# vue3-vnode简析
/packages/runtime-core/src/vnode.ts
vnode（虚拟dom）实际就是一个标识DOM的js对象，渲染时直接根据vnode生成页面。页面更新时，先diffvnode，确定实际需要更新的内容，可以减少对DOM操作数，提升性能
# createNode
type的类型: VNodeTypes | ClassComponent | typeof NULL_DYNAMIC_COMPONENT
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) type = Comment
if (isVNode(type)) {
// createVNode receiving an existing vnode. This happens in cases like <component :is="vnode"/>
// vnode类型直接clone
const cloned = cloneVNode(type, props, true /* mergeRef: true */)
if (children) { // 处理children???
normalizeChildren(cloned, children)
}
return cloned
}
// class component normalization.
if (isClassComponent(type)) type = type.__vccOpts
// 格式化 props/style/class
if (props) {
// for reactive or proxy objects, we need to clone it to enable mutation.
if (isProxy(props) || InternalObjectKey in props) {
props = extend({}, props)
}
let { class: klass, style } = props
if (klass && !isString(klass)) {
props.class = normalizeClass(klass)
}
if (isObject(style)) {
// reactive state objects need to be cloned since they are likely to be
// mutated
if (isProxy(style) && !isArray(style)) {
style = extend({}, style)
}
props.style = normalizeStyle(style)
}
}
// 获取vnode-type标识 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
// 设置vnode
const vnode: VNode = {
__v_isVNode: true,
[ReactiveFlags.SKIP]: true,
type,
props,
key: props && normalizeKey(props), // 获取props.key
ref: props && normalizeRef(props), // 获取props.ref
scopeId: currentScopeId,
slotScopeIds: null,
children: null,
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
}
// 处理children
normalizeChildren(vnode, children)
// normalize suspense children
if (__FEATURE_SUSPENSE__ && shapeFlag & ShapeFlags.SUSPENSE) {
const { content, fallback } = normalizeSuspenseChildren(vnode)
vnode.ssContent = content
vnode.ssFallback = fallback
}
// vnode添加到currentBlock
if (
shouldTrack > 0 &&
// avoid a block node from tracking itself
!isBlockNode &&
// has current parent block
currentBlock &&
// presence of a patch flag indicates this node needs patching on updates.
// component nodes also should always be patched, because even if the
// component doesn't need to update, it needs to persist the instance on to
// the next vnode so that it can be properly unmounted later.
(patchFlag > 0 || shapeFlag & ShapeFlags.COMPONENT) &&
// the EVENTS flag is only for hydration and if it is the only flag, the
// vnode should not be considered dynamic due to handler caching.
patchFlag !== PatchFlags.HYDRATE_EVENTS
) {
currentBlock.push(vnode) // parent block添加vnode
}
return vnode
}
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# normalizeChildren
处理children参数，设置vnode.hildren，并利用|运算符标识当前vnode包含的所有ShapeFlags类型
export function normalizeChildren(vnode: VNode, children: unknown) {
let type = 0
const { shapeFlag } = vnode
if (children == null) {
children = null
} else if (isArray(children)) {
type = ShapeFlags.ARRAY_CHILDREN
} else if (typeof children === 'object') {
// &运算 ELEMENT或者TELEPORT类型
if (shapeFlag & ShapeFlags.ELEMENT || shapeFlag & ShapeFlags.TELEPORT) {
// Normalize slot to plain children for plain element and Teleport
const slot = (children as any).default
if (slot) {
// _c marker is added by withCtx() indicating this is a compiled slot
slot._c && setCompiledSlotRendering(1)
normalizeChildren(vnode, slot()) // 本次未设置type，再次执行设置type
slot._c && setCompiledSlotRendering(-1)
}
return
} else {
type = ShapeFlags.SLOTS_CHILDREN
const slotFlag = (children as RawSlots)._
if (!slotFlag && !(InternalObjectKey in children!)) {
// if slots are not normalized, attach context instance
// (compiled / normalized slots already have context)
;(children as RawSlots)._ctx = currentRenderingInstance
} else if (slotFlag === SlotFlags.FORWARDED && currentRenderingInstance) {
// a child component receives forwarded slots from the parent.
