vue3复习-源码-虚拟dom更新

例子

<script src="../../dist/vue.global.js"></script>  

<div id="demo"> 
  --{{val}}-- 
</div>

<script>
const app = Vue.createApp({ 
  setup() {
   const val = Vue.ref(0)
   setTimeout(() => {
    val.value = val.value + 1
   }, 5000);
    return {
      val, 
    }

  } 
}) 
app.mount('#demo') 
</script>

<style> 
</style>

执行的调用栈

主要是触发了setupRenderEffect的update方法，执行patch

vue3 数据更新流程

1. 根组件数据发生变化
2. 触发setupRenderEffect里面给根组件注册的effect的update方法
3. update走patch方法，更新当前组件与子树
4. 执行processComponent
5. 触发updateComponent 处理子节点
6. 最终调用patchElement处理最后的html元素
7. patchElement 也包含子节点更新和自身信息更新

虚拟dom结构

packages/runtime-core/src/vnode.ts

又开始俄罗斯套娃

createVNode -> _createVNode -> createBaseVNode

export const createVNode = (
  __DEV__ ? createVNodeWithArgsTransform : _createVNode
) as typeof _createVNode


function _createVNode(
  type: VNodeTypes | ClassComponent | typeof NULL_DYNAMIC_COMPONENT,
  props: (Data & VNodeProps) | null = null,
  children: unknown = null,
  patchFlag: number = 0,
  dynamicProps: string[] | null = null,
  isBlockNode = false,
): VNode { 

  return createBaseVNode(
    type,
    props,
    children,
    patchFlag,
    dynamicProps,
    shapeFlag,
    isBlockNode,
    true,
  )
}

function createBaseVNode(
  type: VNodeTypes | ClassComponent | typeof NULL_DYNAMIC_COMPONENT,
  props: (Data & VNodeProps) | null = null,
  children: unknown = null,
  patchFlag = 0,
  dynamicProps: string[] | null = null,
  shapeFlag = type === Fragment ? 0 : ShapeFlags.ELEMENT,
  isBlockNode = false,
  needFullChildrenNormalization = false,
) {
  const vnode = {
    __v_isVNode: true,
    __v_skip: true,
    type,
    props,
    key: props && normalizeKey(props),
    ref: props && normalizeRef(props),
    scopeId: currentScopeId,
    slotScopeIds: null,
    children,
    component: null,
    suspense: null,
    ssContent: null,
    ssFallback: null,
    dirs: null,
    transition: null,
    el: null,
    anchor: null,
    target: null,
    targetAnchor: null,
    staticCount: 0,
    shapeFlag,
    patchFlag,
    dynamicProps,
    dynamicChildren: null,
    appContext: null,
    ctx: currentRenderingInstance,
  } as VNode

  if (needFullChildrenNormalization) {
    normalizeChildren(vnode, children)
    // normalize suspense children
    if (__FEATURE_SUSPENSE__ && shapeFlag & ShapeFlags.SUSPENSE) {
      ;(type as typeof SuspenseImpl).normalize(vnode)
    }
  } else if (children) {
    // compiled element vnode - if children is passed, only possible types are
    // string or Array.
    vnode.shapeFlag |= isString(children)
      ? ShapeFlags.TEXT_CHILDREN
      : ShapeFlags.ARRAY_CHILDREN
  }
  

  return vnode
}

export { createBaseVNode as createElementVNode }

export const createVNode = (
  __DEV__ ? createVNodeWithArgsTransform : _createVNode
) as typeof _createVNode

function _createVNode(
  type: VNodeTypes | ClassComponent | typeof NULL_DYNAMIC_COMPONENT,
  props: (Data & VNodeProps) | null = null,
  children: unknown = null,
  patchFlag: number = 0,
  dynamicProps: string[] | null = null,
  isBlockNode = false,
): VNode {
  if (!type || type === NULL_DYNAMIC_COMPONENT) {
    if (__DEV__ && !type) {
      warn(`Invalid vnode type when creating vnode: ${type}.`)
    }
    type = Comment
  }

  if (isVNode(type)) { 
    const cloned = cloneVNode(type, props, true /* mergeRef: true */)
    if (children) {
      normalizeChildren(cloned, children)
    }
    if (isBlockTreeEnabled > 0 && !isBlockNode && currentBlock) {
      if (cloned.shapeFlag & ShapeFlags.COMPONENT) {
        currentBlock[currentBlock.indexOf(type)] = cloned
      } else {
        currentBlock.push(cloned)
      }
    }
    cloned.patchFlag = PatchFlags.BAIL
    return cloned
  }
 

