react-redux connect() typings based on Sam's Goldman example

react-redux_v5.x.x.js

// see here for details
// https://medium.com/@samgoldman/ville-saukkonen-thanks-and-thanks-for-your-thoughtful-questions-24aedcfed518
// https://github.com/facebook/flow/issues/7125

/*
  S = State
  A = Action
  OP = OwnProps
  SP = StateProps
  DP = DispatchProps
  MP = Merge props
  MDP = Map dispatch to props object
  RSP = Returned state props
  RDP = Returned dispatch props
  RMP = Returned merge props
  CP = Props for returned component
  Com = React Component
  ST = Static properties of Com
  EFO = Extra factory options (used only in connectAdvanced)
*/

declare module 'react-redux' {
    // A connected component wraps some component WC. Note that S (State) and D (Action)
    // are "phantom" type parameters, as they are not constrained by the definition but
    // rather by the context at the use site.
    declare class ConnectedComponent<-S, -D, OP, +WC> extends React$Component<OP> {
        static +WrappedComponent: WC;
        getWrappedInstance(): React$ElementRef<WC>;
    }

    declare type MapStateToProps<-S, -OP, +SP> = (state: S, ownProps: OP) => SP;

    // Same as above, but the derivation is based on dispatch instead of state.
    declare type MapDispatchToPropsFn<-D, -OP, +DP> = (dispatch: D, ownProps: OP) => DP;

    declare type MergeProps<-SP, -DP, -OP, +MP> = (
        stateProps: SP,
        dispatchProps: DP,
        ownProps: OP,
    ) => MP;

    // The connector function actaully perfoms the wrapping, giving us a connected
    // component.
    declare type Connector<-S, -D, OP, WC> = (WC) => Class<ConnectedComponent<S, D, OP, WC>>;

    // Putting it all together.
    declare export function connect<S, D, OP, SP, DP>(
        mapStateToProps: MapStateToProps<S, OP, SP>,
        mapDispatchToProps: MapDispatchToPropsFn<D, OP, DP>,
    ): Connector<S, D, OP, React$ComponentType<{| ...OP, ...SP, ...DP |}>>;

    declare export function connect<S, D, OP, SP, DP>(
        mapStateToProps: MapStateToProps<S, OP, SP>,
        mapDispatchToProps: DP,
    ): Connector<S, D, OP, React$ComponentType<{| ...OP, ...SP, ...DP |}>>;

    declare export function connect<S, D, OP, SP>(
        mapStateToProps: MapStateToProps<S, OP, SP>,
    ): Connector<S, D, OP, React$ComponentType<{| ...OP, ...SP |}>>;

    declare export function connect<S, D, OP, SP, DP, MP>(
      mapStateToProps: MapStateToProps<S, OP, DP>,
      mapDispatchToProps: MapDispatchToPropsFn<D, OP, SP>,
      mergeProps: MergeProps<SP, DP, OP, MP>,
    ): Connector<S, D, OP, React$ComponentType<MP>>;
}