Create troubleshooting helpers. (#89)

.vscode/launch.json

@@ -11,6 +11,12 @@
  "type": "dart",
  "program": "main.dart",
  },
+ {
+ "name": "pub_get",
+ "request": "launch",
+ "type": "node-terminal",
+ "command": "sh tool/pub_get.sh",
+ },
  {
  "name": "minimal_flutter",
  "cwd": "examples/minimal_flutter",

doc/TROUBLESHOOT.md

@@ -9,11 +9,11 @@ This page describes how to troubleshoot memory leaks. See other information on m
 If leak tracker detected a leak in your application or test, first check if the leak matches a [known simple case](#known-simple-cases), and, if no,
 switch to [more complicated troubleshooting](#more-complicated-cases).
 
-## Known simple cases
+## Check known simple cases
 
 ### 1. The test holds a disposed object
 
-TODO: add steps.
+TODO: add example and steps.
 
 ## Collect additional information
 
@@ -44,7 +44,15 @@ For collecting debugging information in tests, temporarily pass an instance of `
 ```
  testWidgets('My test', (WidgetTester tester) async {
  ...
- }, leakTrackingConfig: LeakTrackingTestConfig.debug());
+ }, leakTrackingTestConfig: LeakTrackingTestConfig.debug());
+```
+
+Or, you can temporarily set global flag, to make all tests collecting debug information:
+
+```
+setUpAll(() {
+ collectDebugInformationForLeaks = true;
+});
 ```
 
 **Applications**
@@ -56,6 +64,27 @@ For collecting debugging information in your running application, the options ar
 
 TODO: link DevTools documentation with explanation
 
+## Verify object references
+
+If you expect an object to be not referenced at some point,
+but not sure, you can validate it by temporaryly adding assertion.
+
+```
+final ref = WeakReference(myObject);
+myObject = null;
+await forceGC();
+if (ref.target == null) {
+ throw StateError('Validated that myObject is not held from garbage collection.');
+} else {
+ print(await formattedRetainingPath(ref));
+ throw StateError('myObject is reachable from root. See console output for the retaining path.');
+}
+```
+
+IMPORTANT: this code will not work in release mode, so
+you need to run it with flag `--debug` or `--profile`, or,
+if it is test, by clicking `Debug` near your test name in IDE.
+
 ## Known complicated cases
 
 ### 1. More than one closure context

pkgs/leak_tracker/CHANGELOG.md

@@ -1,3 +1,8 @@
+# 7.0.6
+
+* Add helpers for troubleshooting.
+* Handle generic arguments for retaining path detection.
+
 # 7.0.5
 
 * Convert to multi-package.

pkgs/leak_tracker/lib/src/leak_tracking/_formatting.dart

@@ -11,7 +11,7 @@ import '../shared/_util.dart';
 String contextToString(Object? object) {
  return switch (object) {
  StackTrace() => _formatStackTrace(object),
- RetainingPath() => _retainingPathToString(object),
+ RetainingPath() => retainingPathToString(object),
  _ => object.toString(),
  };
 }
@@ -42,7 +42,7 @@ String removeLeakTrackingLines(String stackTrace) {
  return lines.join('\n');
 }
 
-String _retainingPathToString(RetainingPath retainingPath) {
+String retainingPathToString(RetainingPath retainingPath) {
  final StringBuffer buffer = StringBuffer();
  buffer.writeln(
  'References that retain the object from garbage collection.',

pkgs/leak_tracker/lib/src/leak_tracking/_gc_counter.dart

@@ -10,7 +10,7 @@ class GcCounter {
  int get gcCount => reachabilityBarrier;
 }
 
-/// Delta of GC time, enough for a non reachable object to be GCed.
+/// Delta of GC cycles, enough for a non reachable object to be GCed.
 ///
 /// Theoretically, 2 should be enough, however it gives false positives
 /// if there is no activity in the application for ~5 minutes.

pkgs/leak_tracker/lib/src/leak_tracking/leak_tracker_model.dart

@@ -4,6 +4,9 @@
 
 import '../shared/shared_model.dart';
 
+/// If true, the leak tracker will collect debug information for leaks.
+bool collectDebugInformationForLeaks = false;
+
 /// Handler to collect leak summary.
 typedef LeakSummaryCallback = void Function(LeakSummary);
 

pkgs/leak_tracker/lib/src/leak_tracking/orchestration.dart

@@ -5,12 +5,12 @@
 import 'dart:async';
 import 'dart:developer';
 
-import 'package:clock/clock.dart';
-
 import '../shared/shared_model.dart';
+import '_formatting.dart';
 import '_gc_counter.dart';
 import 'leak_tracker.dart';
 import 'leak_tracker_model.dart';
+import 'retaining_path/_retaining_path.dart';
 
