Derived State: Fully uncontrolled component with a key

Hi,

In the article You Probably Don't Need Derived State, one of the recommended ways to avoid deriving state from props, is to have "Fully uncontrolled component with a key".

However, there is no way to actually force the user to provide a 'key' property to the component, since declaring it in propTypes as "key: PropTypes.any.isRequired" won't work, because it's value is always 'undefined', which leads to a warning message:

Warning: MyComponent: key is not a prop. Trying to access it will result in undefined being returned. If you need to access the same value within the child component, you should pass it as a different prop.

And without declaring the 'key' prop type, we cannot assume, that the user will use the component in a proper manner.

How to mitigate this?

從連結的「You Probably Don't Need Derived State」文章以及回報的存取 key 時發生的 PropTypes 警告開始。判斷文件是否需要釐清帶有 key 的完全非受控元件；完成的標準是文章說明有效的緩解方式，或明確記錄這項限制。