Addresses the feedbacks in #95738 (#97457)

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

@@ -1340,12 +1340,38 @@ class ProxyDomain extends Domain {
   Future<String> connect(Map<String, dynamic> args) async {
     final int targetPort = _getIntArg(args, 'port', required: true);
     final String id = 'portForwarder_${targetPort}_${_id++}';
-    final Socket socket = await Socket.connect('127.0.0.1', targetPort);
+
+    Socket socket;
+
+    try {
+      socket = await Socket.connect(InternetAddress.loopbackIPv4, targetPort);
+    } on SocketException {
+      globals.logger.printTrace('Connecting to localhost:$targetPort failed with IPv4');
+    }
+
+    try {
+      // If connecting to IPv4 loopback interface fails, try IPv6.
+      socket ??= await Socket.connect(InternetAddress.loopbackIPv6, targetPort);
+    } on SocketException {
+      globals.logger.printError('Connecting to localhost:$targetPort failed');
+    }
+
+    if (socket == null) {
+      throw Exception('Failed to connect to the port');
+    }
+
     _forwardedConnections[id] = socket;
     socket.listen((List<int> data) {
       sendEvent('proxy.data.$id', null, data);
+    }, onError: (dynamic error, StackTrace stackTrace) {
+      // Socket error, probably disconnected.
+      globals.logger.printTrace('Socket error: $error, $stackTrace');
     });
-    unawaited(socket.done.then((dynamic _) {
+
+    unawaited(socket.done.catchError((dynamic error, StackTrace stackTrace) {
+      // Socket error, probably disconnected.
+      globals.logger.printTrace('Socket error: $error, $stackTrace');
+    }).then((dynamic _) {
       sendEvent('proxy.disconnected.$id');
     }));
     return id;
@@ -1376,7 +1402,7 @@ class ProxyDomain extends Domain {
   @override
   Future<void> dispose() async {
     for (final Socket connection in _forwardedConnections.values) {
-      await connection.close();
+      connection.destroy();
     }
     await _tempDirectory?.delete(recursive: true);
   }

packages/flutter_tools/lib/src/daemon.dart

@@ -98,39 +98,11 @@ class DaemonInputStreamConverter {
 
   // Processes a single chunk received in the input stream.
   void _processChunk(List<int> chunk) {
-    const int LF = 10; // The '\n' character
 
     int start = 0;
     while (start < chunk.length) {
       if (state == _InputStreamParseState.json) {
-        // Search for newline character.
-        final int indexOfNewLine = chunk.indexOf(LF, start);
-        if (indexOfNewLine < 0) {
-          bytesBuilder.add(chunk.sublist(start));
-          start = chunk.length;
-        } else {
-          bytesBuilder.add(chunk.sublist(start, indexOfNewLine + 1));
-          start = indexOfNewLine + 1;
-
-          // Process chunk here
-          final Uint8List combinedChunk = bytesBuilder.takeBytes();
-          String jsonString = utf8.decode(combinedChunk).trim();
-          if (jsonString.startsWith('[{') && jsonString.endsWith('}]')) {
-            jsonString = jsonString.substring(1, jsonString.length - 1);
-            final Map<String, Object?>? value = castStringKeyedMap(json.decode(jsonString));
-            if (value != null) {
-              // Check if we need to consume another binary blob.
-              if (value[_binaryLengthKey] != null) {
-                remainingBinaryLength = value[_binaryLengthKey]! as int;
-                currentBinaryStream = StreamController<List<int>>();
-                state = _InputStreamParseState.binary;
-                _controller.add(DaemonMessage(value, currentBinaryStream.stream));
-              } else {
-                _controller.add(DaemonMessage(value));
-              }
-            }
-          }
-        }
+        start += _processChunkInJsonMode(chunk, start);
       } else if (state == _InputStreamParseState.binary) {
         final int bytesSent = _addBinaryChunk(chunk, start, remainingBinaryLength);
         start += bytesSent;
@@ -146,6 +118,41 @@ class DaemonInputStreamConverter {
     }
   }
 
