We're switching Atom to React, but we want to support backward-compatible shims to our previous view framework.

In the old framework, views were represented as jQuery-wrapped DOM elements. Ideally, we'd like to provide backward-compatible shims by simply rendering the React component and wrapping its root element in a jQuery wrapper with an API that's compatible to our old editor views. That would essentially look like this:

``` javascript
var editorRoot = document.createElement('div')
React.renderComponentWithRootElement(Editor(props), editorRoot)

// the element would actually be wrapped in a custom subclass of jQuery,
// but this is clearer for this example
var editorShim = $(editorRoot) 
```

Currently, this isn't possible because React components need to be rendered into a container. So instead we need to create a wrapper element and render the component inside it. This is sad because it adds an extra layer of markup which confuses styling, and also means that the editor has a wrapper when used via the shim layer but no wrapper when embedded as a child via React itself.

Is there something fundamental preventing React from adopting DOM nodes directly without the parent? Is this something we could even hack in in a way that would be somewhat maintainable?

:heart:

const {groovy, doovy, separator} = this.state;
        return <div>{`${groovy}${separator}${doovy}`}</div>;
      }
    }
    const shallowRenderer = createRenderer();
    const result = shallowRenderer.render(<SimpleComponent />);
    expect(result).toEqual(<div>doovy-doovy</div>);
  });
  it('can setState in componentWillReceiveProps when shallow rendering', () => {
    class SimpleComponent extends React.Component {
      state = {count: 0};
      UNSAFE_componentWillReceiveProps(nextProps) {
        if (nextProps.updateState) {
          this.setState({count: 1});
        }
      }
      render() {
        return <div>{this.state.count}</div>;
      }
    }
    const shallowRenderer = createRenderer();
    let result = shallowRenderer.render(
      <SimpleComponent updateState={false} />,
    );
    expect(result.props.children).toEqual(0);
    result = shallowRenderer.render(<SimpleComponent updateState={true} />);
    expect(result.props.children).toEqual(1);
  });
  it('can update state with static getDerivedStateFromProps when shallow rendering', () => {
    class SimpleComponent extends React.Component {