vue/test/unit/modules/vdom/patch/hydration.spec.js

import Vue from 'vue'
import { patch } from 'web/runtime/patch'
import VNode from 'core/vdom/vnode'

describe('hydration', () => {
  let vnode0
  beforeEach(() => {
    vnode0 = new VNode('p', { attrs: { id: '1' }}, [createTextVNode('hello world')])
    patch(null, vnode0)
  })

  it('should hydrate elements when server-rendered DOM tree is same as virtual DOM tree', () => {
    const result = []
    function init (vnode) { result.push(vnode) }
    function createServerRenderedDOM () {
      const root = document.createElement('div')
      root.setAttribute('server-rendered', 'true')
      const span = document.createElement('span')
      root.appendChild(span)
      const div = document.createElement('div')
      const child1 = document.createElement('span')
      const child2 = document.createElement('span')
      child1.textContent = 'hi'
      child2.textContent = 'ho'
      div.appendChild(child1)
      div.appendChild(child2)
      root.appendChild(div)
      return root
    }
    const node0 = createServerRenderedDOM()
    const vnode1 = new VNode('div', {}, [
      new VNode('span', {}),
      new VNode('div', { hook: { init }}, [
        new VNode('span', {}, [new VNode(undefined, undefined, undefined, 'hi')]),
        new VNode('span', {}, [new VNode(undefined, undefined, undefined, 'ho')])
      ])
    ])
    patch(node0, vnode1)
    expect(result.length).toBe(1)

    function traverseAndAssert (vnode, element) {
      expect(vnode.elm).toBe(element)
      if (vnode.children) {
        vnode.children.forEach((node, i) => {
          traverseAndAssert(node, element.childNodes[i])
        })
      }
    }
    // ensure vnodes are correctly associated with actual DOM
    traverseAndAssert(vnode1, node0)

    // check update
    const vnode2 = new VNode('div', { props: { id: 'foo' }}, [
      new VNode('span', { props: { id: 'bar' }}),
      new VNode('div', { hook: { init }}, [
        new VNode('span', {}),
        new VNode('span', {})
      ])
    ])
    patch(vnode1, vnode2)
    expect(node0.id).toBe('foo')
    expect(node0.children[0].id).toBe('bar')
  })

  it('should warn message that virtual DOM tree is not matching when hydrate element', () => {
    function createServerRenderedDOM () {
      const root = document.createElement('div')
      root.setAttribute('server-rendered', 'true')
      const span = document.createElement('span')
      root.appendChild(span)
      const div = document.createElement('div')
      const child1 = document.createElement('span')
      div.appendChild(child1)
      root.appendChild(div)
      return root
    }
    const node0 = createServerRenderedDOM()
    const vnode1 = new VNode('div', {}, [
      new VNode('span', {}),
      new VNode('div', {}, [
        new VNode('span', {}),
        new VNode('span', {})
      ])
    ])
    patch(node0, vnode1)
    expect('The client-side rendered virtual DOM tree is not matching').toHaveBeenWarned()
  })

  // component hydration is better off with a more e2e approach
  it('should hydrate components when server-rendered DOM tree is same as virtual DOM tree', done => {
    const dom = document.createElement('div')
    dom.setAttribute('server-rendered', 'true')
    dom.innerHTML = '<span>foo</span><div class="b a"><span>foo qux</span></div>'
    const originalNode1 = dom.children[0]
    const originalNode2 = dom.children[1]

    const vm = new Vue({
      template: '<div><span>{{msg}}</span><test class="a" :msg="msg"></test></div>',
      data: {
        msg: 'foo'
      },
      components: {
        test: {
          props: ['msg'],
          data () {
            return { a: 'qux' }
          },
          template: '<div class="b"><span>{{msg}} {{a}}</span></div>'
        }
      }
    })

    expect(() => { vm.$mount(dom) }).not.toThrow()
    expect('not matching server-rendered content').not.toHaveBeenWarned()
    expect(vm.$el).toBe(dom)
    expect(vm.$children[0].$el).toBe(originalNode2)
    expect(vm.$el.children[0]).toBe(originalNode1)
    expect(vm.$el.children[1]).toBe(originalNode2)
    vm.msg = 'bar'
    waitForUpdate(() => {
      expect(vm.$el.innerHTML).toBe('<span>bar</span><div class="b a"><span>bar qux</span></div>')
      vm.$children[0].a = 'ququx'
    }).then(() => {
      expect(vm.$el.innerHTML).toBe('<span>bar</span><div class="b a"><span>bar ququx</span></div>')
    }).then(done)
  })

  it('should warn failed hydration for non-matching DOM in child component', () => {
    const dom = document.createElement('div')
    dom.setAttribute('server-rendered', 'true')
    dom.innerHTML = '<div><span>foo</span></div>'

    const vm = new Vue({
      template: '<div><test :msg="msg"></test></div>',
      components: {
        test: {
          data () {
            return { a: 'qux' }
          },
          template: '<div><span>{{a}}</span></div>'
        }
      }
    })

    vm.$mount(dom)
    expect('not matching server-rendered content').toHaveBeenWarned()
  })
})