From a3d038e9ec1ba98fc9bba9cc7b01faf5bc94ce98 Mon Sep 17 00:00:00 2001
From: Andrei Vorobev <andrei.vorobev@devexpress.com>
Date: Fri, 29 May 2026 16:45:07 +0300
Subject: [PATCH 1/6] Autocomplete: fixed eslint, tsexpect errors, warnings

---
 .../ui/drop_down_editor/m_drop_down_list.ts   | 11 +--
 .../js/__internal/ui/m_autocomplete.ts        | 84 +++++++++++--------
 .../js/__internal/ui/m_select_box.ts          |  8 +-
 .../devextreme/js/__internal/ui/m_tag_box.ts  |  3 -
 4 files changed, 54 insertions(+), 52 deletions(-)

diff --git a/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_list.ts b/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_list.ts
index 080378951fdf..00a705735d19 100644
--- a/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_list.ts
+++ b/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_list.ts
@@ -57,10 +57,13 @@ interface DropDownListProperties extends Omit<dxDropDownListOptions<DropDownList
   displayCustomValue?: boolean;
   items?: Item[];
 }
-
 class DropDownList<
   TProperties extends DropDownListProperties = DropDownListProperties,
 > extends DropDownEditor<TProperties> {
+  declare protected _displayGetter: (item: unknown) => string; // DataExpressionMixin workaround
+
+  declare protected _compileDisplayGetter: () => void; // DataExpressionMixin workaround
+
   _list?: List;
 
   _$list?: dxElementWrapper;
@@ -418,9 +421,8 @@ class DropDownList<
     this.option('displayValue', displayValue);
   }
 
-  _displayValue(item: Item): string {
-    // @ts-expect-error refactor DataExpressionMixin
-    return this._displayGetter(item) as string;
+  _displayValue(item): string {
+    return this._displayGetter(item);
   }
 
   _refreshSelected(): void {
@@ -1033,7 +1035,6 @@ class DropDownList<
 
   _setSubmitValue(): void {
     const { value } = this.option();
-    // @ts-expect-error refactor DataExpressionMixin
     const submitValue = this._shouldUseDisplayValue(value) ? this._displayGetter(value) : value;
 
     this._getSubmitElement().val(submitValue);
diff --git a/packages/devextreme/js/__internal/ui/m_autocomplete.ts b/packages/devextreme/js/__internal/ui/m_autocomplete.ts
index 39da053ba0e7..41f7fd9b8f4a 100644
--- a/packages/devextreme/js/__internal/ui/m_autocomplete.ts
+++ b/packages/devextreme/js/__internal/ui/m_autocomplete.ts
@@ -1,30 +1,38 @@
-import { isCommandKeyPressed } from '@js/common/core/events/utils/index';
-import registerComponent from '@js/core/component_registrator';
+import registerComponent from '@js/core/component_registrator'; // couldn't change import due inconsistent typings for registerComponent
+import type { dxElementWrapper } from '@js/core/renderer';
 import $ from '@js/core/renderer';
-import { Deferred } from '@js/core/utils/deferred';
-import { extend } from '@js/core/utils/extend';
+import type { DataSourceOptions } from '@js/data/data_source';
+import type { DxEvent, PointerInteractionEvent } from '@js/events/events.types';
 import type { Properties } from '@js/ui/autocomplete';
-import { isDefined } from '@ts/core/utils/m_type';
+import type { ItemClickEvent, PageLoadMode } from '@js/ui/list';
+import { Deferred } from '@ts/core/utils/m_deferred';
 import type { OptionChanged } from '@ts/core/widget/types';
+import { isCommandKeyPressed } from '@ts/events/utils/index';
 import DropDownList from '@ts/ui/drop_down_editor/m_drop_down_list';
+import type { ListBaseProperties } from '@ts/ui/list/list.base';
 
 const AUTOCOMPLETE_CLASS = 'dx-autocomplete';
 const AUTOCOMPLETE_POPUP_WRAPPER_CLASS = 'dx-autocomplete-popup-wrapper';
 
-export interface AutocompleteProperties extends Omit<Properties, 'onItemClick' | 'onSelectionChanged'> {}
+export interface AutocompleteProperties extends Omit<
+  Properties, 'onItemClick' | 'onSelectionChanged'
+> {
+
+}
 
 class Autocomplete extends DropDownList<AutocompleteProperties> {
   _supportedKeys(): Record<string, (e: KeyboardEvent) => boolean> {
-    let item = this._list ? this._list.option('focusedElement') : null;
+    let item: dxElementWrapper | null = null;
+    if (this._list) {
+      const { focusedElement } = this._list.option();
+      item = focusedElement ? $(focusedElement) : null;
+    }
     const parent = super._supportedKeys();
-    // @ts-expect-error ts-error
-    item = item && $(item);
 
     return {
       ...parent,
-      upArrow(e): boolean {
-        // @ts-expect-error ts-error
-        if (parent.upArrow.apply(this, arguments) && !isCommandKeyPressed(e)) {
+      upArrow: (e): boolean => {
+        if (parent.upArrow.call(this, e) && !isCommandKeyPressed(e)) {
           e.preventDefault();
           e.stopPropagation();
           if (item && !this._calcNextItem(-1)) {
@@ -34,9 +42,8 @@ class Autocomplete extends DropDownList<AutocompleteProperties> {
         }
         return true;
       },
-      downArrow(e): boolean {
-        // @ts-expect-error ts-error
-        if (parent.downArrow.apply(this, arguments) && !isCommandKeyPressed(e)) {
+      downArrow: (e): boolean => {
+        if (parent.downArrow.call(this, e) && !isCommandKeyPressed(e)) {
           e.preventDefault();
           e.stopPropagation();
           if (item && !this._calcNextItem(1)) {
@@ -46,7 +53,7 @@ class Autocomplete extends DropDownList<AutocompleteProperties> {
         }
         return true;
       },
-      enter(e): boolean {
+      enter: (e): boolean => {
         if (!item) {
           this.close();
         }
@@ -54,7 +61,7 @@ class Autocomplete extends DropDownList<AutocompleteProperties> {
         if (opened) {
           e.preventDefault();
         }
-        return opened;
+        return Boolean(opened);
       },
     };
   }
@@ -78,17 +85,17 @@ class Autocomplete extends DropDownList<AutocompleteProperties> {
   _getAriaAutocomplete(): string {
     const { disabled, readOnly } = this.option();
 
-    // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
-    const isInputEditable = !(readOnly || disabled);
+    const isInputEditable = !(readOnly ?? disabled);
 
     return isInputEditable ? 'list' : 'none';
   }
 
-  _displayGetterExpr() {
-    return this.option('valueExpr');
+  _displayGetterExpr(): undefined | string | ((item: unknown) => string | number | boolean) {
+    const { valueExpr } = this.option();
+    return valueExpr;
   }
 
