { a2: { a3: { a4: { a5: { a6: { a7: { a8: { a9: { a10: { a11: { a12: { a13: { a14: { a15: { a16: { a17: { a18: { a19: { a20: { a21: { a22: { a23: { a24: { a25: { a26: { a27: { a28: { a29: { a30: { a31: { a32: { a33: { a34: { a35: { a36: { a37: { a38: { a39: { a40: { a41: { a42: { a43: { a44: { a45: { a46: { a47: { a48: { a49: { a50: { a51: { a52: { a53: { a54: { a55: { a56: { a57: { a58: { a59: { a60: { key: 'a' } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } } }

type JoinPath<
  A extends string,
  B extends string
> = [A] extends [never] ? B : [B] extends [never] ? A : `${A}.${B}`;

type AllPaths<T, Path extends string = never, R extends string = never> =
    T extends Record<string, unknown>
      ? keyof T extends infer K
        ? K extends string
          ? AllPaths<T[K], JoinPath<Path, K>,  R | JoinPath<Path, K>>
          : never
        : never
      : R;

type Result2 = AllPaths<typeof hugeObj>;

type Display2 = Result2;
//    ^?