原版

<van-search
  v-model="value"
  show-action
  label="地址"
  placeholder="请输入搜索关键词"
  @search="onSearch"
>
  <template #action>
    <div @click="onSearch">搜索</div>
  </template>
</van-search>

#action 修改成 slot=“action”

<van-search
  v-model="value"
  show-action
  label="地址"
  placeholder="请输入搜索关键词"
  @search="onSearch"
>
  <template slot="action">
    <div @click="onSearch">搜索</div>
  </template>
</van-search>