Reland "Make sure all isolates start during flutter driver tests" (#64432)

packages/flutter_driver/lib/src/driver/vmservice_driver.dart

@@ -37,8 +37,21 @@ class VMServiceFlutterDriver extends FlutterDriver {
         bool logCommunicationToFile = true,
       }) : _printCommunication = printCommunication,
         _logCommunicationToFile = logCommunicationToFile,
+        _isolateSubscription = _initIsolateHandler(_serviceClient),
         _driverId = _nextDriverId++;
 
+  // The Dart VM may be running with --pause-isolates-on-start.
+  // Set a listener to unpause new isolates as they are ready to run,
+  // otherwise they'll hang indefinitely.
+  static StreamSubscription<VMIsolateRef> _initIsolateHandler(
+      VMServiceClient serviceClient) {
+    return serviceClient.onIsolateRunnable.listen(
+      (VMIsolateRef isolateRef) async {
+        await _resumeLeniently(isolateRef);
+      }
+    );
+  }
+
   /// Connects to a Flutter application.
   ///
   /// See [FlutterDriver.connect] for more documentation.
@@ -100,9 +113,12 @@ class VMServiceFlutterDriver extends FlutterDriver {
         null ? vm.isolates.first :
     vm.isolates.firstWhere(
             (VMIsolateRef isolate) => isolate.number == isolateNumber);
-    _log('Isolate found with number: ${isolateRef.number}');
 
+    _log('Isolate found with number: ${isolateRef.number}');
+    // There is a race condition here, the isolate may have been destroyed before
+    // we get around to loading it.
     VMIsolate isolate = await isolateRef.loadRunnable();
+    _log('Loaded isolate: ${isolate.number}');
 
     // TODO(yjbanov): vm_service_client does not support "None" pause event yet.
     // It is currently reported as null, but we cannot rely on it because
@@ -117,9 +133,22 @@ class VMServiceFlutterDriver extends FlutterDriver {
         isolate.pauseEvent is! VMPauseExceptionEvent &&
         isolate.pauseEvent is! VMPauseInterruptedEvent &&
         isolate.pauseEvent is! VMResumeEvent) {
+      _log('Reloading first isolate.');
       isolate = await isolateRef.loadRunnable();
+      _log('Reloaded first isolate.');
     }
 
+    // Tells the Dart VM Service to notify us about "Isolate" events.
+    //
+    // This is a workaround for an issue in package:vm_service_client, which
+    // subscribes to the "Isolate" stream lazily upon subscription, which
+    // results in lost events.
+    //
+    // Details: https://github.com/dart-lang/vm_service_client/issues/17
+    await connection.peer.sendRequest('streamListen', <String, String>{
+      'streamId': 'Isolate',
+    });
+
     final VMServiceFlutterDriver driver = VMServiceFlutterDriver.connectedTo(
       client, connection.peer, isolate,
       printCommunication: printCommunication,
@@ -128,27 +157,6 @@ class VMServiceFlutterDriver extends FlutterDriver {
 
     driver._dartVmReconnectUrl = dartVmServiceUrl;
 
-    // Attempts to resume the isolate, but does not crash if it fails because
-    // the isolate is already resumed. There could be a race with other tools,
-    // such as a debugger, any of which could have resumed the isolate.
-    Future<dynamic> resumeLeniently() {
-      _log('Attempting to resume isolate');
-      return isolate.resume().catchError((dynamic e) {
-        const int vmMustBePausedCode = 101;
-        if (e is rpc.RpcException && e.code == vmMustBePausedCode) {
-          // No biggie; something else must have resumed the isolate
-          _log(
-              'Attempted to resume an already resumed isolate. This may happen '
-                  'when we lose a race with another tool (usually a debugger) that '
-                  'is connected to the same isolate.'
-          );
-        } else {
-          // Failed to resume due to another reason. Fail hard.
-          throw e;
-        }
-      });
-    }
-
     /// Waits for a signal from the VM service that the extension is registered.
     ///
     /// Looks at the list of loaded extensions for the current [isolateRef], as
@@ -183,42 +191,8 @@ class VMServiceFlutterDriver extends FlutterDriver {
       ]);
     }
 
