Fix multiple items showing selection in tree when clicking twisties (#276847)

* Initial plan

* Fix: Prevent multiple items from having focus in tree when clicking twisties

Replace focus instead of merging when splicing nodes with focus trait

Co-authored-by: dmitrivMS <[email protected]>

* Add test for focus behavior when collapsing/expanding tree nodes

Co-authored-by: dmitrivMS <[email protected]>

* Revert "Fix: Prevent multiple items from having focus in tree when clicking twisties"

This reverts commit 6449075.

* Revert "Add test for focus behavior when collapsing/expanding tree nodes"

This reverts commit 0c85d5a.

* Updates

* PR feedback, remove tests

* PR feedback

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: dmitrivMS <[email protected]>
Co-authored-by: Dmitriy Vasyura <[email protected]>

Author: Copilot

src/vs/platform/quickinput/browser/tree/quickInputTreeController.ts

@@ -115,6 +115,7 @@ export class QuickInputTreeController extends Disposable {
 			}
 		));
 		this.registerCheckboxStateListeners();
+		this.registerOnDidChangeFocus();
 	}
 
 	get tree(): WorkbenchObjectTree<IQuickTreeItem, IQuickTreeFilterData> {
@@ -341,6 +342,14 @@ export class QuickInputTreeController extends Disposable {
 		this._onDidCheckedLeafItemsChange.fire(this.getCheckedLeafItems());
 	}
 
+	registerOnDidChangeFocus() {
+		// Ensure that selection follows focus
+		this._register(this._tree.onDidChangeFocus(e => {
+			const item = this._tree.getFocus().findLast(item => item !== null);
+			this._tree.setSelection(item ? [item] : [], e.browserEvent);
+		}));
+	}
+
 	getCheckedLeafItems() {
 		const lookedAt = new Set<IQuickTreeItem>();
 		const toLookAt = [...this._tree.getNode().children];