// its slot type is determined by its parent's slot type.
if (
currentRenderingInstance.vnode.patchFlag & PatchFlags.DYNAMIC_SLOTS
) {
;(children as RawSlots)._ = SlotFlags.DYNAMIC
vnode.patchFlag |= PatchFlags.DYNAMIC_SLOTS
} else {
;(children as RawSlots)._ = SlotFlags.STABLE
}
}
}
} else if (isFunction(children)) {
children = { default: children, _ctx: currentRenderingInstance }
type = ShapeFlags.SLOTS_CHILDREN
} else {
children = String(children)
// force teleport children to array so it can be moved around
if (shapeFlag & ShapeFlags.TELEPORT) {
type = ShapeFlags.ARRAY_CHILDREN
children = [createTextVNode(children as string)]
} else {
type = ShapeFlags.TEXT_CHILDREN
}
}
vnode.children = children as VNodeNormalizedChildren
vnode.shapeFlag |= type
}
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# ShapeFlags
packages/shared/src/shapeFlags.ts
模拟9位二进制数据，标识vnode及其children包含的所有类型
export const enum ShapeFlags {
ELEMENT = 1,
FUNCTIONAL_COMPONENT = 1 << 1,
STATEFUL_COMPONENT = 1 << 2,
TEXT_CHILDREN = 1 << 3,
ARRAY_CHILDREN = 1 << 4,
SLOTS_CHILDREN = 1 << 5,
TELEPORT = 1 << 6,
SUSPENSE = 1 << 7,
COMPONENT_SHOULD_KEEP_ALIVE = 1 << 8,
COMPONENT_KEPT_ALIVE = 1 << 9,
COMPONENT = ShapeFlags.STATEFUL_COMPONENT | ShapeFlags.FUNCTIONAL_COMPONENT
}
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# cloneVnode
vnode的类型，直接clone
export function cloneVNode<T, U>(
vnode: VNode<T, U>,
extraProps?: Data & VNodeProps | null,
mergeRef = false
): VNode<T, U> {
// This is intentionally NOT using spread or extend to avoid the runtime
// key enumeration cost.
const { props, ref, patchFlag, children } = vnode
const mergedProps = extraProps ? mergeProps(props || {}, extraProps) : props
return {
__v_isVNode: true,
[ReactiveFlags.SKIP]: true,
type: vnode.type,
props: mergedProps,
key: mergedProps && normalizeKey(mergedProps),
ref:
extraProps && extraProps.ref
? // #2078 in the case of <component :is="vnode" ref="extra"/>
// if the vnode itself already has a ref, cloneVNode will need to merge
// the refs so the single vnode can be set on multiple refs
mergeRef && ref
? isArray(ref)
? ref.concat(normalizeRef(extraProps)!)
: [ref, normalizeRef(extraProps)!]
: normalizeRef(extraProps)
: ref,
scopeId: vnode.scopeId,
slotScopeIds: vnode.slotScopeIds,
children:
__DEV__ && patchFlag === PatchFlags.HOISTED && isArray(children)
? (children as VNode[]).map(deepCloneVNode)
: children,
target: vnode.target,
targetAnchor: vnode.targetAnchor,
staticCount: vnode.staticCount,
shapeFlag: vnode.shapeFlag,
// if the vnode is cloned with extra props, we can no longer assume its
// existing patch flag to be reliable and need to add the FULL_PROPS flag.
// note: perserve flag for fragments since they use the flag for children
// fast paths only.
patchFlag:
extraProps && vnode.type !== Fragment
? patchFlag === -1 // hoisted node
? PatchFlags.FULL_PROPS
: patchFlag | PatchFlags.FULL_PROPS
: patchFlag,
dynamicProps: vnode.dynamicProps,
dynamicChildren: vnode.dynamicChildren,
appContext: vnode.appContext,
dirs: vnode.dirs,
transition: vnode.transition,
// These should technically only be non-null on mounted VNodes. However,
// they *should* be copied for kept-alive vnodes. So we just always copy
// them since them being non-null during a mount doesn't affect the logic as
// they will simply be overwritten.
component: vnode.component,
suspense: vnode.suspense,
ssContent: vnode.ssContent && cloneVNode(vnode.ssContent),
ssFallback: vnode.ssFallback && cloneVNode(vnode.ssFallback),
el: vnode.el,
anchor: vnode.anchor
}
}
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# deepCloneVNode
__DEV__环境下处理vnode.children
function deepCloneVNode(vnode: VNode): VNode {
const cloned = cloneVNode(vnode)
if (isArray(vnode.children)) {
cloned.children = (vnode.children as VNode[]).map(deepCloneVNode)
}
return cloned
}
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