Remove optional argument, document reason for looking at args

src/vs/editor/common/commands/trimTrailingWhitespaceCommand.ts

@@ -17,7 +17,7 @@ export class TrimTrailingWhitespaceCommand implements editorCommon.ICommand {
 	private selectionId: string;
 	private cursors: Position[];
 
-	constructor(selection: Selection, cursors: Position[] = []) {
+	constructor(selection: Selection, cursors: Position[]) {
 		this.selection = selection;
 		this.cursors = cursors;
 	}

src/vs/editor/contrib/linesOperations/common/linesOperations.ts

@@ -209,8 +209,11 @@ export class TrimTrailingWhitespaceAction extends EditorAction {
 
 	public run(accessor: ServicesAccessor, editor: ICommonCodeEditor, args: any): void {
 
-		var cursors: Position[];
+		let cursors: Position[] = [];
 		if (args.reason === 'auto-save') {
+			// See https://github.com/editorconfig/editorconfig-vscode/issues/47
+			// It is very convenient for the editor config extension to invoke this action.
+			// So, if we get a reason:'auto-save' passed in, let's preserve cursor positions.
 			cursors = editor.getSelections().map(s => new Position(s.positionLineNumber, s.positionColumn));
 		}
 

src/vs/editor/test/common/commands/trimTrailingWhitespaceCommand.test.ts

@@ -14,7 +14,7 @@ import { withEditorModel } from 'vs/editor/test/common/editorTestUtils';
 
 function assertTrimTrailingWhitespaceCommand(text: string[], expected: IIdentifiedSingleEditOperation[]): void {
 	return withEditorModel(text, (model) => {
-		var op = new TrimTrailingWhitespaceCommand(new Selection(1, 1, 1, 1));
+		var op = new TrimTrailingWhitespaceCommand(new Selection(1, 1, 1, 1), []);
 		var actual = getEditOperation(model, op);
 		assert.deepEqual(actual, expected);
 	});