Modify treeDataChange event (#125214) (#16907)

Modify treeDataChange event to support firing arrays.

src/vs/vscode.proposed.d.ts

@@ -954,6 +954,15 @@ declare module 'vscode' {
 
 	//#region Custom Tree View Drag and Drop https://github.com/microsoft/vscode/issues/32592
 	export interface TreeViewOptions<T> {
+		/**
+		 * An optional event to signal that elements or the root have changed.
+		 * This will trigger the view to update the changed element/root and its children recursively (if shown).
+		 * To signal that root has changed, do not pass any argument or pass `undefined` or `null`.
+		 */
+		onDidChangeTreeData?: Event<T | T[] | undefined | null | void>;
+		/**
+		* An optional interface to implement drag and drop in the tree view.
+		*/
 		dragAndDropController?: DragAndDropController<T>;
 	}
 

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

@@ -205,7 +205,7 @@ export class ExtHostTreeViews implements ExtHostTreeViewsShape {
 }
 
 export type Root = null | undefined | void; // {{SQL CARBON EDIT}} export interface
-type TreeData<T> = { message: boolean, element: T | Root | false };
+type TreeData<T> = { message: boolean, element: T | T[] | Root | false };
 
 export interface TreeNode extends IDisposable { // {{SQL CARBON EDIT}} export interface
 	item: ITreeItem;
@@ -292,7 +292,11 @@ export class ExtHostTreeView<T> extends Disposable {
 					refreshingPromise = new Promise(c => promiseCallback = c);
 					this.refreshPromise = this.refreshPromise.then(() => refreshingPromise!);
 				}
-				result.elements.push(current.element);
+				if (Array.isArray(current.element)) {
+					result.elements.push(...current.element);
+				} else {
+					result.elements.push(current.element);
+				}
 			}
 			if (current.message) {
 				result.message = true;