feat(transition): support transition to teleport component child

packages/runtime-core/src/componentRenderUtils.ts

@@ -27,7 +27,7 @@ import {
   warnDeprecation,
 } from './compat/compatConfig'
 import { shallowReadonly } from '@vue/reactivity'
-import { setTransitionHooks } from './components/BaseTransition'
+import { getInnerChild, setTransitionHooks } from './components/BaseTransition'
 
 /**
  * dev only flag to track whether $attrs was used during render.
@@ -248,13 +248,14 @@ export function renderComponentRoot(
   }
   // inherit transition data
   if (vnode.transition) {
-    if (__DEV__ && !isElementRoot(root)) {
+    const child = getInnerChild(root) ?? root
+    if (__DEV__ && !isElementRoot(child)) {
       warn(
         `Component inside <Transition> renders non-element root node ` +
           `that cannot be animated.`,
       )
     }
-    setTransitionHooks(root, vnode.transition)
+    setTransitionHooks(child, vnode.transition)
   }
 
   if (__DEV__ && setRoot) {

packages/runtime-core/src/components/BaseTransition.ts

@@ -484,7 +484,7 @@ function emptyPlaceholder(vnode: VNode): VNode | undefined {
   }
 }
 
-function getInnerChild(vnode: VNode): VNode | undefined {
+export function getInnerChild(vnode: VNode): VNode | undefined {
   if (!isKeepAlive(vnode)) {
     if (isTeleport(vnode.type) && vnode.children) {
       return findNonCommentChild(vnode.children as VNode[])

packages/vue/__tests__/e2e/Transition.spec.ts

@@ -2310,7 +2310,86 @@ describe('e2e: Transition', () => {
         )
       },
       E2E_TIMEOUT,
-    )
+    ),
+      test(
+        'apply transition to teleport component child',
+        async () => {
+          await page().evaluate(() => {
+            const { createApp, ref } = (window as any).Vue
+            createApp({
+              template: `
+            <div id="target"></div>
+            <div id="container">
+              <transition>
+                  <Comp v-if="toggle"></Comp>
+              </transition>
+            </div>
+            <button id="toggleBtn" @click="click">button</button>
+          `,
+              components: {
+                Comp: {
+                  template: `
+                    <Teleport to="#target">
+                      <div class="test">content</div>
+                    </Teleport>
+                  `,
+                },
+              },
+              setup: () => {
+                const toggle = ref(false)
+                const click = () => (toggle.value = !toggle.value)
+                return { toggle, click }
+              },
+            }).mount('#app')
+          })
+
+          expect(await html('#target')).toBe('')
+          expect(await html('#container')).toBe('<!--v-if-->')
+
+          const classWhenTransitionStart = () =>
+            page().evaluate(() => {
+              ;(document.querySelector('#toggleBtn') as any)!.click()
+              return Promise.resolve().then(() => {
+                // find the class of teleported node
+                return document
+                  .querySelector('#target div')!
+                  .className.split(/\s+/g)
+              })
+            })
+
+          // enter
+          expect(await classWhenTransitionStart()).toStrictEqual([
+            'test',
+            'v-enter-from',
+            'v-enter-active',
+          ])
+          await nextFrame()
+          expect(await classList('.test')).toStrictEqual([
+            'test',
+            'v-enter-active',
+            'v-enter-to',
+          ])
+          await transitionFinish()
+          expect(await html('#target')).toBe('<div class="test">content</div>')
+
+          // leave
+          expect(await classWhenTransitionStart()).toStrictEqual([
+            'test',
+            'v-leave-from',
+            'v-leave-active',
+          ])
+          await nextFrame()
+          expect(await classList('.test')).toStrictEqual([
+            'test',
+            'v-leave-active',
+            'v-leave-to',
+          ])
+          await transitionFinish()
+          expect(await html('#target')).toBe('')
+          expect(await html('#container')).toBe('<!--v-if-->')
+        },
+        E2E_TIMEOUT,
+      )
   })
 
   describe('transition with v-show', () => {