::v-deep usage as a combinator has been deprecated. Use :deep() instead.
原因新的vue3.0 单文件规范::v-deep写法已经被废弃了
修改成 如下写法,不要加空格
//报错 <style scoped> ::v-deep .demo{ background: yellow; } </style>
//正确 <style scoped> :deep(.demo){ background: yellow; } </style>