updates for flutter run --machine (#7183)

* have flutter run --machine log to stdout

* add a test

* add docs; fix type annotation lint

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

@@ -76,7 +76,8 @@ typedef Future<dynamic> CommandHandler(Map<String, dynamic> args);
 class Daemon {
   Daemon(Stream<Map<String, dynamic>> commandStream, this.sendCommand, {
     this.daemonCommand,
-    this.notifyingLogger
+    this.notifyingLogger,
+    this.logToStdout: false
   }) {
     // Set up domains.
     _registerDomain(daemonDomain = new DaemonDomain(this));
@@ -100,6 +101,7 @@ class Daemon {
   final DispatchCommand sendCommand;
   final DaemonCommand daemonCommand;
   final NotifyingLogger notifyingLogger;
+  final bool logToStdout;
 
   final Completer<int> _onExitCompleter = new Completer<int>();
   final Map<String, Domain> _domainMap = <String, Domain>{};
@@ -226,17 +228,29 @@ class DaemonDomain extends Domain {
     registerHandler('shutdown', shutdown);
 
     _subscription = daemon.notifyingLogger.onMessage.listen((LogMessage message) {
-      if (message.stackTrace != null) {
-        sendEvent('daemon.logMessage', <String, dynamic>{
-          'level': message.level,
-          'message': message.message,
-          'stackTrace': message.stackTrace.toString()
-        });
+      if (daemon.logToStdout) {
+        if (message.level == 'status') {
+          // We use `print()` here instead of `stdout.writeln()` in order to
+          // capture the print output for testing.
+          print(message.message);
+        } else if (message.level == 'error') {
+          stderr.writeln(message.message);
+          if (message.stackTrace != null)
+            stderr.writeln(message.stackTrace.toString().trimRight());
+        }
       } else {
-        sendEvent('daemon.logMessage', <String, dynamic>{
-          'level': message.level,
-          'message': message.message
-        });
+        if (message.stackTrace != null) {
+          sendEvent('daemon.logMessage', <String, dynamic>{
+            'level': message.level,
+            'message': message.message,
+            'stackTrace': message.stackTrace.toString()
+          });
+        } else {
+          sendEvent('daemon.logMessage', <String, dynamic>{
+            'level': message.level,
+            'message': message.message
+          });
+        }
       }
     });
   }
@@ -345,7 +359,7 @@ class AppDomain extends Domain {
       );
     }
 
-    AppInstance app = new AppInstance(_getNewAppId(), runner);
+    AppInstance app = new AppInstance(_getNewAppId(), runner: runner, logToStdout: daemon.logToStdout);
     _apps.add(app);
     _sendAppEvent(app, 'start', <String, dynamic>{
       'deviceId': device.id,
@@ -652,10 +666,11 @@ class NotifyingLogger extends Logger {
 
 /// A running application, started by this daemon.
 class AppInstance {
-  AppInstance(this.id, [this.runner]);
+  AppInstance(this.id, { this.runner, this.logToStdout = false });
 
   final String id;
   final ResidentRunner runner;
+  final bool logToStdout;
 
   _AppRunLogger _logger;
 
@@ -671,7 +686,7 @@ class AppInstance {
 
   dynamic _runInZone(AppDomain domain, dynamic method()) {
     if (_logger == null)
-      _logger = new _AppRunLogger(domain, this);
+      _logger = new _AppRunLogger(domain, this, logToStdout: logToStdout);
 
     AppContext appContext = new AppContext();
     appContext.setVariable(Logger, _logger);
@@ -681,31 +696,42 @@ class AppInstance {
 
 /// A [Logger] which sends log messages to a listening daemon client.
 class _AppRunLogger extends Logger {
-  _AppRunLogger(this.domain, this.app);
+  _AppRunLogger(this.domain, this.app, { this.logToStdout: false });
 
   AppDomain domain;
   final AppInstance app;
+  final bool logToStdout;
   int _nextProgressId = 0;
 
   @override
   void printError(String message, [StackTrace stackTrace]) {
-    if (stackTrace != null) {
-      _sendLogEvent(<String, dynamic>{
-        'log': message,
-        'stackTrace': stackTrace.toString(),
-        'error': true
-      });
+    if (logToStdout) {
+      stderr.writeln(message);
+      if (stackTrace != null)
+        stderr.writeln(stackTrace.toString().trimRight());
     } else {
-      _sendLogEvent(<String, dynamic>{
-        'log': message,
-        'error': true
-      });
+      if (stackTrace != null) {
+        _sendLogEvent(<String, dynamic>{
+          'log': message,
+          'stackTrace': stackTrace.toString(),
+          'error': true
+        });
+      } else {
+        _sendLogEvent(<String, dynamic>{
+          'log': message,
+          'error': true
+        });
+      }
     }
   }
 
   @override
   void printStatus(String message, { bool emphasis: false, bool newline: true, String ansiAlternative }) {
-    _sendLogEvent(<String, dynamic>{ 'log': message });
+    if (logToStdout) {
+      print(message);
+    } else {
+      _sendLogEvent(<String, dynamic>{ 'log': message });
+    }
   }
 
   @override

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

@@ -170,13 +170,14 @@ class RunCommand extends RunCommandBase {
 
     if (argResults['machine']) {
       Daemon daemon = new Daemon(stdinCommandStream, stdoutCommandResponse,
-          notifyingLogger: new NotifyingLogger());
+          notifyingLogger: new NotifyingLogger(), logToStdout: true);
       AppInstance app = daemon.appDomain.startApp(
         device, Directory.current.path, targetFile, route,
         getBuildMode(), argResults['start-paused'], hotMode);
       int result = await app.runner.waitForAppToFinish();
       if (result != 0)
         throwToolExit(null, exitCode: result);
+      return null;
     }
 
     int debugPort;

packages/flutter_tools/test/daemon_test.dart

@@ -85,6 +85,30 @@ void main() {
       });
     });
 
+    _testUsingContext('daemon.logMessage logToStdout', () async {
+      StringBuffer buffer = new StringBuffer();
+
+      await runZoned(() async {
+        return appContext.runInZone(() async {
+          StreamController<Map<String, dynamic>> commands = new StreamController<Map<String, dynamic>>();
+          StreamController<Map<String, dynamic>> responses = new StreamController<Map<String, dynamic>>();
+          daemon = new Daemon(
+            commands.stream,
+            (Map<String, dynamic> result) => responses.add(result),
+            notifyingLogger: notifyingLogger,
+            logToStdout: true
+          );
+          printStatus('daemon.logMessage test');
+          // Service the event loop.
+          await new Future<Null>.value();
+        });
+      }, zoneSpecification: new ZoneSpecification(print: (Zone self, ZoneDelegate parent, Zone zone, String line) {
+        buffer.writeln(line);
+      }));
+
+      expect(buffer.toString().trim(), 'daemon.logMessage test');
+    });
+
     _testUsingContext('daemon.shutdown', () async {
       StreamController<Map<String, dynamic>> commands = new StreamController<Map<String, dynamic>>();
       StreamController<Map<String, dynamic>> responses = new StreamController<Map<String, dynamic>>();