[flutter_tools] fix --use-existing-app (#69237)

dev/devicelab/bin/tasks/routing_test.dart

@@ -82,6 +82,9 @@ void main() {
         });
       int result;
       result = await drive.exitCode;
+      await flutter('install', options: <String>[
+        '--uninstall-only',
+      ]);
       if (result != 0)
         throw 'Failed to drive test app (exit code $result).';
       result = await run.exitCode;

dev/devicelab/manifest.yaml

@@ -440,7 +440,6 @@ tasks:
       Verifies that `flutter drive --route` still works. No performance numbers.
     stage: devicelab
     required_agent_capabilities: ["linux/android"]
-    flaky: true
 
   linux_chrome_dev_mode:
     description: >

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

@@ -186,22 +186,35 @@ class DriveCommand extends RunCommandBase {
       ? null
       : _fileSystem.file(stringArg('use-application-binary'));
 
-    await driverService.start(
-      buildInfo,
-      device,
-      debuggingOptions,
-      ipv6,
-      applicationBinary: applicationBinary,
-      route: route,
-      userIdentifier: userIdentifier,
-      mainPath: targetFile,
-      platformArgs: <String, Object>{
-        if (traceStartup)
-          'trace-startup': traceStartup,
-        if (web)
-          '--no-launch-chrome': true,
+    if (stringArg('use-existing-app') == null) {
+      await driverService.start(
+        buildInfo,
+        device,
+        debuggingOptions,
+        ipv6,
+        applicationBinary: applicationBinary,
+        route: route,
+        userIdentifier: userIdentifier,
+        mainPath: targetFile,
+        platformArgs: <String, Object>{
+          if (traceStartup)
+            'trace-startup': traceStartup,
+          if (web)
+            '--no-launch-chrome': true,
+        }
+      );
+    } else {
+      final Uri uri = Uri.tryParse(stringArg('use-existing-app'));
+      if (uri == null) {
+        throwToolExit('Invalid VM Service URI: ${stringArg('use-existing-app')}');
       }
-    );
+      await driverService.reuseApplication(
+        uri,
+        device,
+        debuggingOptions,
+        ipv6,
+      );
+    }
 
     final int testResult = await driverService.startTest(
       testFile,

packages/flutter_tools/lib/src/drive/drive_service.dart

@@ -64,6 +64,14 @@ abstract class DriverService {
     Map<String, Object> platformArgs = const <String, Object>{},
   });
 
+  /// If --use-existing-app is provided, configured the correct VM Service URI.
+  Future<void> reuseApplication(
+    Uri vmServiceUri,
+    Device device,
+    DebuggingOptions debuggingOptions,
+    bool ipv6,
+  );
+
   /// Start the test file with the provided [arguments] and [environment], returning
   /// the test process exit code.
   Future<int> startTest(
@@ -168,10 +176,26 @@ class FlutterDriverService extends DriverService {
     if (result == null || !result.started) {
       throwToolExit('Application failed to start. Will not run test. Quitting.', exitCode: 1);
     }
-    _vmServiceUri = result.observatoryUri.toString();
+    return reuseApplication(
+      result.observatoryUri,
+      device,
+      debuggingOptions,
+      ipv6,
+    );
+  }
+
+  @override
+  Future<void> reuseApplication(
+    Uri vmServiceUri,
+    Device device,
+    DebuggingOptions debuggingOptions,
+    bool ipv6,
+  ) async {
+    _vmServiceUri = vmServiceUri.toString();
+    _device = device;
     try {
       await device.dds.startDartDevelopmentService(
-        result.observatoryUri,
+        vmServiceUri,
         debuggingOptions.ddsPort,
         ipv6,
         debuggingOptions.disableServiceAuthCodes,
@@ -228,20 +252,24 @@ class FlutterDriverService extends DriverService {
       );
       await sharedSkSlWriter(_device, result, outputFile: writeSkslOnExit, logger: _logger);
     }
-    try {
+    // If the application package is available, stop and uninstall.
+    if (_applicationPackage != null) {
       if (!await _device.stopApp(_applicationPackage, userIdentifier: userIdentifier)) {
         _logger.printError('Failed to stop app');
       }
-    } on Exception catch (err) {
-      _logger.printError('Failed to stop app due to unhandled error: $err');
-    }
-
-    try {
       if (!await _device.uninstallApp(_applicationPackage, userIdentifier: userIdentifier)) {
-       _logger.printError('Failed to uninstall app');
+        _logger.printError('Failed to uninstall app');
       }
-    } on Exception catch (err) {
-      _logger.printError('Failed to uninstall app due to unhandled error: $err');
+    } else if (_device.supportsFlutterExit) {
+      // Otherwise use the VM Service URI to stop the app as a best effort approach.
+      final vm_service.VM vm = await _vmService.getVM();
+      final vm_service.IsolateRef isolateRef = vm.isolates
+        .firstWhere((vm_service.IsolateRef element) {
+          return !element.isSystemIsolate;
+        }, orElse: () => null);
+      unawaited(_vmService.flutterExit(isolateId: isolateRef.id));
+    } else {
+      _logger.printTrace('No application package for $_device, leaving app running');
     }
     await _device.dispose();
   }

