ReactDOM.render()/unstable_renderIntoContainer() doesn't return instance if called during an update

[seanlandsman]

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

Bug

What is the current behavior?

ReactDOM.render and ReactDOM.unstable_renderSubtreeIntoContainer no longer return created React component instances

If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem via https://jsfiddle.net or similar (template: https://jsfiddle.net/84v837e9/).

this.eParentElement = document.createElement('div');
const ReactComponent = React.createElement(this.reactComponent, params);
this.componentRef = ReactDOM.render(ReactComponent, this.eParentElement);

What is the expected behavior?

After the steps above this.componentRef should be an instance just created - it is now null with React 16 beta.

It's entirely possible that I should be doing something different now, but if so it's not clear what that should be

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

React 16 beta
Chrome
OSX

thanks

[gaearon]

Seems like the same issue as #10294 (comment).

[jlongster]

This does seem related. I posted the small test case here that errors for me: https://github.com/jlongster/fiber-modal-error

In this case the react-modal library is calling renderSubtreeIntoContainer and also expecting an instance back.

I was going to file a new bug but this one seems like it?

[jlongster]

Although it is weird because my above test cases works if you always render <Modal> instead of doing this.state.open && <Modal> like we do. So apparently is does get an instance back in the former case?

[gaearon]

@jlongster

So apparently is does get an instance back in the former case?

In your example, it only fails to get the instance on first render. This is why it only fails with {this.state.open && <Modal />} since that makes each render “first”.

[seanlandsman]

@gaearon Yes, it def looks related

I was working on a reproducible example too, but this isn't a trivial exercise trying to extricate only the relevant bits

Interestingly everything renders correctly as it did before, its just not returning an instance (which is important for actions down the line)

[gaearon]

@seanlandsman

Can you please provide example? I just recreated your example in fiddle and it does return an object.
https://jsfiddle.net/dLqbryo6/

[jlongster]

I will file a new bug with mine because it might not be related, feel free to dupe to this one.

[seanlandsman]

@gaearon Great, ok - I'll take a look now

I actually came to the same point that @jlongster did in #10294 - containerFiber.child is null in getPublicRootInstance

I'll take a look at your example and try see what's different to mine - thanks

[gaearon]

I reproduced it!
https://jsfiddle.net/x7c7bdh0/

This only happens when ReactDOM.render is called during an update (e.g. in componentDidMount).

[seanlandsman]

Ah, great! I'll continue to see what I can find in the meantime though, but I am pleased you've managed to reproduce it!

[jlongster]

I filed my bug here: #10310

Still not sure if this is related. I think renderSubtreeIntoContainer might never return an instance just like here, because the modal library only ever tries to access this.portal in componentWillUnmount here: https://github.com/reactjs/react-modal/blob/master/src/components/Modal.js#L129

If we render it like <Modal isOpen={this.state.open} /> componentWillUnmount will never be called and we don't realize that this.portal is null.