el-menu 折叠后小箭头不会消失-官方示例

<template>
  <el-radio-group v-model="isCollapse" style="margin-bottom: 20px">
    <el-radio-button :value="false">expand</el-radio-button>
    <el-radio-button :value="true">collapse</el-radio-button>
  </el-radio-group>
  <el-menu
    default-active="2"
    class="el-menu-vertical-demo"
    :collapse="isCollapse"
    @open="handleOpen"
    @close="handleClose"
  >
    <el-sub-menu index="1">
      <template #title>
        <el-icon><location /></el-icon>
        <span>Navigator One</span>
      </template>
      <el-menu-item-group>
        <template #title><span>Group One</span></template>
        <el-menu-item index="1-1">item one</el-menu-item>
        <el-menu-item index="1-2">item two</el-menu-item>
      </el-menu-item-group>
      <el-menu-item-group title="Group Two">
        <el-menu-item index="1-3">item three</el-menu-item>
      </el-menu-item-group>
      <el-sub-menu index="1-4">
        <template #title><span>item four</span></template>
        <el-menu-item index="1-4-1">item one</el-menu-item>
      </el-sub-menu>
    </el-sub-menu>
    <el-menu-item index="2">
      <el-icon><icon-menu /></el-icon>
      <template #title>Navigator Two</template>
    </el-menu-item>
    <el-menu-item index="3" disabled>
      <el-icon><document /></el-icon>
      <template #title>Navigator Three</template>
    </el-menu-item>
    <el-menu-item index="4">
      <el-icon><setting /></el-icon>
      <template #title>Navigator Four</template>
    </el-menu-item>
  </el-menu>
</template>