microsoft / microsoft/TypeScript
Shouldn't TypeScript be able to polyfill `import defer` with `Proxy` to work with `"module": "commonjs"`?
- 主要语言
- Go
- 星标
- 111k
- 派生
- 14.3k
- 平均合并
- 2 天 4 小时
- 30 天内合并 PR
- 132
描述
### 🔍 Search Terms
import defer commonjs
import defer require
### ✅ Viability Checklist
- [x] This wouldn't be a breaking change in existing TypeScript/JavaScript code
- [x] This wouldn't change the runtime behavior of existing JavaScript code
- [x] This could be implemented without emitting different JS based on the types of the expressions
- [x] This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
- [x] This isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
- [x] This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals
### ⭐ Suggestion
Since the TypeScript beta announcement, I tried it in the playground. But setting `"module"` to `"commonjs"` sadly revealed that `import defer` only work with `"module": "esnext"` or `"module": "preserve"`.
But `Proxy` can polyfill this exact behavior.
### 📃 Motivating Example
This code:
```typescript
import defer * as MyModule from 'my-module'
```
should output something like this:
```javascript
let _module
const MyModule = new Proxy({}, {
get(_target, prop) {
if (!_module) {
_module = require('my-module') // the real code would obviously more complicated as it needs to force `_module` to be an object
}
return _module[prop]
}
})
```
### 💻 Use Cases
1. What do you want to use this for? Using `import defer` for legacy targets
2. What shortcomings exist with current approaches? `await import` forces `Promise`
3. What workarounds are you using in the meantime? `await import`
贡献指南
调研方向
首先跟踪当 `module` 为 `commonjs` 时 TypeScript 如何处理 `import defer`,并将其与现有的 `esnext` 和 `preserve` 行为进行比较。使用作为动机的 `Proxy` 示例和所述的 legacy-target 用例来定义预期输出,然后添加覆盖测试以显示同步延迟访问是否能够在不引入 `Promise` 的情况下工作。
由索引模型根据 Issue 内容生成。
评估
- 技术栈
- javascript, typescript
- 领域
- compilers
- Issue 类型
- 功能
- 难度
- 5/5
- 预计耗时
- 一周以上
- 活跃度
- 停滞
- 描述清晰度
- 基本清楚
- 新手友好度
- 28/100