NestedPartal.ts

NestedPartial.ts

type Primitive = string | number | boolean | undefined | null

type UnionToIntersection<U> = (
  U extends unknown ? (k: U) => void : never
) extends (k: infer I) => void
  ? I
  : never

type AddPrefixToKeys<
  Prefix extends string,
  T extends Record<string, unknown>
> = {
  [K in keyof T & string as `${Prefix}.${K}`]+?: T[K]
}

type NestedUpdateFields<T extends Record<string, unknown>> =
  UnionToIntersection<
    {
      [K in keyof T & string]: ChildUpdateFields<K, T[K]>
    }[keyof T & string]
  >

type ChildUpdateFields<K extends string, V> = V extends Record<string, unknown>
  ? AddPrefixToKeys<K, NestedPartial<V>>
  : never

export type NestedPartial<T> = T extends Primitive
  ? T
  : T extends {}
  ? { [K in keyof T]?: NestedPartial<T[K]> } & NestedUpdateFields<T>
  : never