 /// Asynchronous callback.
 ///
@@ -100,8 +100,8 @@ Future<Leaks> withLeakTracking(
  await checkNonGCed();
  }
 
- await _forceGC(
- gcCycles: gcCountBuffer,
+ await forceGC(
+ fullGcCycles: gcCountBuffer,
  timeout: timeoutForFinalGarbageCollection,
  );
 
@@ -124,22 +124,57 @@ Future<Leaks> withLeakTracking(
 }
 
 /// Forces garbage collection by aggressive memory allocation.
-Future<void> _forceGC({required int gcCycles, Duration? timeout}) async {
- final start = clock.now();
- final barrier = reachabilityBarrier;
+///
+/// Verifies that garbage collection happened using [reachabilityBarrier].
+/// Does not work in web and in release mode.
+///
+/// Use [timeout] to limit waiting time.
+/// Use [fullGcCycles] to force multiple garbage collections.
+///
+/// The method is helpful for testing in combination with [WeakReference] to ensure
+/// an object is not held by another object from garbage collection.
+///
+/// For code example see
+/// https://github.com/dart-lang/leak_tracker/blob/main/doc/TROUBLESHOOT.md
+Future<void> forceGC({
+ Duration? timeout,
+ int fullGcCycles = 1,
+}) async {
+ final Stopwatch? stopwatch = timeout == null ? null : (Stopwatch()..start());
+ final int barrier = reachabilityBarrier;
 
- final storage = <List<DateTime>>[];
+ final List<List<DateTime>> storage = <List<DateTime>>[];
 
  void allocateMemory() {
- storage.add(Iterable.generate(10000, (_) => DateTime.now()).toList());
- if (storage.length > 100) storage.removeAt(0);
+ storage.add(
+ Iterable<DateTime>.generate(10000, (_) => DateTime.now()).toList(),
+ );
+ if (storage.length > 100) {
+ storage.removeAt(0);
+ }
  }
 
- while (reachabilityBarrier < barrier + gcCycles) {
- if (timeout != null && clock.now().difference(start) > timeout) {
+ while (reachabilityBarrier < barrier + fullGcCycles) {
+ if ((stopwatch?.elapsed ?? Duration.zero) > (timeout ?? Duration.zero)) {
  throw TimeoutException('forceGC timed out', timeout);
  }
- await Future.delayed(const Duration());
+ await Future<void>.delayed(Duration.zero);
  allocateMemory();
  }
 }
+
+/// Returns nicely formatted retaining path for the [ref.target].
+///
+/// If the object is garbage collected or not retained, returns null.
+///
+/// Does not work in web and in release mode.
+Future<String?> formattedRetainingPath(WeakReference ref) async {
+ if (ref.target == null) return null;
+ final path = await obtainRetainingPath(
+ ref.target.runtimeType,
+ identityHashCode(ref.target),
+ );
+
+ if (path == null) return null;
+ return retainingPathToString(path);
+}

pkgs/leak_tracker/lib/src/leak_tracking/retaining_path/_connection.dart

@@ -14,7 +14,7 @@ final _log = Logger('_connection.dart');
 class Connection {
  Connection(this.service, this.isolates);
 
- final List<String> isolates;
+ final List<IsolateRef> isolates;
  final VmService service;
 }
 
@@ -45,7 +45,7 @@ Future<Connection> connect() async {
  throw error ?? Exception('Error connecting to service protocol');
  });
  await service.getVersion(); // Warming up and validating the connection.
- final isolates = await _getIdForTwoIsolates(service);
+ final isolates = await _getTwoIsolates(service);
 
  final result = Connection(service, isolates);
  completer.complete(result);
@@ -57,10 +57,10 @@ Future<Connection> connect() async {
 /// Depending on environment (command line / IDE, Flutter / Dart), isolates may have different names,
 /// and there can be one or two. Sometimes the second one appears with latency.
 /// And sometimes there are two isolates with name 'main'.
-Future<List<String>> _getIdForTwoIsolates(VmService service) async {
+Future<List<IsolateRef>> _getTwoIsolates(VmService service) async {
  _log.info('Started loading isolates...');
 
