Add daemon handler to start devtools (#62608)

packages/flutter_tools/doc/daemon.md

@@ -252,6 +252,12 @@ The returned `params` will contain:
 - `emulatorName` - the name of the emulator created; this will have been auto-generated if you did not supply one
 - `error` - when `success`=`false`, a message explaining why the creation of the emulator failed
 
+### devtools domain
+
+#### devtools.serve
+
+The `serve()` command starts a DevTools server if one isn't already running and prints out the host and port of the server.
+
 ## 'flutter run --machine' and 'flutter attach --machine'
 
 When running `flutter run --machine` or `flutter attach --machine` the following subset of the daemon is available:

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

@@ -82,6 +82,7 @@ class Daemon {
     _registerDomain(appDomain = AppDomain(this));
     _registerDomain(deviceDomain = DeviceDomain(this));
     _registerDomain(emulatorDomain = EmulatorDomain(this));
+    _registerDomain(devToolsDomain = DevToolsDomain(this));
 
     // Start listening.
     _commandSubscription = commandStream.listen(
@@ -98,6 +99,7 @@ class Daemon {
   AppDomain appDomain;
   DeviceDomain deviceDomain;
   EmulatorDomain emulatorDomain;
+  DevToolsDomain devToolsDomain;
   StreamSubscription<Map<String, dynamic>> _commandSubscription;
   int _outgoingRequestId = 1;
   final Map<String, Completer<dynamic>> _outgoingRequestCompleters = <String, Completer<dynamic>>{};
@@ -182,6 +184,7 @@ class Daemon {
   void _send(Map<String, dynamic> map) => sendCommand(map);
 
   Future<void> shutdown({ dynamic error }) async {
+    await devToolsDomain?.dispose();
     await _commandSubscription?.cancel();
     for (final Domain domain in _domainMap.values) {
       await domain.dispose();
@@ -886,6 +889,29 @@ class DeviceDomain extends Domain {
   }
 }
 
+class DevToolsDomain extends Domain {
+  DevToolsDomain(Daemon daemon) : super(daemon, 'devtools') {
+    registerHandler('serve', serve);
+  }
+
+  DevtoolsLauncher _devtoolsLauncher;
+
+  Future<void> serve([ Map<String, dynamic> args ]) async {
+    _devtoolsLauncher ??= DevtoolsLauncher.instance;
+    final HttpServer server = await _devtoolsLauncher.serve();
+
+    sendEvent('devtools.serve', <String, dynamic>{
+      'host': server.address.host,
+      'port': server.port,
+    });
+  }
+
+  @override
+  Future<void> dispose() async {
+    await _devtoolsLauncher?.close();
+  }
+}
+
 Stream<Map<String, dynamic>> get stdinCommandStream => globals.stdio.stdin
   .transform<String>(utf8.decoder)
   .transform<String>(const LineSplitter())

packages/flutter_tools/lib/src/resident_runner.dart

@@ -1731,9 +1731,7 @@ class DevtoolsLauncher {
   io.HttpServer _devtoolsServer;
   Future<void> launch(Uri observatoryAddress) async {
     try {
-      _devtoolsServer ??= await devtools_server.serveDevTools(
-        enableStdinCommands: false,
-      );
+      await serve();
       await devtools_server.launchDevTools(
         <String, dynamic>{
           'reuseWindows': true,
@@ -1748,6 +1746,17 @@ class DevtoolsLauncher {
     }
   }
 