-  _closeOutsideDropDownHandler({ target }): boolean {
+  _closeOutsideDropDownHandler({ target }: DxEvent<PointerInteractionEvent>): boolean {
     return !$(target).closest(this.$element()).length;
   }
 
@@ -103,18 +110,18 @@ class Autocomplete extends DropDownList<AutocompleteProperties> {
     return `${super._popupWrapperClass()} ${AUTOCOMPLETE_POPUP_WRAPPER_CLASS}`;
   }
 
-  _listConfig() {
-    return extend(super._listConfig(), {
-      pageLoadMode: 'none',
-      onSelectionChanged: (e) => {
+  _listConfig(): ListBaseProperties {
+    return {
+      ...super._listConfig(),
+      pageLoadMode: 'none' as PageLoadMode,
+      onSelectionChanged: (e): void => {
         this._setSelectedItem(e.addedItems[0]);
       },
-    });
+    };
   }
 
-  _listItemClickHandler(e) {
+  _listItemClickHandler(e: ItemClickEvent): void {
     this._saveValueChangeEvent(e.event);
-    // @ts-expect-error ts-error
     const value = this._displayGetter(e.itemData);
     this.option('value', value);
     this.close();
@@ -129,20 +136,25 @@ class Autocomplete extends DropDownList<AutocompleteProperties> {
     super._setListDataSource();
   }
 
-  _refreshSelected(): void {}
+  // eslint-disable-next-line class-methods-use-this
+  _refreshSelected(): void {
+    // Autocomplete has no persistent selection state — suppress parent behavior
+    // _refreshSelected is called in parent, so we need to override here
+    // hence we don't need this functionality in Autocomplete
+  }
 
   _searchCanceled(): void {
     super._searchCanceled();
     this.close();
   }
 
-  _loadItem(value, cache) {
-    const selectedItem = this._getItemFromPlain(value, cache);
+  _loadItem(value: unknown, cache: Record<string, unknown>): ReturnType<typeof Deferred> {
+    const selectedItem = this._getItemFromPlain(value, cache) as unknown;
 
     return Deferred().resolve(selectedItem).promise();
   }
 
-  _dataSourceOptions() {
+  _dataSourceOptions(): DataSourceOptions {
     const { maxItemCount } = this.option();
     return {
       paginate: true,
@@ -171,7 +183,7 @@ class Autocomplete extends DropDownList<AutocompleteProperties> {
     return 'input keyup';
   }
 
-  _valueChangeEventHandler(e): void {
+  _valueChangeEventHandler(e: KeyboardEvent): void {
     const value = this._input().val() || null;
     return super._valueChangeEventHandler(e, value);
   }
@@ -184,11 +196,9 @@ class Autocomplete extends DropDownList<AutocompleteProperties> {
         this._setDefaultAria();
         break;
       case 'maxItemCount':
-        // @ts-expect-error ts-error
-        this._searchDataSource();
+        this._searchDataSource(this._searchValue());
         break;
       case 'valueExpr':
-        // @ts-expect-error ts-error
         this._compileDisplayGetter();
         this._setListOption('displayExpr', this._displayGetterExpr());
         super._optionChanged(args);
diff --git a/packages/devextreme/js/__internal/ui/m_select_box.ts b/packages/devextreme/js/__internal/ui/m_select_box.ts
index d3c35d847391..2e054af22306 100644
--- a/packages/devextreme/js/__internal/ui/m_select_box.ts
+++ b/packages/devextreme/js/__internal/ui/m_select_box.ts
@@ -449,7 +449,6 @@ class SelectBox<
     const fieldTemplate = this._getTemplate(fieldTemplateOption);
 
     if (!(fieldTemplate && fieldTemplateOption)) {
-      // @ts-expect-error ts-error
       const text = this._displayGetter(item);
 
       this.option('text', text);
@@ -559,7 +558,6 @@ class SelectBox<
       return false;
     }
 
-    // @ts-expect-error ts-error
     const value = this._displayGetter(initialSelectedItem);
     const displayValue = value ? String(value) : '';
     const inputText = this._searchValue();
@@ -693,7 +691,6 @@ class SelectBox<
 
   _clearTextValue(): void {
     const selectedItem = this.option('selectedItem');
-    // @ts-expect-error ts-error
     const selectedItemText = this._displayGetter(selectedItem);
     const shouldRestoreValue = selectedItem && selectedItemText !== '';
 
@@ -815,10 +812,9 @@ class SelectBox<
     return this._loadItemDeferred;
   }
 
-  _isCustomItemSelected() {
+  _isCustomItemSelected(): boolean {
     const selectedItem = this.option('selectedItem');
     const searchValue = this._searchValue();
-    // @ts-expect-error ts-error
     const selectedItemText = this._displayGetter(selectedItem);
 
     return !selectedItemText || searchValue !== selectedItemText.toString();
@@ -881,7 +877,6 @@ class SelectBox<
     this._cancelSearchIfNeed();
     // @ts-expect-error ts-error
     this._setValue(this._valueGetter(item));
-    // @ts-expect-error ts-error
     this._renderDisplayText(this._displayGetter(item));
     this._isValueChanging = false;
   }
@@ -960,7 +955,6 @@ class SelectBox<
     }
 
     const inputElement = $input.get(0) as HTMLInputElement;
-    // @ts-expect-error ts-error
     const displayValue = this._displayGetter(item).toString();
     inputElement.value = displayValue;
     this._caret({ start: valueLength, end: displayValue.length });
diff --git a/packages/devextreme/js/__internal/ui/m_tag_box.ts b/packages/devextreme/js/__internal/ui/m_tag_box.ts
index ce929c7f33fb..7b4708058658 100644
--- a/packages/devextreme/js/__internal/ui/m_tag_box.ts
+++ b/packages/devextreme/js/__internal/ui/m_tag_box.ts
@@ -439,7 +439,6 @@ class TagBox<
 
         $container.append($tagContent);
       }, ['text'], this.option('integrationOptions.watchMethod'), {
-        // @ts-expect-error ts-error
         text: this._displayGetter,
       }),
     });
@@ -488,7 +487,6 @@ class TagBox<
 
       $options.push(
         $('<option>')
-          // @ts-expect-error ts-error
           .val(useDisplayText ? this._displayGetter(value[i]) : value[i])
           .attr('selected', 'selected'),
       );
@@ -1304,7 +1302,6 @@ class TagBox<
     }
 
     let $tag = this._getTag(value);
-    // @ts-expect-error ts-error
     const displayValue = this._displayGetter(item);
     const itemModel = this._getItemModel(item, displayValue);
 

From 0184ee3aede29b0922ffc6ed912bb945885229a9 Mon Sep 17 00:00:00 2001
From: Andrei Vorobev <andrei.vorobev@devexpress.com>
Date: Tue, 2 Jun 2026 10:19:23 +0300
Subject: [PATCH 2/6] DropDown: temporary commit to update branch

