Fix crash when pushing the same VC twice in Reader (#23907)

Author: kean

RELEASE-NOTES.txt

@@ -15,6 +15,7 @@
 * [*] Fix minor appearance issues in the Blaze campaign list [#23891]
 * [*] Improve the sidebar animations and layout on some iPad models [#23886]
 * [*] Fix an issue with posts shown embedded in the notifications popover on iPad [#23889]
+* [*] Fix a couple of rare crashes in Reader [#23907]
 * [*] The post cover now uses the standard aspect ratio for covers, so there is no jumping. There are also a few minor improvements to the layout and animations of the cover [#23897]
 * [*] Move the "Reading Preferences" button to the "More" menu [#23897]
 

WordPress/Classes/System/Root View/ReaderPresenter.swift

@@ -92,7 +92,7 @@ final class ReaderPresenter: NSObject, SplitViewDisplayable {
         } else {
             if let latestContentVC {
                 // Return to the previous view controller preserving its state
-                mainNavigationController.pushViewController(latestContentVC, animated: true)
+                mainNavigationController.safePushViewController(latestContentVC, animated: true)
             }
         }
     }
@@ -191,7 +191,7 @@ final class ReaderPresenter: NSObject, SplitViewDisplayable {
             splitViewController.setViewController(navigationVC, for: .secondary)
         } else {
             latestContentVC = viewController
-            mainNavigationController.pushViewController(viewController, animated: true)
+            mainNavigationController.safePushViewController(viewController, animated: true)
         }
     }
 
@@ -201,9 +201,9 @@ final class ReaderPresenter: NSObject, SplitViewDisplayable {
         if let splitViewController {
             let navigationVC = splitViewController.viewController(for: .secondary) as? UINavigationController
             wpAssert(navigationVC != nil)
-            navigationVC?.pushViewController(viewController, animated: true)
+            navigationVC?.safePushViewController(viewController, animated: true)
         } else {
-            mainNavigationController.pushViewController(viewController, animated: true)
+            mainNavigationController.safePushViewController(viewController, animated: true)
         }
     }
 
@@ -248,3 +248,14 @@ final class ReaderPresenter: NSObject, SplitViewDisplayable {
         }
     }
 }
+
+private extension UINavigationController {
+    // TODO: fix when stack trace becomes available
+    // A workaround for https://a8c.sentry.io/issues/3140539221.
+    func safePushViewController(_ viewController: UIViewController, animated: Bool) {
+        guard !children.contains(viewController) else {
+            return wpAssertionFailure("pushing the same view controller more than once", userInfo: ["viewController": "\(viewController)"])
+        }
+        pushViewController(viewController, animated: animated)
+    }
+}