Extracted from https://github.com/facebook/react/issues/12643.

We're currently diff a host node in the complete phase even if it has bailed out in the begin phase. By itself, this just means we're doing a little bit more work than necessary. But it also has some observable effects. In particular, https://github.com/facebook/react/issues/13424 (which by itself would be very rare and probably not worth fixing) is made worse because we end up committing update to inputs from another component.

I have a fix for this in https://github.com/facebook/react/pull/13423. Filing this for posterity.
ReactDOM.unmountComponentAtNode(container);
    expect(portalContainer.innerHTML).toBe('');
    expect(container.innerHTML).toBe('');
  });
  it('should render many portals', () => {
    const portalContainer1 = document.createElement('div');
    const portalContainer2 = document.createElement('div');
    const ops = [];
    class Child extends React.Component {
      componentDidMount() {
        ops.push(`${this.props.name} componentDidMount`);
      }
      componentDidUpdate() {
        ops.push(`${this.props.name} componentDidUpdate`);
      }
      componentWillUnmount() {
        ops.push(`${this.props.name} componentWillUnmount`);
      }
      render() {
        return <div>{this.props.name}</div>;
      }
    }
    class Parent extends React.Component {
      componentDidMount() {
        ops.push(`Parent:${this.props.step} componentDidMount`);
      }
      componentDidUpdate() {
        ops.push(`Parent:${this.props.step} componentDidUpdate`);
      }
      componentWillUnmount() {