---
 .../data/data_controller/data_controller.ts         |  8 ++------
 .../js/__internal/ui/m_drop_down_button.ts          | 13 ++++++-------
 packages/devextreme/js/ui/drop_down_button.d.ts     |  6 +++---
 3 files changed, 11 insertions(+), 16 deletions(-)

diff --git a/packages/devextreme/js/__internal/data/data_controller/data_controller.ts b/packages/devextreme/js/__internal/data/data_controller/data_controller.ts
index 0730af1df864..3d85e0db0943 100644
--- a/packages/devextreme/js/__internal/data/data_controller/data_controller.ts
+++ b/packages/devextreme/js/__internal/data/data_controller/data_controller.ts
@@ -6,7 +6,7 @@ import { normalizeDataSourceOptions } from '../../../common/data/data_source/uti
 import { extend } from '../../../core/utils/extend';
 import { isDefined } from '../../../core/utils/type';
 
-interface DataSourceType {
+export interface DataSourceType {
   _userData: unknown;
   _pageSize: number;
   dispose: () => void;
@@ -47,7 +47,6 @@ interface DataControllerOptions extends Record<string, unknown> {
 class DataController {
   private _isSharedDataSource = false;
 
-  // eslint-disable-next-line @typescript-eslint/ban-ts-comment
   // @ts-expect-error
   private _dataSource: DataSourceType;
 
@@ -75,7 +74,6 @@ class DataController {
   }
 
   _updateDataSourceByItems(items: unknown[]): void {
-    // eslint-disable-next-line @typescript-eslint/ban-ts-comment
     this._dataSource = new DataSource({
       store: new ArrayStore({
         key: this.key(),
@@ -93,7 +91,6 @@ class DataController {
         this._dataSource.dispose();
       }
 
-      // eslint-disable-next-line @typescript-eslint/ban-ts-comment
       // @ts-expect-error
       delete this._dataSource;
     }
@@ -126,9 +123,8 @@ class DataController {
   }
 
   loadNextPage(): Promise<unknown> {
-    // eslint-disable-next-line @typescript-eslint/ban-ts-comment
     // @ts-expect-error
-    // eslint-disable-next-line @typescript-eslint/restrict-plus-operands
+
     this.pageIndex(1 + this.pageIndex());
 
     return this.load();
diff --git a/packages/devextreme/js/__internal/ui/m_drop_down_button.ts b/packages/devextreme/js/__internal/ui/m_drop_down_button.ts
index b4537adfaf85..cf70838bfd18 100644
--- a/packages/devextreme/js/__internal/ui/m_drop_down_button.ts
+++ b/packages/devextreme/js/__internal/ui/m_drop_down_button.ts
@@ -1,7 +1,4 @@
-import messageLocalization from '@js/common/core/localization/message';
 import registerComponent from '@js/core/component_registrator';
-import { getPublicElement } from '@js/core/element';
-import Guid from '@js/core/guid';
 import type { dxElementWrapper } from '@js/core/renderer';
 import $ from '@js/core/renderer';
 import { FunctionTemplate } from '@js/core/templates/function_template';
@@ -19,8 +16,12 @@ import type {
 } from '@js/ui/button_group';
 import ButtonGroup from '@js/ui/button_group';
 import type { Item, Properties } from '@js/ui/drop_down_button';
+import messageLocalization from '@ts/core/localization/message';
+import { getPublicElement } from '@ts/core/m_element';
+import { Guid } from '@ts/core/m_guid';
 import type { OptionChanged } from '@ts/core/widget/types';
 import Widget from '@ts/core/widget/widget';
+import type { DataSourceType } from '@ts/data/data_controller/data_controller';
 import { getElementWidth } from '@ts/ui/drop_down_editor/m_utils';
 import type { ListBaseProperties } from '@ts/ui/list/list.base';
 import List from '@ts/ui/list/list.edit.search';
@@ -81,7 +82,6 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
       itemTemplate: 'item',
       keyExpr: 'this',
       selectedItem: null,
-      // @ts-expect-error ts-error
       selectedItemKey: null,
       stylingMode: 'outlined',
       deferRendering: true,
@@ -89,7 +89,6 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
       useSelectMode: false,
       splitButton: false,
       showArrowIcon: true,
-      // @ts-expect-error ts-error
       template: null,
       text: '',
       type: 'normal',
@@ -738,7 +737,7 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
     this._setListOption('keyExpr', this._dataController.key());
   }
 
-  focus() {
+  focus(): void {
     this._buttonGroup.focus();
   }
 
@@ -858,7 +857,7 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
     }
   }
 
-  getDataSource() {
+  getDataSource(): DataSourceType | null {
     return this._dataController.getDataSource();
   }
 }
diff --git a/packages/devextreme/js/ui/drop_down_button.d.ts b/packages/devextreme/js/ui/drop_down_button.d.ts
index 726515766ce4..22a3935ae0cb 100644
--- a/packages/devextreme/js/ui/drop_down_button.d.ts
+++ b/packages/devextreme/js/ui/drop_down_button.d.ts
@@ -249,13 +249,13 @@ export interface dxDropDownButtonOptions extends WidgetOptions<dxDropDownButton>
      * @readonly
      * @public
      */
-    selectedItem?: string | number | any;
+    selectedItem?: string | number | any | null;
     /**
      * @docid
      * @default null
      * @public
      */
-    selectedItemKey?: string | number;
+    selectedItemKey?: string | number | null;
     /**
      * @docid
      * @default true
@@ -279,7 +279,7 @@ export interface dxDropDownButtonOptions extends WidgetOptions<dxDropDownButton>
      * @type_function_return string|Element|jQuery
      * @public
      */
-    template?: template | ((data: TemplateData, contentElement: DxElement) => string | UserDefinedElement);
+    template?: null | template | ((data: TemplateData, contentElement: DxElement) => string | UserDefinedElement);
     /**
      * @docid
      * @default ""

From bb5482b87c56f95659b8c7f1fbcaba4e3b3fbbe8 Mon Sep 17 00:00:00 2001
From: Andrei Vorobev <andrei.vorobev@devexpress.com>
Date: Tue, 2 Jun 2026 17:26:53 +0300
Subject: [PATCH 3/6] DropDown: temporary commit to update branch

---
 .../ui/drop_down_editor/m_drop_down_list.ts   |  4 +--
 .../js/__internal/ui/m_drop_down_button.ts    | 36 +++++++++----------
 .../devextreme/js/ui/drop_down_button.d.ts    |  4 ---
 3 files changed, 18 insertions(+), 26 deletions(-)

diff --git a/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_list.ts b/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_list.ts
index 00a705735d19..3f8f89aefc35 100644
--- a/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_list.ts
+++ b/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_list.ts
@@ -60,9 +60,9 @@ interface DropDownListProperties extends Omit<dxDropDownListOptions<DropDownList
 class DropDownList<
   TProperties extends DropDownListProperties = DropDownListProperties,
 > extends DropDownEditor<TProperties> {
-  declare protected _displayGetter: (item: unknown) => string; // DataExpressionMixin workaround
+  declare _displayGetter: (item: unknown) => string; // DataExpressionMixin workaround
 
