ensure leaving transitions are up-to-date for dynamic transitions

Author: yyx990803

src/platforms/web/runtime/components/transition-group.js

@@ -61,6 +61,7 @@ export default {
       const removed = []
       for (let i = 0; i < prevChildren.length; i++) {
         const c = prevChildren[i]
+        c.data.transition = transitionData
         c.data.pos = c.elm.getBoundingClientRect()
         if (map[c.key]) {
           kept.push(c)

src/platforms/web/runtime/components/transition.js

@@ -4,7 +4,7 @@
 // supports transition mode (out-in / in-out)
 
 import { warn } from 'core/util/index'
-import { camelize } from 'shared/util'
+import { camelize, extend } from 'shared/util'
 import { getRealChild, mergeVNodeHook } from 'core/vdom/helpers'
 
 export const transitionProps = {
@@ -100,9 +100,12 @@ export default {
     const oldRawChild = this._vnode
     const oldChild: any = getRealChild(oldRawChild)
 
-    // handle transition mode
-    if (mode && oldChild && oldChild.data && oldChild.key !== child.key) {
-      const oldData = oldChild.data.transition
+    if (oldChild && oldChild.data && oldChild.key !== child.key) {
+      // replace old child transition data with fresh one
+      // important for dynamic transitions!
+      const oldData = oldChild.data.transition = extend({}, data)
+
+      // handle transition mode
       if (mode === 'out-in') {
         // return empty node and queue update when leave finishes
         mergeVNodeHook(oldData, 'afterLeave', () => {