reducer.js

import { ACTION_TYPES } from '../actions/branchActions';
const {
  NEAREST_BRANCH_SUCCESS,
  NEAREST_BRANCH_REQUEST,
  NEAREST_BRANCH_FAILURE
} = ACTION_TYPES;

export const INITIAL_STATE = { searching: false, nearestBranch: null };

export default (state = INITIAL_STATE, action) => {
  let reducer;
  console.log(action.type);
  switch (action.type) {
    case NEAREST_BRANCH_REQUEST:
      reducer = nearestBranchRequest;

    case NEAREST_BRANCH_SUCCESS:
      reducer = nearestBranchSuccess;

    case NEAREST_BRANCH_FAILURE:
      reducer = nearestBranchFailure;

    default:
      reducer = (state, action) => state;
  }

  return reducer(state, action);
};

export const nearestBranchRequest = (
  state,
  { payload: { latitude, longitude } }
) => {
  return {
    ...state,
    latitude,
    longitude,
    searching: true
  };
};

export const nearestBranchSuccess = (state, { payload: { nearestBranch } }) => {
  return {
    ...state,
    nearestBranch: nearestBranch,
    searching: false
  };
};

export const nearestBranchFailure = (state, action) => {
  return {
    ...state,
    searching: false
  };
};

j'imagine que tu dépasse 80 char ou whatever la limite acceptable dans tes réglages de linter... just curious!