Add a command-line option to set the exit code on a formatting change.

lib/src/formatter_options.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.formatter_options;
 
 import 'dart:convert';
 import 'dart:io';
 
 import 'source_code.dart';
@@ skipping 111 matching lines @@
       } on FileSystemException catch (err) {
         stderr.writeln("Could not overwrite $label: "
             "${err.osError.message} (error code ${err.osError.errorCode})");
       }
     } else {
       print("Unchanged $label");
     }
   }
 }
 
+/// Base clase for a reporter that decorates an inner reporter.
+abstract class _ReporterDecorator implements OutputReporter {
+  final OutputReporter _inner;
+
+  _ReporterDecorator(this._inner);
+
+  void showDirectory(String path) {
+    _inner.showDirectory(path);
+  }
+
+  void showSkippedLink(String path) {
+    _inner.showSkippedLink(path);
+  }
+
+  void showHiddenPath(String path) {
+    _inner.showHiddenPath(path);
+  }
+
+  void beforeFile(File file, String label) {
+    _inner.beforeFile(file, label);
+  }
+
+  void afterFile(File file, String label, SourceCode output, {bool changed}) {
+    _inner.afterFile(file, label, output, changed: changed);
+  }
+}
+
 /// A decorating reporter that reports how long it took for format each file.
-class ProfileReporter implements OutputReporter {
-  final OutputReporter _inner;
-
+class ProfileReporter extends _ReporterDecorator {
   /// The files that have been started but have not completed yet.
   ///
   /// Maps a file label to the time that it started being formatted.
   final Map<String, DateTime> _ongoing = {};
 
   /// The elapsed time it took to format each completed file.
   final Map<String, Duration> _elapsed = {};
 
   /// The number of files that completed so fast that they aren't worth
   /// tracking.
   int _elided = 0;
 
-  ProfileReporter(this._inner);
+  ProfileReporter(OutputReporter inner) : super(inner);
 
   /// Show the times for the slowest files to format.
   void showProfile() {
     // Everything should be done.
     assert(_ongoing.isEmpty);
 
     var files = _elapsed.keys.toList();
     files.sort((a, b) => _elapsed[b].compareTo(_elapsed[a]));
 
     for (var file in files) {
       print("${_elapsed[file]}: $file");
     }
 
     if (_elided >= 1) {
       var s = _elided > 1 ? 's' : '';
       print("...$_elided more file$s each took less than 10ms.");
     }
   }
 
-  /// Describe the directory whose contents are about to be processed.
-  void showDirectory(String path) {
-    _inner.showDirectory(path);
-  }
-
-  /// Describe the symlink at [path] that wasn't followed.
-  void showSkippedLink(String path) {
-    _inner.showSkippedLink(path);
-  }
-
-  /// Describe the hidden [path] that wasn't processed.
-  void showHiddenPath(String path) {
-    _inner.showHiddenPath(path);
-  }
-
   /// Called when [file] is about to be formatted.
   void beforeFile(File file, String label) {
-    _inner.beforeFile(file, label);
-
+    super.beforeFile(file, label);
     _ongoing[label] = new DateTime.now();
   }
 
   /// Describe the processed file at [path] whose formatted result is [output].
   ///
   /// If the contents of the file are the same as the formatted output,
   /// [changed] will be false.
   void afterFile(File file, String label, SourceCode output, {bool changed}) {
     var elapsed = new DateTime.now().difference(_ongoing.remove(label));
     if (elapsed.inMilliseconds >= 10) {
       _elapsed[label] = elapsed;
     } else {
       _elided++;
     }
 
-    _inner.afterFile(file, label, output, changed: changed);
+    super.afterFile(file, label, output, changed: changed);
   }
 }
+
+/// A decorating reporter that sets the exit code to 1 if any changes are made.
+class SetExitReporter extends _ReporterDecorator {
+  SetExitReporter(OutputReporter inner) : super(inner);
+
+  /// Describe the processed file at [path] whose formatted result is [output].
+  ///
+  /// If the contents of the file are the same as the formatted output,
+  /// [changed] will be false.
+  void afterFile(File file, String label, SourceCode output, {bool changed}) {
+    if (changed) exitCode = 1;
+
+    super.afterFile(file, label, output, changed: changed);
+  }
+}