JSX: a way to make all the properties of value-based elements optional

It's not documented, but currently, if the JSX.ElementAttributesProperty interface is declared empty,

declare namespace JSX { interface ElementAttributesProperty {} }

then the element attributes type becomes same as the element instance type. However, if the element instance type is a class, this leads to a situation where the compiler requires that all the members of the class be represented as attributes since they're not optional (and even cannot be marked as such as the class syntax doesn't allow optional members).

class MyComponent {
  myProp: string;
  private myMethod(): void;
}
var a = <MyComponent myProp='value'/>;
// error: Property 'myMethod' is missing in type MyComponent

This prevents me from using JSX for type-checking Angular 1 templates (you can find my experiments in this area here).

What if we introduce some way to tell the compiler that not all the properties are required, but only some of them? E.g. those having a certain decorator?

A related issue: #5151

该 issue 没有指出文件、测试或编译器入口点。首先定位 JSX ElementAttributesProperty 的处理逻辑以及相关 issue #5151，然后检查现有的 JSX 类型检查测试；要完成此工作，需要就一种使选定的基于值的元素属性变为可选的机制达成一致，并添加覆盖 class 示例的测试。