[react-redux] injecting props HOC and forced exact type of OwnProps

Currently OwnProps have to be Exact Type. Is it possible to use current connect<…> typings to create injecting-props HOC, like injectProp example in HOC docs?

https://flow.org/en/docs/react/hoc/

function injectProp<Config: {}>(
  Component: React.AbstractComponent<Config>
): React.AbstractComponent<$Diff<Config, {foo: number | void}>> {
  return function WrapperComponent(
    props: $Diff<Config, {foo: number | void}>,
  ) {
    return <Component {...props} foo={42} />;
  };
}

this doesn’t work and complains about OwnProps is incompatible with exact type

type Props = { ...OwnProps, foo: number };
type OwnProps = {};
const mapStateToProps = () => ({ foo: 5 });
export default connect<Props, OwnProps, _, _, _, _>(mapStateToProps);

(cc @peter-leonov)

[peter-leonov]

The example is unfortunately not working in my case

Maybe it’s because of my bad copy-paste skill 😃 Please, try using the code from the PR directly. It passes unit tests for types, even in Flow 0.90 😎

I don’t know if that is in the same scope, but i wanted to share one concern - I don’t know how recompose typings (which are old) do that, but for some reasons i don’t have to write annotations when using withProps recompose function. On the other hand, to use withProps i have to use HOC<...> type exported by recompose

• it doesn’t work with React.AbstractComponent 😦

As far as I understood, the pre React.AbstractComponent type used everywhere React.ComponentType is now an alias type ComponentType<T> = AbstractComponent<T, any>. So, theoretically, it should be fine if other libraries internally used the proper types. But I’m not 100% sure.

Having the ability to just write one type annotation for the whole compose function makes it easier to work with. Imagine having 10 HOCs inside compose() function and having to annotate all the in/out props for every HOC

This is 100% true. I guess, Flow should allow this because (as far as I understand) it just needs the very tip of the exported type to be declared. If you get any success making it work, please, share 🤓

[peter-leonov]

Quick guess:

-type OwnProps = {};
+type OwnProps = {||};