fix(tracing): Generate new trace on navigation

dart/lib/src/hub.dart

@@ -6,7 +6,6 @@
 import '../sentry.dart';
 import 'client_reports/discard_reason.dart';
 import 'profiling.dart';
-import 'propagation_context.dart';
 import 'sentry_tracer.dart';
 import 'sentry_traces_sampler.dart';
 import 'transport/data_category.dart';
@@ -454,10 +453,7 @@
         SentryLevel.warning,
         "Instance is disabled and this 'startTransaction' call is a no-op.",
       );
-    } else if (!_options.isTracingEnabled()) {
-      final item = _peek();
-      item.scope.propagationContext = PropagationContext();
-    } else {
+    } else if (_options.isTracingEnabled()) {
       final item = _peek();
 
       // if transactionContext has no sampled decision, run the traces sampler
@@ -470,6 +466,7 @@
       }
 
       transactionContext.origin ??= SentryTraceOrigins.manual;
+      transactionContext.traceId = scope.propagationContext.traceId;
 
       SentryProfiler? profiler;
       if (_profilerFactory != null &&
@@ -497,6 +494,11 @@
     return NoOpSentrySpan();
   }
 
+  @internal
+  void generateNewTraceId() {
+    scope.propagationContext.traceId = SentryId.newId();
+  }
+
   /// Gets the current active transaction or span.
   ISentrySpan? getSpan() {
     ISentrySpan? span;

dart/lib/src/hub_adapter.dart

@@ -159,6 +159,9 @@
         customSamplingContext: customSamplingContext,
       );
 
+  @override
+  void generateNewTraceId() => Sentry.currentHub.generateNewTraceId();
+
   @override
   void setSpanContext(
     dynamic throwable,

dart/lib/src/noop_hub.dart

@@ -121,6 +121,9 @@
   }) =>
       NoOpSentrySpan();
 
+  @override
+  void generateNewTraceId() {}
+
   @override
   ISentrySpan? getSpan() => null;
 

dart/lib/src/propagation_context.dart

@@ -5,11 +5,20 @@ import 'sentry_baggage.dart';
 
 @internal
 class PropagationContext {
-  late SentryId traceId = SentryId.newId();
-  late SpanId spanId = SpanId.newId();
+  /// Either represents the incoming `traceId` or the `traceId` generated by the current SDK, if there was no incoming trace.
+  SentryId traceId = SentryId.newId();
+
+  /// A span ID that should be used for the `trace` context of various event type, when performance is disabled or when there is no active span.
+  /// If this value is undefined on the propagation context, the SDK will generate a random span ID for `trace` contexts and trace propagation.
+  final SpanId spanId = SpanId.newId();
+
+  /// The dynamic sampling context.
   SentryBaggage? baggage;
 
+  /// Baggage header to attach to http headers.
   SentryBaggageHeader? toBaggageHeader() =>
       baggage != null ? SentryBaggageHeader.fromBaggage(baggage!) : null;
+
+  /// Sentry trace header to attach to http headers.
   SentryTraceHeader toSentryTrace() => SentryTraceHeader(traceId, spanId);
 }

dart/lib/src/scope.dart

@@ -43,6 +43,17 @@ class Scope {
   /// Returns active transaction or null if there is no active transaction.
   ISentrySpan? span;
 
+  /// The propagation context for connecting errors and spans to traces.
+  /// There should always be a propagation context available at all times.
+  ///
+  /// Default behaviour of trace generation in Flutter:
+  ///
+  /// If `SentryNavigatorObserver` is available:
+  ///  - new trace on navigation for all platforms
+  ///
+  /// if `SentryNavigatorObserver` is not available:
+  ///  - Mobile: traces will be cycled with the background/foreground hooks, similar to how sessions are defined in mobile
+  ///  - Web: traces will stick until the next refresh (this might change in the future)
   @internal
   PropagationContext propagationContext = PropagationContext();
 
@@ -246,6 +257,7 @@ class Scope {
     _extra.clear();
     _eventProcessors.clear();
     _replayId = null;
+    propagationContext = PropagationContext();
 
