log for specific adb devices

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

@@ -307,7 +307,7 @@ class AndroidDevice extends Device {
   TargetPlatform get platform => TargetPlatform.android;
 
   void clearLogs() {
-    runSync(adbCommandForDevice(<String>['logcat', '-c']));
+    runSync(adbCommandForDevice(<String>['-s', id, 'logcat', '-c']));
   }
 
   DeviceLogReader createLogReader() => new _AdbLogReader(this);
@@ -325,7 +325,9 @@ class AndroidDevice extends Device {
   // Return the most recent timestamp in the Android log. The format can be
   // passed to logcat's -T option.
   String lastLogcatTimestamp() {
-    String output = runCheckedSync(adbCommandForDevice(<String>['logcat', '-v', 'time', '-t', '1']));
+    String output = runCheckedSync(adbCommandForDevice(<String>[
+      '-s', id, 'logcat', '-v', 'time', '-t', '1'
+    ]));
 
     RegExp timeRegExp = new RegExp(r'^\d{2}-\d{2} \d{2}:\d{2}:\d{2}\.\d{3}', multiLine: true);
     Match timeMatch = timeRegExp.firstMatch(output);
@@ -350,7 +352,9 @@ class AndroidDevice extends Device {
     String tracePath = null;
     bool isComplete = false;
     while (!isComplete) {
-      String logs = runCheckedSync(adbCommandForDevice(<String>['logcat', '-d', '-T', beforeStop]));
+      String logs = runCheckedSync(adbCommandForDevice(<String>[
+        '-s', id, 'logcat', '-d', '-T', beforeStop
+      ]));
       Match fileMatch = traceRegExp.firstMatch(logs);
       if (fileMatch != null && fileMatch[1] != null) {
         tracePath = fileMatch[1];
@@ -484,16 +488,15 @@ List<AndroidDevice> getAdbDevices() {
   return devices;
 }
 
-/// A log reader that logs from `adb logcat`. This will have the same output as
-/// another copy of [_AdbLogReader], and the two instances will be equivalent.
+/// A log reader that logs from `adb logcat`.
 class _AdbLogReader extends DeviceLogReader {
   _AdbLogReader(this.device);
 
   final AndroidDevice device;
 
-  String get name => 'Android';
+  String get name => device.name;
 
-  Future<int> logs({bool clear: false}) async {
+  Future<int> logs({ bool clear: false, bool showPrefix: false }) async {
     if (!device.isConnected())
       return 2;
 
@@ -501,6 +504,8 @@ class _AdbLogReader extends DeviceLogReader {
       device.clearLogs();
 
     return await runCommandAndStreamOutput(device.adbCommandForDevice(<String>[
+      '-s',
+      device.id,
       'logcat',
       '-v',
       'tag', // Only log the tag and the message
@@ -509,15 +514,16 @@ class _AdbLogReader extends DeviceLogReader {
       'ActivityManager:W',
       'System.err:W',
       '*:F',
-    ]), prefix: '[Android] ');
+    ]), prefix: showPrefix ? '[$name] ' : '');
   }
 
-  // Intentionally constant; overridden because we've overridden the `operator ==` method below.
   int get hashCode => name.hashCode;
 
   bool operator ==(dynamic other) {
     if (identical(this, other))
       return true;
-    return other is _AdbLogReader;
+    if (other is! _AdbLogReader)
+      return false;
+    return other.device.id == device.id;
   }
 }

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

@@ -35,15 +35,15 @@ class LogsCommand extends FlutterCommand {
 
     bool clear = argResults['clear'];
 
-    Set<DeviceLogReader> readers = new Set<DeviceLogReader>();
+    List<DeviceLogReader> readers = new List<DeviceLogReader>();
     for (Device device in devices) {
       readers.add(device.createLogReader());
     }
 
-    printStatus('Showing logs for ${readers.join(', ')}:');
+    printStatus('Showing ${readers.join(', ')} logs:');
 
     List<int> results = await Future.wait(readers.map((DeviceLogReader reader) async {
-      int result = await reader.logs(clear: clear);
+      int result = await reader.logs(clear: clear, showPrefix: devices.length > 1);
       if (result != 0)
         printError('Error listening to $reader logs.');
       return result;

packages/flutter_tools/lib/src/device.dart

@@ -189,7 +189,7 @@ abstract class Device {
 abstract class DeviceLogReader {
   String get name;
 
-  Future<int> logs({ bool clear: false });
+  Future<int> logs({ bool clear: false, bool showPrefix: false });
 
   int get hashCode;
   bool operator ==(dynamic other);

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

@@ -232,13 +232,13 @@ class _IOSDeviceLogReader extends DeviceLogReader {
   String get name => device.name;
 
   // TODO(devoncarew): Support [clear].
-  Future<int> logs({ bool clear: false }) async {
+  Future<int> logs({ bool clear: false, bool showPrefix: false }) async {
     if (!device.isConnected())
       return 2;
 
     return await runCommandAndStreamOutput(
       <String>[device.loggerPath],
-      prefix: '[$name] ',
+      prefix: showPrefix ? '[$name] ' : '',
       filter: new RegExp(r'Runner')
     );
   }

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

@@ -410,7 +410,7 @@ class _IOSSimulatorLogReader extends DeviceLogReader {
 
   String get name => device.name;
 
-  Future<int> logs({ bool clear: false }) async {
+  Future<int> logs({ bool clear: false, bool showPrefix: false }) async {
     if (!device.isConnected())
       return 2;
 
@@ -432,7 +432,7 @@ class _IOSSimulatorLogReader extends DeviceLogReader {
 
     Future<int> result = runCommandAndStreamOutput(
       <String>['tail', '-n', '+0', '-F', device.logFilePath],
-      prefix: '[$name] ',
+      prefix: showPrefix ? '[$name] ' : '',
       mapFunction: (String string) {
         Match match = mapRegex.matchAsPrefix(string);
         if (match != null) {
@@ -465,7 +465,7 @@ class _IOSSimulatorLogReader extends DeviceLogReader {
     // ReportCrash[37965]: Saved crash report for FlutterRunner[37941]...
     runCommandAndStreamOutput(
       <String>['tail', '-F', '/private/var/log/system.log'],
-      prefix: '[$name] ',
+      prefix: showPrefix ? '[$name] ' : '',
       filter: new RegExp(r' FlutterRunner\[\d+\] '),
       mapFunction: (String string) {
         Match match = mapRegex.matchAsPrefix(string);