-  declare protected _compileDisplayGetter: () => void; // DataExpressionMixin workaround
+  declare _compileDisplayGetter: () => void; // DataExpressionMixin workaround
 
   _list?: List;
 
diff --git a/packages/devextreme/js/__internal/ui/m_drop_down_button.ts b/packages/devextreme/js/__internal/ui/m_drop_down_button.ts
index cf70838bfd18..f2c1f90f5078 100644
--- a/packages/devextreme/js/__internal/ui/m_drop_down_button.ts
+++ b/packages/devextreme/js/__internal/ui/m_drop_down_button.ts
@@ -1,15 +1,12 @@
 import registerComponent from '@js/core/component_registrator';
 import type { dxElementWrapper } from '@js/core/renderer';
 import $ from '@js/core/renderer';
-import { FunctionTemplate } from '@js/core/templates/function_template';
-import { ensureDefined } from '@js/core/utils/common';
 import { compileGetter } from '@js/core/utils/data';
 import type { DeferredObj } from '@js/core/utils/deferred';
 import { Deferred } from '@js/core/utils/deferred';
 import { extend } from '@js/core/utils/extend';
 import { getImageContainer } from '@js/core/utils/icon';
-import { isDefined, isObject, isPlainObject } from '@js/core/utils/type';
-import DataController from '@js/data_controller';
+import type { DataSourceLike } from '@js/data/data_source';
 import type {
   Item as ButtonGroupItem,
   Properties as ButtonGroupProperties,
@@ -19,9 +16,13 @@ import type { Item, Properties } from '@js/ui/drop_down_button';
 import messageLocalization from '@ts/core/localization/message';
 import { getPublicElement } from '@ts/core/m_element';
 import { Guid } from '@ts/core/m_guid';
+import { FunctionTemplate } from '@ts/core/templates/m_function_template';
+import { ensureDefined } from '@ts/core/utils/m_common';
+import { isDefined, isObject, isPlainObject } from '@ts/core/utils/m_type';
 import type { OptionChanged } from '@ts/core/widget/types';
 import Widget from '@ts/core/widget/widget';
 import type { DataSourceType } from '@ts/data/data_controller/data_controller';
+import DataController from '@ts/data/data_controller/data_controller';
 import { getElementWidth } from '@ts/ui/drop_down_editor/m_utils';
 import type { ListBaseProperties } from '@ts/ui/list/list.base';
 import List from '@ts/ui/list/list.edit.search';
@@ -92,15 +93,11 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
       template: null,
       text: '',
       type: 'normal',
-      // @ts-expect-error ts-error
-      onButtonClick: null,
-      // @ts-expect-error ts-error
-      onSelectionChanged: null,
-      // @ts-expect-error ts-error
-      onItemClick: null,
+      onButtonClick: undefined,
+      onSelectionChanged: undefined,
+      onItemClick: undefined,
       opened: false,
-      // @ts-expect-error ts-error
-      items: null,
+      items: undefined,
       dataSource: null,
       focusStateEnabled: true,
       hoverStateEnabled: true,
@@ -146,7 +143,6 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
 
   _initTemplates(): void {
     this._templateManager.addDefaultTemplates({
-      // @ts-expect-error ts-error
       content: new FunctionTemplate((options) => {
         const $popupContent = $(options.container);
         const $listContainer = $('<div>').appendTo($popupContent);
@@ -163,8 +159,10 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
   }
 
   _compileKeyGetter(): void {
-    // @ts-expect-error ts-error
-    this._keyGetter = compileGetter(this._dataController.key());
+    const key = this._dataController.key();
+    if (key !== undefined) {
+      this._keyGetter = compileGetter(key);
+    }
   }
 
   _compileDisplayGetter(): void {
@@ -216,9 +214,8 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
     const selectedItemKey = this.option('selectedItemKey');
     // @ts-expect-error ts-error
     this._dataController.loadSingle(selectedItemKey)
-      // @ts-expect-error ts-error
-      .done(d.resolve)
-      .fail(() => {
+      .then((item) => { d.resolve(item); })
+      .catch(() => {
         d.reject(null);
       });
 
@@ -456,8 +453,7 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
       displayExpr,
       itemTemplate,
       items,
-      // @ts-expect-error ts-error
-      dataSource: this._dataController.getDataSource(),
+      dataSource: this._dataController.getDataSource() as DataSourceLike<Item> | null,
       onItemClick: (e) => {
         if (!this.option('useSelectMode')) {
           this._lastSelectedItemData = e.itemData;
diff --git a/packages/devextreme/js/ui/drop_down_button.d.ts b/packages/devextreme/js/ui/drop_down_button.d.ts
index 22a3935ae0cb..82921c4728e4 100644
--- a/packages/devextreme/js/ui/drop_down_button.d.ts
+++ b/packages/devextreme/js/ui/drop_down_button.d.ts
@@ -194,7 +194,6 @@ export interface dxDropDownButtonOptions extends WidgetOptions<dxDropDownButton>
     /**
      * @docid
      * @type Array<dxDropDownButtonItem | any>
-     * @default null
      * @public
      */
     items?: Array<Item | any>;
@@ -212,7 +211,6 @@ export interface dxDropDownButtonOptions extends WidgetOptions<dxDropDownButton>
     noDataText?: string;
     /**
      * @docid
-     * @default null
      * @type function
      * @type_function_param1 e:{ui/drop_down_button:ButtonClickEvent}
      * @action
@@ -221,7 +219,6 @@ export interface dxDropDownButtonOptions extends WidgetOptions<dxDropDownButton>
     onButtonClick?: ((e: ButtonClickEvent) => void) | string;
     /**
      * @docid
-     * @default null
      * @type function
      * @type_function_param1 e:{ui/drop_down_button:ItemClickEvent}
      * @action
@@ -230,7 +227,6 @@ export interface dxDropDownButtonOptions extends WidgetOptions<dxDropDownButton>
     onItemClick?: ((e: ItemClickEvent) => void) | string;
     /**
      * @docid
-     * @default null
      * @type function
      * @type_function_param1 e:{ui/drop_down_button:SelectionChangedEvent}
      * @action

From 0c8fcf21ed2119d9a4933cf0a97d2520f13c2818 Mon Sep 17 00:00:00 2001
From: Andrei Vorobev <andrei.vorobev@devexpress.com>
Date: Thu, 4 Jun 2026 08:29:24 +0300
Subject: [PATCH 4/6] DropDown: temporary commit to update branch

