title: MongoDB Aggregate Projection working differently than find Projection
body: <p>I have a question about using a projection in my find query of MongoDB. My question is the following, my documents look like:</p>
  
  <pre><code>{
      "_id" : ObjectId("55e59045cded246cb8e8183e"),
      "name" : "Acrobatics",
      "category" : {
          "title" : "Combat",
          "key" : "combat"
      },
      "calculationType" : "Skill",
      "statistics" : "INI",
      "title" : "Acrobatics"
  }
  </code></pre>
  
  <p>My aggregate query looks like:</p>
  
  <pre><code>db.getCollection('skills').aggregate([
      { $match: { "category.title": "Combat" } },
      { $project: { "_id": 0, "name": 1, "category": "$category.title" } }
  ]);
  </code></pre>
  
  <p>The result is as you would expect:</p>
  
  <pre><code>{
      "result" : [ 
          {
              "name" : "Acrobatics",
              "category" : "Combat"
          }
      ],
      "ok" : 1.0000000000000000
  }
  </code></pre>
  
  <p>Now I want to do the same projection using the find method instead of the aggregate, my query looks like:</p>
  
  <pre><code>db.getCollection('skills').find(
      { "category.key": "combat" },
      { "_id": 0, "name": 1, "category": "$category.title" }
  );
  </code></pre>
  
  <p>And the result looks like: </p>
  
  <pre><code>[{
      "name" : "Acrobatics",
      "category" : {
          "title" : "Combat",
          "key" : "combat"
      }
  }]
  </code></pre>
  
  <p>As you can see with the find the result of the subdocument <em>category</em> is not folded. I expected the same <em>form</em> as the aggregate function; minus the result and OK properties. </p>
  
  <p>Am I doing something wrong? Or is my expectation just wrong? Thank you for reading this.</p>