From e3ef24faacf464ea354a052f84714d88a555c3dc Mon Sep 17 00:00:00 2001
From: Kael <kaelwd@gmail.com>
Date: Fri, 20 Oct 2023 19:25:06 +1100
Subject: [PATCH] fix(runtime-core): delete stale slots which are present but
 undefined (#6484)

close #9109
---
 packages/runtime-core/__tests__/componentSlots.spec.ts | 4 +++-
 packages/runtime-core/src/componentSlots.ts            | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/packages/runtime-core/__tests__/componentSlots.spec.ts b/packages/runtime-core/__tests__/componentSlots.spec.ts
index f08f1910cd4..708fb20c423 100644
--- a/packages/runtime-core/__tests__/componentSlots.spec.ts
+++ b/packages/runtime-core/__tests__/componentSlots.spec.ts
@@ -134,9 +134,11 @@ describe('component: slots', () => {
     }
 
     const oldSlots = {
-      header: 'header'
+      header: 'header',
+      footer: undefined
     }
     const newSlots = {
+      header: undefined,
       footer: 'footer'
     }
 
diff --git a/packages/runtime-core/src/componentSlots.ts b/packages/runtime-core/src/componentSlots.ts
index afc5f03933b..980ee799186 100644
--- a/packages/runtime-core/src/componentSlots.ts
+++ b/packages/runtime-core/src/componentSlots.ts
@@ -234,7 +234,7 @@ export const updateSlots = (
   // delete stale slots
   if (needDeletionCheck) {
     for (const key in slots) {
-      if (!isInternalKey(key) && !(key in deletionComparisonTarget)) {
+      if (!isInternalKey(key) && deletionComparisonTarget[key] == null) {
         delete slots[key]
       }
     }