[Bug] umi + mobx decorator don't work

[sorrycc]

What happens?

Mini Showcase Repository(REQUIRED)

Please provide a minimal reproduction then upload to your GitHub. 请提供 最小重现，并上传到你的 GitHub 仓库

How To Reproduce

Steps to reproduce the behavior: 1. 2.

Expected behavior 1. 2.

$ umi g page index
$ vi pages/index.tsx

加入以下内容，

import { makeObservable, observable } from 'mobx';
class A {
  @observable
  loading = '1';
  constructor() {
    makeObservable(this);
  }
}
class B extends A {
  loading = '2';
}
const b = new B();
console.log(b);

启动 umi dev，

$ umi dev

报错，

Context

• Umi Version:
• Node Version:
• Platform:

[sorrycc]

解法：

新增 plugin.ts，内容如下，

export default (api: any) => {
  api.modifyBabelPresetOpts((memo) => {
    memo.presetEnv.loose = true;
    return memo;
  })
}