React warning logged when using renderProp

[lo1tuma]

Current behavior

When a renderProp function renders a string or null I see the following react warning being logged at stdout:

Warning: Failed prop type: The prop `children` is marked as required in `SimpleSFCWrapper`, but its value is `null`.
    in SimpleSFCWrapper

Same for a string:

Warning: Failed prop type: Invalid prop `children` of type `string` supplied to `SimpleSFCWrapper`, expected a single ReactElement.
   in SimpleSFCWrapper

Expected behavior

I wouldn’t expect to see such a warning since everything works just fine when using null or string values.

Your environment

I’ve created a minimal example to reproduce this issue:

• run npm i react@16.8.3 enzyme@3.9.0 enzyme-adapter-react-16@1.10.0 react-dom@16.8.3
• create a file test.js which the following content:

'use strict';

const Enzyme = require('enzyme');
const Adapter = require('enzyme-adapter-react-16');
const React = require('react');

Enzyme.configure({ adapter: new Adapter() });

const { shallow } = Enzyme;

function MyComponent() {
    return React.createElement('div', {},
        React.createElement(ComponentWithRenderProp, {}, function (value) {
            return value;
        })
    );
}

function ComponentWithRenderProp(props) {
    return props.children('foo');
}

const myComponent = shallow(React.createElement(MyComponent));

myComponent.find(ComponentWithRenderProp).renderProp('children')('bar');

• run node test.js

API

• shallow
• mount
• render

Version

library	version
enzyme	3.9.0
react	16.8.3
react-dom	16.8.3
react-test-renderer	16.8.3
adapter (below)	1.10.0

Adapter

• enzyme-adapter-react-16
• enzyme-adapter-react-16.3
• enzyme-adapter-react-16.2
• enzyme-adapter-react-16.1
• enzyme-adapter-react-15
• enzyme-adapter-react-15.4
• enzyme-adapter-react-14
• enzyme-adapter-react-13
• enzyme-adapter-react-helper
• others ( )

[lo1tuma]

I’ve just noticed this has been only fixed partially.
With enzyme-adapter-react-16@1.11.2 I still get the following warning when returning null from a renderProp.

Warning: Failed prop type: The prop `children` is marked as required in `SimpleSFCWrapper`, but its value is `null`.
    in SimpleSFCWrapper

[ljharb]

@lo1tuma please file another issue; making a wrapper around null seems strange.