fixing a bug with sequelize.where in model scope

lib/model.js

@@ -1532,7 +1532,14 @@ class Model {
       if (scope) {
         _.assignWith(self._scope, scope, (objectValue, sourceValue, key) => {
           if (key === 'where') {
-            return Array.isArray(sourceValue) ? sourceValue : Object.assign(objectValue || {}, sourceValue);
+            if (Array.isArray(sourceValue)) {
+              return sourceValue;
+            } else {
+              if (sourceValue instanceof Utils.SequelizeMethod) {
+                sourceValue = { [Op.and]: sourceValue };
+              }
+              return Object.assign(objectValue || {}, sourceValue);
+            }
           } else if (['attributes', 'include', 'group'].indexOf(key) >= 0 && Array.isArray(objectValue) && Array.isArray(sourceValue)) {
             return objectValue.concat(sourceValue);
           }

test/integration/model/scope.test.js

@@ -50,6 +50,9 @@ describe(Support.getTestDialectTeaser('Model'), () => {
               },
               access_level: 5
             }
+          },
+          like_t: {
+            where: Sequelize.where(Sequelize.fn('LOWER', Sequelize.col('username')), 'LIKE', '%t%')
           }
         }
       });
@@ -108,5 +111,12 @@ describe(Support.getTestDialectTeaser('Model'), () => {
           return this.ScopeMe.scope('issue8473').findAll();
         });
     });
+
+    it('should not throw error with sequelize.where', function() {
+      return this.ScopeMe.scope('like_t').findAll()
+        .then(records => {
+          expect(records).to.have.length(2);
+        });
+    });
   });
 });

test/unit/model/scope.test.js

@@ -2,6 +2,8 @@
 
 const chai = require('chai'),
   expect = chai.expect,
+  Sequelize = require(__dirname + '/../../../index'),
+  Op = Sequelize.Op,
   Support   = require(__dirname + '/../support'),
   DataTypes = require(__dirname + '/../../../lib/data-types'),
   current   = Support.sequelize;
@@ -28,6 +30,9 @@ describe(Support.getTestDialectTeaser('Model'), () => {
         something: false
       }
     },
+    sequelize_where: {
+      where: Sequelize.where()
+    },
     users: {
       include: [
         { model: User }
@@ -135,10 +140,11 @@ describe(Support.getTestDialectTeaser('Model'), () => {
     });
 
     it('should be able to merge scopes', () => {
-      expect(Company.scope('somethingTrue', 'somethingFalse')._scope).to.deep.equal({
+      expect(Company.scope('somethingTrue', 'somethingFalse', 'sequelize_where')._scope).to.deep.equal({
         where: {
           something: false,
-          somethingElse: 42
+          somethingElse: 42,
+          [Op.and]: Sequelize.where()
         },
         limit: 5
       });