React.Children.count returns invalid number of children

Do you want to request a feature or report a bug?

BUG

What is the current behavior?

nextProps.children false

React.Children.count(nextProps.children) 1

React.Children.toArray(nextProps.children).length 0

React.version “16.4.2”

If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem. Your bug will get fixed much faster if we can run your code and it doesn’t have dependencies other than React. Paste the link to your JSFiddle (https://jsfiddle.net/Luktwrdm/) or CodeSandbox (https://codesandbox.io/s/new) example below:

What is the expected behavior?

That React.Children.count(false) behaviour is somehow aligned with React.Children.toArray(false)

Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?

[amannn]

I also just noticed that render prop children are not counted as children:

Children.count(() => <span>hello</span>); // 0
Children.map(() => <span>hello</span>); // []

[nhunzaker]

Ah, you’re totally right, and I apologize:

Here’s a test case: https://codesandbox.io/s/rwk4qr61po

I think this is, indeed, a bug.