Allow command-line API to pass in selection to preserve. Fix #194.

lib/src/io.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart_style.src.io;
 
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
 
 import 'dart_formatter.dart';
 import 'formatter_options.dart';
 import 'formatter_exception.dart';
+import 'source_code.dart';
 
 /// Runs the formatter on every .dart file in [path] (and its subdirectories),
 /// and replaces them with their formatted output.
 ///
 /// Returns `true` if successful or `false` if an error occurred in any of the
 /// files.
 bool processDirectory(FormatterOptions options, Directory directory) {
   options.reporter.showDirectory(directory.path);
 
   var success = true;
@@ skipping 16 matching lines @@
 
     if (!processFile(options, entry, label: relative)) success = false;
   }
 
   return success;
 }
 
 /// Runs the formatter on [file].
 ///
 /// Returns `true` if successful or `false` if an error occurred.
-bool processFile(FormatterOptions options, File file,
-    {String label}) {
+bool processFile(FormatterOptions options, File file, {String label}) {
   if (label == null) label = file.path;
 
   var formatter = new DartFormatter(pageWidth: options.pageWidth);
   try {
-    var source = file.readAsStringSync();
-    var output = formatter.format(source, uri: file.path);
-    options.reporter.showFile(file, label, output, changed: source != output);
+    var source = new SourceCode(file.readAsStringSync(), uri: file.path);
+    var output = formatter.formatSource(source);
+    options.reporter.showFile(file, label, output,
+        changed: source.text != output.text);
     return true;
   } on FormatterException catch (err) {
     stderr.writeln(err.message());
   } catch (err, stack) {
     stderr.writeln('''Hit a bug in the formatter when formatting $label.
 Please report at: github.com/dart-lang/dart_style/issues
 $err
 $stack''');
   }
 
   return false;
 }