merge-option.js

var _ = require('./index')
var extend = _.extend

/**
 * Option overwriting strategies are functions that handle
 * how to merge a parent option value and a child option
 * value into the final value.
 *
 * All strategy functions follow the same signature:
 *
 * @param {*} parentVal
 * @param {*} childVal
 * @param {Vue} [vm]
 */

var strats = Object.create(null)

/**
 * Helper that recursively merges two data objects together.
 */

function mergeData (to, from) {
  var key, toVal, fromVal
  for (key in from) {
    toVal = to[key]
    fromVal = from[key]
    if (!to.hasOwnProperty(key)) {
      to.$add(key, fromVal)
    } else if (_.isObject(toVal) && _.isObject(fromVal)) {
      mergeData(toVal, fromVal)
    }
  }
  return to
}

/**
 * Data
 */

strats.data = function (parentVal, childVal, vm) {
  if (!vm) {
    // in a Vue.extend merge, both should be functions
    if (!childVal) {
      return parentVal
    }
    if (typeof childVal !== 'function') {
      _.warn(
        'The "data" option should be a function ' +
        'that returns a per-instance value in component ' +
        'definitions.'
      )
      return parentVal
    }
    if (!parentVal) {
      return childVal
    }
    // when parentVal & childVal are both present,
    // we need to return a function that returns the
    // merged result of both functions... no need to
    // check if parentVal is a function here because
    // it has to be a function to pass previous merges.
    return function mergedDataFn () {
      return mergeData(
        childVal.call(this),
        parentVal.call(this)
      )
    }
  } else {
    // instance merge, return raw object
    var instanceData = typeof childVal === 'function'
      ? childVal.call(vm)
      : childVal
    var defaultData = typeof parentVal === 'function'
      ? parentVal.call(vm)
      : undefined
    if (instanceData) {
      return mergeData(instanceData, defaultData)
    } else {
      return defaultData
    }
  }
}

/**
 * El
 */

strats.el = function (parentVal, childVal, vm) {
  if (!vm && childVal && typeof childVal !== 'function') {
    _.warn(
      'The "el" option should be a function ' +
      'that returns a per-instance value in component ' +
      'definitions.'
    )
    return
  }
  var ret = childVal || parentVal
  // invoke the element factory if this is instance merge
  return vm && typeof ret === 'function'
    ? ret.call(vm)
    : ret
}

/**
 * Hooks and param attributes are merged as arrays.
 */

strats.created =
strats.ready =
strats.attached =
strats.detached =
strats.beforeCompile =
strats.compiled =
strats.beforeDestroy =
strats.destroyed =
strats.props = function (parentVal, childVal) {
  return childVal
    ? parentVal
      ? parentVal.concat(childVal)
      : _.isArray(childVal)
        ? childVal
        : [childVal]
    : parentVal
}

/**
 * Assets
 *
 * When a vm is present (instance creation), we need to do
 * a three-way merge between constructor options, instance
 * options and parent options.
 */

strats.directives =
strats.filters =
strats.transitions =
strats.components =
strats.elementDirectives = function (parentVal, childVal, vm, key) {
  var ret = Object.create(
    vm && vm.$parent
      ? vm.$parent.$options[key]
      : _.Vue.options[key]
  )
  if (parentVal) {
    var keys = Object.keys(parentVal)
    var i = keys.length
    var field
    while (i--) {
      field = keys[i]
      ret[field] = parentVal[field]
    }
  }
  if (childVal) extend(ret, childVal)
  return ret
}

/**
 * Events & Watchers.
 *
 * Events & watchers hashes should not overwrite one
 * another, so we merge them as arrays.
 */

strats.watch =
strats.events = function (parentVal, childVal) {
  if (!childVal) return parentVal
  if (!parentVal) return childVal
  var ret = {}
  extend(ret, parentVal)
  for (var key in childVal) {
    var parent = ret[key]
    var child = childVal[key]
    if (parent && !_.isArray(parent)) {
      parent = [parent]
    }
    ret[key] = parent
      ? parent.concat(child)
      : [child]
  }
  return ret
}

/**
 * Other object hashes.
 */

strats.methods =
strats.computed = function (parentVal, childVal) {
  if (!childVal) return parentVal
  if (!parentVal) return childVal
  var ret = Object.create(parentVal)
  extend(ret, childVal)
  return ret
}

/**
 * Default strategy.
 */

var defaultStrat = function (parentVal, childVal) {
  return childVal === undefined
    ? parentVal
    : childVal
}

/**
 * Make sure component options get converted to actual
 * constructors.
 *
 * @param {Object} components
 */

function guardComponents (components) {
  if (components) {
    var def
    for (var key in components) {
      def = components[key]
      if (_.isPlainObject(def)) {
        def.name = key
        components[key] = _.Vue.extend(def)
      }
    }
  }
}

/**
 * Merge two option objects into a new one.
 * Core utility used in both instantiation and inheritance.
 *
 * @param {Object} parent
 * @param {Object} child
 * @param {Vue} [vm] - if vm is present, indicates this is
 *                     an instantiation merge.
 */

module.exports = function mergeOptions (parent, child, vm) {
  guardComponents(child.components)
  var options = {}
  var key
  if (child.mixins) {
    for (var i = 0, l = child.mixins.length; i < l; i++) {
      parent = mergeOptions(parent, child.mixins[i], vm)
    }
  }
  for (key in parent) {
    merge(key)
  }
  for (key in child) {
    if (!(parent.hasOwnProperty(key))) {
      merge(key)
    }
  }
  function merge (key) {
    var strat = strats[key] || defaultStrat
    options[key] = strat(parent[key], child[key], vm, key)
  }
  return options
}