Provide a parameter to bubble up the error while adding/removing workspace folders through API

src/vs/workbench/api/electron-browser/mainThreadFileSystem.ts

@@ -45,7 +45,7 @@ export class MainThreadFileSystem implements MainThreadFileSystemShape {
 	}
 
 	$onDidAddFileSystemRoot(uri: URI): void {
-		this._workspaceEditingService.addFolders([{ uri }]);
+		this._workspaceEditingService.addFolders([{ uri }], true);
 	}
 
 	$onFileSystemChange(handle: number, changes: IFileChange[]): void {

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

@@ -16,14 +16,16 @@ export interface IWorkspaceEditingService {
 	_serviceBrand: ServiceIdentifier<any>;
 
 	/**
-	 * Add folders to the existing workspace
+	 * Add folders to the existing workspace.
+	 * When `donotNotifyError` is `true`, error will be bubbled up otherwise, the service handles the error with proper message and action
 	 */
-	addFolders(folders: IWorkspaceFolderCreationData[]): TPromise<void>;
+	addFolders(folders: IWorkspaceFolderCreationData[], donotNotifyError?: boolean): TPromise<void>;
 
 	/**
 	 * Remove folders from the existing workspace
+	 * When `donotNotifyError` is `true`, error will be bubbled up otherwise, the service handles the error with proper message and action
 	 */
-	removeFolders(folders: URI[]): TPromise<void>;
+	removeFolders(folders: URI[], donotNotifyError?: boolean): TPromise<void>;
 
 	/**
 	 * creates a new workspace with the provided folders and opens it. if path is provided

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

@@ -51,7 +51,7 @@ export class WorkspaceEditingService implements IWorkspaceEditingService {
 	) {
 	}
 
-	public addFolders(foldersToAdd: IWorkspaceFolderCreationData[]): TPromise<void> {
+	public addFolders(foldersToAdd: IWorkspaceFolderCreationData[], donotNotifyError: boolean = false): TPromise<void> {
 		const state = this.contextService.getWorkbenchState();
 
 		// If we are in no-workspace or single-folder workspace, adding folders has to
@@ -71,10 +71,10 @@ export class WorkspaceEditingService implements IWorkspaceEditingService {
 
 		// Delegate addition of folders to workspace service otherwise
 		return this.contextService.addFolders(foldersToAdd)
-			.then(() => null, error => this.handleWorkspaceConfigurationEditingError(error));
+			.then(() => null, error => donotNotifyError ? TPromise.wrapError(error) : this.handleWorkspaceConfigurationEditingError(error));
 	}
 
-	public removeFolders(foldersToRemove: URI[]): TPromise<void> {
+	public removeFolders(foldersToRemove: URI[], donotNotifyError: boolean = false): TPromise<void> {
 
 		// If we are in single-folder state and the opened folder is to be removed,
 		// we close the workspace and enter the empty workspace state for the window.
@@ -87,7 +87,7 @@ export class WorkspaceEditingService implements IWorkspaceEditingService {
 
 		// Delegate removal of folders to workspace service otherwise
 		return this.contextService.removeFolders(foldersToRemove)
-			.then(() => null, error => this.handleWorkspaceConfigurationEditingError(error));
+			.then(() => null, error => donotNotifyError ? TPromise.wrapError(error) : this.handleWorkspaceConfigurationEditingError(error));
 	}
 
 	public createAndEnterWorkspace(folders?: IWorkspaceFolderCreationData[], path?: string): TPromise<void> {