React.cloneElement handles `undefined` props differently to React.createElement

I’m not sure if this is expected but it caught me out earlier:

// Without clone
function MyComponent() {}

MyComponent.defaultProps = {
    foo: 'foo'
};

let element = React.createElement(MyComponent, {
    foo: undefined
});

console.log(element.props.foo); // 'foo'

// With clone
function MyComponent() {}

MyComponent.defaultProps = {
    foo: 'foo'
};

let element = React.createElement(MyComponent);
element = React.cloneElement(element, {
    foo: undefined
});

console.log(element.props.foo); // undefined

[arjunsharma]

It does the same thing as React.createElement, which is to set the property to the value in defaultProps. So item # 2 in your list.

If you want to look at the PR that fixed this, it was fixed in #5997.

[mattzeunert]

Why would it restore the default value? It’s not the behavior I would expect intuitively.