React propTypes component class?

Question

How can I validate that the supplied prop is a component class (not instance)?

e.g.

export default class TimelineWithPicker extends React.PureComponent {

    static propTypes = {
        component: PropTypes.any, // <-- how can I validate that this is a component class (or stateless functional component)?
    };

    render() {
        return (
            <this.props.component {...this.props} start={this.state.start}/>
        );
    }
}

Answer 1

For anyone using PropTypes >= 15.7.0 a new PropTypes.elementType was added in this pull request and was released on february 10, 2019.

This prop type supports all components (native components, stateless components, stateful components, forward refs React.forwardRef, context providers/consumers).

And it throws a warning when is not any of those elements, it also throws a warning when the prop passed is an element (PropTypes.element) and not a type.

Finally you can use it like any other prop type:

const propTypes = {
    component: PropTypes.elementType,
    requiredComponent: PropTypes.elementType.isRequired,
};

Answer 2

EDITED: Added React's FancyButton example to codesandbox as well as a custom prop checking function that works with the new React.forwardRef api in React 16.3. The React.forwardRef api returns an object with a render function. I'm using the following custom prop checker to verify this prop type. - Thanks for Ivan Samovar for noticing this need.

FancyButton: function (props, propName, componentName) {
  if(!props[propName] || typeof(props[propName].render) != 'function') {
    return new Error(`${propName}.render must be a function!`);
  }
}

You'll want to use PropTypes.element. Actually... PropType.func works for both stateless functional components and class components.

I've made a sandbox to prove that this works... Figured this was needed considering I gave you erroneous information at first. Very sorry about that!

Working sandbox example!

Here is the code for the test in case link goes dead:

import React from 'react';
import { render } from 'react-dom';
import PropTypes from "prop-types";

class ClassComponent extends React.Component {
  render() {
    return <p>I'm a class component</p>
  }
}

const FancyButton = React.forwardRef((props, ref) => (
  <button ref={ref} className="FancyButton">
    {props.children}
  </button>
));

// You can now get a ref directly to the DOM button:
const ref = React.createRef();
<FancyButton ref={ref}>Click me!</FancyButton>;

const FSComponent = () => (
    <p>I'm a functional stateless component</p>
);

const Test = ({ ClassComponent, FSComponent, FancyButton }) => (
  <div>
    <ClassComponent />
    <FSComponent />
    <FancyButton />
  </div>
);
Test.propTypes = {
  ClassComponent: PropTypes.func.isRequired,
  FSComponent: PropTypes.func.isRequired,
  FancyButton: function (props, propName, componentName) {
    if(!props[propName] || typeof(props[propName].render) != 'function') {
      return new Error(`${propName}.render must be a function!`);
    }
  },
}

render(<Test
         ClassComponent={ ClassComponent }
         FSComponent={ FSComponent }
         FancyButton={ FancyButton } />, document.getElementById('root'));