[flutter_tools] trim trailing newline from vm service logging events (#63976)

packages/flutter_tools/lib/src/build_runner/resident_web_runner.dart

@@ -22,7 +22,6 @@ import '../base/terminal.dart';
 import '../base/utils.dart';
 import '../build_info.dart';
 import '../cache.dart';
-import '../convert.dart';
 import '../dart/language_version.dart';
 import '../dart/pub.dart';
 import '../devfs.dart';
@@ -731,14 +730,13 @@ class _ResidentWebRunner extends ResidentWebRunner {
       _connectionResult = await webDevFS.connect(useDebugExtension);
       unawaited(_connectionResult.debugConnection.onDone.whenComplete(_cleanupAndExit));
 
-      _stdOutSub = _vmService.onStdoutEvent.listen((vmservice.Event log) {
-        final String message = utf8.decode(base64.decode(log.bytes));
-        globals.printStatus(message, newline: false);
-      });
-      _stdErrSub = _vmService.onStderrEvent.listen((vmservice.Event log) {
-        final String message = utf8.decode(base64.decode(log.bytes));
-        globals.printStatus(message, newline: false);
-      });
+      void onLogEvent(vmservice.Event event)  {
+        final String message = processVmServiceMessage(event);
+        globals.printStatus(message);
+      }
+
+      _stdOutSub = _vmService.onStdoutEvent.listen(onLogEvent);
+      _stdErrSub = _vmService.onStderrEvent.listen(onLogEvent);
       _extensionEventSub =
           _vmService.onExtensionEvent.listen(printStructuredErrorLog);
       try {

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

@@ -24,6 +24,7 @@ import '../macos/xcode.dart';
 import '../mdns_discovery.dart';
 import '../project.dart';
 import '../protocol_discovery.dart';
+import '../vmservice.dart';
 import 'fallback_discovery.dart';
 import 'ios_deploy.dart';
 import 'ios_workflow.dart';
@@ -678,7 +679,7 @@ class IOSDeviceLogReader extends DeviceLogReader {
     }
 
     void logMessage(vm_service.Event event) {
-      final String message = utf8.decode(base64.decode(event.bytes));
+      final String message = processVmServiceMessage(event);
       if (message.isNotEmpty) {
         _linesController.add(message);
       }

packages/flutter_tools/lib/src/vmservice.dart

@@ -900,3 +900,13 @@ enum Brightness {
   /// For example, the color might be bright white, requiring black text.
   light,
 }
+
+/// Process a VM service log event into a string message.
+String processVmServiceMessage(vm_service.Event event) {
+  final String message = utf8.decode(base64.decode(event.bytes));
+  // Remove extra trailing newlines appended by the vm service.
+  if (message.endsWith('\n')) {
+    return message.substring(0, message.length - 1);
+  }
+  return message;
+}

packages/flutter_tools/test/general.shard/vmservice_test.dart

@@ -402,6 +402,16 @@ void main() {
     expect(vmService.httpAddress, null);
     expect(vmService.wsAddress, null);
   });
+
+  testWithoutContext('Can process log events from the vm service', () {
+    final vm_service.Event event = vm_service.Event(
+      bytes: base64.encode(utf8.encode('Hello There\n')),
+      timestamp: 0,
+      kind: vm_service.EventKind.kLogging,
+    );
+
+    expect(processVmServiceMessage(event), 'Hello There');
+  });
 }
 
 class MockDevice extends Mock implements Device {}