patch-render.js

import { createStubFromComponent } from './create-component-stubs'
import { resolveComponent, semVerGreaterThan } from 'shared/util'
import { isReservedTag } from 'shared/validators'
import { addHook } from './add-hook'
import Vue from 'vue'

const isWhitelisted = (el, whitelist) => resolveComponent(el, whitelist)
const isAlreadyStubbed = (el, stubs) => stubs.has(el)
const isDynamicComponent = cmp => typeof cmp === 'function' && !cmp.cid

const CREATE_ELEMENT_ALIAS = semVerGreaterThan(Vue.version, '2.1.5')
  ? '_c'
  : '_h'
const LIFECYCLE_HOOK = semVerGreaterThan(Vue.version, '2.1.8')
  ? 'beforeCreate'
  : 'beforeMount'

function shouldExtend (component, _Vue) {
  return (
    (typeof component === 'function' && !isDynamicComponent(component)) ||
    (component && component.extends)
  )
}

function extend (component, _Vue) {
  const stub = _Vue.extend(component.options)
  stub.options.$_vueTestUtils_original = component
  return stub
}

function createStubIfNeeded (shouldStub, component, _Vue, el) {
  if (shouldStub) {
    return createStubFromComponent(component || {}, el)
  }

  if (shouldExtend(component, _Vue)) {
    return extend(component, _Vue)
  }
}

function shouldNotBeStubbed (el, whitelist, modifiedComponents) {
  return (
    (typeof el === 'string' && isReservedTag(el)) ||
    isWhitelisted(el, whitelist) ||
    isAlreadyStubbed(el, modifiedComponents)
  )
}

function isConstructor (el) {
  return typeof el === 'function'
}

export function patchRender (_Vue, stubs, stubAllComponents) {
  // This mixin patches vm.$createElement so that we can stub all components
  // before they are rendered in shallow mode. We also need to ensure that
  // component constructors were created from the _Vue constructor. If not,
  // we must replace them with components created from the _Vue constructor
  // before calling the original $createElement. This ensures that components
  // have the correct instance properties and stubs when they are rendered.
  function patchRenderMixin () {
    const vm = this

    if (vm.$options.$_doNotStubChildren || vm._isFunctionalContainer) {
      return
    }

    const modifiedComponents = new Set()
    const originalCreateElement = vm.$createElement
    const originalComponents = vm.$options.components

    const createElement = (el, ...args) => {
      if (shouldNotBeStubbed(el, stubs, modifiedComponents)) {
        return originalCreateElement(el, ...args)
      }

      if (isConstructor(el)) {
        if (stubAllComponents) {
          const stub = createStubFromComponent(el, el.name || 'anonymous')
          return originalCreateElement(stub, ...args)
        }

        const Constructor = shouldExtend(el, _Vue) ? extend(el, _Vue) : el

        return originalCreateElement(Constructor, ...args)
      }

      if (typeof el === 'string') {
        let original = resolveComponent(el, originalComponents)

        if (!original) {
          return originalCreateElement(el, ...args)
        }

        if (
          original.options &&
          original.options.$_vueTestUtils_original
        ) {
          original = original.options.$_vueTestUtils_original
        }

        if (isDynamicComponent(original)) {
          return originalCreateElement(el, ...args)
        }

        const stub = createStubIfNeeded(stubAllComponents, original, _Vue, el)

        if (stub) {
          vm.$options.components = {
            ...vm.$options.components,
            [el]: stub
          }
          modifiedComponents.add(el)
        }
      }

      return originalCreateElement(el, ...args)
    }

    vm[CREATE_ELEMENT_ALIAS] = createElement
    vm.$createElement = createElement
  }

  addHook(_Vue.options, LIFECYCLE_HOOK, patchRenderMixin)
}