+  /// Processes a chunk in JSON mode, and returns the number of bytes processed.
+  int _processChunkInJsonMode(List<int> chunk, int start) {
+    const int LF = 10; // The '\n' character
+
+    // Search for newline character.
+    final int indexOfNewLine = chunk.indexOf(LF, start);
+    if (indexOfNewLine < 0) {
+      bytesBuilder.add(chunk.sublist(start));
+      return chunk.length - start;
+    }
+
+    bytesBuilder.add(chunk.sublist(start, indexOfNewLine + 1));
+
+    // Process chunk here
+    final Uint8List combinedChunk = bytesBuilder.takeBytes();
+    String jsonString = utf8.decode(combinedChunk).trim();
+    if (jsonString.startsWith('[{') && jsonString.endsWith('}]')) {
+      jsonString = jsonString.substring(1, jsonString.length - 1);
+      final Map<String, Object?>? value = castStringKeyedMap(json.decode(jsonString));
+      if (value != null) {
+        // Check if we need to consume another binary blob.
+        if (value[_binaryLengthKey] != null) {
+          remainingBinaryLength = value[_binaryLengthKey]! as int;
+          currentBinaryStream = StreamController<List<int>>();
+          state = _InputStreamParseState.binary;
+          _controller.add(DaemonMessage(value, currentBinaryStream.stream));
+        } else {
+          _controller.add(DaemonMessage(value));
+        }
+      }
+    }
+
+    return indexOfNewLine + 1 - start;
+  }
+
   int _addBinaryChunk(List<int> chunk, int start, int maximumSizeToRead) {
     if (start == 0 && chunk.length <= remainingBinaryLength) {
       currentBinaryStream.add(chunk);
@@ -170,6 +177,32 @@ class DaemonStreams {
     inputStream = DaemonInputStreamConverter(rawInputStream).convertedStream,
     _logger = logger;
 
+  /// Creates a [DaemonStreams] that uses stdin and stdout as the underlying streams.
+  DaemonStreams.fromStdio(Stdio stdio, { required Logger logger })
+    : this(stdio.stdin, stdio.stdout, logger: logger);
+
+  /// Creates a [DaemonStreams] that uses [Socket] as the underlying streams.
+  DaemonStreams.fromSocket(Socket socket, { required Logger logger })
+    : this(socket, socket, logger: logger);
+
+  /// Connects to a server and creates a [DaemonStreams] from the connection as the underlying streams.
+  factory DaemonStreams.connect(String host, int port, { required Logger logger }) {
+    final Future<Socket> socketFuture = Socket.connect(host, port);
+    final StreamController<List<int>> inputStreamController = StreamController<List<int>>();
+    final StreamController<List<int>> outputStreamController = StreamController<List<int>>();
+    socketFuture.then((Socket socket) {
+      inputStreamController.addStream(socket);
+      socket.addStream(outputStreamController.stream);
+    }).onError((Object error, StackTrace stackTrace) {
+      logger.printError('Socket error: $error');
+      logger.printTrace('$stackTrace');
+      // Propagate the error to the streams.
+      inputStreamController.addError(error, stackTrace);
+      unawaited(outputStreamController.close());
+    });
+    return DaemonStreams(inputStreamController.stream, outputStreamController.sink, logger: logger);
+  }
+
   final StreamSink<List<int>> _outputSink;
   final Logger _logger;
 
@@ -197,28 +230,6 @@ class DaemonStreams {
   Future<void> dispose() async {
     unawaited(_outputSink.close());
   }
-
-  /// Creates a [DaemonStreams] that uses stdin and stdout as the underlying streams.
-  static DaemonStreams fromStdio(Stdio stdio, { required Logger logger }) {
-    return DaemonStreams(stdio.stdin, stdio.stdout, logger: logger);
-  }
-
-  /// Creates a [DaemonStreams] that uses [Socket] as the underlying streams.
-  static DaemonStreams fromSocket(Socket socket, { required Logger logger }) {
-    return DaemonStreams(socket, socket, logger: logger);
-  }
-
-  /// Connects to a server and creates a [DaemonStreams] from the connection as the underlying streams.
-  static DaemonStreams connect(String host, int port, { required Logger logger }) {
-    final Future<Socket> socketFuture = Socket.connect(host, port);
-    final StreamController<List<int>> inputStreamController = StreamController<List<int>>();
-    final StreamController<List<int>> outputStreamController = StreamController<List<int>>();
-    socketFuture.then((Socket socket) {
-      inputStreamController.addStream(socket);
-      socket.addStream(outputStreamController.stream);
-    });
-    return DaemonStreams(inputStreamController.stream, outputStreamController.sink, logger: logger);
-  }
 }
 
 /// Connection between a flutter daemon and a client.

