sproptypes_user_with_proptypes.jsx

const User = ({ name, friends }) => (
  <div>
    Name: {name}
    {friends && friends.map(friend => <User key={friend.name} {...friend} />)}
  </div>
);

User.propTypes = {
  name: PropTypes.string.isRequired,
  friends: PropTypes.arrayOf(
    PropTypes.shape({
      name: PropTypes.string.isRequired
    })
  )
};