when setting up the log reader for a device during flutter run, discard any RPCError thrown due to the device being disconnected (#155049)

Fixes https://github.com/flutter/flutter/issues/154903

This PR contains some refactoring. To make the actual change easier to figure out, I've tried to separate parts of the change into multiple commits for easier reviewing 🙂.

**I plan on cherry-picking this change to stable.**

packages/flutter_tools/lib/src/resident_runner.dart

@@ -416,8 +416,19 @@ class FlutterDevice {
     _loggingSubscription = null;
   }
 
-  Future<void> initLogReader() async {
+  /// Attempts to set up reading logs from the Flutter app on the device.
-    final vm_service.VM vm = await vmService!.service.getVM();
+  ///
+  /// This can fail if the device if no longer connected.
+  Future<void> tryInitLogReader() async {
+    final vm_service.VM? vm = await vmService!.getVmGuarded();
+    if (vm == null) {
+      globals.printError(
+        'Unable to initiate log reader for device'
+        '${device?.name}, because the Flutter VM service connection '
+        'is closed.',
+      );
+      return;
+    }
     final DeviceLogReader logReader = await device!.getLogReader(app: package);
     logReader.appPid = vm.pid;
   }

packages/flutter_tools/lib/src/run_cold.dart

@@ -104,7 +104,7 @@ class ColdRunner extends ResidentRunner {
       if (device!.vmService == null) {
         continue;
       }
-      await device.initLogReader();
+      await device.tryInitLogReader();
       globals.printTrace('Connected to ${device.device!.name}');
     }
 
@@ -154,7 +154,7 @@ class ColdRunner extends ResidentRunner {
     }
 
     for (final FlutterDevice? device in flutterDevices) {
-      await device!.initLogReader();
+      await device!.tryInitLogReader();
     }
     for (final FlutterDevice? device in flutterDevices) {
       final List<FlutterView> views = await device!.vmService!.getFlutterViews();

packages/flutter_tools/lib/src/run_hot.dart

@@ -261,7 +261,7 @@ class HotRunner extends ResidentRunner {
     }
 
     for (final FlutterDevice? device in flutterDevices) {
-      await device!.initLogReader();
+      await device!.tryInitLogReader();
       device
         .developmentShaderCompiler
         .configureCompiler(device.targetPlatform);

packages/flutter_tools/lib/src/vmservice.dart

@@ -491,6 +491,22 @@ class FlutterVmService {
   final Uri? wsAddress;
   final Uri? httpAddress;
 
+  /// Calls [service.getVM]. However, in the case that an [vm_service.RPCError]
+  /// is thrown due to the service being disconnected, the error is discarded
+  /// and null is returned.
+  Future<vm_service.VM?> getVmGuarded() async {
+    try {
+      return await service.getVM();
+    } on vm_service.RPCError catch (err) {
+      if (err.code == RPCErrorCodes.kServiceDisappeared ||
+          err.message.contains('Service connection disposed')) {
+        globals.printTrace('VmService.getVm call failed: $err');
+        return null;
+      }
+      rethrow;
+    }
+  }
+
   Future<vm_service.Response?> callMethodWrapper(
     String method, {
     String? isolateId,

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

@@ -165,7 +165,7 @@ class FakeFlutterDevice extends Fake implements FlutterDevice {
   }
 
   @override
-  Future<void> initLogReader() async { }
+  Future<void> tryInitLogReader() async { }
 }
 
 class FakeDevice extends Fake implements Device {

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

@@ -228,7 +228,7 @@ class FakeFlutterDevice extends Fake implements FlutterDevice {
   Future<void> stopEchoingDeviceLog() async { }
 
   @override
-  Future<void> initLogReader() async { }
+  Future<void> tryInitLogReader() async { }
 
   @override
   Future<Uri> setupDevFS(String fsName, Directory rootDirectory) async {

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

@@ -1934,6 +1934,43 @@ flutter:
     ProcessManager: () => FakeProcessManager.any(),
   });
 
+  testUsingContext('FlutterDevice does not throw when unable to initiate log reader due to VM service disconnection', () async {
+    fakeVmServiceHost = FakeVmServiceHost(
+      requests: <VmServiceExpectation>[
+        const FakeVmServiceRequest(
+          method: 'getVM',
+          error: FakeRPCError(
+            code: RPCErrorCodes.kServerError,
+            error: 'Service connection disposed',
+          ),
+        ),
+      ],
+    );
+    final TestFlutterDevice flutterDevice = TestFlutterDevice(device);
+    flutterDevice.vmService = fakeVmServiceHost!.vmService;
+    await flutterDevice.tryInitLogReader();
+    final BufferLogger logger = globals.logger as BufferLogger;
+    expect(
+      logger.traceText,
+      contains(
+        'VmService.getVm call failed: getVM: (-32000) '
+        'Service connection disposed\n',
+      ),
+    );
+    expect(
+      logger.errorText,
+      contains(
+        'Unable to initiate log reader for deviceFakeDevice, because '
+        'the Flutter VM service connection is closed.\n',
+      ),
+    );
+  }, overrides: <Type, Generator>{
+    Logger: () => BufferLogger.test(),
+    Artifacts: () => Artifacts.test(),
+    FileSystem: () => MemoryFileSystem.test(),
+    ProcessManager: () => FakeProcessManager.any(),
+  });
+
   testUsingContext('Uses existing DDS URI from exception field', () => testbed.run(() async {
     fakeVmServiceHost = FakeVmServiceHost(requests: <VmServiceExpectation>[]);
     final FakeDevice device = FakeDevice()

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

@@ -1755,7 +1755,7 @@ class FakeFlutterDevice extends Fake implements FlutterDevice {
   Future<void> stopEchoingDeviceLog() async {}
 
   @override
-  Future<void> initLogReader() async {}
+  Future<void> tryInitLogReader() async {}
 
   @override
   Future<Uri?> setupDevFS(String fsName, Directory rootDirectory) async {