https://codesandbox.io/s/xl7k7j1k6w

Not sure if this is intended or not, the longer term existence of these hooks suggested to me that they have their purposes still, so might be needed in conjunction with gDSFP. The particular use-case that caused me to discover this was a migrating: https://github.com/react-bootstrap/react-bootstrap/blob/master/src/Dropdown.js#L137 where document focus needs to be checked _prior_ to an update flushing because the update changes visual state and drops focus. I could move this to `render()` but React has traditionally yelled at me when doing ref stuff there. Admittedly in the migrated code i don't need `findDOMNode` so it'd be fine.
if (element == null) {
    return '#empty';
  } else if (typeof element === 'string' || typeof element === 'number') {
    return '#text';
  } else if (typeof element.type === 'string') {
    return element.type;
  } else {
    return element.type.displayName || element.type.name || 'Unknown';
  }
}
function getStackAddendum() {
  let stack = '';
  if (currentlyValidatingElement) {
    const name = getDisplayName(currentlyValidatingElement);
    const owner = currentlyValidatingElement._owner;
    stack += describeComponentFrame(
      name,
      currentlyValidatingElement._source,
      owner && getComponentName(owner),
    );
  }
  return stack;
}
function getName(type, instance) {