-    /// Tells the Dart VM Service to notify us about "Isolate" events.
-    ///
-    /// This is a workaround for an issue in package:vm_service_client, which
-    /// subscribes to the "Isolate" stream lazily upon subscription, which
-    /// results in lost events.
-    ///
-    /// Details: https://github.com/dart-lang/vm_service_client/issues/17
-    Future<void> enableIsolateStreams() async {
-      await connection.peer.sendRequest('streamListen', <String, String>{
-        'streamId': 'Isolate',
-      });
-    }
-
     // Attempt to resume isolate if it was paused
-    if (isolate.pauseEvent is VMPauseStartEvent) {
-      _log('Isolate is paused at start.');
-
-      await resumeLeniently();
-    } else if (isolate.pauseEvent is VMPauseExitEvent ||
-        isolate.pauseEvent is VMPauseBreakpointEvent ||
-        isolate.pauseEvent is VMPauseExceptionEvent ||
-        isolate.pauseEvent is VMPauseInterruptedEvent) {
-      // If the isolate is paused for any other reason, assume the extension is
-      // already there.
-      _log('Isolate is paused mid-flight.');
-      await resumeLeniently();
-    } else if (isolate.pauseEvent is VMResumeEvent) {
-      _log('Isolate is not paused. Assuming application is ready.');
-    } else {
-      _log(
-          'Unknown pause event type ${isolate.pauseEvent.runtimeType}. '
-              'Assuming application is ready.'
-      );
-    }
-
-    await enableIsolateStreams();
+    await _resumeLeniently(isolate);
 
     // We will never receive the extension event if the user does not register
     // it. If that happens, show a message but continue waiting.
@@ -241,6 +215,58 @@ class VMServiceFlutterDriver extends FlutterDriver {
     return driver;
   }
 
+  static bool _alreadyRunning(VMIsolate isolate) {
+    // Expected pause events.
+    if (isolate.pauseEvent is VMPauseStartEvent ||
+        isolate.pauseEvent is VMPauseExitEvent ||
+        isolate.pauseEvent is VMPauseBreakpointEvent ||
+        isolate.pauseEvent is VMPauseExceptionEvent ||
+        isolate.pauseEvent is VMPauseInterruptedEvent ||
+        isolate.pauseEvent is VMNoneEvent) {
+      return false;
+    }
+    // Already running.
+    if (isolate.pauseEvent is VMResumeEvent) {
+      _log('Isolate is not paused. Assuming application is ready.');
+      return true;
+    }
+    _log('Unknown pause event type ${isolate.pauseEvent.runtimeType}. '
+        'Assuming application is ready.');
+    return true;
+  }
+
+  /// Attempts to resume the isolate, but does not crash if it fails because
+  /// the isolate is already resumed. There could be a race with other tools,
+  /// such as a debugger, any of which could have resumed the isolate.
+  /// Returns the isolate if it is runnable, null otherwise.
+  static Future<void> _resumeLeniently(VMIsolateRef isolateRef) async {
+    try {
+      _log('New runnable isolate ${isolateRef.number}');
+      final VMIsolate isolate = await isolateRef.load();
+      if (_alreadyRunning(isolate)) {
+        return;
+      }
+      _log('Attempting to resume isolate ${isolate.number}');
+      await isolate.resume();
+      _log('Resumed isolate ${isolate.number}');
+    } on VMSentinelException {
+      // Probably OK, the isolate vanished before we got to it.
+      _log('Failed to load isolate, proceeding.');
+    } on rpc.RpcException catch (e) {
+      const int vmMustBePausedCode = 101;
+      if (e.code == vmMustBePausedCode) {
+        // No biggie; something else must have resumed the isolate
+        _log('Attempted to resume an already resumed isolate. This may happen '
+             'when we lose a race with another tool (usually a debugger) that '
+             'is connected to the same isolate.'
+        );
+      } else {
+        // Failed to resume due to another reason. Fail hard.
+        rethrow;
+      }
+    }
+  }
+
   static int _nextDriverId = 0;
 
   static const String _flutterExtensionMethodName = 'ext.flutter.driver';
@@ -275,6 +301,9 @@ class VMServiceFlutterDriver extends FlutterDriver {
   /// would like to instrument.
   final VMServiceClient _serviceClient;
 
+  /// Subscription to isolate events happening in the app.
+  final StreamSubscription<VMIsolateRef> _isolateSubscription;
+
   /// JSON-RPC client useful for sending raw JSON requests.
   rpc.Peer _peer;
 
