Typescript Redux selector wrapper, useful for keeping selector logic within its own state module

_wrapSelector.ts

type Selector<State, R = any> = (state: State) => R

// TODO:
// Preferred call signature:
// ```
// wrapSelector<S>(fn, key)
// ```
// But currently not possible due to "all-or-nothing" type arguments:
// https://github.com/Microsoft/TypeScript/issues/10571
export const wrapSelector = <S, SS extends Selector<S[keyof S]>>(
  selector: SS,
  key: keyof S,
) => {
  return (s: S) => selector(s[key])
}

export const wrapSelectors = <S, SS extends {[k: string]: Selector<S[keyof S]>}>(selectors: SS, key: keyof S) => {
  return Object.keys(selectors).reduce<{[P in keyof typeof selectors]: Selector<S, ReturnType<(typeof selectors)[P]>>}>((wrappedSelectors: any, skey) => {
    const selector = selectors[skey]
    const wrappedSelector = wrapSelector<S, typeof selector>(selector, key)
    return {
      ...wrappedSelectors,
      [skey]: wrappedSelector,
    }
  }, {} as any)
}

hogwarts.ts

export type State = {
  harry: string,
}

const selectHarry = (s: State) => s.harry
export const selectors = {
  selectHarry,
}

store.ts

import {State as HogwartsState, selectors as hogwartsSelectors} from './hogwarts'
import {wrapSelectors} from './_wrapSelector'

type State = {
  hoggos: HogwartsState,
}
const selectors = {
  ...wrapSelectors(hogwartsSelectors, 'hoggos'),
}