refactor(v-on): do not generate persistent flag when no listener modifier is present

packages/compiler-dom/src/transforms/vOn.ts

@@ -5,7 +5,9 @@ import {
   createCallExpression,
   createObjectExpression,
   createSimpleExpression,
-  NodeTypes
+  NodeTypes,
+  CallExpression,
+  ObjectExpression
 } from '@vue/compiler-core'
 import { V_ON_MODIFIERS_GUARD, V_ON_KEYS_GUARD } from '../runtimeHelpers'
 
@@ -32,6 +34,7 @@ export const transformOn: DirectiveTransform = (dir, node, context) => {
   const { modifiers } = dir
   const baseResult = baseTransform(dir, node, context)
   if (!modifiers.length) return baseResult
+
   const { key, value } = baseResult.props[0]
   const runtimeModifiers = modifiers.filter(m => !(m in EVENT_OPTION_MODIFIERS))
   let handler = createCallExpression(context.helper(V_ON_MODIFIERS_GUARD), [
@@ -49,17 +52,15 @@ export const transformOn: DirectiveTransform = (dir, node, context) => {
       JSON.stringify(runtimeModifiers.filter(m => !(m in NOT_KEY_MODIFIERS)))
     ])
   }
-  const properties = [
-    createObjectProperty('handler', handler),
-    // so the runtime knows the options never change
-    createObjectProperty('persistent', createSimpleExpression('true', false))
-  ]
+
+  let returnExp: CallExpression | ObjectExpression = handler
 
   const eventOptionModifiers = modifiers.filter(
     modifier => modifier in EVENT_OPTION_MODIFIERS
   )
   if (eventOptionModifiers.length) {
-    properties.push(
+    returnExp = createObjectExpression([
+      createObjectProperty('handler', handler),
       createObjectProperty(
         'options',
         createObjectExpression(
@@ -70,12 +71,14 @@ export const transformOn: DirectiveTransform = (dir, node, context) => {
             )
           )
         )
-      )
-    )
+      ),
+      // so the runtime knows the options never change
+      createObjectProperty('persistent', createSimpleExpression('true', false))
+    ])
   }
 
   return {
-    props: [createObjectProperty(key, createObjectExpression(properties))],
+    props: [createObjectProperty(key, returnExp)],
     needRuntime: false
   }
 }