fix(populate): handle slice projections correctly when automatically selecting populated fields

Fix #5737

Author: vkarpov15

lib/query.js

@@ -15,6 +15,7 @@ var mquery = require('mquery');
 var readPref = require('./drivers').ReadPreference;
 var selectPopulatedFields = require('./services/query/selectPopulatedFields');
 var setDefaultsOnInsert = require('./services/setDefaultsOnInsert');
+var slice = require('sliced');
 var updateValidators = require('./services/updateValidators');
 var util = require('util');
 var utils = require('./utils');
@@ -263,6 +264,49 @@ Query.prototype.toConstructor = function toConstructor() {
  * @api public
  */
 
+Query.prototype.slice = function() {
+  if (arguments.length === 0) {
+    return this;
+  }
+
+  this._validate('slice');
+
+  var path;
+  var val;
+
+  if (arguments.length === 1) {
+    var arg = arguments[0];
+    if (typeof arg === 'object' && !Array.isArray(arg)) {
+      var keys = Object.keys(arg);
+      var numKeys = keys.length;
+      for (var i = 0; i < numKeys; ++i) {
+        this.slice(keys[i], arg[keys[i]]);
+      }
+      return this;
+    }
+    this._ensurePath('slice');
+    path = this._path;
+    val = arguments[0];
+  } else if (arguments.length === 2) {
+    if ('number' === typeof arguments[0]) {
+      this._ensurePath('slice');
+      path = this._path;
+      val = slice(arguments);
+    } else {
+      path = arguments[0];
+      val = arguments[1];
+    }
+  } else if (arguments.length === 3) {
+    path = arguments[0];
+    val = slice(arguments, 1);
+  }
+
+  var p = {};
+  p[path] = { $slice: val };
+  return this.select(p);
+};
+
+
 /**
  * Specifies the complementary comparison value for paths specified with `where()`
  *

lib/services/query/selectPopulatedFields.js

@@ -41,5 +41,5 @@ function isPathInFields(userProvidedFields, path) {
     }
     cur += '.' + pieces[i];
   }
-  return false;
+  return userProvidedFields[cur] != null;
 }