From 12fef2d57aecf5cb91d3e642301a0ae5be73fcce Mon Sep 17 00:00:00 2001
From: daiwei <daiwei521@126.com>
Date: Wed, 20 Nov 2024 09:56:53 +0800
Subject: [PATCH 1/3] fix(ssr): properly handle ssr slot and fallback

---
 packages/server-renderer/src/helpers/ssrRenderSlot.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/server-renderer/src/helpers/ssrRenderSlot.ts b/packages/server-renderer/src/helpers/ssrRenderSlot.ts
index 19aa4ce63b7..260e5a3bb33 100644
--- a/packages/server-renderer/src/helpers/ssrRenderSlot.ts
+++ b/packages/server-renderer/src/helpers/ssrRenderSlot.ts
@@ -62,7 +62,7 @@ export function ssrRenderSlotInner(
       parentComponent,
       slotScopeId ? ' ' + slotScopeId : '',
     )
-    if (isArray(ret)) {
+    if (isArray(ret) && slotBuffer.length === 0) {
       const validSlotContent = ensureValidVNode(ret)
       if (validSlotContent) {
         // normal slot

From 659c0bfc908605b078cd852a167edabeb4280c9f Mon Sep 17 00:00:00 2001
From: daiwei <daiwei521@126.com>
Date: Wed, 20 Nov 2024 10:20:43 +0800
Subject: [PATCH 2/3] test: add test case

---
 .../server-renderer/__tests__/ssrSlot.spec.ts | 34 ++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/packages/server-renderer/__tests__/ssrSlot.spec.ts b/packages/server-renderer/__tests__/ssrSlot.spec.ts
index 02872274ab6..4cc7fd97ef2 100644
--- a/packages/server-renderer/__tests__/ssrSlot.spec.ts
+++ b/packages/server-renderer/__tests__/ssrSlot.spec.ts
@@ -1,4 +1,4 @@
-import { createApp } from 'vue'
+import { createApp, defineAsyncComponent, h } from 'vue'
 import { renderToString } from '../src/renderToString'
 
 const components = {
@@ -154,6 +154,38 @@ describe('ssr: slot', () => {
     ).toBe(`<div><p>1</p><p>2</p></div>`)
   })
 
+  // #12438
+  test('async component slot with v-if true', async () => {
+    const Layout = defineAsyncComponent(() =>
+      Promise.resolve({
+        template: `<div><slot name="header">default header</slot></div>`,
+      }),
+    )
+    const LayoutLoader = {
+      setup(_: any, context: any) {
+        return () => h(Layout, {}, context.slots)
+      },
+    }
+    expect(
+      await renderToString(
+        createApp({
+          components: {
+            LayoutLoader,
+          },
+          template: `
+            <Suspense>
+              <LayoutLoader>
+                <template v-if="true" #header>
+                  new header
+                </template>
+              </LayoutLoader>
+            </Suspense>
+          `,
+        }),
+      ),
+    ).toBe(`<div><!--[--> new header <!--]--></div>`)
+  })
+
   // #11326
   test('dynamic component slot', async () => {
     expect(

From 413c9239b1751498364d2ff7e3e0cdd642ede377 Mon Sep 17 00:00:00 2001
From: daiwei <daiwei521@126.com>
Date: Wed, 20 Nov 2024 21:37:51 +0800
Subject: [PATCH 3/3] chore: update

---
 packages/runtime-core/src/component.ts                | 2 +-
 packages/server-renderer/src/helpers/ssrRenderSlot.ts | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/runtime-core/src/component.ts b/packages/runtime-core/src/component.ts
index 3ed42ed0b55..5b094a0d611 100644
--- a/packages/runtime-core/src/component.ts
+++ b/packages/runtime-core/src/component.ts
@@ -806,7 +806,7 @@ export function setupComponent(
   const { props, children } = instance.vnode
   const isStateful = isStatefulComponent(instance)
   initProps(instance, props, isStateful, isSSR)
-  initSlots(instance, children, optimized)
+  initSlots(instance, children, optimized || isSSR)
 
   const setupResult = isStateful
     ? setupStatefulComponent(instance, isSSR)
diff --git a/packages/server-renderer/src/helpers/ssrRenderSlot.ts b/packages/server-renderer/src/helpers/ssrRenderSlot.ts
index 260e5a3bb33..19aa4ce63b7 100644
--- a/packages/server-renderer/src/helpers/ssrRenderSlot.ts
+++ b/packages/server-renderer/src/helpers/ssrRenderSlot.ts
@@ -62,7 +62,7 @@ export function ssrRenderSlotInner(
       parentComponent,
       slotScopeId ? ' ' + slotScopeId : '',
     )
-    if (isArray(ret) && slotBuffer.length === 0) {
+    if (isArray(ret)) {
       const validSlotContent = ensureValidVNode(ret)
       if (validSlotContent) {
         // normal slot