+  Future<io.HttpServer> serve() async {
+    try {
+      _devtoolsServer ??= await devtools_server.serveDevTools(
+        enableStdinCommands: false,
+      );
+    } on Exception catch (e, st) {
+      globals.printTrace('Failed to serve DevTools: $e\n$st');
+    }
+    return _devtoolsServer;
+  }
+
   Future<void> close() async {
     await _devtoolsServer?.close();
     _devtoolsServer = null;

packages/flutter_tools/test/commands.shard/hermetic/daemon_test.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:async';
+import 'dart:io';
 
 import 'package:flutter_tools/src/android/android_workflow.dart';
 import 'package:flutter_tools/src/base/common.dart';
@@ -13,6 +14,7 @@ import 'package:flutter_tools/src/fuchsia/fuchsia_workflow.dart';
 import 'package:flutter_tools/src/globals.dart' as globals;
 import 'package:flutter_tools/src/ios/ios_workflow.dart';
 import 'package:flutter_tools/src/resident_runner.dart';
+import 'package:mockito/mockito.dart';
 import 'package:quiver/testing/async.dart';
 
 import '../../src/common.dart';
@@ -23,11 +25,13 @@ void main() {
   Daemon daemon;
   NotifyingLogger notifyingLogger;
   BufferLogger bufferLogger;
+  DevtoolsLauncher mockDevToolsLauncher;
 
   group('daemon', () {
     setUp(() {
       bufferLogger = BufferLogger.test();
       notifyingLogger = NotifyingLogger(verbose: false, parent: bufferLogger);
+      mockDevToolsLauncher = MockDevToolsLauncher();
     });
 
     tearDown(() {
@@ -299,6 +303,33 @@ void main() {
       await output.close();
       await input.close();
     });
+
+    testUsingContext('devtools.serve command should return host and port', () async {
+      final StreamController<Map<String, dynamic>> commands = StreamController<Map<String, dynamic>>();
+      final StreamController<Map<String, dynamic>> responses = StreamController<Map<String, dynamic>>();
+      daemon = Daemon(
+        commands.stream,
+        responses.add,
+        notifyingLogger: notifyingLogger,
+      );
+      final HttpServer mockDevToolsServer = MockDevToolsServer();
+      final InternetAddress mockInternetAddress = MockInternetAddress();
+      when(mockDevToolsServer.address).thenReturn(mockInternetAddress);
+      when(mockInternetAddress.host).thenReturn('127.0.0.1');
+      when(mockDevToolsServer.port).thenReturn(1234);
+
+      when(mockDevToolsLauncher.serve()).thenAnswer((_) async => mockDevToolsServer);
+
+      commands.add(<String, dynamic>{'id': 0, 'method': 'devtools.serve'});
+      final Map<String, dynamic> response = await responses.stream.firstWhere(_isDevToolsEvent);
+      expect(response['params'], isNotEmpty);
+      expect(response['params']['host'], equals('127.0.0.1'));
+      expect(response['params']['port'], equals(1234));
+      await responses.close();
+      await commands.close();
+    }, overrides: <Type, Generator>{
+      DevtoolsLauncher: () => mockDevToolsLauncher,
+    });
   });
 
   testUsingContext('notifyingLogger outputs trace messages in verbose mode', () async {
@@ -435,6 +466,8 @@ bool _notEvent(Map<String, dynamic> map) => map['event'] == null;
 
 bool _isConnectedEvent(Map<String, dynamic> map) => map['event'] == 'daemon.connected';
 
+bool _isDevToolsEvent(Map<String, dynamic> map) => map['event'] == 'devtools.serve';
+
 class MockFuchsiaWorkflow extends FuchsiaWorkflow {
   MockFuchsiaWorkflow({ this.canListDevices = true });
 
@@ -455,3 +488,5 @@ class MockIOSWorkflow extends IOSWorkflow {
   @override
   final bool canListDevices;
 }
+
+class MockDevToolsLauncher extends Mock implements DevtoolsLauncher {}

packages/flutter_tools/test/src/mocks.dart

@@ -741,6 +741,9 @@ class MockStdIn extends Mock implements IOSink {
 
 class MockStream extends Mock implements Stream<List<int>> {}
 
+class MockDevToolsServer extends Mock implements HttpServer {}
+class MockInternetAddress extends Mock implements InternetAddress {}
+
 class AlwaysTrueBotDetector implements BotDetector {
   const AlwaysTrueBotDetector();