title: (Mongoose/MongoDB) Push to empty array?
body: <p>I'm got an empty array in my model that I am trying to push an array to but Compass does not show any changes to the document.</p>
  
  <p>I've tried setting the type of my <code>user_list</code> property to <code>array</code> in my model, as well as just setting it as an empty array with <code>[]</code>. I have also deleted and recreated the entire database as well to make sure it wasn't a memory issue.</p>
  
  <p>Model:</p>
  
  <pre><code>const guildSchema = new Schema({
      guild_name: String,
      guild_id: { type: String, unique: true },
      ...
      user_list: []
  })
  </code></pre>
  
  <p>Fetching the array and trying to push:</p>
  
  <pre><code>bot.on("guildUpdate", (oldGuild, newGuild) =&gt; {
      let userList = newGuild.fetchMembers().then(function(results){ console.log(results.members.keyArray()); userList = results.members.keyArray();
          Guild.findOneAndUpdate({guild_id: oldGuild.id}, {"$set": {"guild_name": newGuild.name, "guild_icon": newGuild.iconURL}}, {"$push": {"user_list": userList}}, function(err) {
              if (err) throw (err);
          });
      }).catch(console.error)
  })
  </code></pre>
  
  <p><code>console.log(results.members.keyArray())</code> returns the simple array that I am trying to push just fine. Compass shows updates made with <code>$set</code> just fine as well. Something is going wrong when trying to push to <code>user_list</code>, as Compass continues to just show a blank array upon update.</p>