We should be able to look at see if the child has a data-react-id attribute but isn't rendered by this copy of React and consequently warn.

See https://groups.google.com/forum/#!topic/reactjs/mdwfKKJ0L2Q.

return node.getAttribute && node.getAttribute(ATTR_NAME) || '';
}
/**
 * Mounts this component and inserts it into the DOM.
 *
 * @param {ReactComponent} componentInstance The instance to mount.
 * @param {DOMElement} container DOM element to mount into.
 * @param {ReactReconcileTransaction} transaction
 * @param {boolean} shouldReuseMarkup If true, do not insert markup
 */
function mountComponentIntoNode(
  wrapperInstance,
  container,
  transaction,
  shouldReuseMarkup,
  context
) {
  var markerName;
  if (ReactFeatureFlags.logTopLevelRenders) {
    var wrappedElement = wrapperInstance._currentElement.props.child;
    var type = wrappedElement.type;
    markerName = 'React mount: ' + (
      typeof type === 'string' ? type :
      type.displayName || type.name
    );