[PLAT-6816] Detect hangs during launch of scene based apps

Bugsnag/Helpers/BSGAppHangDetector.m

@@ -22,6 +22,7 @@
 @interface BSGAppHangDetector ()
 
 @property (weak, nonatomic) id<BSGAppHangDetectorDelegate> delegate;
+@property (nonatomic) BOOL runLoopIsRunning;
 @property (nonatomic) BOOL recordAllThreads;
 @property (nonatomic) CFRunLoopObserverRef observer;
 @property (atomic) dispatch_time_t processingDeadline;
@@ -81,6 +82,7 @@ - (void)startWithDelegate:(id<BSGAppHangDetectorDelegate>)delegate {
                 // Each iteration indicates a separate unit of work so the hang detection should be reset accordingly.
                 dispatch_semaphore_signal(self.processingFinished);
             }
+            self.runLoopIsRunning = YES;
             self.processingDeadline = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(threshold * NSEC_PER_SEC));
             dispatch_semaphore_signal(self.processingStarted);
             isProcessing = YES;
@@ -104,9 +106,9 @@ - (void)startWithDelegate:(id<BSGAppHangDetectorDelegate>)delegate {
     self.observer = CFRunLoopObserverCreateWithHandler(NULL, activities, true, order, observerBlock);
 
     // Start monitoring immediately so that app hangs during launch can be detected.
-    // Note that because scene-based apps start in UIApplicationStateBackground, hangs in
-    // -[AppDelegate application:didFinishLaunchingWithOptions:] will be ignored.
-    observerBlock(self.observer, kCFRunLoopAfterWaiting);
+    self.processingDeadline = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(threshold * NSEC_PER_SEC));
+    dispatch_semaphore_signal(self.processingStarted);
+    isProcessing = YES;
 
     CFRunLoopAddObserver(CFRunLoopGetMain(), self.observer, kCFRunLoopCommonModes);
 
@@ -146,7 +148,9 @@ - (void)detectAppHangs {
         }
 #endif
 
-        if (shouldReportAppHang && !bsg_kscrashstate_currentState()->applicationIsInForeground) {
+        // Ignore background state if the runloop has not yet ticked so that hangs in `didFinishLaunching` in UIScene-based
+        // apps are detected. UIScene-based apps always start in UIApplicationStateBackground, unlike those without scenes.
+        if (shouldReportAppHang && !bsg_kscrashstate_currentState()->applicationIsInForeground && self.runLoopIsRunning) {
             bsg_log_debug(@"Ignoring app hang because app is in the background");
             shouldReportAppHang = NO;
         }

CHANGELOG.md

@@ -5,6 +5,8 @@ Changelog
 
 ### Bug fixes
 
+* Detect hangs during launch of UIScene based apps.
+  [#1263](https://github.com/bugsnag/bugsnag-cocoa/pull/1263)
 * Fix some potential deadlocks that could occur if a crash handler crashes.
   [#1252](https://github.com/bugsnag/bugsnag-cocoa/pull/1252)
 

features/fixtures/shared/scenarios/AppHangScenarios.swift

@@ -70,7 +70,10 @@ class AppHangFatalOnlyScenario: Scenario {
 
     override func run() {
         NSLog("Hanging indefinitely...")
-        while true {}
+        // Use asyncAfter to allow the Appium click event to be handled
+        DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
+            while true {}
+        }
     }
 }
 
@@ -84,7 +87,10 @@ class AppHangFatalDisabledScenario: Scenario {
 
     override func run() {
         NSLog("Hanging indefinitely...")
-        while true {}
+        // Use asyncAfter to allow the Appium click event to be handled
+        DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
+            while true {}
+        }
     }
 }