Fix issue where deep-clone doesn't preserve sequelize functions

lib/utils.js

@@ -95,6 +95,8 @@ var Utils = module.exports = {
   },
   cloneDeep: function(obj, fn) {
     return lodash.cloneDeep(obj, function (elem) {
+      // Preserve special data-types like `fn` across clones. _.get() is used for checking up the prototype chain
+      if (!!Utils._.get(elem, 'clone') && typeof elem.clone === 'function') {return elem.clone(); }
       // Unfortunately, lodash.cloneDeep doesn't preserve Buffer.isBuffer, which we have to rely on for binary data
       if (Buffer.isBuffer(elem)) { return elem; }
 
@@ -421,4 +423,8 @@ Utils.fn.prototype._isSequelizeMethod =
 Utils.col.prototype._isSequelizeMethod =
 Utils.json.prototype._isSequelizeMethod = true;
 
+Utils.fn.prototype.clone = function() {
+  return new Utils.fn(this.fn, this.args);
+};
+
 Utils.Promise = require('./promise');

test/integration/model/upsert.test.js

@@ -223,6 +223,31 @@ describe(Support.getTestDialectTeaser('Model'), function() {
           expect(user.baz).to.equal('oof');
         });
       });
+
+      it('works with database functions', function() {
+        return this.User.upsert({ id: 42, username: 'john', foo: this.sequelize.fn('upper', 'mixedCase1')}).bind(this).then(function(created) {
+          if (dialect === 'sqlite') {
+            expect(created).to.be.undefined;
+          } else {
+            expect(created).to.be.ok;
+          }
+          return this.sequelize.Promise.delay(1000).bind(this).then(function() {
+            return this.User.upsert({ id: 42, username: 'doe', foo: this.sequelize.fn('upper', 'mixedCase2') });
+          });
+        }).then(function(created) {
+          if (dialect === 'sqlite') {
+            expect(created).to.be.undefined;
+          } else {
+            expect(created).not.to.be.ok;
+          }
+          return this.User.findById(42);
+        }).then(function(user) {
+          expect(user.createdAt).to.be.ok;
+          expect(user.username).to.equal('doe');
+          expect(user.foo).to.equal('MIXEDCASE2');
+        });
+      });
+
     });
   }
 });