function updatePortalComponent(current, workInProgress, renderExpirationTime) {
  pushHostContainer(workInProgress, workInProgress.stateNode.containerInfo);
  const nextChildren = workInProgress.pendingProps;
  if (hasLegacyContextChanged()) {
    // Normally we can bail out on props equality but if context has changed
    // we don't do the bailout and we have to reuse existing props instead.
  } else if (workInProgress.memoizedProps === nextChildren) {
    return bailoutOnAlreadyFinishedWork(current, workInProgress);
  }

  if (current === null) {
    // Portals are special because we don't append the children during mount
    // but at commit. Therefore we need to track insertions which the normal
    // flow doesn't do during mount. This doesn't happen at the root because
    // the root always starts with a "current" with a null child.
    // TODO: Consider unifying this with how the root works.
    workInProgress.child = reconcileChildFibers(
      workInProgress,
      null,
      nextChildren,
      renderExpirationTime,
    );
    memoizeProps(workInProgress, nextChildren);
  } else {
    reconcileChildren(current, workInProgress, nextChildren);
    memoizeProps(workInProgress, nextChildren);
  }
  return workInProgress.child;
}