40 columns                              |
>>> Force at least one newline between directives.
import 'a.dart';import 'b.dart';export 'c.dart';
<<<
import 'a.dart';
import 'b.dart';
export 'c.dart';
>>> Remove leading and trailing blank lines.


import 'a.dart';


<<<
import 'a.dart';
>>> Preserve up to one blank line between directives.
import 'a.dart';
import 'b.dart';

export 'c.dart';


export 'd.dart';
<<<
import 'a.dart';
import 'b.dart';

export 'c.dart';

export 'd.dart';