export const getUser = (state, login) => state.entities.users[login]
export const getRepo = (state, fullName) => state.entities.repos[fullName]

import { getUser } from '../reducers/selectors'

// load user unless it is cached
function* loadUser(login, requiredFields) {
  const user = yield select(getUser, login)
  if (!user || requiredFields.some(key => !user.hasOwnProperty(key))) {
    yield call(fetchUser, login)
  }
}