---
 .../js/__internal/core/widget/widget.ts       |   6 +-
 .../data/data_controller/data_controller.ts   |   2 +-
 .../ui/drop_down_editor/m_drop_down_editor.ts |   1 -
 .../js/__internal/ui/m_drop_down_button.ts    | 213 ++++++++++--------
 .../__internal/ui/radio_group/radio_group.ts  |   1 -
 packages/devextreme/js/ui/overlay.d.ts        |   2 +-
 6 files changed, 127 insertions(+), 98 deletions(-)

diff --git a/packages/devextreme/js/__internal/core/widget/widget.ts b/packages/devextreme/js/__internal/core/widget/widget.ts
index 1b3fe71e4dcb..5811ae473a4b 100644
--- a/packages/devextreme/js/__internal/core/widget/widget.ts
+++ b/packages/devextreme/js/__internal/core/widget/widget.ts
@@ -427,8 +427,7 @@ class Widget<
     // eslint-disable-next-line @typescript-eslint/no-unsafe-return
     keyboardListeners.forEach((listener) => listener?._keyboardHandler(options));
 
-    // eslint-disable-next-line @typescript-eslint/no-unused-expressions
-    onKeyboardHandled && onKeyboardHandled(options);
+    onKeyboardHandled?.(options);
 
     return true;
   }
@@ -570,13 +569,12 @@ class Widget<
     this.$element().toggleClass('dx-state-independent', ignoreParentReadOnly);
   }
 
-  _setWidgetOption(widgetName: string, args: Record<string, unknown>): void {
+  _setWidgetOption(widgetName: string, args: [string, unknown?] | Record<string, unknown>): void {
     if (!this[widgetName]) {
       return;
     }
 
     if (isPlainObject(args[0])) {
-      // @ts-expect-error
       each(args[0], (option, value) => this._setWidgetOption(widgetName, [option, value]));
 
       return;
diff --git a/packages/devextreme/js/__internal/data/data_controller/data_controller.ts b/packages/devextreme/js/__internal/data/data_controller/data_controller.ts
index 3d85e0db0943..535c78cbcfef 100644
--- a/packages/devextreme/js/__internal/data/data_controller/data_controller.ts
+++ b/packages/devextreme/js/__internal/data/data_controller/data_controller.ts
@@ -185,7 +185,7 @@ class DataController {
     }
   }
 
-  updateDataSource(items: unknown[] | DataSourceType, key?: string): void {
+  updateDataSource(items?: unknown[] | DataSourceType, key?: string): void {
     const dataSourceOptions = items ?? this.items();
 
     if (key) {
diff --git a/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_editor.ts b/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_editor.ts
index 07007901474c..21a32e8608dc 100644
--- a/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_editor.ts
+++ b/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_editor.ts
@@ -915,7 +915,6 @@ class DropDownEditor<
       toolbarItems: this._getPopupToolbarItems(),
       onPositioned: this._popupPositionedHandler.bind(this),
       fullScreen: false,
-      // @ts-expect-error should be added on Popup level
       contentTemplate: null,
       _hideOnParentScrollTarget: this.$element(),
       _wrapperClassExternal: DROP_DOWN_EDITOR_OVERLAY,
diff --git a/packages/devextreme/js/__internal/ui/m_drop_down_button.ts b/packages/devextreme/js/__internal/ui/m_drop_down_button.ts
index f2c1f90f5078..5eba20d5c448 100644
--- a/packages/devextreme/js/__internal/ui/m_drop_down_button.ts
+++ b/packages/devextreme/js/__internal/ui/m_drop_down_button.ts
@@ -1,4 +1,6 @@
+import type { PositionConfig } from '@js/common/core/animation';
 import registerComponent from '@js/core/component_registrator';
+import type { DxElement } from '@js/core/element';
 import type { dxElementWrapper } from '@js/core/renderer';
 import $ from '@js/core/renderer';
 import { compileGetter } from '@js/core/utils/data';
@@ -13,6 +15,8 @@ import type {
 } from '@js/ui/button_group';
 import ButtonGroup from '@js/ui/button_group';
 import type { Item, Properties } from '@js/ui/drop_down_button';
+import type { ItemClickEvent } from '@js/ui/list';
+import type { PositionAlignment } from '@js/ui/popup';
 import messageLocalization from '@ts/core/localization/message';
 import { getPublicElement } from '@ts/core/m_element';
 import { Guid } from '@ts/core/m_guid';
@@ -50,6 +54,15 @@ export interface DropDownButtonProperties extends Properties {
   _cached_dropDownOptions?: PopupProperties;
 }
 
+export interface AriaAttributes {
+  expanded?: boolean;
+  haspopup?: string;
+  label?: string;
+  owns?: string;
+}
+
+type ItemClickActionType = (event?: Partial<ItemClickEvent>) => Partial<ItemClickEvent> | boolean;
+
 class DropDownButton extends Widget<DropDownButtonProperties> {
   _popup?: Popup;
 
@@ -67,15 +80,15 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
 
   _selectionChangedAction!: (event?: Record<string, unknown>) => void;
 
-  _itemClickAction!: (event?: Record<string, unknown>) => void;
+  _itemClickAction!: ItemClickActionType;
 
   _actionClickAction!: (event?: Record<string, unknown>) => void;
 
   _actionItem?: unknown;
 
-  _keyGetter?: unknown;
+  _keyGetter?: (obj: unknown) => unknown;
 
-  _displayGetter?: unknown;
+  _displayGetter?: (obj: unknown) => unknown;
 
   _getDefaultOptions(): DropDownButtonProperties {
     return {
@@ -136,9 +149,12 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
   }
 
   _initDataController(): void {
-    const dataSource = this.option('dataSource');
-    // @ts-expect-error ts-error
-    this._dataController = new DataController(dataSource ?? this.option('items'), { key: this.option('keyExpr') });
+    const { dataSource, items, keyExpr } = this.option();
+    this._dataController = new DataController(
+      // @ts-expect-error datacontroller constructor typing need to be fixed
+      dataSource ?? items,
+      { key: keyExpr },
+    );
   }
 
   _initTemplates(): void {
@@ -161,13 +177,13 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
   _compileKeyGetter(): void {
     const key = this._dataController.key();
     if (key !== undefined) {
-      this._keyGetter = compileGetter(key);
+      this._keyGetter = compileGetter(key) as (obj: unknown) => unknown;
     }
   }
 
   _compileDisplayGetter(): void {
     const { displayExpr } = this.option();
-    // @ts-expect-error ts-error
+    // @ts-expect-error core/utils compileGetter fn typing needs to be fixed
     this._displayGetter = compileGetter(displayExpr);
   }
 
@@ -183,6 +199,7 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
   }
 
   // T977758
+  // eslint-disable-next-line class-methods-use-this
   _renderFocusTarget(): void {}
 