  // encode the vnode type information into a bitmap
  const shapeFlag = isString(type)
    ? ShapeFlags.ELEMENT
    : __FEATURE_SUSPENSE__ && isSuspense(type)
      ? ShapeFlags.SUSPENSE
      : isTeleport(type)
        ? ShapeFlags.TELEPORT
        : isObject(type)
          ? ShapeFlags.STATEFUL_COMPONENT
          : isFunction(type)
            ? ShapeFlags.FUNCTIONAL_COMPONENT
            : 0

  if (__DEV__ && shapeFlag & ShapeFlags.STATEFUL_COMPONENT && isProxy(type)) {
    type = toRaw(type)
    warn(
      `Vue received a Component that was made a reactive object. This can ` +
        `lead to unnecessary performance overhead and should be avoided by ` +
        `marking the component with \`markRaw\` or using \`shallowRef\` ` +
        `instead of \`ref\`.`,
      `\nComponent that was made reactive: `,
      type,
    )
  }

  return createBaseVNode(
    type,
    props,
    children,
    patchFlag,
    dynamicProps,
    shapeFlag,
    isBlockNode,
    true,
  )
} 

/**
 * @private
 */
export function createTextVNode(text: string = ' ', flag: number = 0): VNode {
  return createVNode(Text, null, text, flag)
}

/**
 * @private
 */
export function createStaticVNode(
  content: string,
  numberOfNodes: number,
): VNode {
  // A static vnode can contain multiple stringified elements, and the number
  // of elements is necessary for hydration.
  const vnode = createVNode(Static, null, content)
  vnode.staticCount = numberOfNodes
  return vnode
}

/**
 * @private
 */
export function createCommentVNode(
  text: string = '',
  // when used as the v-else branch, the comment node must be created as a
  // block to ensure correct updates.
  asBlock: boolean = false,
): VNode {
  return asBlock
    ? (openBlock(), createBlock(Comment, null, text))
    : createVNode(Comment, null, text)
}

setupRenderEffect

1. 首次渲染走 patch( null, subTree,...)
2. 非首次走 更新自身+创建子树

• updateComponentPreRenderer 更新solt和属性
• renderComponentRoot 创建子树tree

  const setupRenderEffect: SetupRenderEffectFn = (
    instance,
    initialVNode,
    container,
    anchor,
    parentSuspense,
    namespace: ElementNamespace,
    optimized,
  ) => {
    const componentUpdateFn = () => {
      if (!instance.isMounted) {//首次渲染
        let vnodeHook: VNodeHook | null | undefined
        const { el, props } = initialVNode
        const { bm, m, parent } = instance
        const isAsyncWrapperVNode = isAsyncWrapper(initialVNode)
        if (el && hydrateNode) { 
 
        } else {
          //第一次走path
          patch(
            null,
            subTree,
            container,
            anchor,
            instance,
            parentSuspense,
            namespace,
          ) 
          initialVNode.el = subTree.el
        }
        
        instance.isMounted = true
 
      } else {
        let { next, bu, u, parent, vnode } = instance 
        // updateComponent
        // This is triggered by mutation of component's own state (next: null)
        // OR parent calling processComponent (next: VNode)
        let originNext = next
        let vnodeHook: VNodeHook | null | undefined

        // Disallow component effect recursion during pre-lifecycle hooks.
        toggleRecurse(instance, false)
        if (next) {
          next.el = vnode.el
          //更新组件信息
          updateComponentPreRender(instance, next, optimized)
        } else {
          next = vnode
        }

        // beforeUpdate hook
        if (bu) {
          invokeArrayFns(bu)
        }
        // onVnodeBeforeUpdate
        if ((vnodeHook = next.props && next.props.onVnodeBeforeUpdate)) {
          invokeVNodeHook(vnodeHook, parent, next, vnode)
        }
         
