fix: Finish TTID when viewWillAppear is skipped

CHANGELOG.md

@@ -11,6 +11,7 @@
 - Edge case for swizzleClassNameExclude (#4405): Skip creating transactions for UIViewControllers ignored for swizzling
 via the option `swizzleClassNameExclude`.
 - Add TTID/TTFD spans when loadView gets skipped (#4415)
+- Finish TTID correctly when viewWillAppear is skipped (#4417)
 - Swizzling RootUIViewController if ignored by `swizzleClassNameExclude` (#4407)
 
 ## 8.38.0-beta.1

Sources/Sentry/SentryUIViewControllerPerformanceTracker.m

@@ -198,10 +198,7 @@ - (void)viewControllerViewWillAppear:(UIViewController *)controller
         };
 
         [self.tracker activateSpan:spanId duringBlock:duringBlock];
-
-        SentryTimeToDisplayTracker *ttdTracker
-            = objc_getAssociatedObject(controller, &SENTRY_UI_PERFORMANCE_TRACKER_TTD_TRACKER);
-        [ttdTracker reportInitialDisplay];
+        [self reportInitialDisplay:controller];
     };
 
     [self limitOverride:@"viewWillAppear"
@@ -320,6 +317,15 @@ - (void)viewControllerViewWillLayoutSubViews:(UIViewController *)controller
                 OBJC_ASSOCIATION_RETAIN_NONATOMIC);
         };
         [self.tracker activateSpan:spanId duringBlock:duringBlock];
+
+        // According to the Apple docs
+        // (https://developer.apple.com/documentation/uikit/uiviewcontroller/1621510-viewwillappear),
+        // viewWillAppear should be called for before the UIViewController is added to the view
+        // hierarchy. There are some edge cases, though, when this doesn't happen, and we saw
+        // customers' transactions also proofing this. Therefore, we must also report the initial
+        // display here, as the customers' transactions had spans for `viewWillLayoutSubviews`.
+
+        [self reportInitialDisplay:controller];
     };
 
     [self limitOverride:@"viewWillLayoutSubviews"
@@ -421,6 +427,13 @@ - (void)measurePerformance:(NSString *)description
     }
 }
 
+- (void)reportInitialDisplay:(UIViewController *)controller
+{
+    SentryTimeToDisplayTracker *ttdTracker
+        = objc_getAssociatedObject(controller, &SENTRY_UI_PERFORMANCE_TRACKER_TTD_TRACKER);
+    [ttdTracker reportInitialDisplay];
+}
+
 @end
 
 #endif // SENTRY_HAS_UIKIT

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

@@ -267,6 +267,90 @@ class SentryUIViewControllerPerformanceTrackerTests: XCTestCase {
         wait(for: [callbackExpectation], timeout: 0)
     }
 
+    func testReportInitialDisplay_WhenViewWillAppear() throws {
+        let sut = fixture.getSut()
+        let viewController = fixture.viewController
+        let tracker = fixture.tracker
+        var tracer: SentryTracer?
+
+        sut.viewControllerLoadView(viewController) {
+            let spans = self.getStack(tracker)
+            tracer = spans.first as? SentryTracer
+        }
+        sut.viewControllerViewWillAppear(viewController) {
+            self.advanceTime(bySeconds: 0.1)
+        }
+
+        reportFrame()
+        let expectedTTIDTimestamp = fixture.dateProvider.date()
+
+        let children: [Span]? = Dynamic(tracer).children as [Span]?
+
+        let ttidSpan = try XCTUnwrap(children?.first)
+        XCTAssertEqual("ui.load.initial_display", ttidSpan.operation)
+        XCTAssertEqual("TestViewController initial display", ttidSpan.spanDescription)
+        XCTAssertEqual(expectedTTIDTimestamp, ttidSpan.timestamp)
+        XCTAssertTrue(ttidSpan.isFinished)
+    }
+
+    func testReportInitialDisplay_WhenViewWillAppearSkipped_WillLayoutSubViewsCalled() throws {
+        let sut = fixture.getSut()
+        let viewController = fixture.viewController
+        let tracker = fixture.tracker
+        var tracer: SentryTracer?
+
+        sut.viewControllerLoadView(viewController) {
+            let spans = self.getStack(tracker)
+            tracer = spans.first as? SentryTracer
+        }
+
+        sut.viewControllerViewWillLayoutSubViews(viewController) {
+            self.advanceTime(bySeconds: 0.1)
+        }
+
+        reportFrame()
+        let expectedTTIDTimestamp = fixture.dateProvider.date()
+
+        let children: [Span]? = Dynamic(tracer).children as [Span]?
+
+        let ttidSpan = try XCTUnwrap(children?.first)
+        XCTAssertEqual("ui.load.initial_display", ttidSpan.operation)
+        XCTAssertEqual("TestViewController initial display", ttidSpan.spanDescription)
+        XCTAssertEqual(expectedTTIDTimestamp, ttidSpan.timestamp)
+        XCTAssertTrue(ttidSpan.isFinished)
+    }
+
+    func testReportInitialDisplay_WhenViewWillAppearAndWillLayoutSubviews() throws {
+        let sut = fixture.getSut()
+        let viewController = fixture.viewController
+        let tracker = fixture.tracker
+        var tracer: SentryTracer?
+
+        sut.viewControllerLoadView(viewController) {
+            let spans = self.getStack(tracker)
+            tracer = spans.first as? SentryTracer
+        }
+        sut.viewControllerViewWillAppear(viewController) {
+            self.advanceTime(bySeconds: 0.1)
+        }
+
+        reportFrame()
+        let expectedTTIDTimestamp = fixture.dateProvider.date()
+
+        // It's doubtful that the OS renders a frame between viewWillAppear and viewWillLayoutSubViews, but if it does, we need to pick the end TTID on viewWillAppear.
+        sut.viewControllerViewWillLayoutSubViews(viewController) {
+            self.advanceTime(bySeconds: 0.1)
+        }
+
+        let children: [Span]? = Dynamic(tracer).children as [Span]?
+
+        let ttidSpan = try XCTUnwrap(children?.first)
+        XCTAssertEqual("ui.load.initial_display", ttidSpan.operation)
+        XCTAssertEqual("TestViewController initial display", ttidSpan.spanDescription)
+        XCTAssertEqual(expectedTTIDTimestamp, ttidSpan.timestamp)
+        XCTAssertTrue(ttidSpan.isFinished)
+    }
+
     func testReportFullyDisplayed() throws {
         let sut = fixture.getSut()
         sut.enableWaitForFullDisplay = true