Bug: React.Node should not have true, or PropTypes.node warns it

[ypresto]

React version: 16.8.6

Steps To Reproduce

import PropTypes from 'prop-types';

type Props = {
  component: React.Node
};

function Container(props: Props) {
  return ...;
}

Container.propTypes = {
  component: PropTypes.node
}

<Container component={true} />

The current behavior

Flow does not emit error (as React.Node accepts true), but PropTypes.node emits below runtime error in browser's console.

Invalid prop `component` supplied to `Container`, expected a ReactNode.

The expected behavior

Flow emits type error.

---

According to a maintainer of prop-types, formerly React itself did not accept true for JSX node (in flow React.Node) (so not changing prop-types for now), is it right?

[ljharb]

Note; I’m not claiming that, I’m suggesting it as a possible history. Clarification would be appreciated.

[bvaughn]

The expected behavior

Flow emits type error.

Why is this the expected behavior?

The React docs say:

Booleans, Null, and Undefined Are Ignored

false, null, undefined, and true are valid children. They simply don’t render. These JSX expressions will all render to the same thing:

<div />
<div></div>
<div>{false}</div>
<div>{null}</div>
<div>{undefined}</div>
<div>{true}</div>

The docs have said this since back through 2016 (when I stopped tracing).

type Props = {
  component: React.Node
};

IMO this prop type says "I require something React can render to be passed as a component prop" - a case which true satisfies.

[ljharb]

I’m wondering if perhaps true was invalid prior to react 15?

[bvaughn]

Not sure! I wasn't on the team before v15. 🙂

I don't think that would change my stance on this issue though. I don't think this is a bug or requires any change from React.

[ljharb]

It requires a change in prop-types, however, (which i maintain) so it’d be useful to determine exactly when it changed. That said, there’s probably nothing actionable for react to do at this point and the issue can be closed.

[bvaughn]

Right, my comment was only meant for React. Looks like there's a separate issue filed against prop-types (facebook/prop-types#310). I'm going to go ahead and close this issue down.

[ljharb]

Did some testing; looks like React 15 disallowed true; React 16 allows it. I'll update the prop-types package.