@@ -552,6 +581,7 @@ class VMServiceFlutterDriver extends FlutterDriver {
   @override
   Future<void> close() async {
     // Don't leak vm_service_client-specific objects, if any
+    await _isolateSubscription.cancel();
     await _serviceClient.close();
     await _peer.close();
   }

packages/flutter_driver/test/flutter_driver_test.dart

@@ -35,6 +35,7 @@ void main() {
     MockVM mockVM;
     MockIsolate mockIsolate;
     MockPeer mockPeer;
+    MockIsolate otherIsolate;
 
     void expectLogContains(String message) {
       expect(log, anyElement(contains(message)));
@@ -45,10 +46,15 @@ void main() {
       mockClient = MockVMServiceClient();
       mockVM = MockVM();
       mockIsolate = MockIsolate();
+      otherIsolate = MockIsolate();
       mockPeer = MockPeer();
       when(mockClient.getVM()).thenAnswer((_) => Future<MockVM>.value(mockVM));
+      when(mockClient.onIsolateRunnable).thenAnswer((Invocation invocation) {
+        return Stream<VMIsolateRef>.fromIterable(<VMIsolateRef>[otherIsolate]);
+      });
       when(mockVM.isolates).thenReturn(<VMRunnableIsolate>[mockIsolate]);
       when(mockIsolate.loadRunnable()).thenAnswer((_) => Future<MockIsolate>.value(mockIsolate));
+      when(mockIsolate.load()).thenAnswer((_) => Future<MockIsolate>.value(mockIsolate));
       when(mockIsolate.extensionRpcs).thenReturn(<String>[]);
       when(mockIsolate.onExtensionAdded).thenAnswer((Invocation invocation) {
         return Stream<String>.fromIterable(<String>['ext.flutter.driver']);
@@ -60,6 +66,10 @@ void main() {
           VMServiceClientConnection(mockClient, mockPeer)
         );
       };
+      when(otherIsolate.load()).thenAnswer((_) => Future<MockIsolate>.value(otherIsolate));
+      when(otherIsolate.resume()).thenAnswer((Invocation invocation) {
+        return Future<dynamic>.value(null);
+      });
     });
 
     tearDown(() async {
@@ -77,15 +87,20 @@ void main() {
         connectionLog.add('resume');
         return Future<dynamic>.value(null);
       });
+      when(otherIsolate.pauseEvent).thenReturn(MockVMPauseStartEvent());
       when(mockIsolate.onExtensionAdded).thenAnswer((Invocation invocation) {
         connectionLog.add('onExtensionAdded');
         return Stream<String>.fromIterable(<String>['ext.flutter.driver']);
       });
+      when(otherIsolate.resume()).thenAnswer((Invocation invocation) {
+        connectionLog.add('other-resume');
+        return Future<dynamic>.value(null);
+      });
 
       final FlutterDriver driver = await FlutterDriver.connect(dartVmServiceUrl: '');
       expect(driver, isNotNull);
-      expectLogContains('Isolate is paused at start');
-      expect(connectionLog, <String>['resume', 'streamListen', 'onExtensionAdded']);
+      expectLogContains('Attempting to resume isolate');
+      expect(connectionLog, <String>['streamListen', 'resume', 'other-resume', 'onExtensionAdded']);
     });
 
     test('connects to isolate paused mid-flight', () async {
@@ -94,7 +109,7 @@ void main() {
 
       final FlutterDriver driver = await FlutterDriver.connect(dartVmServiceUrl: '');
       expect(driver, isNotNull);
-      expectLogContains('Isolate is paused mid-flight');
+      expectLogContains('Attempting to resume isolate');
     });
 
     // This test simulates a situation when we believe that the isolate is
@@ -160,6 +175,9 @@ void main() {
       mockClient = MockVMServiceClient();
       mockPeer = MockPeer();
       mockIsolate = MockIsolate();
+      when(mockClient.onIsolateRunnable).thenAnswer((Invocation invocation) {
+        return Stream<VMIsolateRef>.fromIterable(<VMIsolateRef>[]);
+      });
       driver = VMServiceFlutterDriver.connectedTo(mockClient, mockPeer, mockIsolate);
     });
 
@@ -790,6 +808,9 @@ void main() {
       mockClient = MockVMServiceClient();
       mockPeer = MockPeer();
       mockIsolate = MockIsolate();
+      when(mockClient.onIsolateRunnable).thenAnswer((Invocation invocation) {
+        return Stream<VMIsolateRef>.fromIterable(<VMIsolateRef>[]);
+      });
       driver = VMServiceFlutterDriver.connectedTo(mockClient, mockPeer, mockIsolate);
     });