packages/flutter_tools/lib/src/device.dart

@@ -39,15 +39,11 @@ class Category {
   String toString() => value;
 
   static Category? fromString(String category) {
-    switch (category) {
-      case 'web':
-        return web;
-      case 'desktop':
-        return desktop;
-      case 'mobile':
-        return mobile;
-    }
-    return null;
+    return <String, Category>{
+      'web': web,
+      'desktop': desktop,
+      'mobile': mobile,
+    }[category];
   }
 }
 
@@ -70,25 +66,16 @@ class PlatformType {
   String toString() => value;
 
   static PlatformType? fromString(String platformType) {
-    switch (platformType) {
-      case 'web':
-        return web;
-      case 'android':
-        return android;
-      case 'ios':
-        return ios;
-      case 'linux':
-        return linux;
-      case 'macos':
-        return macos;
-      case 'windows':
-        return windows;
-      case 'fuchsia':
-        return fuchsia;
-      case 'custom':
-        return custom;
-    }
-    return null;
+    return <String, PlatformType>{
+      'web': web,
+      'android': android,
+      'ios': ios,
+      'linux': linux,
+      'macos': macos,
+      'windows': windows,
+      'fuchsia': fuchsia,
+      'custom': custom,
+    }[platformType];
   }
 }
 

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

@@ -11,6 +11,8 @@
 @Tags(<String>['no-shuffle'])
 
 import 'dart:async';
+import 'dart:io' as io;
+import 'dart:typed_data';
 
 import 'package:fake_async/fake_async.dart';
 import 'package:file/src/interface/file.dart';
@@ -564,6 +566,115 @@ void main() {
     }, overrides: <Type, Generator>{
       DevtoolsLauncher: () => FakeDevtoolsLauncher(null),
     });
+
+    testUsingContext('proxy.connect tries to connect to an ipv4 address and proxies the connection correctly', () async {
+      final TestIOOverrides ioOverrides = TestIOOverrides();
+      await io.IOOverrides.runWithIOOverrides(() async {
+        final FakeSocket socket = FakeSocket();
+        bool connectCalled = false;
+        int connectPort;
+        ioOverrides.connectCallback = (dynamic host, int port) async {
+          connectCalled = true;
+          connectPort = port;
+          if (host == io.InternetAddress.loopbackIPv4) {
+            return socket;
+          }
+          throw const io.SocketException('fail');
+        };
+
+        daemon = Daemon(
+          daemonConnection,
+          notifyingLogger: notifyingLogger,
+        );
+        daemonStreams.inputs.add(DaemonMessage(<String, dynamic>{'id': 0, 'method': 'proxy.connect', 'params': <String, dynamic>{'port': 123}}));
+
+        final Stream<DaemonMessage> broadcastOutput = daemonStreams.outputs.stream.asBroadcastStream();
+        final DaemonMessage firstResponse = await broadcastOutput.firstWhere(_notEvent);
+        expect(firstResponse.data['id'], 0);
+        expect(firstResponse.data['result'], isNotNull);
+        expect(connectCalled, true);
+        expect(connectPort, 123);
+
+        final Object id = firstResponse.data['result'];
+
+        // Can send received data as event.
+        socket.controller.add(Uint8List.fromList(<int>[10, 11, 12]));
+        final DaemonMessage dataEvent = await broadcastOutput.firstWhere(
+          (DaemonMessage message) => message.data['event'] != null && message.data['event'] == 'proxy.data.$id',
+        );
+        expect(dataEvent.binary, isNotNull);
+        final List<List<int>> data = await dataEvent.binary.toList();
+        expect(data[0], <int>[10, 11, 12]);
+
+        // Can proxy data to the socket.
+        daemonStreams.inputs.add(DaemonMessage(<String, dynamic>{'id': 0, 'method': 'proxy.write', 'params': <String, dynamic>{'id': id}}, Stream<List<int>>.value(<int>[21, 22, 23])));
+        await pumpEventQueue();
+        expect(socket.addedData[0], <int>[21, 22, 23]);
+
+        // Closes the connection when disconnect request received.
+        expect(socket.closeCalled, false);
+        daemonStreams.inputs.add(DaemonMessage(<String, dynamic>{'id': 0, 'method': 'proxy.disconnect', 'params': <String, dynamic>{'id': id}}));
+        await pumpEventQueue();
+        expect(socket.closeCalled, true);
+
+        // Sends disconnected event when socket.done completer finishes.
+        socket.doneCompleter.complete();
+        final DaemonMessage disconnectEvent = await broadcastOutput.firstWhere(
+          (DaemonMessage message) => message.data['event'] != null && message.data['event'] == 'proxy.disconnected.$id',
+        );
+        expect(disconnectEvent.data, isNotNull);
+      }, ioOverrides);
+    });
+
+    testUsingContext('proxy.connect connects to ipv6 if ipv4 failed', () async {
+      final TestIOOverrides ioOverrides = TestIOOverrides();
+      await io.IOOverrides.runWithIOOverrides(() async {
+        final FakeSocket socket = FakeSocket();
+        bool connectIpv4Called = false;
+        int connectPort;
+        ioOverrides.connectCallback = (dynamic host, int port) async {
+          connectPort = port;
+          if (host == io.InternetAddress.loopbackIPv4) {
+            connectIpv4Called = true;
+          } else if (host == io.InternetAddress.loopbackIPv6) {
+            return socket;
+          }
+          throw const io.SocketException('fail');
+        };
+
+        daemon = Daemon(
+          daemonConnection,
+          notifyingLogger: notifyingLogger,
+        );
+        daemonStreams.inputs.add(DaemonMessage(<String, dynamic>{'id': 0, 'method': 'proxy.connect', 'params': <String, dynamic>{'port': 123}}));
+
+        final Stream<DaemonMessage> broadcastOutput = daemonStreams.outputs.stream.asBroadcastStream();
+        final DaemonMessage firstResponse = await broadcastOutput.firstWhere(_notEvent);
+        expect(firstResponse.data['id'], 0);
+        expect(firstResponse.data['result'], isNotNull);
+        expect(connectIpv4Called, true);
+        expect(connectPort, 123);
+      }, ioOverrides);
+    });
+
+    testUsingContext('proxy.connect fails if both ipv6 and ipv4 failed', () async {
+      final TestIOOverrides ioOverrides = TestIOOverrides();
+      await io.IOOverrides.runWithIOOverrides(() async {
+        ioOverrides.connectCallback = (dynamic host, int port) => throw const io.SocketException('fail');
+
+        daemon = Daemon(
+          daemonConnection,
+          notifyingLogger: notifyingLogger,
+        );
+        daemonStreams.inputs.add(DaemonMessage(<String, dynamic>{'id': 0, 'method': 'proxy.connect', 'params': <String, dynamic>{'port': 123}}));
+
+        final Stream<DaemonMessage> broadcastOutput = daemonStreams.outputs.stream.asBroadcastStream();
+        final DaemonMessage firstResponse = await broadcastOutput.firstWhere(_notEvent);
+        expect(firstResponse.data['id'], 0);
+        expect(firstResponse.data['result'], isNull);
+        expect(firstResponse.data['error'], isNotNull);
+      }, ioOverrides);
+    });
   });
 