   _render(): void {
@@ -193,7 +210,7 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
     super._render();
   }
 
-  _renderContentImpl() {
+  _renderContentImpl(): void | Promise<void> {
     if (this._popup) {
       this._renderPopupContent();
     }
@@ -211,43 +228,49 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
     }
     this._lastSelectedItemData = undefined;
 
-    const selectedItemKey = this.option('selectedItemKey');
-    // @ts-expect-error ts-error
-    this._dataController.loadSingle(selectedItemKey)
-      .then((item) => { d.resolve(item); })
-      .catch(() => {
-        d.reject(null);
-      });
+    const { selectedItemKey } = this.option();
+
+    if (isDefined(selectedItemKey)) {
+      this._dataController.loadSingle(this._dataController.key() as string, selectedItemKey)
+        .then((item) => { d.resolve(item); })
+        .catch(() => {
+          d.reject(null);
+        });
+    } else {
+      d.reject(null);
+    }
 
     this._loadSingleDeferred = d;
-    // @ts-expect-error ts-error
-    return d.promise();
+
+    return d;
   }
 
-  _createActionClickAction() {
+  _createActionClickAction(): void {
     this._actionClickAction = this._createActionByOption('onButtonClick');
   }
 
-  _createSelectionChangedAction() {
+  _createSelectionChangedAction(): void {
     this._selectionChangedAction = this._createActionByOption('onSelectionChanged');
   }
 
-  _createItemClickAction() {
-    this._itemClickAction = this._createActionByOption('onItemClick');
+  _createItemClickAction(): void {
+    this._itemClickAction = this._createActionByOption('onItemClick') as ItemClickActionType;
   }
 
-  _fireSelectionChangedAction({ previousValue, value }) {
+  _fireSelectionChangedAction({ previousValue, value }): void {
     this._selectionChangedAction({
       item: value,
       previousItem: previousValue,
     });
   }
 
-  _fireItemClickAction({ event, itemElement, itemData }) {
+  _fireItemClickAction(
+    { event, itemElement, itemData }: ItemClickEvent,
+  ): Partial<ItemClickEvent> | boolean {
     return this._itemClickAction({
       event,
       itemElement,
-      itemData: this._actionItem || itemData,
+      itemData: this._actionItem ?? itemData,
     });
   }
 
@@ -259,18 +282,22 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
     }
 
     return splitButton || !showArrowIcon
-      ? 'content' : ({ text, icon }, buttonContent) => {
+      ? 'content' : ({ text, icon }: ButtonGroupItem, buttonContent: DxElement): void => {
         const $firstIcon = getImageContainer(icon);
         const $textContainer = text ? $('<span>').text(text).addClass(DX_BUTTON_TEXT_CLASS) : undefined;
-        // @ts-expect-error ts-error
-        const $secondIcon = getImageContainer('spindown').addClass(DX_ICON_RIGHT_CLASS);
+        const $secondIcon = getImageContainer('spindown');
+        if ($secondIcon !== null) {
+          $secondIcon.addClass(DX_ICON_RIGHT_CLASS);
+        }
 
-        // @ts-expect-error ts-error
-        $(buttonContent).append($firstIcon, $textContainer, $secondIcon);
+        const $container = $(buttonContent);
+        if ($firstIcon) $container.append($firstIcon);
+        if ($textContainer) $container.append($textContainer);
+        if ($secondIcon) $container.append($secondIcon);
       };
   }
 
-  _getActionButtonConfig() {
+  _getActionButtonConfig(): ButtonGroupItem {
     const {
       icon, text, type, splitButton,
     } = this.option();
@@ -280,18 +307,16 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
       icon,
       type,
       template: this._getButtonTemplate(),
-      elementAttr: { class: DROP_DOWN_BUTTON_ACTION_CLASS },
+      elementAttr: {
+        class: DROP_DOWN_BUTTON_ACTION_CLASS,
+        role: splitButton ? 'menuitem' : undefined,
+      },
     };
 
-    if (splitButton) {
-      // @ts-expect-error ts-error
-      actionButtonConfig.elementAttr.role = 'menuitem';
-    }
-
     return actionButtonConfig;
   }
 
-  _getSpinButtonConfig() {
+  _getSpinButtonConfig(): ButtonGroupItem {
     const { type } = this.option();
 
     const config = {
@@ -312,7 +337,6 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
     const items = [this._getActionButtonConfig()];
 
     if (splitButton) {
-      // @ts-expect-error ts-error
       items.push(this._getSpinButtonConfig());
     }
 
@@ -385,14 +409,27 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
     return result;
   }
 
-  _popupOptions() {
+  _popupOptions(): PopupProperties {
     const horizontalAlignment = this.option('rtlEnabled') ? 'right' : 'left';
 
-    return extend({
+    const {
+      deferRendering,
+      opened,
+      _cached_dropDownOptions: cachedDropDownOptions,
+    } = this.option();
+
+    const position: PositionConfig = {
+      of: getPublicElement(this.$element()),
+      collision: 'flipfit',
+      my: `${horizontalAlignment} top` as PositionAlignment,
+      at: `${horizontalAlignment} bottom` as PositionAlignment,
+    };
+
+    return {
       dragEnabled: false,
       focusStateEnabled: false,
-      deferRendering: this.option('deferRendering'),
-      hideOnOutsideClick: (e) => {
+      deferRendering,
+      hideOnOutsideClick: (e): boolean => {
         const $element = this.$element();
         const $buttonClicked = $(e.target).closest(`.${DROP_DOWN_BUTTON_CLASS}`);
         return !$buttonClicked.is($element);
@@ -409,15 +446,12 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
       width: getElementWidth(this.$element()),
       height: 'auto',
       shading: false,
-      position: {
-        of: this.$element(),
-        collision: 'flipfit',
-        my: `${horizontalAlignment} top`,
-        at: `${horizontalAlignment} bottom`,
-      },
+      position,
       _wrapperClassExternal: DROP_DOWN_EDITOR_OVERLAY_CLASS,
       contentTemplate: null,
-    }, this._options.cache('dropDownOptions'), { visible: this.option('opened') });
+      ...cachedDropDownOptions,
+      ...{ visible: opened },
+    };
   }
 
   _listOptions(): ListBaseProperties {
@@ -443,7 +477,7 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
       focusStateEnabled,
       hoverStateEnabled,
       useItemTextAsTitle,
-      // eslint-disable-next-line
+      // eslint-disable-next-line @typescript-eslint/no-misused-promises
       onContentReady: () => this._fireContentReadyAction(),
       selectedItemKeys: isDefined(selectedItemKey) && useSelectMode ? [selectedItemKey] : [],
       grouped,
@@ -454,16 +488,14 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
       itemTemplate,
       items,
       dataSource: this._dataController.getDataSource() as DataSourceLike<Item> | null,
-      onItemClick: (e) => {
+      onItemClick: (e): void => {
         if (!this.option('useSelectMode')) {
           this._lastSelectedItemData = e.itemData;
         }
-        // @ts-expect-error ts-error
-        this.option('selectedItemKey', this._keyGetter(e.itemData));
-        // @ts-expect-error ts-error
+        this.option('selectedItemKey', this._keyGetter?.(e.itemData));
         const actionResult = this._fireItemClickAction(e);
-        // @ts-expect-error ts-error
         if (actionResult !== false) {
+          // eslint-disable-next-line @typescript-eslint/no-floating-promises
           this.toggle(false);
           this._buttonGroup.focus();
         }
@@ -534,10 +566,8 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
     }
   }
 