- final result = <String>[];
+ final result = <IsolateRef>[];
 
  const isolatesToGet = 2;
  const watingTime = Duration(seconds: 2);
@@ -69,7 +69,7 @@ Future<List<String>> _getIdForTwoIsolates(VmService service) async {
  result.clear();
  await _forEachIsolate(
  service,
- (IsolateRef r) async => result.add(r.id!),
+ (IsolateRef r) async => result.add(r),
  );
  if (result.length < isolatesToGet) {
  await Future.delayed(const Duration(milliseconds: 100));

pkgs/leak_tracker/lib/src/leak_tracking/retaining_path/_retaining_path.dart

@@ -17,7 +17,7 @@ Future<RetainingPath?> obtainRetainingPath(Type type, int code) async {
  if (theObject == null) return null;
 
  final result = await connection.service.getRetainingPath(
- theObject.isolateId,
+ theObject.isolateRef.id!,
  theObject.itemId,
  100000,
  );
@@ -30,20 +30,30 @@ class _ObjectFingerprint {
 
  final Type type;
  final int code;
+
+ String get typeNameWithoutArgs {
+ final name = type.toString();
+ final index = name.indexOf('<');
+ if (index == -1) return name;
+ return name.substring(0, index);
+ }
 }
 
 Future<_ItemInIsolate?> _objectInIsolate(
  Connection connection,
  _ObjectFingerprint object,
 ) async {
- final classes = await _findClasses(connection, object.type.toString());
+ final classes = await _findClasses(connection, object.typeNameWithoutArgs);
 
  for (final theClass in classes) {
- const pathLengthLimit = 10000000;
+ // TODO(polina-c): remove when issue is fixed
+ // https://github.com/dart-lang/sdk/issues/52893
+ if (theClass.name == 'TypeParameters') continue;
+
  final instances = (await connection.service.getInstances(
- theClass.isolateId,
+ theClass.isolateRef.id!,
  theClass.itemId,
- pathLengthLimit,
+ 1000000000,
  ))
  .instances ??
  <ObjRef>[];
@@ -53,7 +63,10 @@ Future<_ItemInIsolate?> _objectInIsolate(
  objRef is InstanceRef && objRef.identityHashCode == object.code,
  );
  if (result != null) {
- return _ItemInIsolate(isolateId: theClass.isolateId, itemId: result.id!);
+ return _ItemInIsolate(
+ isolateRef: theClass.isolateRef,
+ itemId: result.id!,
+ );
  }
  }
 
@@ -64,13 +77,16 @@ Future<_ItemInIsolate?> _objectInIsolate(
 ///
 /// It can be class or object.
 class _ItemInIsolate {
- _ItemInIsolate({required this.isolateId, required this.itemId});
+ _ItemInIsolate({required this.isolateRef, required this.itemId, this.name});
 
- /// Id of the isolate.
- final String isolateId;
+ /// The isolate.
+ final IsolateRef isolateRef;
 
  /// Id of the item in the isolate.
  final String itemId;
+
+ /// Name of the item, for debugging purposes.
+ final String? name;
 }
 
 Future<List<_ItemInIsolate>> _findClasses(
@@ -79,27 +95,31 @@ Future<List<_ItemInIsolate>> _findClasses(
 ) async {
  final result = <_ItemInIsolate>[];
 
- for (final isolateId in connection.isolates) {
- var classes = await connection.service.getClassList(isolateId);
+ for (final isolate in connection.isolates) {
+ var classes = await connection.service.getClassList(isolate.id!);
 
  const watingTime = Duration(seconds: 2);
  final stopwatch = Stopwatch()..start();
 
  // In the beginning list of classes may be empty.
  while (classes.classes?.isEmpty ?? true && stopwatch.elapsed < watingTime) {
  await Future.delayed(const Duration(milliseconds: 100));
- classes = await connection.service.getClassList(isolateId);
+ classes = await connection.service.getClassList(isolate.id!);
  }
  if (classes.classes?.isEmpty ?? true) {
  throw StateError('Could not get list of classes.');
  }
 
  final filtered =
  classes.classes?.where((ref) => runtimeClassName == ref.name) ?? [];
+
  result.addAll(
  filtered.map(
- (classRef) =>
- _ItemInIsolate(itemId: classRef.id!, isolateId: isolateId),
+ (classRef) => _ItemInIsolate(
+ itemId: classRef.id!,
+ isolateRef: isolate,
+ name: classRef.name,
+ ),
  ),
  );
  }

pkgs/leak_tracker/pubspec.yaml

@@ -1,5 +1,5 @@
 name: leak_tracker
-version: 7.0.4
+version: 7.0.6
 description: A framework for memory leak tracking for Dart and Flutter applications.
 repository: https://github.com/dart-lang/leak_tracker/tree/main/pkgs/leak_tracker
 
@@ -13,7 +13,7 @@ dependencies:
  logging: ^1.1.1
  meta: ^1.8.0
  path: ^1.8.3
- vm_service: '>=11.6.0 <13.0.0'
+ vm_service: '>=11.7.2 <13.0.0'
  web_socket_channel: ^2.1.0
 
 dev_dependencies:

pkgs/leak_tracker/test/debug/README.md

@@ -4,3 +4,5 @@ To run them locally:
 ```
 dart test --debug test/dart_debug
 ```
+
+Or click 'Debug' near the test name in your IDE.