         
        //创建子树tree
        const nextTree = renderComponentRoot(instance) 
        const prevTree = instance.subTree
        instance.subTree = nextTree 
         
        //执行patch
        patch(
          prevTree,
          nextTree,
          // parent may have changed if it's in a teleport
          hostParentNode(prevTree.el!)!,
          // anchor may have changed if it's in a fragment
          getNextHostNode(prevTree),
          instance,
          parentSuspense,
          namespace,
        ) 
        next.el = nextTree.el
        
      }
    }

    // create reactive effect for rendering 
    const effect = (instance.effect = new ReactiveEffect(
      componentUpdateFn,
      NOOP,
      () => queueJob(update),
      instance.scope, // track it in component's effect scope
    ))

    const update: SchedulerJob = (instance.update = () => {
      if (effect.dirty) {
        effect.run()
      }
    })
    update.id = instance.uid
    update()
  }


  //更新组件solt和属性
  const updateComponentPreRender = (
    instance: ComponentInternalInstance,
    nextVNode: VNode,
    optimized: boolean,
  ) => {
    nextVNode.component = instance
    const prevProps = instance.vnode.props
    instance.vnode = nextVNode
    instance.next = null
    updateProps(instance, nextVNode.props, prevProps, optimized)
    updateSlots(instance, nextVNode.children, optimized)

    pauseTracking()
    // props update may have triggered pre-flush watchers.
    // flush them before the render update.
    flushPreFlushCbs(instance)
    resetTracking()
  }

patch

更新走processComponent

  // Note: functions inside this closure should use `const xxx = () => {}`
  // style in order to prevent being inlined by minifiers.
  const patch: PatchFn = (
    n1,
    n2,
    container,
    anchor = null,
    parentComponent = null,
    parentSuspense = null,
    namespace = undefined,
    slotScopeIds = null,
    optimized = __DEV__ && isHmrUpdating ? false : !!n2.dynamicChildren,
  ) => {
    if (n1 === n2) {
      return
    }

    // patching & not same type, unmount old tree
    if (n1 && !isSameVNodeType(n1, n2)) {
      anchor = getNextHostNode(n1)
      unmount(n1, parentComponent, parentSuspense, true)
      n1 = null
    }

    if (n2.patchFlag === PatchFlags.BAIL) {
      optimized = false
      n2.dynamicChildren = null
    }

    const { type, ref, shapeFlag } = n2
    switch (type) {
      case Text:
        processText(n1, n2, container, anchor)
        break
      case Comment:
        processCommentNode(n1, n2, container, anchor)
        break
      case Static:
        if (n1 == null) {
          mountStaticNode(n2, container, anchor, namespace)
        } else if (__DEV__) {
          patchStaticNode(n1, n2, container, namespace)
        }
        break
      case Fragment:
        processFragment(
          n1,
          n2,
          container,
          anchor,
          parentComponent,
          parentSuspense,
          namespace,
          slotScopeIds,
          optimized,
        )
        break
      default:
        if (shapeFlag & ShapeFlags.ELEMENT) {
          processElement(
            n1,
            n2,
            container,
            anchor,
            parentComponent,
            parentSuspense,
            namespace,
            slotScopeIds,
            optimized,
          )
        } else if (shapeFlag & ShapeFlags.COMPONENT) {
          processComponent(
            n1,
            n2,
            container,
            anchor,
            parentComponent,
            parentSuspense,
            namespace,
            slotScopeIds,
            optimized,
          )
        } else if (shapeFlag & ShapeFlags.TELEPORT) {
          ;(type as typeof TeleportImpl).process(
            n1 as TeleportVNode,
            n2 as TeleportVNode,
            container,
            anchor,
            parentComponent,
            parentSuspense,
            namespace,
            slotScopeIds,
            optimized,
            internals,
          )
        } else if (__FEATURE_SUSPENSE__ && shapeFlag & ShapeFlags.SUSPENSE) {
          ;(type as typeof SuspenseImpl).process(
            n1,
            n2,
            container,
            anchor,
            parentComponent,
            parentSuspense,
            namespace,
            slotScopeIds,
            optimized,
            internals,
          )
        } else if (__DEV__) {
          warn('Invalid VNode type:', type, `(${typeof type})`)
        }
    }

