fix(keep-alive): avoid duplicate mounts of deactivate components

packages/runtime-core/__tests__/components/KeepAlive.spec.ts

@@ -1173,4 +1173,48 @@ describe('KeepAlive', () => {
     expect(deactivatedHome).toHaveBeenCalledTimes(0)
     expect(unmountedHome).toHaveBeenCalledTimes(1)
   })
+
+  // #12017
+  test('avoid duplicate mounts of deactivate components', async () => {
+    const About = {
+      name: 'About',
+      setup() {
+        return () => h('h1', 'About')
+      },
+    }
+    const mountedHome = vi.fn()
+    const Home = {
+      name: 'Home',
+      setup() {
+        onMounted(mountedHome)
+        return () => h('h1', 'Home')
+      },
+    }
+    const activeView = shallowRef(About)
+    const HomeView = {
+      name: 'HomeView',
+      setup() {
+        return () => h(activeView.value)
+      },
+    }
+
+    const App = createApp({
+      setup() {
+        return () => {
+          return [
+            h(KeepAlive, null, [
+              h(HomeView, {
+                key: activeView.value.name,
+              }),
+            ]),
+          ]
+        }
+      },
+    })
+    App.mount(nodeOps.createElement('div'))
+    expect(mountedHome).toHaveBeenCalledTimes(0)
+    activeView.value = Home
+    await nextTick()
+    expect(mountedHome).toHaveBeenCalledTimes(1)
+  })
 })

packages/runtime-core/src/component.ts

@@ -506,9 +506,12 @@ export interface ComponentInternalInstance {
    */
   asyncResolved: boolean
 
+  keepAliveEffect: Function[]
+
   // lifecycle
   isMounted: boolean
   isUnmounted: boolean
+  isActivated: boolean
   isDeactivated: boolean
   /**
    * @internal
@@ -669,10 +672,13 @@ export function createComponentInstance(
     asyncDep: null,
     asyncResolved: false,
 
+    keepAliveEffect: [],
+
     // lifecycle hooks
     // not using enums here because it results in computed properties
     isMounted: false,
     isUnmounted: false,
+    isActivated: false,
     isDeactivated: false,
     bc: null,
     c: null,

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

@@ -48,6 +48,7 @@ import { devtoolsComponentAdded } from '../devtools'
 import { isAsyncWrapper } from '../apiAsyncComponent'
 import { isSuspense } from './Suspense'
 import { LifecycleHooks } from '../enums'
+import { queuePostFlushCb } from '../scheduler'
 
 type MatchPattern = string | RegExp | (string | RegExp)[]
 
@@ -136,6 +137,7 @@ const KeepAliveImpl: ComponentOptions = {
       optimized,
     ) => {
       const instance = vnode.component!
+      instance.isActivated = false
       move(vnode, container, anchor, MoveType.ENTER, parentSuspense)
       // in case props have changed
       patch(
@@ -149,6 +151,11 @@ const KeepAliveImpl: ComponentOptions = {
         vnode.slotScopeIds,
         optimized,
       )
+
+      const effects = instance.keepAliveEffect
+      queuePostFlushCb(effects)
+      instance.keepAliveEffect.length = 0
+
       queuePostRenderEffect(() => {
         instance.isDeactivated = false
         if (instance.a) {
@@ -168,6 +175,7 @@ const KeepAliveImpl: ComponentOptions = {
 
     sharedContext.deactivate = (vnode: VNode) => {
       const instance = vnode.component!
+      instance.isActivated = true
       invalidateMount(instance.m)
       invalidateMount(instance.a)
 

packages/runtime-core/src/renderer.ts

@@ -1431,6 +1431,16 @@ function baseCreateRenderer(
       } else {
         let { next, bu, u, parent, vnode } = instance
 
+        const keepAliveParent = locateDeactiveKeepAlive(instance)
+        if (keepAliveParent) {
+          keepAliveParent.keepAliveEffect.push(() => {
+            if (!instance.isUnmounted) {
+              componentUpdateFn()
+            }
+          })
+          return
+        }
+
         if (__FEATURE_SUSPENSE__) {
           const nonHydratedAsyncRoot = locateNonHydratedAsyncRoot(instance)
           // we are trying to update some async comp before hydration
@@ -2542,6 +2552,19 @@ function locateNonHydratedAsyncRoot(
   }
 }
 
+function locateDeactiveKeepAlive(instance: ComponentInternalInstance | null) {
+  while (instance) {
+    if (instance.isActivated) {
+      return instance
+    }
+    if (isKeepAlive(instance.vnode)) {
+      break
+    }
+    instance = instance.parent
+  }
+  return null
+}
+
 export function invalidateMount(hooks: LifecycleHook): void {
   if (hooks) {
     for (let i = 0; i < hooks.length; i++)