Callback of `setState` is called at not expected time.

See the following code:

class A extends React.Component {
  componentWillMount() {
    this.setState({
        a: 'a'
    }, () => {
      console.log('setState');
    })
  }
  render() {
    return <B></B>
  }
}

class B extends React.Component{
  render() {
    return <div>B</div>;
  }
  componentDidMount() {
    console.log('didMount');
  }
}


ReactDOM.render(<A/>, mountNode);

Preact will log:

setState
didMount

React will log:

didMount
setState

I’m not sure if this is a bug？It will be error when access domNode of child component in callback.

[JoviDeCroock]

Oh, the state doesn’t seem to be updated in the callback but it is in the render, will try to look into it soon.

[planttheidea]

@ForsakenHarmony I suppose it depends on your definition of long-term. The non-prefixed versions will be deprecated after version 16, however “UNSAFE_” will still work and be maintained throughout version 17. No guarantees for version 18 and beyond, however that is a distant future. Should we dismiss the use-case because one day, years down the line, the API may be gone entirely?