Qfyilyi

I'm struggling with types of injected props by HOC.

It's just simple, in App Component, there are two props: title and message.

However title is provided by HOC.

Here's the code for this:

/* @flow */

import React, { Component } from 'react';

import type { ComponentType } from 'react';



interface AppProps {

    title: string;

    message: string;

}



class App extends Component<AppProps, {}> {

    static defaultProps = {

        message: 'Helloworld'

    }

    render() {

        return (

            <div>

                <div>Title: {this.props.title}</div>

                <div>Message: {this.props.message}</div>

            </div>

        );

    }

}



function injectProp<Props: {}>(

    Component: ComponentType<{ title: string } & Props>

): ComponentType<Props> {

    return function EnhancedComponent(props: Props) {

        return <Component title="Hello" {...props} />;

    }

};



export default injectProp(App);

It seems fine, however when I run the flow, it fails with

Missing type annotation for Props.

32| export default injectProp(App);

So I tried this, but no luck:

export default injectProp<AppProps>(App);

Now I got bunch of error messages.

> babel-react-webpack-flow-boilerplate@1.0.0 flow F:devwebproptype-test

> flow



Error ----------------------------------------------------------------------------------- src/js/components/App.js:32:16



Cannot compare boolean [1] to statics of `App` [2].



   src/js/components/App.js:32:16

   32| export default injectProp<AppProps>(App);



                      ^^^^^^^^^^^^^^^^^^^ [1]



References:

   src/js/components/App.js:10:7

   10| class App extends Component<AppProps, {}> {



             ^^^ [2]





Error ----------------------------------------------------------------------------------- src/js/components/App.js:32:27



Cannot reference type `AppProps` [1] from a value position.



   src/js/components/App.js:32:27

   32| export default injectProp<AppProps>(App);



                                 ^^^^^^^^



References:

   src/js/components/App.js:5:11

    5| interface AppProps {



                 ^^^^^^^^ [1]





Error --------------------------------------------------------------------------------------------- src/js/index.js:17:1



Cannot call `ReactDOM.render` because boolean [1] is not a React component.



   src/js/index.js:17:1

   17| ReactDOM.render(<App message="A" />, entryEl);



       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^



References:

   src/js/components/App.js:32:16

   32| export default injectProp<AppProps>(App);



                      ^^^^^^^^^^^^^^^^^^^^^^^^^ [1]





Error -------------------------------------------------------------------------------------------- src/js/index.js:17:17



Cannot call `ReactDOM.render` with `<App />` bound to `element` because boolean [1] is incompatible with string [2] in

type argument `ElementType` [3].



   src/js/index.js:17:17

    17| ReactDOM.render(<App message="A" />, entryEl);



                        ^^^^^^^^^^^^^^^^^^^



References:

   src/js/components/App.js:32:16

    32| export default injectProp<AppProps>(App);



                       ^^^^^^^^^^^^^^^^^^^^^^^^^ [1]

   C:UsersUserAppDataLocalTempflowflowlib_6db8195react.js:159:5

   159|   | string



            ^^^^^^ [2]

   C:UsersUserAppDataLocalTempflowflowlib_6db8195react.js:167:29

   167| declare type React$Element<+ElementType: React$ElementType> = {|



                                    ^^^^^^^^^^^ [3]





Error -------------------------------------------------------------------------------------------- src/js/index.js:17:17



Cannot create `App` element because boolean [1] is not a React component.



   src/js/index.js:17:17

   17| ReactDOM.render(<App message="A" />, entryEl);



                       ^^^^^^^^^^^^^^^^^^^



References:

   src/js/components/App.js:32:16

   32| export default injectProp<AppProps>(App);



                      ^^^^^^^^^^^^^^^^^^^^^^^^^ [1]







Found 5 errors



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Using flow-bin@0.69.0 and React@16.3.0. What am I missing? Why keep Flow complains about type annotation that doesn't needed?

This problem will resolve by export module like this:

export default injectProp<AppProps>(App);

And update to latest version(0.86.0) will works.

I made repo for this:
https://github.com/rico345100/hoc-prop-types-test

Might be helpful to people who has same issue like me.