Function resolveTransitionHooks

packages/runtime-core/src/components/BaseTransition.ts:332–495

(
  vnode: VNode,
  props: BaseTransitionProps<any>,
  state: TransitionState,
  instance: ComponentInternalInstance,
  postClone?: (hooks: TransitionHooks) => void,
)

// The transition hooks are attached to the vnode as vnode.transition
// and will be called at appropriate timing in the renderer.
export function resolveTransitionHooks(
  vnode: VNode,
  props: BaseTransitionProps<any>,
  state: TransitionState,
  instance: ComponentInternalInstance,
  postClone?: (hooks: TransitionHooks) => void,
): TransitionHooks {
  const {
    appear,
    mode,
    persisted = false,
    onBeforeEnter,
    onEnter,
    onAfterEnter,
    onEnterCancelled,
    onBeforeLeave,
    onLeave,
    onAfterLeave,
    onLeaveCancelled,
    onBeforeAppear,
    onAppear,
    onAfterAppear,
    onAppearCancelled,
  } = props
  const key = String(vnode.key)
  const leavingVNodesCache = getLeavingNodesForType(state, vnode)

  const callHook: TransitionHookCaller = (hook, args) => {
    hook &&
      callWithAsyncErrorHandling(
        hook,
        instance,
        ErrorCodes.TRANSITION_HOOK,
        args,
      )
  }

  const callAsyncHook = (
    hook: Hook<(el: any, done: () => void) => void>,
    args: [TransitionElement, () => void],
  ) => {
    const done = args[1]
    callHook(hook, args)
    if (isArray(hook)) {
      if (hook.every(hook => hook.length <= 1)) done()
    } else if (hook.length <= 1) {
      done()
    }
  }

  const hooks: TransitionHooks<TransitionElement> = {
    mode,
    persisted,
    beforeEnter(el) {
      let hook = onBeforeEnter
      if (!state.isMounted) {
        if (appear) {
          hook = onBeforeAppear || onBeforeEnter