     _clearBreadcrumbsSync();
     _setUserSync(null);

dart/test/sentry_client_test.dart

@@ -6,6 +6,7 @@ import 'package:collection/collection.dart';
 import 'package:sentry/sentry.dart';
 import 'package:sentry/src/client_reports/discard_reason.dart';
 import 'package:sentry/src/client_reports/noop_client_report_recorder.dart';
+import 'package:sentry/src/event_processor/exception/exception_group_event_processor.dart';
 import 'package:sentry/src/platform/mock_platform.dart';
 import 'package:sentry/src/sentry_item_type.dart';
 import 'package:sentry/src/sentry_stack_trace_factory.dart';
@@ -15,9 +16,8 @@ import 'package:sentry/src/transport/data_category.dart';
 import 'package:sentry/src/transport/noop_transport.dart';
 import 'package:sentry/src/transport/spotlight_http_transport.dart';
 import 'package:sentry/src/utils/iterable_utils.dart';
-import 'package:sentry/src/event_processor/exception/exception_group_event_processor.dart';
-
 import 'package:test/test.dart';
+
 import 'mocks.dart';
 import 'mocks/mock_client_report_recorder.dart';
 import 'mocks/mock_hub.dart';

flutter/lib/src/navigation/sentry_navigator_observer.dart

@@ -152,6 +152,7 @@ class SentryNavigatorObserver extends RouteObserver<PageRoute<dynamic>> {
       return;
     }
 
+    _hub.generateNewTraceId();
     _setCurrentRouteName(route);
     _setCurrentRouteNameAsTransaction(route);
 
@@ -180,6 +181,7 @@ class SentryNavigatorObserver extends RouteObserver<PageRoute<dynamic>> {
       return;
     }
 
+    _hub.generateNewTraceId();
     _setCurrentRouteName(newRoute);
     _setCurrentRouteNameAsTransaction(newRoute);
 
@@ -201,6 +203,7 @@ class SentryNavigatorObserver extends RouteObserver<PageRoute<dynamic>> {
       return;
     }
 
+    _hub.generateNewTraceId();
     _setCurrentRouteName(previousRoute);
     _setCurrentRouteNameAsTransaction(previousRoute);
 

flutter/test/sentry_navigator_observer_test.dart → flutter/test/navigation/sentry_navigator_observer_test.dart

@@ -15,9 +15,9 @@ import 'package:sentry_flutter/src/navigation/time_to_display_tracker.dart';
 import 'package:sentry_flutter/src/navigation/time_to_full_display_tracker.dart';
 import 'package:sentry_flutter/src/navigation/time_to_initial_display_tracker.dart';
 
-import 'fake_frame_callback_handler.dart';
-import 'mocks.dart';
-import 'mocks.mocks.dart';
+import '../fake_frame_callback_handler.dart';
+import '../mocks.dart';
+import '../mocks.mocks.dart';
 
 void main() {
   late Fixture fixture;
@@ -1340,6 +1340,9 @@ class Fixture {
     AdditionalInfoExtractor? additionalInfoProvider,
     List<String>? ignoreRoutes,
   }) {
+    if (hub is MockHub) {
+      when(hub.generateNewTraceId()).thenAnswer((_) => {});
+    }
     final frameCallbackHandler = FakeFrameCallbackHandler(
         postFrameCallbackDelay: Duration(milliseconds: 10));
     timeToInitialDisplayTracker = TimeToInitialDisplayTracker(

