fix: Finish TTID span when transaction finishes (#3610)

The tracer finishes when the screen is fully displayed. Therefore, we
must also finish the TTID span.

Author: philipphofmann

CHANGELOG.md

@@ -9,6 +9,8 @@
 ### Fixes
 
 - Don't use main thread for app hang screenshot and view hierarchy (#3547)
+- Finish TTID span when transaction finishes (#3610)
+
 
 ## 8.20.0
 

Sources/Sentry/SentryTimeToDisplayTracker.m

@@ -64,7 +64,23 @@ - (void)startForTracer:(SentryTracer *)tracer
     self.initialDisplaySpan.startTimestamp = tracer.startTimestamp;
 
     [SentryDependencyContainer.sharedInstance.framesTracker addListener:self];
+
+    [tracer setShouldIgnoreWaitForChildrenCallback:^(id<SentrySpan> span) {
+        if (span.origin == SentryTraceOriginAutoUITimeToDisplay) {
+            return YES;
+        } else {
+            return NO;
+        }
+    }];
     [tracer setFinishCallback:^(SentryTracer *_tracer) {
+        [SentryDependencyContainer.sharedInstance.framesTracker removeListener:self];
+
+        // The tracer finishes when the screen is fully displayed. Therefore, we must also finish
+        // the TTID span.
+        if (self.initialDisplaySpan.isFinished == NO) {
+            [self.initialDisplaySpan finish];
+        }
+
         // If the start time of the tracer changes, which is the case for app start transactions, we
         // also need to adapt the start time of our spans.
         self.initialDisplaySpan.startTimestamp = _tracer.startTimestamp;

Sources/Sentry/SentryTracer.m

@@ -476,6 +476,10 @@ - (BOOL)hasUnfinishedChildSpansToWaitFor
 
     @synchronized(_children) {
         for (id<SentrySpan> span in _children) {
+            if (self.shouldIgnoreWaitForChildrenCallback != nil
+                && self.shouldIgnoreWaitForChildrenCallback(span)) {
+                continue;
+            }
             if (![span isFinished])
                 return YES;
         }
@@ -519,6 +523,10 @@ - (void)finishInternal
         self.finishCallback = nil;
     }
 
+    if (self.shouldIgnoreWaitForChildrenCallback) {
+        self.shouldIgnoreWaitForChildrenCallback = nil;
+    }
+
     // Prewarming can execute code up to viewDidLoad of a UIViewController, and keep the app in the
     // background. This can lead to auto-generated transactions lasting for minutes or even hours.
     // Therefore, we drop transactions lasting longer than SENTRY_AUTO_TRANSACTION_MAX_DURATION.

Sources/Sentry/include/SentryTracer.h

@@ -34,6 +34,8 @@ static const NSTimeInterval SENTRY_AUTO_TRANSACTION_MAX_DURATION = 500.0;
 
 @property (nullable, nonatomic, copy) void (^finishCallback)(SentryTracer *);
 
+@property (nullable, nonatomic, copy) BOOL (^shouldIgnoreWaitForChildrenCallback)(id<SentrySpan>);
+
 /**
  * Retrieves a trace context from this tracer.
  */

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

@@ -202,6 +202,33 @@ class SentryTimeToDisplayTrackerTest: XCTestCase {
 
         expect(Dynamic(self.fixture.framesTracker).listeners.count) == 0
     }
+    
+    func testTracerFinishesBeforeReportInitialDisplay_FinishesInitialDisplaySpan() 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)
+        expect(tracer.children.count) == 1
+        expect(Dynamic(self.fixture.framesTracker).listeners.count) == 1
+
+        let ttidSpan = try XCTUnwrap(tracer.children.first, "Expected a TTID span")
+        expect(ttidSpan.startTimestamp) == fixture.dateProvider.date()
+
+        fixture.dateProvider.setDate(date: Date(timeIntervalSince1970: 9))
+        
+        tracer.finish()
+
+        expect(ttidSpan.timestamp) == fixture.dateProvider.date()
+        expect(ttidSpan.isFinished) == true
+        expect(ttidSpan.spanDescription) == "UIViewController initial display"
+        expect(ttidSpan.status) == .ok
+
+        assertMeasurement(tracer: tracer, name: "time_to_initial_display", duration: 2_000)
+
+        expect(Dynamic(self.fixture.framesTracker).listeners.count) == 0
+    }
 
     func testCheckInitialTime() throws {
         fixture.dateProvider.setDate(date: Date(timeIntervalSince1970: 9))

Tests/SentryTests/Transaction/SentryTracerTests.swift

@@ -152,6 +152,31 @@ class SentryTracerTests: XCTestCase {
             XCTAssertEqual(tracerTimestamp.timeIntervalSince1970, span["timestamp"] as? TimeInterval)
         }
     }
+    
+    func testFinish_ShouldIgnoreWaitForChildrenCallback() throws {
+        let sut = fixture.getSut()
+        
+        sut.shouldIgnoreWaitForChildrenCallback = { _ in
+            return true
+        }
+        let child = sut.startChild(operation: fixture.transactionOperation)
+        sut.finish()
+        
+        expect(child.status) == .deadlineExceeded
+        
+        assertOneTransactionCaptured(sut)
+    
+        let serialization = try getSerializedTransaction()
+        let spans = serialization["spans"]! as! [[String: Any]]
+        
+        let tracerTimestamp: NSDate = sut.timestamp! as NSDate
+        
+        expect(spans.count) == 1
+        let span = try XCTUnwrap(spans.first, "Expected first span not to be nil")
+        expect(span["timestamp"] as? TimeInterval) == tracerTimestamp.timeIntervalSince1970
+        
+        expect(sut.shouldIgnoreWaitForChildrenCallback) == nil
+    }
 
     func testDeadlineTimer_FinishesTransactionAndChildren() {
         fixture.dispatchQueue.blockBeforeMainBlock = { true }