getComponents.js

import { mapAsync } from './AsyncUtils'
import { canUseMembrane } from './deprecateObjectProperties'
import warning from './routerWarning'

function getComponentsForRoute(nextState, route, callback) {
  if (route.component || route.components) {
    callback(null, route.component || route.components)
    return
  }

  const getComponent = route.getComponent || route.getComponents
  if (!getComponent) {
    callback()
    return
  }

  const { location } = nextState
  let nextStateWithLocation

  if (__DEV__ && canUseMembrane) {
    nextStateWithLocation = { ...nextState }

    // I don't use deprecateObjectProperties here because I want to keep the
    // same code path between development and production, in that we just
    // assign extra properties to the copy of the state object in both cases.
    for (const prop in location) {
      if (!Object.prototype.hasOwnProperty.call(location, prop)) {
        continue
      }

      Object.defineProperty(nextStateWithLocation, prop, {
        get() {
          warning(false, 'Accessing location properties from the first argument to `getComponent` and `getComponents` is deprecated. That argument is now the router state (`nextState`) rather than the location. To access the location, use `nextState.location`.')
          return location[prop]
        }
      })
    }
  } else {
    nextStateWithLocation = { ...nextState, ...location }
  }

  getComponent.call(route, nextStateWithLocation, callback)
}

/**
 * Asynchronously fetches all components needed for the given router
 * state and calls callback(error, components) when finished.
 *
 * Note: This operation may finish synchronously if no routes have an
 * asynchronous getComponents method.
 */
function getComponents(nextState, callback) {
  mapAsync(nextState.routes, function (route, index, callback) {
    getComponentsForRoute(nextState, route, callback)
  }, callback)
}

export default getComponents