Warn when reading from event which has been returned to the pool

The title is an assumption based on my experience upgrading. Here’s an example of what I’m seeing:

const App = React.createClass({
  getInitialState() {
    return {clicked: 0}
  },
  handleClick(e) {
    console.log('e.target before callback is null?', e.target === null) // e.target is not null here
    this.setState({
      clicked: this.state.clicked + 1
    }, () => {
      console.log('e.target after callback is null?', e.target === null) // e.target is null here
    })
  },
  render() {
    return (
      <div
        onClick={this.handleClick}
      >
        Click me {this.state.clicked}
      </div>
    )
  }
})

ReactDOM.render(<App />, document.getElementById('root'))

Here’s a jsbin that demonstrates the behavior with 0.14.6: https://jsbin.com/gasozit/edit?js,console,output

Here’s a jsbin with 0.14.7: https://jsbin.com/vaberi/edit?js,console,output

Notice in the console, that the log inside the callback is logging that e.target === null evaluates to true. In my app, I’m passing the event to an onChange handler which utilizes the target. So this update breaks that situation.

This may or may not be a bug. It may just be necessary for avoiding the memory leak. If that’s the case, then it’s a support request 😄 How should I handle this if I’m passing the event to another callback and I want that event to have references to things like target?

[gaearon]

I didn’t know persist() existed! This made my day.

[kentcdodds]

I’d love to make this my first contribution if you don’t mind holding off for a bit for me to work on it. 😄