React.Component undocumented templated class

[barbu110]

I see that React.Component is used with three template parameters that are documented nowhere. (or I simply couldn't find the docs).

I was able to deduce that the second and third are the types of props and state respectively. However, I coudn't figure it out about the first template parameter.

Are these documented anywhere, please?

[Hypnosphi]

Kinda. The first parameter is the type of defaultProps. Note that currently you can't use intersection types (like CommonProps & {foo: Foo}) for this.

[barbu110]

Could you please point me to the internal source file that defines class Component<...>? I couldn't find it...

[Hypnosphi]

It's in Flow codebase, weirdly: https://github.com/facebook/flow/blob/master/lib/react.js#L16. I guess this is because React codebase is yet only partially typed

[barbu110]

Strange thing. Thank you very much!

I will try to work on a PR to update the documentation. It's pretty confusing when you try to get deeper into React

[gaearon]

React documentation doesn't have a section about Flow (should it?) So I am not fully sure where you would like to document this.

However, there is a section about React on the Flow website. Does it not help?

[barbu110]

@gaearon the section about React on the Flow website is a guide and it does not present the entire API reference.

And yes, I think React should have a section about Flow. Currently, the React docs section Typechecking with PropTypes explains that

React.PropTypes is deprecated as of React v15.5.

In my opinion this comes as a way to encourage the usage of TypeScript or Flow for static typechecking. Hence, this is part of the reason why there should be a Flow section in the React documentation. What do you think?

[gaearon]

The wording on React doc is really unfortunate. It shouldn't say "deprecated", it should say "moved". We're not deprecating PropTypes—just moving them to a separate package.

Although I agree that in general we think Flow/TS is a better way to do it. I'm open to having a new guide called "Static Type Checking" here that shows how to use React from Flow and from TypeScript, and describes main API definitions. Would you like to work on it?

[barbu110]

@gaearon, yes, I would like to help as much as I can!

[bvaughn]

Thank you for filing this issue! 😄

The documentation and source code for reactjs.org now lives in a different repository: reactjs/reactjs.org. (For more info on why we made this move, see issue #11075.)

I've moved your issue to the new repo: reactjs/react.dev#76

Let's continue the discussion there! Sorry for the inconvenience.