DataGrid - The pageIndex method should return a promise if dataSource is null (T1256070) (#28279)

Author: markallenramirez

packages/devextreme/js/__internal/grids/grid_core/data_controller/m_data_controller.ts

@@ -57,6 +57,10 @@ const changePaging = function (that, optionName, value) {
     return dataSource[optionName]();
   }
 
+  if (optionName === 'pageIndex' && value !== undefined) {
+    return Deferred().resolve().promise();
+  }
+
   return 0;
 };
 

packages/devextreme/testing/testcafe/tests/dataGrid/pager.ts

@@ -238,3 +238,16 @@ test('Page index should not reset when scrolling while the grid is being refresh
   },
   height: 440,
 }));
+
+test('No error should occur if dataSource is not defined and pageIndex is promise chained (T1256070)', async (t) => {
+  const dataGrid = new DataGrid('#container');
+
+  // assert
+  await t
+    .expect(dataGrid.isReady())
+    .ok();
+}).before(() => createWidget('dxDataGrid', {
+  onContentReady(e) {
+    e.component.pageIndex(1).then(() => {}, () => {});
+  },
+}));