    // set ref
    if (ref != null && parentComponent) {
      setRef(ref, n1 && n1.ref, parentSuspense, n2 || n1, !n2)
    }
  }

processComponent

更新走 updateComponent

  const processComponent = (
    n1: VNode | null,
    n2: VNode,
    container: RendererElement,
    anchor: RendererNode | null,
    parentComponent: ComponentInternalInstance | null,
    parentSuspense: SuspenseBoundary | null,
    namespace: ElementNamespace,
    slotScopeIds: string[] | null,
    optimized: boolean,
  ) => {
    n2.slotScopeIds = slotScopeIds
    if (n1 == null) {
      if (n2.shapeFlag & ShapeFlags.COMPONENT_KEPT_ALIVE) {
        ;(parentComponent!.ctx as KeepAliveContext).activate(
          n2,
          container,
          anchor,
          namespace,
          optimized,
        )
      } else {
        mountComponent(
          n2,
          container,
          anchor,
          parentComponent,
          parentSuspense,
          namespace,
          optimized,
        )
      }
    } else {
      updateComponent(n1, n2, optimized)
    }
  }

updateComponent

主要调用的了update方法

shouldUpdateComponent判断是否需要更新，instance.update()执行update，又再进入setupRenderEffect的patch 子树，一直递归到处理html的内容

  const updateComponent = (n1: VNode, n2: VNode, optimized: boolean) => {
    const instance = (n2.component = n1.component)!
    if (shouldUpdateComponent(n1, n2, optimized)) { 
        // normal update
        instance.next = n2
        // in case the child component is also queued, remove it to avoid
        // double updating the same child component in the same flush.
        invalidateJob(instance.update)
        // instance.update is the reactive effect.
        instance.effect.dirty = true
        // 还是重新执行的update方法
        instance.update() 
    } else {
      // no update needed. just copy over properties
      n2.el = n1.el
      instance.vnode = n2
    }
  }

patchElement

处理两种情况

1. 子节点更新
2. 节点自身更新

  const patchElement = (
    n1: VNode,
    n2: VNode,
    parentComponent: ComponentInternalInstance | null,
    parentSuspense: SuspenseBoundary | null,
    namespace: ElementNamespace,
    slotScopeIds: string[] | null,
    optimized: boolean,
  ) => {
    const el = (n2.el = n1.el!) 
    let { patchFlag, dynamicChildren, dirs } = n2
    // #1426 take the old vnode's patch flag into account since user may clone a
    // compiler-generated vnode, which de-opts to FULL_PROPS
    patchFlag |= n1.patchFlag & PatchFlags.FULL_PROPS
    const oldProps = n1.props || EMPTY_OBJ
    const newProps = n2.props || EMPTY_OBJ
    let vnodeHook: VNodeHook | undefined | null

    // disable recurse in beforeUpdate hooks
    parentComponent && toggleRecurse(parentComponent, false)
    if ((vnodeHook = newProps.onVnodeBeforeUpdate)) {
      invokeVNodeHook(vnodeHook, parentComponent, n2, n1)
    }
    if (dirs) {
      invokeDirectiveHook(n2, n1, parentComponent, 'beforeUpdate')
    }
    parentComponent && toggleRecurse(parentComponent, true)
 
    if (dynamicChildren) {
      patchBlockChildren(
        n1.dynamicChildren!,
        dynamicChildren,
        el,
        parentComponent,
        parentSuspense,
        resolveChildrenNamespace(n2, namespace),
        slotScopeIds,
      ) 
    } else if (!optimized) {
      // full diff
      patchChildren(
        n1,
        n2,
        el,
        null,
        parentComponent,
        parentSuspense,
        resolveChildrenNamespace(n2, namespace),
        slotScopeIds,
        false,
      )
    }

    if (patchFlag > 0) {
      if (patchFlag & PatchFlags.FULL_PROPS) {
        // element props contain dynamic keys, full diff needed
        patchProps(
          el,
          n2,
          oldProps,
          newProps,
          parentComponent,
          parentSuspense,
          namespace,
        )
      } else {
        // class
        // this flag is matched when the element has dynamic class bindings.
        if (patchFlag & PatchFlags.CLASS) {
          if (oldProps.class !== newProps.class) {
            hostPatchProp(el, 'class', null, newProps.class, namespace)
          }
        }

