fix: Long-lasting TTID/TTFD spans

CHANGELOG.md

@@ -13,6 +13,7 @@
 
 - Skip UI crumbs when target or sender is nil (#4211)
 - Guard FramesTracker start and stop (#4224)
+- Long-lasting TTID/TTFD spans (#4225). Avoid long TTID spans when the FrameTracker isn't running, which is the case when the app is in the background.
 
 ## 8.32.0
 

Sources/Sentry/SentryTimeToDisplayTracker.m

@@ -54,8 +54,14 @@ - (instancetype)initForController:(UIViewController *)controller
     return self;
 }
 
-- (void)startForTracer:(SentryTracer *)tracer
+- (BOOL)startForTracer:(SentryTracer *)tracer
 {
+    if (SentryDependencyContainer.sharedInstance.framesTracker.isRunning == NO) {
+        SENTRY_LOG_DEBUG(@"Skipping TTID/TTFD spans, because can't report them correctly when the "
+                         @"frames tracker isn't running.");
+        return NO;
+    }
+
     SENTRY_LOG_DEBUG(@"Starting initial display span");
     self.initialDisplaySpan = [tracer
         startChildWithOperation:SentrySpanOperationUILoadInitialDisplay
@@ -116,6 +122,8 @@ - (void)startForTracer:(SentryTracer *)tracer
             stringWithFormat:@"%@ - Deadline Exceeded", self.fullDisplaySpan.spanDescription];
         [self addTimeToDisplayMeasurement:self.fullDisplaySpan name:@"time_to_full_display"];
     }];
+
+    return YES;
 }
 
 - (void)reportInitialDisplay

Sources/Sentry/SentryUIViewControllerPerformanceTracker.m

@@ -147,11 +147,14 @@ - (void)createTimeToDisplay:(UIViewController *)controller
                                            waitForFullDisplay:self.enableWaitForFullDisplay
                                          dispatchQueueWrapper:_dispatchQueueWrapper];
 
-    objc_setAssociatedObject(controller, &SENTRY_UI_PERFORMANCE_TRACKER_TTD_TRACKER, ttdTracker,
-        OBJC_ASSOCIATION_ASSIGN);
-    [ttdTracker startForTracer:(SentryTracer *)vcSpan];
+    if ([ttdTracker startForTracer:(SentryTracer *)vcSpan]) {
+        objc_setAssociatedObject(controller, &SENTRY_UI_PERFORMANCE_TRACKER_TTD_TRACKER, ttdTracker,
+            OBJC_ASSOCIATION_ASSIGN);
 
-    self.currentTTDTracker = ttdTracker;
+        self.currentTTDTracker = ttdTracker;
+    } else {
+        self.currentTTDTracker = nil;
+    }
 }
 
 - (void)reportFullyDisplayed

Sources/Sentry/include/SentryTimeToDisplayTracker.h

@@ -29,7 +29,7 @@ SENTRY_NO_INIT
                waitForFullDisplay:(BOOL)waitForFullDisplay
              dispatchQueueWrapper:(SentryDispatchQueueWrapper *)dispatchQueueWrapper;
 
-- (void)startForTracer:(SentryTracer *)tracer;
+- (BOOL)startForTracer:(SentryTracer *)tracer;
 
 - (void)reportInitialDisplay;
 

Tests/SentryTests/Integrations/Performance/UIViewController/SentryTimeToDisplayTrackerTest.swift

@@ -47,14 +47,32 @@ class SentryTimeToDisplayTrackerTest: XCTestCase {
         super.tearDown()
         clearTestState()
     }
+
+    /// This can happen when a UIViewController is presented when the app is in the background.
+    func testNoSpansCreated_WhenFramesTrackerNotRunning() throws {
+        fixture.framesTracker.stop()
+
+        let sut = fixture.getSut(for: UIViewController(), waitForFullDisplay: false)
+
+        fixture.dateProvider.setDate(date: Date(timeIntervalSince1970: 7))
+        let tracer = try fixture.getTracer()
+
+        XCTAssertFalse(sut.start(for: tracer))
+
+        sut.reportInitialDisplay()
+        sut.reportFullyDisplayed()
+
+        fixture.framesTracker.start()
+        XCTAssertEqual(tracer.children.count, 0)
+    }
 
     func testReportInitialDisplay_notWaitingForFullDisplay() throws {
         let sut = fixture.getSut(for: UIViewController(), waitForFullDisplay: false)
 
         fixture.dateProvider.setDate(date: Date(timeIntervalSince1970: 7))
         let tracer = try fixture.getTracer()
 
-        sut.start(for: tracer)
+        XCTAssertTrue(sut.start(for: tracer))
         XCTAssertEqual(tracer.children.count, 1)
         XCTAssertEqual(Dynamic(self.fixture.framesTracker).listeners.count, 1)
 

Tests/SentryTests/Integrations/Performance/UIViewController/SentryUIViewControllerPerformanceTrackerTests.swift

@@ -40,11 +40,21 @@ class SentryUIViewControllerPerformanceTrackerTests: XCTestCase {
         let tracker = SentryPerformanceTracker.shared
         let dateProvider = TestCurrentDateProvider()
 
+        var displayLinkWrapper = TestDisplayLinkWrapper()
+        var framesTracker: SentryFramesTracker
+
         var viewControllerName: String!
 
         var inAppLogic: SentryInAppLogic {
             return SentryInAppLogic(inAppIncludes: options.inAppIncludes, inAppExcludes: [])
         }
+
+        init() {
+            framesTracker = SentryFramesTracker(displayLinkWrapper: displayLinkWrapper, dateProvider: dateProvider, dispatchQueueWrapper: TestSentryDispatchQueueWrapper(),
+                                                notificationCenter: TestNSNotificationCenterWrapper(), keepDelayedFramesDuration: 0)
+            SentryDependencyContainer.sharedInstance().framesTracker = framesTracker
+            framesTracker.start()
+        }
 
         func getSut() -> SentryUIViewControllerPerformanceTracker {
             SentryDependencyContainer.sharedInstance().dateProvider = dateProvider
@@ -281,6 +291,27 @@ class SentryUIViewControllerPerformanceTrackerTests: XCTestCase {
         XCTAssertEqual(ttfdSpan.isFinished, true)
         XCTAssertEqual(ttfdSpan.timestamp, expectedTTFDTimestamp)
     }
+
+    func testFramesTrackerNotRunning_NoTTDTrackerAndSpans() {
+        fixture.framesTracker.stop()
+        let sut = fixture.getSut()
+        let tracker = fixture.tracker
+        let viewController = fixture.viewController
+        var tracer: SentryTracer?
+
+        sut.viewControllerLoadView(viewController) {
+            let spans = self.getStack(tracker)
+            tracer = spans.first as? SentryTracer
+        }
+
+        let ttdTracker = Dynamic(sut).currentTTDTracker.asObject as? SentryTimeToDisplayTracker
+        XCTAssertNil(ttdTracker)
+
+        sut.reportFullyDisplayed()
+
+        XCTAssertEqual(tracer?.children.filter { $0.operation.contains("initial_display") }.count, 0, "Tracer must not contain a TTID span")
+        XCTAssertEqual(tracer?.children.filter { $0.operation.contains("full_display") }.count, 0, "Tracer must not contain a TTFD span")
+    }
 
     func testSecondViewController() {
         let sut = fixture.getSut()