-  // eslint-disable-next-line @typescript-eslint/no-unused-vars
-  _setPopupOption(optionName, value?): void {
-    // @ts-expect-error ts-error
-    this._setWidgetOption('_popup', arguments);
+  _setPopupOption(...args: unknown[]): void {
+    this._setWidgetOption('_popup', args as unknown as Record<string, unknown>);
   }
 
   _popupShowingHandler(): void {
@@ -553,24 +583,24 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
     this.setAria(elementAria, this.$element());
   }
 
-  _setButtonsAria(value): void {
-    const commonButtonAria = {
+  _setButtonsAria(value: boolean): void {
+    const commonButtonAria: AriaAttributes = {
       expanded: value,
       haspopup: 'listbox',
     };
-    const firstButtonAria = {};
+    const firstButtonAria: AriaAttributes = {};
 
     if (!this.option('text')) {
-      // @ts-expect-error ts-error
       firstButtonAria.label = 'dropdownbutton';
     }
-    // @ts-expect-error ts-error
+
     this._getButtons().each((index, $button) => {
       if (index === 0) {
         this.setAria({ ...firstButtonAria, ...commonButtonAria }, $($button));
       } else {
         this.setAria(commonButtonAria, $($button));
       }
+      return true;
     });
   }
 
@@ -607,8 +637,7 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
 
   _updateArrowClass(): void {
     const hasArrow = this.option('splitButton') || this.option('showArrowIcon');
-    // @ts-expect-error ts-error
-    this.$element().toggleClass(DROP_DOWN_BUTTON_HAS_ARROW_CLASS, hasArrow);
+    this.$element().toggleClass(DROP_DOWN_BUTTON_HAS_ARROW_CLASS, Boolean(hasArrow));
   }
 
   toggle(visible?: boolean): Promise<unknown> | undefined {
@@ -632,10 +661,9 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
     this._list?.option(name, value);
   }
 
-  _getDisplayValue(item): string {
+  _getDisplayValue(item: Item): string {
     const isPrimitiveItem = !isObject(item);
-    // @ts-expect-error ts-error
-    const displayValue = isPrimitiveItem ? item : this._displayGetter(item);
+    const displayValue = isPrimitiveItem ? item : this._displayGetter?.(item);
     return !isObject(displayValue) ? String(ensureDefined(displayValue, '')) : '';
   }
 
@@ -648,8 +676,7 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
     }
 
     this._setOptionWithoutOptionChange('selectedItem', selectedItem);
-    // @ts-expect-error ts-error
-    this._setOptionWithoutOptionChange('selectedItemKey', this._keyGetter(selectedItem));
+    this._setOptionWithoutOptionChange('selectedItemKey', this._keyGetter?.(selectedItem));
   }
 
   _clean(): void {
@@ -659,11 +686,10 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
 
   _selectedItemKeyChanged(value): void {
     this._setListOption('selectedItemKeys', this.option('useSelectMode') && isDefined(value) ? [value] : []);
-    const previousItem = this.option('selectedItem');
+    const { selectedItem: previousItem } = this.option();
     this._loadSelectedItem().always((selectedItem) => {
       this._updateActionButton(selectedItem);
-      // @ts-expect-error ts-error
-      if (this._displayGetter(previousItem) !== this._displayGetter(selectedItem)) {
+      if (this._displayGetter?.(previousItem) !== this._displayGetter?.(selectedItem)) {
         this._fireSelectionChangedAction({
           previousValue: previousItem,
           value: selectedItem,
@@ -680,11 +706,18 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
   _actionButtonOptionChanged({ name, value }): void {
     const newConfig = {};
     newConfig[name] = value;
-    this._updateButtonGroup('items[0]', extend({}, this._getActionButtonConfig(), newConfig));
+    this._updateButtonGroup(
+      'items[0]',
+      extend(
+        {},
+        this._getActionButtonConfig(),
+        newConfig,
+      ),
+    );
     this._popup && this._popup.repaint();
   }
 
-  _selectModeChanged(value): void {
+  _selectModeChanged(value: unknown): void {
     if (value) {
       this._setListOption('selectionMode', 'single');
       const selectedItemKey = this.option('selectedItemKey');
@@ -696,15 +729,14 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
         selectedItemKey: undefined,
         selectedItem: undefined,
       });
-      // @ts-expect-error ts-error
-      this._actionButtonOptionChanged({ text: this.option('text') });
+      const { text } = this.option();
+      this._actionButtonOptionChanged({ name: 'text', value: text });
     }
   }
 
-  _updateItemCollection(optionName): void {
+  _updateItemCollection(optionName: string): void {
     const { selectedItemKey, useSelectMode } = this.option();
     this._setListOption('selectedItem', null);
-    // @ts-expect-error ts-error
     this._setWidgetOption('_list', [optionName]);
 
     if (isDefined(selectedItemKey)) {
@@ -714,17 +746,16 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
             this._setListOption('selectedItemKeys', [selectedItemKey]);
             this._setListOption('selectedItem', selectedItem);
           }
-        // eslint-disable-next-line @typescript-eslint/no-unused-vars
-        }).fail((error) => {
+        }).fail(() => {
           this._setListOption('selectedItemKeys', []);
         })
         .always(this._updateActionButton.bind(this));
     }
   }
 
-  _updateDataController(items?): void {
-    // @ts-expect-error ts-error
-    this._dataController.updateDataSource(items, this.option('keyExpr'));
+  _updateDataController(items?: unknown[] | DataSourceType): void {
+    const { keyExpr } = this.option();
+    this._dataController.updateDataSource(items, keyExpr);
     this._updateKeyExpr();
   }
 
