refactor(query): move selectedInclusively() into separate helper

Re: #5737

Author: vkarpov15

lib/query.js

@@ -11,6 +11,7 @@ var cast = require('./cast');
 var castUpdate = require('./services/query/castUpdate');
 var hasDollarKeys = require('./services/query/hasDollarKeys');
 var helpers = require('./queryhelpers');
+var isInclusive = require('./services/projection/isInclusive');
 var mquery = require('mquery');
 var readPref = require('./drivers').ReadPreference;
 var selectPopulatedFields = require('./services/query/selectPopulatedFields');
@@ -3828,23 +3829,7 @@ Query.prototype.centerSphere = function() {
  */
 
 Query.prototype.selectedInclusively = function selectedInclusively() {
-  if (!this._fields) {
-    return false;
-  }
-
-  var keys = Object.keys(this._fields);
-  if (keys.length === 0) {
-    return false;
-  }
-
-  for (var i = 0; i < keys.length; ++i) {
-    var key = keys[i];
-    if (typeof this._fields[key] !== 'object' && !!this._fields[key]) {
-      return true;
-    }
-  }
-
-  return false;
+  return isInclusive(this._fields);
 };
 
 /**

lib/services/projection/isInclusive.js

@@ -0,0 +1,24 @@
+'use strict';
+
+module.exports = function isInclusive(projection) {
+  if (projection == null) {
+    return false;
+  }
+
+  var props = Object.keys(projection);
+  var numProps = props.length;
+  if (numProps === 0) {
+    return false;
+  }
+
+  for (var i = 0; i < numProps; ++i) {
+    var prop = props[i];
+    // If field is truthy (1, true, etc.) and not an object, then this
+    // projection must be inclusive. If object, assume its $meta, $slice, etc.
+    if (typeof projection[prop] !== 'object' && !!projection[prop]) {
+      return true;
+    }
+  }
+
+  return false;
+};