Crash while popping when using NavigationStackStore

[jrodriguezmedina]

Description

Hi!
We found this crash in the Xcode Organizer, we don't have data about the steps to reproduce, but looks like while popping a view from a NavigationStackStore, the newPath.count was greater than the number of elements in viewStore.path, causing an Index out of range failure.

 public var body: some View {
    NavigationStack(
      path: self.viewStore.binding(
        get: { $0.path },
        send: { newPath in
          if newPath.count > self.viewStore.path.count, let component = newPath.last {
            return .push(id: component.id, state: component.element)
          } else {
            return .popFrom(id: self.viewStore.path[newPath.count].id)
          }
        }
      )
    ) {
      self.root
        .environment(\.navigationDestinationType, State.self)
        .navigationDestination(for: Component<State>.self) { component in
          NavigationDestinationView(component: component, destination: self.destination)
        }
    }
  }
}

Incident Identifier: 87548882-D479-4727-92CA-C68DBCF3C453
Distributor ID:      com.apple.TestFlight
Hardware Model:      iPhone13,4
Process:             MyApp [509]
Path:                /private/var/containers/Bundle/Application/B7D5D05A-9094-4124-B8E8-F2ED56799C43/MyApp.app/MyApp
Version:             2.0.0 (1440)
AppStoreTools:       16C7015
AppVariant:          1:iPhone13,4:18
Beta:                YES
Code Type:           ARM-64 (Native)
Role:                Foreground
Parent Process:      launchd [1]

Date/Time:           2025-04-05 16:14:25.2496 +0530
Launch Time:         2025-04-05 16:05:19.3323 +0530
OS Version:          iPhone OS 18.2.1 (22C161)
Release Type:        User
Baseband Version:    5.20.03
Report Version:      104

Exception Type:  EXC_BREAKPOINT (SIGTRAP)
Exception Codes: 0x0000000000000001, 0x0000000103f86d10
Termination Reason: SIGNAL 5 Trace/BPT trap: 5
Terminating Process: exc handler [509]