   testUsingContext('notifyingLogger outputs trace messages in verbose mode', () async {
@@ -851,3 +962,46 @@ class FakeApplicationPackageFactory implements ApplicationPackageFactory {
 }
 
 class FakeApplicationPackage extends Fake implements ApplicationPackage {}
+
+class TestIOOverrides extends io.IOOverrides {
+  Future<io.Socket> Function(dynamic host, int port) connectCallback;
+
+  @override
+  Future<io.Socket> socketConnect(dynamic host, int port,
+      {dynamic sourceAddress, int sourcePort = 0, Duration timeout}) {
+    return connectCallback(host, port);
+  }
+}
+
+class FakeSocket extends Fake implements io.Socket {
+  bool closeCalled = false;
+  final StreamController<Uint8List> controller = StreamController<Uint8List>();
+  final List<List<int>> addedData = <List<int>>[];
+  final Completer<bool> doneCompleter = Completer<bool>();
+
+  @override
+  StreamSubscription<Uint8List> listen(
+    void Function(Uint8List event) onData, {
+    Function onError,
+    void Function() onDone,
+    bool cancelOnError,
+  }) {
+    return controller.stream.listen(onData, onError: onError, onDone: onDone, cancelOnError: cancelOnError);
+  }
+
+  @override
+  void add(List<int> data) {
+    addedData.add(data);
+  }
+
+  @override
+  Future<void> close() async {
+    closeCalled = true;
+  }
+
+  @override
+  Future<bool> get done => doneCompleter.future;
+
+  @override
+  void destroy() {}
+}