Fix #32012

src/vs/vscode.d.ts

@@ -5089,6 +5089,11 @@ declare module 'vscode' {
 		 */
 		resourceUri?: Uri;
 
+		/**
+		 * The tooltip text when you hover over this item.
+		 */
+		tooltip?: string | undefined;
+
 		/**
 		 * The [command](#Command) which should be run when the tree item is selected.
 		 */

src/vs/workbench/api/node/extHostTreeViews.ts

@@ -185,6 +185,7 @@ class ExtHostTreeView<T> extends Disposable {
 			parentHandle,
 			label: extensionTreeItem.label,
 			resourceUri: extensionTreeItem.resourceUri,
+			tooltip: typeof extensionTreeItem.tooltip === 'string' ? extensionTreeItem.tooltip : void 0,
 			command: extensionTreeItem.command ? this.commands.toInternal(extensionTreeItem.command) : void 0,
 			contextValue: extensionTreeItem.contextValue,
 			icon,

src/vs/workbench/api/node/extHostTypes.ts

@@ -1524,6 +1524,7 @@ export class TreeItem {
 	iconPath?: string | URI | { light: string | URI; dark: string | URI };
 	command?: vscode.Command;
 	contextValue?: string;
+	tooltip?: string;
 
 	constructor(label: string, collapsibleState?: vscode.TreeItemCollapsibleState)
 	constructor(resourceUri: URI, collapsibleState?: vscode.TreeItemCollapsibleState)

src/vs/workbench/browser/parts/views/customView.ts

@@ -404,7 +404,7 @@ class TreeRenderer implements IRenderer {
 
 	public renderElement(tree: ITree, node: ITreeItem, templateId: string, templateData: ITreeExplorerTemplateData): void {
 		const resource = node.resourceUri ? URI.revive(node.resourceUri) : null;
-		const name = node.label ? node.label : resource ? basename(resource.path) : '';
+		const label = node.label ? node.label : resource ? basename(resource.path) : '';
 		const icon = this.themeService.getTheme().type === LIGHT ? node.icon : node.iconDark;
 
 		// reset
@@ -415,11 +415,12 @@ class TreeRenderer implements IRenderer {
 		DOM.removeClass(templateData.resourceLabel.element, 'custom-view-tree-node-item-resourceLabel');
 
 		if (resource && !icon) {
-			templateData.resourceLabel.setLabel({ name, resource }, { fileKind: node.collapsibleState === TreeItemCollapsibleState.Collapsed || node.collapsibleState === TreeItemCollapsibleState.Expanded ? FileKind.FOLDER : FileKind.FILE });
+			templateData.resourceLabel.setLabel({ name: label, resource }, { fileKind: node.collapsibleState === TreeItemCollapsibleState.Collapsed || node.collapsibleState === TreeItemCollapsibleState.Expanded ? FileKind.FOLDER : FileKind.FILE, title: node.tooltip });
 			DOM.addClass(templateData.resourceLabel.element, 'custom-view-tree-node-item-resourceLabel');
 		} else {
-			templateData.label.textContent = name;
+			templateData.label.textContent = label;
 			DOM.addClass(templateData.label, 'custom-view-tree-node-item-label');
+			templateData.label.title = typeof node.tooltip === 'string' ? node.tooltip : label;
 		}
 
 		templateData.icon.treeItem = node;

src/vs/workbench/common/views.ts

@@ -204,6 +204,8 @@ export interface ITreeItem {
 
 	parentHandle: string;
 
+	collapsibleState: TreeItemCollapsibleState;
+
 	label?: string;
 
 	icon?: string;
@@ -212,13 +214,14 @@ export interface ITreeItem {
 
 	resourceUri?: UriComponents;
 
+	tooltip?: string;
+
 	contextValue?: string;
 
 	command?: Command;
 
 	children?: ITreeItem[];
 
-	collapsibleState: TreeItemCollapsibleState;
 }
 
 export interface ITreeViewDataProvider {