implement flutter format (#5606)

Implement flutter format, fixes https://github.com/flutter/flutter/issues/5338

packages/flutter_tools/lib/executable.dart

@@ -21,6 +21,7 @@ import 'src/commands/daemon.dart';
 import 'src/commands/devices.dart';
 import 'src/commands/doctor.dart';
 import 'src/commands/drive.dart';
+import 'src/commands/format.dart';
 import 'src/commands/install.dart';
 import 'src/commands/listen.dart';
 import 'src/commands/logs.dart';
@@ -66,6 +67,7 @@ Future<Null> main(List<String> args) async {
     ..addCommand(new DevicesCommand())
     ..addCommand(new DoctorCommand())
     ..addCommand(new DriveCommand())
+    ..addCommand(new FormatCommand())
     ..addCommand(new InstallCommand())
     ..addCommand(new ListenCommand())
     ..addCommand(new LogsCommand())

packages/flutter_tools/lib/src/commands/format.dart

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+
+import 'package:path/path.dart' as path;
+
+import '../base/process.dart';
+import '../cache.dart';
+import '../globals.dart';
+import '../runner/flutter_command.dart';
+
+class FormatCommand extends FlutterCommand {
+  @override
+  final String name = 'format';
+
+  @override
+  List<String> get aliases => const <String>['dartfmt'];
+
+  @override
+  final String description = 'Format one or more dart files.';
+
+  @override
+  bool get requiresProjectRoot => false;
+
+  @override
+  String get invocation => "${runner.executableName} $name <one or more paths>";
+
+  @override
+  Future<int> runInProject() async {
+    if (argResults.rest.isEmpty) {
+      printStatus('No files specified to be formatted.');
+      printStatus('');
+      printStatus('To format all files in the current directory tree:');
+      printStatus('${runner.executableName} $name .');
+      printStatus('');
+      printStatus(usage);
+      return 1;
+    }
+
+    String dartfmt = path.join(
+        Cache.flutterRoot, 'bin', 'cache', 'dart-sdk', 'bin', 'dartfmt');
+    List<String> cmd = <String>[dartfmt, '-w']..addAll(argResults.rest);
+    return runCommandAndStreamOutput(cmd);
+  }
+}

packages/flutter_tools/test/all.dart

@@ -26,6 +26,7 @@ import 'devfs_test.dart' as devfs_test;
 import 'device_test.dart' as device_test;
 // import 'devices_test.dart' as devices_test;
 import 'drive_test.dart' as drive_test;
+import 'format_test.dart' as format_test;
 import 'install_test.dart' as install_test;
 import 'listen_test.dart' as listen_test;
 import 'logs_test.dart' as logs_test;
@@ -59,6 +60,7 @@ void main() {
   device_test.main();
   // devices_test.main(); // https://github.com/flutter/flutter/issues/4480
   drive_test.main();
+  format_test.main();
   install_test.main();
   listen_test.main();
   logs_test.main();

packages/flutter_tools/test/format_test.dart

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+import 'dart:io';
+
+import 'package:args/command_runner.dart';
+import 'package:flutter_tools/src/cache.dart';
+import 'package:flutter_tools/src/commands/create.dart';
+import 'package:flutter_tools/src/commands/format.dart';
+import 'package:path/path.dart' as path;
+import 'package:test/test.dart';
+
+import 'src/common.dart';
+import 'src/context.dart';
+
+void main() {
+  group('format', () {
+    Directory temp;
+
+    setUp(() {
+      Cache.disableLocking();
+      temp = Directory.systemTemp.createTempSync('flutter_tools');
+    });
+
+    tearDown(() {
+      temp.deleteSync(recursive: true);
+    });
+
+    Future<Null> createProject() async {
+      CreateCommand command = new CreateCommand();
+      CommandRunner runner = createTestCommandRunner(command);
+
+      int code = await runner.run(<String>['create', '--no-pub', temp.path]);
+      expect(code, 0);
+    }
+
+    testUsingContext('a file', () async {
+      await createProject();
+
+      File srcFile = new File(path.join(temp.path, 'lib', 'main.dart'));
+      String original = srcFile.readAsStringSync();
+      srcFile.writeAsStringSync(original.replaceFirst('main()', 'main(  )'));
+
+      FormatCommand command = new FormatCommand();
+      CommandRunner runner = createTestCommandRunner(command);
+      int code = await runner.run(<String>['format', srcFile.path]);
+      expect(code, 0);
+
+      String formatted = srcFile.readAsStringSync();
+      expect(formatted, original);
+    });
+  });
+}