Make DeviceDomain echo a msg if doctor says it can't list anything (#9749)

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packages/flutter_tools/lib/executable.dart

@@ -5,7 +5,6 @@
 import 'dart:async';
 
 import 'package:args/command_runner.dart';
-import 'package:flutter_tools/src/version.dart';
 import 'package:intl/intl_standalone.dart' as intl;
 import 'package:meta/meta.dart';
 import 'package:process/process.dart';
@@ -53,6 +52,7 @@ import 'src/run_hot.dart';
 import 'src/runner/flutter_command.dart';
 import 'src/runner/flutter_command_runner.dart';
 import 'src/usage.dart';
+import 'src/version.dart';
 
 /// Main entry point for commands.
 ///

packages/flutter_tools/lib/src/android/android_device.dart

@@ -17,6 +17,7 @@ import '../base/process_manager.dart';
 import '../build_info.dart';
 import '../commands/build_apk.dart';
 import '../device.dart';
+import '../doctor.dart';
 import '../globals.dart';
 import '../protocol_discovery.dart';
 
@@ -27,11 +28,14 @@ import 'android_sdk.dart';
 const String _defaultAdbPath = 'adb';
 
 class AndroidDevices extends PollingDeviceDiscovery {
-  AndroidDevices() : super('AndroidDevices');
+  AndroidDevices() : super('Android devices');
 
   @override
   bool get supportsPlatform => true;
 
+  @override
+  bool get canListAnything => doctor.androidWorkflow.canListDevices;
+
   @override
   List<Device> pollingGetDevices() => getAdbDevices();
 }

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

@@ -62,12 +62,7 @@ class DaemonCommand extends FlutterCommand {
       final int code = await daemon.onExit;
       if (code != 0)
         throwToolExit('Daemon exited with non-zero exit code: $code', exitCode: code);
-    }, onError: _handleError);
-  }
-
-  dynamic _handleError(dynamic error, StackTrace stackTrace) {
-    printError('Error from flutter daemon: $error', stackTrace: stackTrace);
-    return null;
+    });
   }
 }
 
@@ -76,7 +71,9 @@ typedef void DispatchCommand(Map<String, dynamic> command);
 typedef Future<dynamic> CommandHandler(Map<String, dynamic> args);
 
 class Daemon {
-  Daemon(Stream<Map<String, dynamic>> commandStream, this.sendCommand, {
+  Daemon(
+    Stream<Map<String, dynamic>> commandStream,
+    this.sendCommand, {
     this.daemonCommand,
     this.notifyingLogger,
     this.logToStdout: false
@@ -87,7 +84,7 @@ class Daemon {
     _registerDomain(deviceDomain = new DeviceDomain(this));
 
     // Start listening.
-    commandStream.listen(
+    _commandSubscription = commandStream.listen(
       _handleRequest,
       onDone: () {
         if (!_onExitCompleter.isCompleted)
@@ -99,6 +96,7 @@ class Daemon {
   DaemonDomain daemonDomain;
   AppDomain appDomain;
   DeviceDomain deviceDomain;
+  StreamSubscription<Map<String, dynamic>> _commandSubscription;
 
   final DispatchCommand sendCommand;
   final DaemonCommand daemonCommand;
@@ -143,10 +141,15 @@ class Daemon {
 
   void _send(Map<String, dynamic> map) => sendCommand(map);
 
-  void shutdown() {
+  void shutdown({dynamic error}) {
+    _commandSubscription?.cancel();
     _domainMap.values.forEach((Domain domain) => domain.dispose());
-    if (!_onExitCompleter.isCompleted)
+    if (!_onExitCompleter.isCompleted) {
+      if (error == null)
         _onExitCompleter.complete(0);
+      else
+        _onExitCompleter.completeError(error);
+    }
   }
 }
 
@@ -539,6 +542,18 @@ class DeviceDomain extends Domain {
     if (!discoverer.supportsPlatform)
       return;
 
+    if (!discoverer.canListAnything) {
+      sendEvent(
+        'daemon.showMessage',
+        <String, String>{
+          'title': 'Unable to list devices',
+          'message':
+              'Unable to discover ${discoverer.name}. Please run '
+              '"flutter doctor" to diagnose potential issues',
+        },
+      );
+    }
+
     _discoverers.add(discoverer);
 
     discoverer.onAdded.listen(_onDeviceEvent('device.added'));
@@ -650,7 +665,8 @@ Stream<Map<String, dynamic>> get stdinCommandStream => stdin
   });
 
 void stdoutCommandResponse(Map<String, dynamic> command) {
-  stdout.writeln('[${JSON.encode(command, toEncodable: _jsonEncodeObject)}]');
+  final String encoded = JSON.encode(command, toEncodable: _jsonEncodeObject);
+  stdout.writeln('[$encoded]');
 }
 
 dynamic _jsonEncodeObject(dynamic object) {

packages/flutter_tools/lib/src/device.dart

@@ -92,6 +92,11 @@ class DeviceManager {
 /// An abstract class to discover and enumerate a specific type of devices.
 abstract class DeviceDiscovery {
   bool get supportsPlatform;
+
+  /// Whether this device discovery is capable of listing any devices given the
+  /// current environment configuration.
+  bool get canListAnything;
+
   List<Device> get devices;
 }
 

packages/flutter_tools/lib/src/ios/devices.dart

@@ -27,11 +27,14 @@ const String _kIdeviceinstallerInstructions =
 const Duration kPortForwardTimeout = const Duration(seconds: 10);
 
 class IOSDevices extends PollingDeviceDiscovery {
-  IOSDevices() : super('IOSDevices');
+  IOSDevices() : super('iOS devices');
 
   @override
   bool get supportsPlatform => platform.isMacOS;
 
+  @override
+  bool get canListAnything => doctor.iosWorkflow.canListDevices;
+
   @override
   List<Device> pollingGetDevices() => IOSDevice.getAttachedDevices();
 }

packages/flutter_tools/lib/src/ios/simulators.dart

@@ -16,6 +16,7 @@ import '../base/process.dart';
 import '../base/process_manager.dart';
 import '../build_info.dart';
 import '../device.dart';
+import '../doctor.dart';
 import '../flx.dart' as flx;
 import '../globals.dart';
 import '../protocol_discovery.dart';
@@ -27,11 +28,14 @@ const String _xcrunPath = '/usr/bin/xcrun';
 const String _kFlutterTestDeviceSuffix = '(Flutter)';
 
 class IOSSimulators extends PollingDeviceDiscovery {
-  IOSSimulators() : super('IOSSimulators');
+  IOSSimulators() : super('iOS simulators');
 
   @override
   bool get supportsPlatform => platform.isMacOS;
 
+  @override
+  bool get canListAnything => doctor.iosWorkflow.canListDevices;
+
   @override
   List<Device> pollingGetDevices() => IOSSimulatorUtils.instance.getAttachedDevices();
 }

packages/flutter_tools/test/src/mocks.dart

@@ -42,6 +42,9 @@ class MockPollingDeviceDiscovery extends PollingDeviceDiscovery {
   @override
   bool get supportsPlatform => true;
 
+  @override
+  bool get canListAnything => true;
+
   void addDevice(MockAndroidDevice device) {
     _devices.add(device);