fix(scope): don't modify original scope definition (#12207)

lib/model.js

@@ -1562,7 +1562,8 @@ class Model {
 
       if (scope) {
         this._conformIncludes(scope, this);
-        this._assignOptions(self._scope, scope);
+        // clone scope so it doesn't get modified
+        this._assignOptions(self._scope, Utils.cloneDeep(scope));
         self._scopeNames.push(scopeName ? scopeName : 'defaultScope');
       } else {
         throw new sequelizeErrors.SequelizeScopeError(`Invalid scope ${scopeName} called.`);

test/unit/model/scope.test.js

@@ -207,6 +207,27 @@ describe(Support.getTestDialectTeaser('Model'), () => {
       });
     });
 
+    it('should be keep original scope definition clean', () => {
+      expect(Company.scope('projects', 'users', 'alsoUsers')._scope).to.deep.equal({
+        include: [
+          { model: Project },
+          { model: User, where: { something: 42 } }
+        ]
+      });
+
+      expect(Company.options.scopes.alsoUsers).to.deep.equal({
+        include: [
+          { model: User, where: { something: 42 } }
+        ]
+      });
+
+      expect(Company.options.scopes.users).to.deep.equal({
+        include: [
+          { model: User }
+        ]
+      });
+    });
+
     it('should be able to override the default scope', () => {
       expect(Company.scope('somethingTrue')._scope).to.deep.equal(scopes.somethingTrue);
     });
@@ -516,4 +537,4 @@ describe(Support.getTestDialectTeaser('Model'), () => {
       });
     });
   });
-});
\ No newline at end of file
+});