[MSSQL] Format isolation level as tedious isolation level (#7297)

* [MSSQL] Format isolation level as tedious isolation level

* [ci skip] Added changelog entry

* Added unit test that stubs beginTransaction method

* Fixes jshint error

* Explicitly pass tedious lib instance

changelog.md

 # Future
+- [FIXED] Map isolation level strings to tedious isolation level [MSSQL] [#7296] (https://github.com/sequelize/sequelize/issues/7296)
 - [FEATURE] `addConstraint`, `removeConstraint`, `showConstraint` [#7108](https://github.com/sequelize/sequelize/pull/7108)
 - [FIXED] `changeColumn` generates incorrect query with ENUM type [#7455](https://github.com/sequelize/sequelize/pull/7455)
 - [ADDED] `options.alter` to sequelize.sync() to alter existing tables.[#537](https://github.com/sequelize/sequelize/issues/537)

lib/dialects/mssql/query.js

@@ -51,7 +51,7 @@ class Query extends AbstractQuery {
           } else {
             resolve(this.formatResults());
           }
-        }, this.options.transaction.name, this.options.isolationLevel);
+        }, this.options.transaction.name, Utils.mapIsolationLevelStringToTedious(this.options.isolationLevel, connection.lib));
       } else if (_.startsWith(this.sql, 'COMMIT TRANSACTION')) {
         connection.commitTransaction(err => {
           if (err) {

lib/utils.js

@@ -496,3 +496,23 @@ class Where extends SequelizeMethod {
 exports.Where = Where;
 
 exports.validateParameter = parameterValidator;
+
+
+exports.mapIsolationLevelStringToTedious = (isolationLevel, tedious) => {
+  if (!tedious) {
+    throw new Error('An instance of tedious lib should be passed to this function');
+  }
+  const tediousIsolationLevel = tedious.ISOLATION_LEVEL;
+  switch (isolationLevel) {
+    case 'READ_UNCOMMITTED':
+      return tediousIsolationLevel.READ_UNCOMMITTED;
+    case 'READ_COMMITTED':
+      return tediousIsolationLevel.READ_COMMITTED;
+    case 'REPEATABLE_READ':
+      return tediousIsolationLevel.REPEATABLE_READ;
+    case 'SERIALIZABLE':
+      return tediousIsolationLevel.SERIALIZABLE;
+    case 'SNAPSHOT':
+      return tediousIsolationLevel.SNAPSHOT;
+  }
+};
\ No newline at end of file

test/unit/dialects/mssql/query.js

+'use strict';
+
+const path = require('path');
+const Query = require(path.resolve('./lib/dialects/mssql/query.js'));
+const Support = require(path.resolve('./test/support'));
+const sequelize = Support.sequelize;
+const sinon = require('sinon');
+const expect = require('chai').expect;
+const tedious = require('tedious');
+const tediousIsolationLevel = tedious.ISOLATION_LEVEL;
+const connectionStub = { beginTransaction: () => {}, lib: tedious };
+
+let sandbox, query;
+
+describe('[MSSQL]', () => {
+  describe('beginTransaction', () => {
+    beforeEach(() => {
+      sandbox = sinon.sandbox.create();
+      const options = {
+        transaction: { name: 'transactionName' },
+        isolationLevel: 'REPEATABLE_READ',
+        logging: false
+      };
+      sandbox.stub(connectionStub, 'beginTransaction', cb => {
+        cb();
+      });
+      query = new Query(connectionStub, sequelize, options);
+    });
+
+    it('should call beginTransaction with correct arguments', () => {
+      return query._run(connectionStub, 'BEGIN TRANSACTION')
+        .then(() => {
+          expect(connectionStub.beginTransaction.called).to.equal(true);
+          expect(connectionStub.beginTransaction.args[0][1]).to.equal('transactionName');
+          expect(connectionStub.beginTransaction.args[0][2]).to.equal(tediousIsolationLevel.REPEATABLE_READ);
+        });
+    });
+
+    afterEach(() => {
+      sandbox.restore();
+    });
+  });
+});

test/unit/utils.test.js

@@ -5,6 +5,8 @@ const expect = chai.expect;
 const Support = require(__dirname + '/support');
 const DataTypes = require(__dirname + '/../../lib/data-types');
 const Utils = require(__dirname + '/../../lib/utils');
+const tedious = require('tedious');
+const tediousIsolationLevel = tedious.ISOLATION_LEVEL;
 
 suite(Support.getTestDialectTeaser('Utils'), () => {
   suite('merge', () => {
@@ -265,4 +267,33 @@ suite(Support.getTestDialectTeaser('Utils'), () => {
       expect(testLogger.namespace).to.be.eql('sequelize:test');
     });
   });
+
+  if (Support.getTestDialect() === 'mssql') {
+    suite('mapIsolationLevelStringToTedious', () => {
+      test('READ_UNCOMMITTED', () => {
+        expect(Utils.mapIsolationLevelStringToTedious('READ_UNCOMMITTED', tedious)).to.equal(tediousIsolationLevel.READ_UNCOMMITTED);
+      });
+
+      test('READ_COMMITTED', () => {
+        expect(Utils.mapIsolationLevelStringToTedious('READ_COMMITTED', tedious)).to.equal(tediousIsolationLevel.READ_COMMITTED);
+      });
+
+      test('REPEATABLE_READ', () => {
+        expect(Utils.mapIsolationLevelStringToTedious('REPEATABLE_READ', tedious)).to.equal(tediousIsolationLevel.REPEATABLE_READ);
+      });
+
+      test('SERIALIZABLE', () => {
+        expect(Utils.mapIsolationLevelStringToTedious('SERIALIZABLE', tedious)).to.equal(tediousIsolationLevel.SERIALIZABLE);
+      });
+
+      test('SNAPSHOT', () => {
+        expect(Utils.mapIsolationLevelStringToTedious('SNAPSHOT', tedious)).to.equal(tediousIsolationLevel.SNAPSHOT);
+      });
+
+      test('should throw error if tedious lib is not passed as a parameter', () => {
+        expect(Utils.mapIsolationLevelStringToTedious.bind(Utils, 'SNAPSHOT')).to.throw('An instance of tedious lib should be passed to this function');
+      });
+    });
+  }
+
 });