TagBox: previously rendered tags should not rerender on value change (T1246066)

Author: Zedwag

packages/devextreme/js/__internal/ui/m_tag_box.ts

@@ -34,12 +34,12 @@ function xor(a: boolean, b: boolean): boolean {
 }
 
 const TAGBOX_TAG_DATA_KEY = 'dxTagData';
+const TAGBOX_TAG_DISPLAY_VALUE = 'dxTagDisplayValue';
 
 const TAGBOX_CLASS = 'dx-tagbox';
 const TAGBOX_TAG_CONTAINER_CLASS = 'dx-tag-container';
 const TAGBOX_TAG_CLASS = 'dx-tag';
 const TAGBOX_MULTI_TAG_CLASS = 'dx-tagbox-multi-tag';
-const TAGBOX_CUSTOM_TAG_CLASS = 'dx-tag-custom';
 const TAGBOX_TAG_REMOVE_BUTTON_CLASS = 'dx-tag-remove-button';
 const TAGBOX_ONLY_SELECT_CLASS = 'dx-tagbox-only-select';
 const TAGBOX_SINGLE_LINE_CLASS = 'dx-tagbox-single-line';
@@ -1243,24 +1243,23 @@ class TagBox<
     const itemModel = this._getItemModel(item, displayValue);
 
     if ($tag) {
-      if (isDefined(displayValue)) {
+      const tagDisplayValue = $tag.data(TAGBOX_TAG_DISPLAY_VALUE);
+
+      if (isDefined(displayValue) && !equalByValue(tagDisplayValue, displayValue)) {
         $tag.empty();
         this._applyTagTemplate(itemModel, $tag);
       }
-
-      $tag.removeClass(TAGBOX_CUSTOM_TAG_CLASS);
       this._updateElementAria($tag.attr('id'));
     } else {
       const tagId = `dx-${new Guid()}`;
 
-      $tag = this._createTag(value, $input, tagId);
+      $tag = this._createTag(value, $input, tagId, displayValue);
 
       this._setTagAria($tag, isDefined(displayValue) ? displayValue : value);
 
       if (isDefined(item)) {
         this._applyTagTemplate(itemModel, $tag);
       } else {
-        $tag.addClass(TAGBOX_CUSTOM_TAG_CLASS);
         this._applyTagTemplate(value, $tag);
       }
 
@@ -1303,11 +1302,12 @@ class TagBox<
     return result;
   }
 
-  _createTag(value, $input, tagId): dxElementWrapper {
+  _createTag(value, $input, tagId, displayValue): dxElementWrapper {
     return $('<div>')
       .attr('id', tagId)
       .addClass(TAGBOX_TAG_CLASS)
       .data(TAGBOX_TAG_DATA_KEY, value)
+      .data(TAGBOX_TAG_DISPLAY_VALUE, displayValue)
       .insertBefore($input);
   }
 

packages/devextreme/testing/tests/DevExpress.ui.widgets.editors/tagBox.tests.js

@@ -834,6 +834,63 @@ QUnit.module('tags', moduleSetup, () => {
             });
         });
     });
+
+    QUnit.test('Should not rerender previously rendered tags on value change (T1246066)', function(assert) {
+        let tagRenderCount = 0;
+        const tagBox = $('#tagBox').dxTagBox({
+            items: [{ name: 'one', value: 1 }, { name: 'two', value: 2 }],
+            displayExpr: 'name',
+            valueExpr: 'value',
+            value: [1],
+            tagTemplate(item) {
+                tagRenderCount += 1;
+
+                return $('<div>').text(item);
+            },
+        }).dxTagBox('instance');
+
+        tagBox.option('value', [1]);
+
+        assert.strictEqual(tagRenderCount, 1, 'tag was only rendred once');
+    });
+
+    QUnit.test('Should not rerender previously rendered tags on items change (T1246066)', function(assert) {
+        let tagRenderCount = 0;
+        const tagBox = $('#tagBox').dxTagBox({
+            items: [{ name: 'one', value: 1 }, { name: 'two', value: 2 }],
+            displayExpr: 'name',
+            valueExpr: 'value',
+            value: [1],
+            tagTemplate(item) {
+                tagRenderCount += 1;
+
+                return $('<div>').text(item);
+            },
+        }).dxTagBox('instance');
+
+        tagBox.option('items', [{ name: 'one', value: 1 }]);
+
+        assert.strictEqual(tagRenderCount, 1, 'tag was only rendred once');
+    });
+
+    QUnit.test('Should rerender tag on update item field that is used as displayExpr', function(assert) {
+        const $tagBox = $('#tagBox').dxTagBox({
+            items: [{ name: 'one', value: 1 }, { name: 'two', value: 2 }],
+            displayExpr: 'name',
+            valueExpr: 'value',
+            value: [1],
+        });
+        const tagBox = $tagBox.dxTagBox('instance');
+
+        let tagText = $tagBox.find(`.${TAGBOX_TAG_CLASS}`).text();
+
+        assert.equal(tagText, 'one', 'tag is correct on init');
+
+        tagBox.option('items[0].name', 'zero');
+
+        tagText = $tagBox.find(`.${TAGBOX_TAG_CLASS}`).text();
+        assert.equal(tagText, 'zero', 'tag text is updated');
+    });
 });
 
 QUnit.module('multi tag support', {