upsert fails on MSSQL with composite unique key

[massivex]

What are you doing?

upsert in MSSQL with composite unique key

// Define a Model with a composite unique key
class Project extends Sequelize.Model { }
Project.init({
    department: { type: Sequelize.STRING(20), unique: 'ak__project', allowNull: false },
    code: { type: Sequelize.STRING(20), unique: 'ak__project', allowNull: false }
}, { sequelize, modelName: 'project' });

Project.upsert({ department: 'DEV', code: '' }); // => Error: Primary Key or Unique key should be passed to upsert query

To Reproduce
Steps to reproduce the behavior:

1. Define model with a composite key with at least a string field
2. Execute an upsert with a key set to empty string
3. See error Primary Key or Unique key should be passed to upsert query

What do you expect to happen?

Unique key values specified must be used as where even if a key value is an empty string

What is actually happening?

Sequelize mssql dialect exclude unique keys value from where because one of the key values is an empty string.
This behaviour happens because empty string is evaluated falsy exactly at

sequelize/lib/dialects/mssql/query-generator.js

Line 442 in f3b5f99

if (!clause[key]) {

Environment

Dialect:

• mysql
• postgres
• sqlite
• mssql
• any

Dialect tedious version: 5.0.3
Database version: SQL SERVER 2017 - 14.0.3045.24
Sequelize version: 4.44.2
Node Version: 8.11.2
OS: Linux
If TypeScript related: TypeScript version: XXX

Tested with latest release:

• No
• Yes, specify that version: 5.11.0

[massivex]

I suggest to change this line

sequelize/lib/dialects/mssql/query-generator.js

Line 442 in f3b5f99

if (!clause[key]) {

with

if (typeof clause[key] === 'undefined' || clause[key] == null) {

to esclude undefined and null values but keep string empty and other falsy values like 0 and false that are both valid for unique key values.

[sushantdhiman]

Fixed by #12453