From 6d887aaf591cfa05d5fea978bbd87e3e502bfa86 Mon Sep 17 00:00:00 2001
From: edison <daiwei521@126.com>
Date: Mon, 6 Dec 2021 13:58:45 +0800
Subject: [PATCH] fix(runtime-core): handle initial undefined attrs (#5017)

fix #5016
---
 .../__tests__/componentProps.spec.ts          | 22 +++++++++++++++++++
 packages/runtime-core/src/componentProps.ts   |  2 +-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/packages/runtime-core/__tests__/componentProps.spec.ts b/packages/runtime-core/__tests__/componentProps.spec.ts
index 863b12d0699..40725dfcd13 100644
--- a/packages/runtime-core/__tests__/componentProps.spec.ts
+++ b/packages/runtime-core/__tests__/componentProps.spec.ts
@@ -573,4 +573,26 @@ describe('component props', () => {
       render(h(Comp, { foo: null }), root)
     }).not.toThrow()
   })
+
+  // #5016
+  test('handling attr with undefined value', () => {
+    const Comp = {
+      render(this: any) {
+        return JSON.stringify(this.$attrs) + Object.keys(this.$attrs)
+      }
+    }
+    const root = nodeOps.createElement('div')
+
+    let attrs: any = { foo: undefined }
+
+    render(h(Comp, attrs), root)
+    expect(serializeInner(root)).toBe(
+      JSON.stringify(attrs) + Object.keys(attrs)
+    )
+
+    render(h(Comp, (attrs = { foo: 'bar' })), root)
+    expect(serializeInner(root)).toBe(
+      JSON.stringify(attrs) + Object.keys(attrs)
+    )
+  })
 })
diff --git a/packages/runtime-core/src/componentProps.ts b/packages/runtime-core/src/componentProps.ts
index c999492225c..cf73261fc51 100644
--- a/packages/runtime-core/src/componentProps.ts
+++ b/packages/runtime-core/src/componentProps.ts
@@ -369,7 +369,7 @@ function setFullProps(
             continue
           }
         }
-        if (value !== attrs[key]) {
+        if (!(key in attrs) || value !== attrs[key]) {
           attrs[key] = value
           hasAttrsChanged = true
         }