createWatchersForDependentFields.js

import Vue from 'vue'

export function createWatchersForDependentFields({
  dependentFields,
  form,
  vm
}) {
  return dependentFields.map(it => {
    console.log('watcher for', `form.${it.field}`)
    return vm.$watch(
      `form.${it.field}`,
      function() {
        it.dependents.forEach(({ field, resetValue }) => {
          if (!field.includes('.')) {
            Vue.set(form, field, resetValue())
          } else {
            let paths = field.split('.')
            let lastPath = paths.slice(-1)
            let initialPath = paths.slice(0, -1)
            Vue.set(form[initialPath], lastPath, resetValue())
          }
        })
      }      
    )
  })
}