first cut updateFolders API

src/vs/workbench/services/configuration/node/configurationService.ts

@@ -110,9 +110,9 @@ export class WorkspaceService extends Disposable implements IWorkspaceConfigurat
 		return this.workspace.getFolder(resource);
 	}
 
-	public addFolders(foldersToAdd: IWorkspaceFolderCreationData[]): TPromise<void> {
+	public addFolders(foldersToAdd: IWorkspaceFolderCreationData[], index?: number): TPromise<void> {
 		assert.ok(this.jsonEditingService, 'Workbench is not initialized yet');
-		return this.workspaceEditingQueue.queue(() => this.doAddFolders(foldersToAdd));
+		return this.workspaceEditingQueue.queue(() => this.doAddFolders(foldersToAdd, index));
 	}
 
 	public removeFolders(foldersToRemove: URI[]): TPromise<void> {
@@ -134,7 +134,7 @@ export class WorkspaceService extends Disposable implements IWorkspaceConfigurat
 		return false;
 	}
 
-	private doAddFolders(foldersToAdd: IWorkspaceFolderCreationData[]): TPromise<void> {
+	private doAddFolders(foldersToAdd: IWorkspaceFolderCreationData[], index?: number): TPromise<void> {
 		if (this.getWorkbenchState() !== WorkbenchState.WORKSPACE) {
 			return TPromise.as(void 0); // we need a workspace to begin with
 		}
@@ -176,7 +176,16 @@ export class WorkspaceService extends Disposable implements IWorkspaceConfigurat
 		});
 
 		if (storedFoldersToAdd.length > 0) {
-			return this.setFolders([...currentStoredFolders, ...storedFoldersToAdd]);
+			let newStoredWorkspaceFolders: IStoredWorkspaceFolder[] = [];
+
+			if (typeof index === 'number' && index >= 0 && index < currentStoredFolders.length - 1) {
+				newStoredWorkspaceFolders = currentStoredFolders.slice(0);
+				newStoredWorkspaceFolders.splice(index, 0, ...storedFoldersToAdd);
+			} else {
+				newStoredWorkspaceFolders = [...currentStoredFolders, ...storedFoldersToAdd];
+			}
+
+			return this.setFolders(newStoredWorkspaceFolders);
 		}
 
 		return TPromise.as(void 0);

src/vs/workbench/services/configuration/test/node/configurationService.test.ts

@@ -192,6 +192,34 @@ suite('WorkspaceContextService - Workspace', () => {
 			});
 	});
 
+	test('add folders (at specific index)', () => {
+		const workspaceDir = path.dirname(testObject.getWorkspace().folders[0].uri.fsPath);
+		return testObject.addFolders([{ uri: URI.file(path.join(workspaceDir, 'd')) }, { uri: URI.file(path.join(workspaceDir, 'c')) }], 0)
+			.then(() => {
+				const actual = testObject.getWorkspace().folders;
+
+				assert.equal(actual.length, 4);
+				assert.equal(path.basename(actual[0].uri.fsPath), 'd');
+				assert.equal(path.basename(actual[1].uri.fsPath), 'c');
+				assert.equal(path.basename(actual[2].uri.fsPath), 'a');
+				assert.equal(path.basename(actual[3].uri.fsPath), 'b');
+			});
+	});
+
+	test('add folders (at specific wrong index)', () => {
+		const workspaceDir = path.dirname(testObject.getWorkspace().folders[0].uri.fsPath);
+		return testObject.addFolders([{ uri: URI.file(path.join(workspaceDir, 'd')) }, { uri: URI.file(path.join(workspaceDir, 'c')) }], 10)
+			.then(() => {
+				const actual = testObject.getWorkspace().folders;
+
+				assert.equal(actual.length, 4);
+				assert.equal(path.basename(actual[0].uri.fsPath), 'a');
+				assert.equal(path.basename(actual[1].uri.fsPath), 'b');
+				assert.equal(path.basename(actual[2].uri.fsPath), 'd');
+				assert.equal(path.basename(actual[3].uri.fsPath), 'c');
+			});
+	});
+
 	test('add folders (with name)', () => {
 		const workspaceDir = path.dirname(testObject.getWorkspace().folders[0].uri.fsPath);
 		return testObject.addFolders([{ uri: URI.file(path.join(workspaceDir, 'd')), name: 'DDD' }, { uri: URI.file(path.join(workspaceDir, 'c')), name: 'CCC' }])