        // style
        // this flag is matched when the element has dynamic style bindings
        if (patchFlag & PatchFlags.STYLE) {
          hostPatchProp(el, 'style', oldProps.style, newProps.style, namespace)
        }

        if (patchFlag & PatchFlags.PROPS) {
          // if the flag is present then dynamicProps must be non-null
          const propsToUpdate = n2.dynamicProps!
          for (let i = 0; i < propsToUpdate.length; i++) {
            const key = propsToUpdate[i]
            const prev = oldProps[key]
            const next = newProps[key]
            // #1471 force patch value
            if (next !== prev || key === 'value') {
              hostPatchProp(
                el,
                key,
                prev,
                next,
                namespace,
                n1.children as VNode[],
                parentComponent,
                parentSuspense,
                unmountChildren,
              )
            }
          }
        }
      }

      // text
      // This flag is matched when the element has only dynamic text children.
      if (patchFlag & PatchFlags.TEXT) {
        if (n1.children !== n2.children) {
          hostSetElementText(el, n2.children as string)
        }
      }
    } else if (!optimized && dynamicChildren == null) {
      // unoptimized, full diff
      patchProps(
        el,
        n2,
        oldProps,
        newProps,
        parentComponent,
        parentSuspense,
        namespace,
      )
    }

    if ((vnodeHook = newProps.onVnodeUpdated) || dirs) {
      queuePostRenderEffect(() => {
        vnodeHook && invokeVNodeHook(vnodeHook, parentComponent, n2, n1)
        dirs && invokeDirectiveHook(n2, n1, parentComponent, 'updated')
      }, parentSuspense)
    }
  }

子节点更新

先处理子节点

    // full diff
      patchChildren(
        n1,
        n2,
        el,
        null,
        parentComponent,
        parentSuspense,
        resolveChildrenNamespace(n2, namespace),
        slotScopeIds,
        false,
      )

新老子元素对比：

三个状态

• 文本
• 数组
• 空

交叉9种情况

最复杂就是新老都是数组。

如果有标记key 使用patchKeyedChildren，没有则使用patchUnkeyedChildren

  const patchChildren: PatchChildrenFn = (
    n1,
    n2,
    container,
    anchor,
    parentComponent,
    parentSuspense,
    namespace: ElementNamespace,
    slotScopeIds,
    optimized = false,
  ) => {
    const c1 = n1 && n1.children
    const prevShapeFlag = n1 ? n1.shapeFlag : 0
    const c2 = n2.children

    const { patchFlag, shapeFlag } = n2
    // fast path
    if (patchFlag > 0) {
      if (patchFlag & PatchFlags.KEYED_FRAGMENT) {
        // this could be either fully-keyed or mixed (some keyed some not)
        // presence of patchFlag means children are guaranteed to be arrays
        patchKeyedChildren(
          c1 as VNode[],
          c2 as VNodeArrayChildren,
          container,
          anchor,
          parentComponent,
          parentSuspense,
          namespace,
          slotScopeIds,
          optimized,
        )
        return
      } else if (patchFlag & PatchFlags.UNKEYED_FRAGMENT) {
        // unkeyed
        patchUnkeyedChildren(
          c1 as VNode[],
          c2 as VNodeArrayChildren,
          container,
          anchor,
          parentComponent,
          parentSuspense,
          namespace,
          slotScopeIds,
          optimized,
        )
        return
      }
    }

