Warn for all unsupported lifecycles in stateless Components

[gingur]

Example: https://jsfiddle.net/gingur/u0h2rjae/1/

When generating child context with a stateless Component, the context is not available to the children.

[gingur]

Apparently none of the Component lifecycle events are supported, if it is intended that context is also not supported then suggest a warning to be thrown when using a non-production build of React.

[jimfb]

Yeah, a warning for all the lifecycles is probably a good idea.

[gingur]

Would https://github.com/facebook/react/blob/master/src/renderers/shared/stack/reconciler/ReactCompositeComponent.js#L42 be the correct location to specify the warning?

[jimfb]

Yeah, that sounds like a reasonable place to me. cc @spicyj for confirmation.

[sophiebits]

I don't think this makes much sense because the mental model is that these functions are called, not constructed – so the prototype shouldn't come into play at all. But I guess that's a reasonable place if we do want the warning.

[jimfb]

Yeah, but we sort of violate the mental model with contextTypes and propTypes and related properties that get set on the function. I can see how someone could think they could add a lifecycle function in the same way. There really isn't any harm in adding a warning, and it might help people catch errors in their mental model.

[gingur]

If at a minimum childContextTypes could trigger a warning since contextTypes, propTypes and defaultProps are supported but do not require an additional prototype function such as getChildContext to be available.

[sophiebits]

Yeah, that makes sense. Let's start with childContextTypes and revisit if anyone else is confused after that.