[EuiComboBox] Fix issue with duplicate checkmarks (#4162)

* [EuiComboBox] Fix issue with duplicate checkmarks

* Remove accidentally commited test code

* Add changelog entry

* Fix changelog entry

CHANGELOG.md

@@ -1,6 +1,9 @@
 ## [`master`](https://github.com/elastic/eui/tree/master)
 
-No public interface changes since `30.0.0`.
+**Bug fixes**
+
+- Fix issue with duplicate checkmarks in `EuiComboBox` ([4162](https://github.com/elastic/eui/pull/4162))
+
 
 ## [`30.0.0`](https://github.com/elastic/eui/tree/v30.0.0)
 

src/components/combo_box/combo_box.test.tsx

@@ -208,6 +208,34 @@ describe('props', () => {
   });
 });
 
+test('does not show multiple checkmarks with duplicate labels', () => {
+  const options = [
+    {
+      label: 'Titan',
+      key: 'titan1',
+    },
+    {
+      label: 'Titan',
+      key: 'titan2',
+    },
+    {
+      label: 'Tethys',
+    },
+  ];
+  const component = mount(
+    <EuiComboBox
+      singleSelection={{ asPlainText: true }}
+      options={options}
+      selectedOptions={[options[1]]}
+    />
+  );
+
+  const searchInput = findTestSubject(component, 'comboBoxSearchInput');
+  searchInput.simulate('focus');
+
+  expect(component.find('EuiFilterSelectItem[checked="on"]').length).toBe(1);
+});
+
 describe('behavior', () => {
   describe('hitting "Enter"', () => {
     test('calls the onCreateOption callback when there is input', () => {

src/components/combo_box/combo_box_options_list/combo_box_options_list.tsx

@@ -237,7 +237,8 @@ export class EuiComboBoxOptionsList<T> extends Component<
     if (
       singleSelection &&
       selectedOptions.length &&
-      selectedOptions[0].label === label
+      selectedOptions[0].label === label &&
+      selectedOptions[0].key === key
     ) {
       checked = 'on';
     }