Update flutter clean to remove .dart_tool directory (#27054)

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

diff --git a/packages/flutter_tools/lib/src/commands/clean.dart b/packages/flutter_tools/lib/src/commands/clean.dart
index 740f108..c427e39 100644
--- a/packages/flutter_tools/lib/src/commands/clean.dart
+++ b/packages/flutter_tools/lib/src/commands/clean.dart
@@ -8,6 +8,7 @@
 import '../base/file_system.dart';
 import '../build_info.dart';
 import '../globals.dart';
+import '../project.dart';
 import '../runner/flutter_command.dart';
 
 class CleanCommand extends FlutterCommand {
@@ -19,22 +20,31 @@
   final String name = 'clean';
 
   @override
-  final String description = 'Delete the build/ directory.';
+  final String description = 'Delete the build/ and .dart_tool/ directories.';
 
   @override
   Future<FlutterCommandResult> runCommand() async {
+    final FlutterProject flutterProject = await FlutterProject.current();
     final Directory buildDir = fs.directory(getBuildDirectory());
+
     printStatus("Deleting '${buildDir.path}${fs.path.separator}'.");
-
-    if (!buildDir.existsSync())
-      return null;
-
-    try {
-      buildDir.deleteSync(recursive: true);
-    } catch (error) {
-      throwToolExit(error.toString());
+    if (buildDir.existsSync()) {
+      try {
+        buildDir.deleteSync(recursive: true);
+      } catch (error) {
+        throwToolExit(error.toString());
+      }
     }
 
-    return null;
+    printStatus("Deleting '${flutterProject.dartTool.path}${fs.path.separator}'.");
+    if (flutterProject.dartTool.existsSync()) {
+      try {
+        flutterProject.dartTool.deleteSync(recursive: true);
+      } catch (error) {
+        throwToolExit(error.toString());
+      }
+    }
+    return const FlutterCommandResult(ExitStatus.success);
   }
 }
+

packages/flutter_tools/test/commands/clean_test.dart

diff --git a/packages/flutter_tools/test/commands/clean_test.dart b/packages/flutter_tools/test/commands/clean_test.dart
new file mode 100644
index 0000000..e01129a
--- /dev/null
+++ b/packages/flutter_tools/test/commands/clean_test.dart
@@ -0,0 +1,51 @@
+// Copyright 2019 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 'package:flutter_tools/src/base/config.dart';
+import 'package:flutter_tools/src/base/context.dart';
+import 'package:flutter_tools/src/base/file_system.dart';
+import 'package:flutter_tools/src/commands/clean.dart';
+import 'package:mockito/mockito.dart';
+
+import '../src/common.dart';
+import '../src/context.dart';
+
+
+void main() {
+  final MockFileSystem mockFileSystem = MockFileSystem();
+  final MockDirectory currentDirectory = MockDirectory();
+  final MockDirectory exampleDirectory = MockDirectory();
+  final MockDirectory buildDirectory = MockDirectory();
+  final MockDirectory dartToolDirectory = MockDirectory();
+  final MockFile pubspec = MockFile();
+  final MockFile examplePubspec = MockFile();
+
+  when(mockFileSystem.currentDirectory).thenReturn(currentDirectory);
+  when(currentDirectory.childDirectory('example')).thenReturn(exampleDirectory);
+  when(currentDirectory.childFile('pubspec.yaml')).thenReturn(pubspec);
+  when(pubspec.path).thenReturn('/test/pubspec.yaml');
+  when(exampleDirectory.childFile('pubspec.yaml')).thenReturn(examplePubspec);
+  when(currentDirectory.childDirectory('.dart_tool')).thenReturn(dartToolDirectory);
+  when(examplePubspec.path).thenReturn('/test/example/pubspec.yaml');
+  when(mockFileSystem.isFileSync('/test/pubspec.yaml')).thenReturn(false);
+  when(mockFileSystem.isFileSync('/test/example/pubspec.yaml')).thenReturn(false);
+  when(mockFileSystem.directory('build')).thenReturn(buildDirectory);
+  when(mockFileSystem.path).thenReturn(fs.path);
+  when(buildDirectory.existsSync()).thenReturn(true);
+  when(dartToolDirectory.existsSync()).thenReturn(true);
+  group(CleanCommand, () {
+    testUsingContext('removes build and .dart_tool directories', () async {
+      await CleanCommand().runCommand();
+      verify(buildDirectory.deleteSync(recursive: true)).called(1);
+      verify(dartToolDirectory.deleteSync(recursive: true)).called(1);
+    }, overrides: <Type, Generator>{
+      FileSystem: () => mockFileSystem,
+      Config: () => null,
+    });
+  });
+}
+
+class MockFileSystem extends Mock implements FileSystem {}
+class MockFile extends Mock implements File {}
+class MockDirectory extends Mock implements Directory {}