fix(include): include.attributes set to empty array will no longer force primary key inclusion

changelog.md

 # Next
-- [CHANGED] The `references` property of model attributes has been transformed to an object: `{type: Sequelize.INTEGER, references: { model: SomeModel, key: 'some_key' }}`. The former format is deprecated.
+- [FIXED] `include.attributes = []` will no longer force the inclusion of the primary key, making it possible to write aggregates with includes.
+- [CHANGED] The `references` property of model attributes has been transformed to an object: `{type: Sequelize.INTEGER, references: { model: SomeModel, key: 'some_key' }}`. The former format (`references` and `referecesKey`) still exists but is deprecated and will be removed in 4.0.
 
 # 3.0.0
 

lib/model.js

@@ -2049,11 +2049,14 @@ module.exports = (function() {
 
     if (include.attributes) {
       include.originalAttributes = include.attributes.slice(0);
-      include.model.primaryKeyAttributes.forEach(function(attr) {
-        if (include.attributes.indexOf(attr) === -1) {
-          include.attributes.unshift(attr);
-        }
-      });
+
+      if (include.attributes.length) {
+        include.model.primaryKeyAttributes.forEach(function(attr) {
+          if (include.attributes.indexOf(attr) === -1) {
+            include.attributes.unshift(attr);
+          }
+        });
+      }
     } else {
       include.attributes = Object.keys(include.model.tableAttributes);
     }

test/integration/include/findAll.test.js

@@ -1877,5 +1877,46 @@ describe(Support.getTestDialectTeaser('Include'), function() {
         });
       });
     });
+
+    it('should ignore include with attributes: [] (used for aggregates)', function () {
+      var Post = this.sequelize.define('Post', {
+            title: DataTypes.STRING
+          })
+        , Comment = this.sequelize.define('Comment', {
+            content: DataTypes.TEXT
+          });
+
+      Post.Comments = Post.hasMany(Comment, {as: 'comments'});
+
+      return this.sequelize.sync({force: true}).bind(this).then(function () {
+        return Post.create({
+          title: Math.random().toString(),
+          comments: [
+            {content: Math.random().toString()},
+            {content: Math.random().toString()},
+            {content: Math.random().toString()},
+          ]
+        }, {
+          include: [Post.Comments]
+        });
+      }).then(function () {
+        return Post.findAll({
+          attributes: [
+            'title',
+            [this.sequelize.fn('COUNT', this.sequelize.col('comments.id')), 'commentCount']
+          ],
+          include: [
+            {association: Post.Comments, attributes: []}
+          ]
+        });
+      }).then(function (posts) {
+        expect(posts.length).to.equal(1);
+
+        var post = posts[0];
+
+        expect(post.get('comments')).not.to.be.ok;
+        expect(post.get('commentCount')).to.equal(3);
+      });
+    });
   });
 });