src/vs/workbench/services/workspace/common/workspaceEditing.ts

@@ -27,6 +27,12 @@ export interface IWorkspaceEditingService {
 	 */
 	removeFolders(folders: URI[], donotNotifyError?: boolean): TPromise<void>;
 
+	/**
+	 * Allows to add and remove folders to the existing workspace at once.
+	 * When `donotNotifyError` is `true`, error will be bubbled up otherwise, the service handles the error with proper message and action
+	 */
+	updateFolders(index: number, deleteCount?: number, foldersToAdd?: IWorkspaceFolderCreationData[], donotNotifyError?: boolean): TPromise<void>;
+
 	/**
 	 * creates a new workspace with the provided folders and opens it. if path is provided
 	 * the workspace will be saved into that location.

src/vs/workbench/services/workspace/node/workspaceEditingService.ts

@@ -47,7 +47,40 @@ export class WorkspaceEditingService implements IWorkspaceEditingService {
 	) {
 	}
 
+	public updateFolders(index: number, deleteCount?: number, foldersToAdd?: IWorkspaceFolderCreationData[], donotNotifyError?: boolean): TPromise<void> {
+		const folders = this.contextService.getWorkspace().folders;
+		if (index < 0 || index > folders.length - 1) {
+			return TPromise.wrapError(new Error(nls.localize('errorInvalidIndex', "The index for updating workspace folders is invalid.")));
+		}
+
+		if (typeof deleteCount === 'number' && (deleteCount < 0 || index + deleteCount > folders.length - 1)) {
+			return TPromise.wrapError(new Error(nls.localize('errorInvalidDelete', "The number of workspace folders to delete is invalid.")));
+		}
+
+		const wantsToDelete = typeof deleteCount === 'number';
+		const wantsToAdd = Array.isArray(foldersToAdd) && foldersToAdd.length;
+
+		// Add Folders
+		if (wantsToAdd && !wantsToDelete) {
+			return this.doAddFolders(foldersToAdd, index, donotNotifyError);
+		}
+
+		// Delete Folders
+		if (wantsToDelete && !wantsToAdd) {
+			return this.removeFolders(folders.slice(index, index + deleteCount).map(f => f.uri));
+		}
+
+		// Add & Delete Folders (first remove and then add to allow for updating existing folders)
+		return this.removeFolders(folders.slice(index, index + deleteCount).map(f => f.uri)).then(() => {
+			return this.doAddFolders(foldersToAdd, index, donotNotifyError);
+		});
+	}
+
 	public addFolders(foldersToAdd: IWorkspaceFolderCreationData[], donotNotifyError: boolean = false): TPromise<void> {
+		return this.doAddFolders(foldersToAdd, void 0, donotNotifyError);
+	}
+
+	private doAddFolders(foldersToAdd: IWorkspaceFolderCreationData[], index?: number, donotNotifyError: boolean = false): TPromise<void> {
 		const state = this.contextService.getWorkbenchState();
 
 		// If we are in no-workspace or single-folder workspace, adding folders has to
@@ -66,7 +99,7 @@ export class WorkspaceEditingService implements IWorkspaceEditingService {
 		}
 
 		// Delegate addition of folders to workspace service otherwise
-		return this.contextService.addFolders(foldersToAdd)
+		return this.contextService.addFolders(foldersToAdd, index)
 			.then(() => null, error => donotNotifyError ? TPromise.wrapError(error) : this.handleWorkspaceConfigurationEditingError(error));
 	}