@@ -769,6 +800,7 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
         this._innerWidgetOptionChanged(this._popup, args);
         break;
       case 'opened':
+        // eslint-disable-next-line @typescript-eslint/no-floating-promises
         this.toggle(value);
         break;
       case 'focusStateEnabled':
@@ -778,12 +810,13 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
         super._optionChanged(args);
         break;
       case 'items':
-        this._updateDataController(this.option('items'));
+        // eslint-disable-next-line no-case-declarations
+        const { items } = this.option();
+        this._updateDataController(items);
         this._updateItemCollection(name);
         break;
       case 'dataSource':
-        // @ts-expect-error ts-error
-        this._dataController.updateDataSource(value);
+        this._dataController.updateDataSource(value as unknown[] | DataSourceType);
         this._updateKeyExpr();
         this._updateItemCollection(name);
         break;
@@ -835,7 +868,7 @@ class DropDownButton extends Widget<DropDownButtonProperties> {
         break;
       case 'deferRendering': {
         const { opened } = this.option();
-
+        // eslint-disable-next-line @typescript-eslint/no-floating-promises
         this.toggle(opened);
         break;
       }
diff --git a/packages/devextreme/js/__internal/ui/radio_group/radio_group.ts b/packages/devextreme/js/__internal/ui/radio_group/radio_group.ts
index ce4dbda7c843..22ba94e83fec 100644
--- a/packages/devextreme/js/__internal/ui/radio_group/radio_group.ts
+++ b/packages/devextreme/js/__internal/ui/radio_group/radio_group.ts
@@ -274,7 +274,6 @@ class RadioGroup extends Editor<RadioGroupProperties> {
   }
 
   _setCollectionWidgetOption(...args: [string, unknown]): void {
-    // @ts-expect-error widget._setWidgetOption args should be typed as ArrayLike<unknown>
     this._areRadiosCreated.done(this._setWidgetOption.bind(this, '_radios', args));
   }
 
diff --git a/packages/devextreme/js/ui/overlay.d.ts b/packages/devextreme/js/ui/overlay.d.ts
index f5c83a53c672..37853a4fb908 100644
--- a/packages/devextreme/js/ui/overlay.d.ts
+++ b/packages/devextreme/js/ui/overlay.d.ts
@@ -45,7 +45,7 @@ export interface dxOverlayOptions<TComponent> extends WidgetOptions<TComponent>
      * @type_function_return string|Element|jQuery
      * @public
      */
-    contentTemplate?: template | ((contentElement: DxElement) => string | UserDefinedElement);
+    contentTemplate?: template | ((contentElement: DxElement) => string | UserDefinedElement) | null;
     /**
      * @docid
      * @default true

From 02d48755293bba3e5c8336bcdfeb7060fefc7616 Mon Sep 17 00:00:00 2001
From: Andrei Vorobev <andrei.vorobev@devexpress.com>
Date: Thu, 4 Jun 2026 09:37:27 +0300
Subject: [PATCH 5/6] Autocomplete, Dropdown button: temporary commit to update
 branch

---
 .../js/__internal/ui/drop_down_editor/m_drop_down_editor.ts     | 2 +-
 .../js/__internal/ui/drop_down_editor/m_drop_down_list.ts       | 1 -
 packages/devextreme/js/__internal/ui/m_autocomplete.ts          | 1 +
 3 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_editor.ts b/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_editor.ts
index 21a32e8608dc..22ee63e369e8 100644
--- a/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_editor.ts
+++ b/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_editor.ts
@@ -913,6 +913,7 @@ class DropDownEditor<
       showCloseButton: false,
       dragEnabled: false,
       toolbarItems: this._getPopupToolbarItems(),
+      // @ts-expect-error Should be updated on PopupProperties level
       onPositioned: this._popupPositionedHandler.bind(this),
       fullScreen: false,
       contentTemplate: null,
@@ -1048,7 +1049,6 @@ class DropDownEditor<
   }
 
   _setPopupOption(...args: [string, unknown?]): void {
-    // @ts-expect-error Should be fixed on Widget level
     this._setWidgetOption('_popup', args);
   }
 
diff --git a/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_list.ts b/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_list.ts
index 3f8f89aefc35..85cda5bde6f4 100644
--- a/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_list.ts
+++ b/packages/devextreme/js/__internal/ui/drop_down_editor/m_drop_down_list.ts
@@ -705,7 +705,6 @@ class DropDownList<
   ): void;
   _setListOption(optionName: string, value?: unknown): void;
   _setListOption(...args: [string, unknown?]): void {
-    // @ts-expect-error fix on Widget level
     this._setWidgetOption('_list', args);
   }
 
diff --git a/packages/devextreme/js/__internal/ui/m_autocomplete.ts b/packages/devextreme/js/__internal/ui/m_autocomplete.ts
index 41f7fd9b8f4a..7d5249534dec 100644
--- a/packages/devextreme/js/__internal/ui/m_autocomplete.ts
+++ b/packages/devextreme/js/__internal/ui/m_autocomplete.ts
@@ -6,6 +6,7 @@ import type { DxEvent, PointerInteractionEvent } from '@js/events/events.types';
 import type { Properties } from '@js/ui/autocomplete';
 import type { ItemClickEvent, PageLoadMode } from '@js/ui/list';
 import { Deferred } from '@ts/core/utils/m_deferred';
+import { isDefined } from '@ts/core/utils/m_type';
 import type { OptionChanged } from '@ts/core/widget/types';
 import { isCommandKeyPressed } from '@ts/events/utils/index';
 import DropDownList from '@ts/ui/drop_down_editor/m_drop_down_list';

From 4cfdc312a604468e0752f6d206de01ec170f32e3 Mon Sep 17 00:00:00 2001
From: Andrei Vorobev <andrei.vorobev@devexpress.com>
Date: Thu, 4 Jun 2026 09:37:55 +0300
Subject: [PATCH 6/6] Autocomplete, Dropdown button: temporary commit to update
 branch

---
 packages/devextreme/ts/dx.all.d.ts | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/packages/devextreme/ts/dx.all.d.ts b/packages/devextreme/ts/dx.all.d.ts
index be00d6be8554..cfd19ad60193 100644
--- a/packages/devextreme/ts/dx.all.d.ts
+++ b/packages/devextreme/ts/dx.all.d.ts
@@ -17125,11 +17125,11 @@ declare module DevExpress.ui {
     /**
      * [descr:dxDropDownButtonOptions.selectedItem]
      */
-    selectedItem?: string | number | any;
+    selectedItem?: string | number | any | null;
     /**
      * [descr:dxDropDownButtonOptions.selectedItemKey]
      */
-    selectedItemKey?: string | number;
+    selectedItemKey?: string | number | null;
     /**
      * [descr:dxDropDownButtonOptions.showArrowIcon]
      */
@@ -17146,6 +17146,7 @@ declare module DevExpress.ui {
      * [descr:dxDropDownButtonOptions.template]
      */
     template?:
+      | null
       | template
       | ((
           data: DevExpress.ui.dxButton.TemplateData,
@@ -24270,7 +24271,8 @@ declare module DevExpress.ui {
       | template
       | ((
           contentElement: DevExpress.core.DxElement
-        ) => string | DevExpress.core.UserDefinedElement);
+        ) => string | DevExpress.core.UserDefinedElement)
+      | null;
     /**
      * [descr:dxOverlayOptions.deferRendering]
      */