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?

Start with the linked “You Probably Don't Need Derived State” article and the reported PropTypes warning about accessing key. Determine whether the documentation needs clarification about fully uncontrolled components with a key; done means the article explains a valid mitigation or explicitly documents the limitation.