title: TypeError: Chaining cycle detected for promise
body: <p><code>user</code> is a Mongoose entity object. I want to append some data on user, save it and just proceed to next <code>then()</code> after that entity has been successfully saved on DB. So I am doing:</p>
  
  <pre><code>User
    .findOne({ email: req.body.email })
    .then((user) =&gt; {
      user.data = ...;
      user = user.save().then(() =&gt; user);
      return user;
    })
    .then((user =&gt; ... /* continue after user has been saved */ ))
  </code></pre>
  
  <p>Yet, I am getting a <code>TypeError: Chaining cycle detected for promise</code> and I am not realizing how to solve my requirements.</p>