title: Mongoose findById is not returning all fields
body: <p>I'm calling findById using mongoose and it's not returning all fields, or at least it's not mapping to a field correctly. But it returns that field if I use aggregate</p>
  <p>I have the following schema</p>
  <pre><code>const ratingSchema = new mongoose.Schema({
      rating: {
          type: Number,
          default: 0,
          min: 0,
          max: 5
      }
  })
  
  const locationSchema = new mongoose.Schema({ 
      name: {
          type: String,
          required: true,
      },
      address: {
          type: String,
          required: true,
      },
      rating: ratingSchema,
      
      facilities: [String],
  });
  
  locationSchema.index({coords: '2dsphere'});
  
  mongoose.model('Location', locationSchema);
  </code></pre>
  <p>When I call</p>
  <pre><code>const Loc = mongoose.model('Location');
  
  const locationsReadOne = (req, res) =&gt; {
      Loc
          .findById(req.params.locationid)
          .exec((err, location) =&gt; {
              if (!location) {
                  return res.status(404).json({&quot;message&quot;:&quot;location not found&quot;});
              } else if (err) {
                  return res.status(404).json(err);
              }
              console.log(&quot;locationsReadOne:&quot;,location);
              res.status(200).json(location);
          });
  };
  </code></pre>
  <p>It returns the schema, but the rating field is not being returned. Here is a console.log of the returned object:</p>
  <pre><code>locationsReadOne: {
    facilities: [ 'Hot drinks', 'Food', 'Premium wifi' ],
    _id: 5f88bfdc4df4ca7709462865,
    name: 'Starcups',
    address: '125 High Street, Reading, RG6 1PS'
  }
  </code></pre>
  <p>If I call Loc.aggregate, the rating field is returned:</p>
  <pre><code>{
    _id: 5f8b2ee15b0b6784a847b600,
    facilities: [ 'Tea', ' Restroom' ],
    name: 'Tea Leaf',
    address: '2192 Green St.',
    rating: 0,
  
  }
  {
    _id: 5f88bfdc4df4ca7709462865,
    name: 'Starcups',
    address: '125 High Street, Reading, RG6 1PS',
    rating: 3,
    facilities: [ 'Hot drinks', 'Food', 'Premium wifi' ]
  }
  </code></pre>
  <p>Any idea why this would happen? I can clearly see the rating field in each of the documents in MongoDB compass and they are all listed as type Double. Why are they being returned in aggregate, but not in findById(id) or even in find()?</p>
  <p>Thank you.</p>