flutter/test/navigation/sentry_navigator_observer_traces_test.dart

@@ -0,0 +1,115 @@
+// ignore_for_file: invalid_use_of_internal_member
+
+import 'package:flutter/cupertino.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mockito/mockito.dart';
+import 'package:sentry_flutter/sentry_flutter.dart';
+
+import '../mocks.dart';
+import '../mocks.mocks.dart';
+
+void main() {
+  late Fixture fixture;
+
+  setUp(() {
+    fixture = Fixture();
+  });
+
+  test('didPush generates a new trace', () {
+    final fromRoute = _route(RouteSettings(name: 'From Route'));
+    final toRoute = _route(RouteSettings(name: 'To Route'));
+    final oldTraceId = fixture.hub.scope.propagationContext.traceId;
+
+    final sut = fixture.getSut();
+    sut.didPush(toRoute, fromRoute);
+
+    final newTraceId = fixture.hub.scope.propagationContext.traceId;
+    expect(oldTraceId, isNot(newTraceId));
+  });
+
+  test('didPop generates a new trace', () {
+    final fromRoute = _route(RouteSettings(name: 'From Route'));
+    final toRoute = _route(RouteSettings(name: 'To Route'));
+    final oldTraceId = fixture.hub.scope.propagationContext.traceId;
+
+    final sut = fixture.getSut();
+    sut.didPop(toRoute, fromRoute);
+
+    final newTraceId = fixture.hub.scope.propagationContext.traceId;
+    expect(oldTraceId, isNot(newTraceId));
+  });
+
+  test('didReplace generates a new trace', () {
+    final fromRoute = _route(RouteSettings(name: 'From Route'));
+    final toRoute = _route(RouteSettings(name: 'To Route'));
+    final oldTraceId = fixture.hub.scope.propagationContext.traceId;
+
+    final sut = fixture.getSut();
+    sut.didReplace(newRoute: toRoute, oldRoute: fromRoute);
+
+    final newTraceId = fixture.hub.scope.propagationContext.traceId;
+    expect(oldTraceId, isNot(newTraceId));
+  });
+
+  group('execution order', () {
+    /// Prepares mocks, we don't care about what they exactly do.
+    /// We only test the order of execution in this group.
+    void _prepareMocks() {
+      when(fixture.mockHub.generateNewTraceId()).thenAnswer((_) => {});
+      when(fixture.mockHub.configureScope(any))
+          .thenAnswer((_) => Future.value());
+      when(fixture.mockHub.startTransactionWithContext(
+        any,
+        bindToScope: anyNamed('bindToScope'),
+        waitForChildren: anyNamed('waitForChildren'),
+        autoFinishAfter: anyNamed('autoFinishAfter'),
+        trimEnd: anyNamed('trimEnd'),
+        onFinish: anyNamed('onFinish'),
+        customSamplingContext: anyNamed('customSamplingContext'),
+        startTimestamp: anyNamed('startTimestamp'),
+      )).thenReturn(NoOpSentrySpan());
+    }
+
+    test('didPush generates a new trace before creating transaction spans', () {
+      final fromRoute = _route(RouteSettings(name: 'From Route'));
+      final toRoute = _route(RouteSettings(name: 'To Route'));
+
+      _prepareMocks();
+
+      final sut = fixture.getSut(hub: fixture.mockHub);
+      sut.didPush(toRoute, fromRoute);
+      verifyInOrder([
+        fixture.mockHub.generateNewTraceId(),
+        fixture.mockHub.startTransactionWithContext(
+          any,
+          bindToScope: anyNamed('bindToScope'),
+          waitForChildren: anyNamed('waitForChildren'),
+          autoFinishAfter: anyNamed('autoFinishAfter'),
+          trimEnd: anyNamed('trimEnd'),
+          onFinish: anyNamed('onFinish'),
+          customSamplingContext: anyNamed('customSamplingContext'),
+          startTimestamp: anyNamed('startTimestamp'),
+        ),
+      ]);
+    });
+  });
+}
+
+PageRoute<dynamic> _route(RouteSettings? settings) => PageRouteBuilder<void>(
+      pageBuilder: (_, __, ___) => Container(),
+      settings: settings,
+    );
+
+class Fixture {
+  final options = defaultTestOptions();
+  late final mockHub = MockHub();
+  late final hub = Hub(options);
+
+  SentryNavigatorObserver getSut({Hub? hub}) {
+    hub ??= this.hub;
+    if (hub == mockHub) {
+      when(mockHub.options).thenReturn(options);
+    }
+    return SentryNavigatorObserver(hub: hub);
+  }
+}