feat(associations): belongsTo association setter now supports {save: false}, closes #2582

changelog.md

 # Next
 - [BUG] Fixed issue with subquery creating `include.where` and a paranoid main model.#2749/#2769
 - UniqueConstraintErrors will now extend from ValidationError making it possible to catch both with `.catch(ValidationError)`
+- [FEATURE] Adds `{save: false}` for belongsTo relationship setters. `user.setOrganization(organization, {save: false})` will then only set the foreign key value, but not trigger a save on `user`.
 
 # 2.0.0-rc4
 - [INTERNALS] Update `inflection` dependency to v1.5.3

lib/associations/belongs-to.js

@@ -128,6 +128,8 @@ module.exports = (function() {
 
       this.set(association.identifier, value);
 
+      if (options.save === false) return;
+
       options = Utils._.extend({
         fields: [association.identifier],
         allowNull: [association.identifier],

test/associations/belongs-to.test.js

@@ -261,6 +261,34 @@ describe(Support.getTestDialectTeaser('BelongsTo'), function() {
         });
       });
     });
+
+    it('should set the foreign key value without saving when using save: false', function () {
+      var Comment = this.sequelize.define('comment', {
+        text: DataTypes.STRING
+      });
+
+      var Post = this.sequelize.define('post', {
+        title: DataTypes.STRING
+      });
+
+      Post.hasMany(Comment, {foreignKey: 'post_id'});
+      Comment.belongsTo(Post, {foreignKey: 'post_id'});
+
+      return this.sequelize.sync({force: true}).then(function () {
+        return Promise.join(
+          Post.create(),
+          Comment.create()
+        ).spread(function (post, comment) {
+          expect(comment.get('post_id')).to.be.undefined;
+
+          var setter = comment.setPost(post, {save: false});
+
+          expect(setter).to.be.undefined;
+          expect(comment.get('post_id')).to.equal(post.get('id'));
+          expect(comment.changed('post_id')).to.be.true;
+        });
+      });
+    });
   });
 
   describe('createAssociation', function() {