    // children has 3 possibilities: text, array or no children.
    if (shapeFlag & ShapeFlags.TEXT_CHILDREN) {
      // text children fast path
      if (prevShapeFlag & ShapeFlags.ARRAY_CHILDREN) {
        unmountChildren(c1 as VNode[], parentComponent, parentSuspense)
      }
      if (c2 !== c1) {
        hostSetElementText(container, c2 as string)
      }
    } else {
      if (prevShapeFlag & ShapeFlags.ARRAY_CHILDREN) {
        // prev children was array
        if (shapeFlag & ShapeFlags.ARRAY_CHILDREN) {
          // two arrays, cannot assume anything, do full diff
          patchKeyedChildren(
            c1 as VNode[],
            c2 as VNodeArrayChildren,
            container,
            anchor,
            parentComponent,
            parentSuspense,
            namespace,
            slotScopeIds,
            optimized,
          )
        } else {
          // no new children, just unmount old
          unmountChildren(c1 as VNode[], parentComponent, parentSuspense, true)
        }
      } else {
        // prev children was text OR null
        // new children is array OR null
        if (prevShapeFlag & ShapeFlags.TEXT_CHILDREN) {
          hostSetElementText(container, '')
        }
        // mount new if array
        if (shapeFlag & ShapeFlags.ARRAY_CHILDREN) {
          mountChildren(
            c2 as VNodeArrayChildren,
            container,
            anchor,
            parentComponent,
            parentSuspense,
            namespace,
            slotScopeIds,
            optimized,
          )
        }
      }
    }
  }

节点自身更新

  const patchElement = (
    n1: VNode,
    n2: VNode,
    parentComponent: ComponentInternalInstance | null,
    parentSuspense: SuspenseBoundary | null,
    namespace: ElementNamespace,
    slotScopeIds: string[] | null,
    optimized: boolean,
  ) => {
    const el = (n2.el = n1.el!) 
    let { patchFlag, dynamicChildren, dirs } = n2
  
 
    if (dynamicChildren) {
      patchBlockChildren(
        n1.dynamicChildren!,
        dynamicChildren,
        el,
        parentComponent,
        parentSuspense,
        resolveChildrenNamespace(n2, namespace),
        slotScopeIds,
      ) 
    } else if (!optimized) {
      // full diff
      patchChildren(
        n1,
        n2,
        el,
        null,
        parentComponent,
        parentSuspense,
        resolveChildrenNamespace(n2, namespace),
        slotScopeIds,
        false,
      )
    }
    // 这里开始处理自身的属性比较
    if (patchFlag > 0) {
      if (patchFlag & PatchFlags.FULL_PROPS) {
        // element props contain dynamic keys, full diff needed
        patchProps(
          el,
          n2,
          oldProps,
          newProps,
          parentComponent,
          parentSuspense,
          namespace,
        )
      } else { 
        if (patchFlag & PatchFlags.CLASS) {//class修改
          if (oldProps.class !== newProps.class) {
            hostPatchProp(el, 'class', null, newProps.class, namespace)
          }
        } 
        if (patchFlag & PatchFlags.STYLE) {//style修改
          hostPatchProp(el, 'style', oldProps.style, newProps.style, namespace)
        }

        if (patchFlag & PatchFlags.PROPS) {//porps属性修改
          // if the flag is present then dynamicProps must be non-null
          const propsToUpdate = n2.dynamicProps!
          for (let i = 0; i < propsToUpdate.length; i++) {
            const key = propsToUpdate[i]
            const prev = oldProps[key]
            const next = newProps[key]
            // #1471 force patch value
            if (next !== prev || key === 'value') {
              hostPatchProp(
                el,
                key,
                prev,
                next,
                namespace,
                n1.children as VNode[],
                parentComponent,
                parentSuspense,
                unmountChildren,
              )
            }
          }
        }
      }

      // text
      // This flag is matched when the element has only dynamic text children.
      if (patchFlag & PatchFlags.TEXT) {
        if (n1.children !== n2.children) {
          hostSetElementText(el, n2.children as string)
        }
      }
    } else if (!optimized && dynamicChildren == null) {
      // unoptimized, full diff
      patchProps(
        el,
        n2,
        oldProps,
        newProps,
        parentComponent,
        parentSuspense,
        namespace,
      )
    }

    if ((vnodeHook = newProps.onVnodeUpdated) || dirs) {
      queuePostRenderEffect(() => {
        vnodeHook && invokeVNodeHook(vnodeHook, parentComponent, n2, n1)
        dirs && invokeDirectiveHook(n2, n1, parentComponent, 'updated')
      }, parentSuspense)
    }
  }

参考

玩转vue3