fix(model.destroy): return 0 with truncate (#12281)

lib/dialects/mssql/query.js

@@ -199,7 +199,7 @@ class Query extends AbstractQuery {
       return rowCount;
     }
     if (this.isBulkDeleteQuery()) {
-      return data[0] && data[0].AFFECTEDROWS;
+      return data[0] ? data[0].AFFECTEDROWS : 0;
     }
     if (this.isVersionQuery()) {
       return data[0].version;

lib/dialects/postgres/query.js

@@ -97,7 +97,7 @@ class Query extends AbstractQuery {
         (count, r) => Number.isFinite(r.rowCount) ? count + r.rowCount : count,
         0
       )
-      : queryResult.rowCount;
+      : queryResult.rowCount || 0;
 
     if (this.sequelize.options.minifyAliases && this.options.aliasesMapping) {
       rows = rows
@@ -396,7 +396,6 @@ class Query extends AbstractQuery {
   }
 }
 
-
 module.exports = Query;
 module.exports.Query = Query;
 module.exports.default = Query;

test/integration/model.test.js

@@ -1238,6 +1238,15 @@ describe(Support.getTestDialectTeaser('Model'), () => {
       expect(await User.findAll()).to.have.lengthOf(0);
     });
 
+    it('`truncate` option returns a number', async function() {
+      const User = this.sequelize.define('User', { username: DataTypes.STRING });
+      await this.sequelize.sync({ force: true });
+      await User.bulkCreate([{ username: 'user1' }, { username: 'user2' }]);
+      const affectedRows = await User.destroy({ truncate: true });
+      expect(await User.findAll()).to.have.lengthOf(0);
+      expect(affectedRows).to.be.a('number');
+    });
+
     it('throws an error if no where clause is given', async function() {
       const User = this.sequelize.define('User', { username: DataTypes.STRING });
       await this.sequelize.sync({ force: true });