packages/flutter_tools/lib/src/drive/web_driver_service.dart

@@ -153,6 +153,11 @@ class WebDriverService extends DriverService {
       'ANDROID_CHROME_ON_EMULATOR': (_browserNameToEnum(browserName) == Browser.androidChrome && androidEmulator).toString(),
     };
   }
+
+  @override
+  Future<void> reuseApplication(Uri vmServiceUri, Device device, DebuggingOptions debuggingOptions, bool ipv6) async {
+    throwToolExit('--use-existing-app is not supported with flutter web driver');
+  }
 }
 
 /// A list of supported browsers.

packages/flutter_tools/test/general.shard/drive/drive_service_test.dart

@@ -255,6 +255,47 @@ void main() {
       'data': <String, Object>{'A': 'B'}
     });
   });
+
+  testWithoutContext('Can connect to existing application and stop it during cleanup', () async {
+    final FakeVmServiceHost fakeVmServiceHost = FakeVmServiceHost(requests: <FakeVmServiceRequest>[
+      getVM,
+      getVM,
+      const FakeVmServiceRequest(
+        method: 'ext.flutter.exit',
+        args: <String, Object>{
+          'isolateId': '1',
+        }
+      )
+    ]);
+    final FakeProcessManager processManager = FakeProcessManager.list(<FakeCommand>[]);
+    final DriverService driverService = setUpDriverService(processManager: processManager, vmService: fakeVmServiceHost.vmService);
+    final FakeDevice device = FakeDevice(LaunchResult.failed());
+
+    await driverService.reuseApplication(
+      Uri.parse('http://127.0.0.1:63426/1UasC_ihpXY=/'),
+      device,
+      DebuggingOptions.enabled(BuildInfo.debug),
+      false,
+    );
+    await driverService.stop();
+  });
+
+  testWithoutContext('Does not call flutterExit on device types that do not support it', () async {
+    final FakeVmServiceHost fakeVmServiceHost = FakeVmServiceHost(requests: <FakeVmServiceRequest>[
+      getVM,
+    ]);
+    final FakeProcessManager processManager = FakeProcessManager.list(<FakeCommand>[]);
+    final DriverService driverService = setUpDriverService(processManager: processManager, vmService: fakeVmServiceHost.vmService);
+    final FakeDevice device = FakeDevice(LaunchResult.failed(), supportsFlutterExit: false);
+
+    await driverService.reuseApplication(
+      Uri.parse('http://127.0.0.1:63426/1UasC_ihpXY=/'),
+      device,
+      DebuggingOptions.enabled(BuildInfo.debug),
+      false,
+    );
+    await driverService.stop();
+  });
 }
 
 FlutterDriverService setUpDriverService({
@@ -301,7 +342,7 @@ class FakeApplicationPackageFactory extends Fake implements ApplicationPackageFa
 class FakeApplicationPackage extends Fake implements ApplicationPackage {}
 
 class FakeDevice extends Fake implements Device {
-  FakeDevice(this.result);
+  FakeDevice(this.result, {this.supportsFlutterExit = true});
 
   LaunchResult result;
   bool didStopApp = false;
@@ -312,6 +353,9 @@ class FakeDevice extends Fake implements Device {
   @override
   String get name => 'test';
 
+  @override
+  final bool supportsFlutterExit;
+
   @override
   final DartDevelopmentService dds = FakeDartDevelopmentService();