From d183095d86db4560549e0b00e8dd244e8f5f1986 Mon Sep 17 00:00:00 2001
From: Che Guevara <836934184@qq.com>
Date: Sun, 28 Nov 2021 19:58:32 +0800
Subject: [PATCH 1/3] feat(runtime-core): enhance the warning when not
 explicitly declare the variable

---
 packages/runtime-core/src/componentPublicInstance.ts | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/packages/runtime-core/src/componentPublicInstance.ts b/packages/runtime-core/src/componentPublicInstance.ts
index 8298aff42b1..16c36d8e318 100644
--- a/packages/runtime-core/src/componentPublicInstance.ts
+++ b/packages/runtime-core/src/componentPublicInstance.ts
@@ -386,6 +386,15 @@ export const PublicInstanceProxyHandlers: ProxyHandler<any> = {
             `but is not defined on instance.`
         )
       }
+    } else if (
+      __DEV__ &&
+      !__TEST__ &&
+      !(key[0] === '$' || key[0] === '_')
+    ) {
+      warn(
+        `Property ${JSON.stringify(key)} was accessed during render ` +
+          `but is not defined on instance.`
+      )
     }
   },
 

From 848e27cf280940ee4be0243e1e1f0425ac6f1ec7 Mon Sep 17 00:00:00 2001
From: "autofix-ci[bot]" <114827586+autofix-ci[bot]@users.noreply.github.com>
Date: Thu, 24 Oct 2024 07:00:15 +0000
Subject: [PATCH 2/3] [autofix.ci] apply automated fixes

---
 packages/runtime-core/src/componentPublicInstance.ts | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/packages/runtime-core/src/componentPublicInstance.ts b/packages/runtime-core/src/componentPublicInstance.ts
index e48d0fbd934..215a80b17da 100644
--- a/packages/runtime-core/src/componentPublicInstance.ts
+++ b/packages/runtime-core/src/componentPublicInstance.ts
@@ -526,14 +526,10 @@ export const PublicInstanceProxyHandlers: ProxyHandler<any> = {
             `but is not defined on instance.`,
         )
       }
-    } else if (
-      __DEV__ &&
-      !__TEST__ &&
-      !(key[0] === '$' || key[0] === '_')
-    ) {
+    } else if (__DEV__ && !__TEST__ && !(key[0] === '$' || key[0] === '_')) {
       warn(
         `Property ${JSON.stringify(key)} was accessed during render ` +
-          `but is not defined on instance.`
+          `but is not defined on instance.`,
       )
     }
   },

From d516036ee22ca8d875eb9629ae0c385069daf39a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=9B=B9=E4=BB=B2?= <zhicun.cz@alibaba-inc.com>
Date: Fri, 25 Oct 2024 11:33:42 +0800
Subject: [PATCH 3/3] feat(runtime-core): enhance the warning when not
 explicitly declare the variable

---
 .../src/componentPublicInstance.ts            |  2 +-
 packages/vue/__tests__/index.spec.ts          | 23 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/packages/runtime-core/src/componentPublicInstance.ts b/packages/runtime-core/src/componentPublicInstance.ts
index 215a80b17da..8a769b97180 100644
--- a/packages/runtime-core/src/componentPublicInstance.ts
+++ b/packages/runtime-core/src/componentPublicInstance.ts
@@ -526,7 +526,7 @@ export const PublicInstanceProxyHandlers: ProxyHandler<any> = {
             `but is not defined on instance.`,
         )
       }
-    } else if (__DEV__ && !__TEST__ && !(key[0] === '$' || key[0] === '_')) {
+    } else if (__DEV__ && !__TEST__ && !isReservedPrefix(key[0])) {
       warn(
         `Property ${JSON.stringify(key)} was accessed during render ` +
           `but is not defined on instance.`,
diff --git a/packages/vue/__tests__/index.spec.ts b/packages/vue/__tests__/index.spec.ts
index 0c969f15981..e76577e138a 100644
--- a/packages/vue/__tests__/index.spec.ts
+++ b/packages/vue/__tests__/index.spec.ts
@@ -311,4 +311,27 @@ describe('compiler + runtime integration', () => {
     app.mount(root)
     expect(root.innerHTML).toBe('<div>60000000100000111</div>')
   })
+
+  test('Warning when use undeclared variable in template', () => {
+    const app = createApp({
+      template: `
+        <div @click="handler">handler</div>
+        <div>dddd{{dddd}}</div>
+        <div>no warn: {{message}}</div>
+      `,
+      setup() {
+        return {
+          message: 'hello',
+        }
+      },
+    })
+    const root = document.createElement('div')
+    app.mount(root)
+    expect(
+      `[Vue warn]: Property "handler" was accessed during render but is not defined on instance.`,
+    ).toHaveBeenWarned()
+    expect(
+      `[Vue warn]: Property "dddd" was accessed during render but is not defined on instance.`,
+    ).toHaveBeenWarned()
+  })
 })