Bad use of reselect

[guillaumearm]

Hi redpelicans team.
Recently, i worked with reselect, and I noticed that we use wrong

An example :

export const viewPersonSelector = createSelector(
  personId,
  companies,
  persons,
  missions,
  pendingRequests,
  (personId, companies, persons, missions, pendingRequests) => {
    return {
      person: persons.get(personId),
      company: personId ? companies.get(persons.get(personId).get('companyId')) : null,
      missions: missions.filter(getFilterMissionsById(personId)),
      companies: companies,
      persons: persons,
      isLoading: !!pendingRequests
    }
  }
)

Here, when a change occurs on pendingRequests, missions are filtered again.
The solution is to make lots of small selectors and compsoe them together.

// No need to memoize selectors that compute nothing
const getPersonId = state => state.routing.location && state.routing.location.state && state.routing.location.state.personId
const getIsLoading = state => !!state.pendingRequests
const getMissions = state => state.missions.data

// Here, missions are filtered only when 'missions.data' or 'personId' are updated.
const getFilteredMissions => createSelector(
  getMissions,
  getPersonId,
  (missions, personId) => missions.filter(getFilterMissionsById(personId))
)

const viewPersonSelector = createSelector(
  getIsLoading,
  getFilteredMissions,
  (isLoading, missions) => ({
    isLoading,
    missions,
    // etc...
  })
)