Triggered by Thread:  0



Thread 0 Crashed:
0   MyApp               	0x0000000103f86d10 Swift runtime failure: Index out of range + 4 (/<compiler-generated>:0)
1   MyApp               	0x0000000103f86d10 specialized ContiguousArray.subscript.getter + 4 (/<compiler-generated>:0)
2   MyApp               	0x0000000103f86d10 specialized OrderedSet.subscript.getter + 4 (/<compiler-generated>:0)
3   MyApp               	0x0000000103f86d10 StackState.PathView.subscript.read + 4 (NavigationStackStore.swift:266)
4   MyApp               	0x0000000103f86d10 closure #2 in NavigationStackStore.body.getter + 1792 (NavigationStackStore.swift:102)
5   MyApp               	0x0000000103fd7e38 thunk for @escaping @callee_guaranteed (@in_guaranteed A1) -> (@out B) + 4 (/<compiler-generated>:0)
6   MyApp               	0x0000000103fd7e38 partial apply for thunk for @escaping @callee_guaranteed (@in_guaranteed A1) -> (@out B) + 32
7   MyApp               	0x0000000103fd8148 closure #1 in ViewStore.subscript.setter + 176 (ViewStore.swift:563)
8   MyApp               	0x0000000103fd8d00 specialized TaskLocal.withValue<A>(_:operation:file:line:) + 48 (<stdin>:0)
9   MyApp               	0x0000000103fd8d00 specialized ViewStore.subscript.setter + 116 (ViewStore.swift:562)
10  MyApp               	0x0000000103fd7dd4 ViewStore.subscript.setter + 20 (/<compiler-generated>:0)
11  MyApp               	0x0000000103fd7dd4 key path setter for ViewStore.subscript<A>(get:send:) : <A, B><A1>ViewStore<A, B>ABA1 + 80
12  libswiftCore.dylib            	0x000000019b92d044 NonmutatingWritebackBuffer.__deallocating_deinit + 328 (KeyPath.swift:970)
13  libswiftCore.dylib            	0x000000019bb8517c _swift_release_dealloc + 56 (HeapObject.cpp:847)
14  libswiftCore.dylib            	0x000000019bb86290 bool swift::RefCounts<swift::RefCountBitsT<(swift::RefCountInlinedness)1>>::doDecrementSlow<(swift::PerformDeinit)1>(swift::RefCountBitsT<(swift::RefCountInlinedness)1>, unsigned int) + 160 (RefCount.h:0)
15  SwiftUICore                   	0x0000000260642654 closure #1 in ObjectLocation.set(_:transaction:) + 224 (Binding+ObjectLocation.swift:39)
16  SwiftUICore                   	0x00000002606426b0 partial apply for closure #1 in ObjectLocation.set(_:transaction:) + 32 (<compiler-generated>:0)
17  SwiftUICore                   	0x000000025ff6e1dc specialized closure #1 in withTransaction<A>(_:_:) + 304 (Transaction.swift:258)
18  SwiftUICore                   	0x000000026064254c ObjectLocation.set(_:transaction:) + 392 (Binding+ObjectLocation.swift:37)
19  SwiftUICore                   	0x000000025fdabf3c LocationBox.set(_:transaction:) + 300 (Location.swift:109)
20  SwiftUICore                   	0x000000025fdabd50 protocol witness for Location.set(_:transaction:) in conformance LocationBox<A> + 24 (<compiler-generated>:0)
21  SwiftUICore                   	0x000000025fdac104 ProjectedLocation.set(_:transaction:) + 312 (Location.swift:195)
22  SwiftUICore                   	0x000000025fdabf3c LocationBox.set(_:transaction:) + 300 (Location.swift:109)
23  SwiftUICore                   	0x000000025fdabfbc Binding.ScopedLocation.set(_:transaction:) + 56 (Binding.swift:482)
24  SwiftUICore                   	0x000000025fdabf3c LocationBox.set(_:transaction:) + 300 (Location.swift:109)
25  SwiftUI                       	0x00000001a2299e20 closure #3 in NavigationColumnState.pop(_:request:splitViewState:) + 420 (NavigationColumnState.swift:764)
26  SwiftUICore                   	0x000000025fcdf008 partial apply for thunk for @escaping @callee_guaranteed () -> () + 28 (<compiler-generated>:0)
27  SwiftUICore                   	0x000000025fcdee14 static Update.dispatchActions() + 1256 (Update.swift:189)
28  SwiftUICore                   	0x000000025fcde280 static Update.end() + 212 (Update.swift:91)
29  SwiftUI                       	0x00000001a1b05284 NavigationAuthority.enqueueRequest(_:) + 972 (NavigationAuthority.swift:157)
30  SwiftUI                       	0x00000001a1c8f144 NavigationStackCoordinator.navigationController(_:willShow:animated:) + 1716 (NavigationStackCore_UIKit.swift:980)
31  SwiftUI                       	0x00000001a1c8ea5c @objc NavigationStackCoordinator.navigationController(_:willShow:animated:) + 88 (<compiler-generated>:0)
32  UIKitCore                     	0x00000001a0413688 -[UINavigationController transitionConductor:didStartCustomTransitionWithContext:] + 1392 (UINavigationController.m:11190)
33  UIKitCore                     	0x00000001a0c9b700 -[_UIViewControllerTransitionConductor _startCustomTransition:] + 340 (_UIViewControllerTransitionConductor.m:385)
34  UIKitCore                     	0x000000019fc275d0 -[_UIViewControllerTransitionConductor startDeferredTransitionIfNeeded] + 584 (_UIViewControllerTransitionConductor.m:220)
35  UIKitCore                     	0x000000019faf99f4 -[UINavigationController __viewWillLayoutSubviews] + 84 (UINavigationController.m:8076)
36  UIKitCore                     	0x000000019fda4728 -[UILayoutContainerView layoutSubviews] + 172 (UILayoutContainerView.m:147)
37  UIKit                         	0x000000025a9598f0 -[UILayoutContainerViewAccessibility layoutSubviews] + 60 (:-1)
38  UIKitCore                     	0x000000019fa177f8 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 2424 (UIView.m:19896)
39  QuartzCore                    	0x000000019ed28c30 CA::Layer::layout_if_needed(CA::Transaction*) + 496 (CALayer.mm:10952)
40  QuartzCore                    	0x000000019ed287bc CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 148 (CALayer.mm:2645)
41  QuartzCore                    	0x000000019ed7d89c CA::Context::commit_transaction(CA::Transaction*, double, double*) + 472 (CAContextInternal.mm:2613)
42  QuartzCore                    	0x000000019ecf456c CA::Transaction::commit() + 648 (CATransactionInternal.mm:420)
43  QuartzCore                    	0x000000019ecf3f78 CA::Transaction::flush_as_runloop_observer(bool) + 88 (CATransactionInternal.mm:928)
44  UIKitCore                     	0x000000019fa7f3c4 _UIApplicationFlushCATransaction + 52 (UIApplication.m:3322)
45  UIKitCore                     	0x000000019fa7c890 __setupUpdateSequence_block_invoke_2 + 332 (_UIUpdateScheduler.m:1652)
46  UIKitCore                     	0x000000019fa7c704 _UIUpdateSequenceRun + 84 (_UIUpdateSequence.mm:136)
47  UIKitCore                     	0x000000019fa7f034 schedulerStepScheduledMainSection + 172 (_UIUpdateScheduler.m:1171)
48  UIKitCore                     	0x000000019fa7cc50 runloopSourceCallback + 92 (_UIUpdateScheduler.m:1334)
49  CoreFoundation                	0x000000019d233f3c __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 28 (CFRunLoop.c:1970)
50  CoreFoundation                	0x000000019d233ed0 __CFRunLoopDoSource0 + 176 (CFRunLoop.c:2014)
51  CoreFoundation                	0x000000019d236b30 __CFRunLoopDoSources0 + 244 (CFRunLoop.c:2051)
52  CoreFoundation                	0x000000019d235d2c __CFRunLoopRun + 840 (CFRunLoop.c:2969)
53  CoreFoundation                	0x000000019d288274 CFRunLoopRunSpecific + 588 (CFRunLoop.c:3434)
54  GraphicsServices              	0x00000001ea4014c0 GSEventRunModal + 164 (GSEvent.c:2196)
55  UIKitCore                     	0x000000019fdce77c -[UIApplication _run] + 816 (UIApplication.m:3846)
56  UIKitCore                     	0x000000019f9f4e64 UIApplicationMain + 340 (UIApplication.m:5503)
57  MyApp               	0x0000000102f95c5c main + 1412 (AppDelegate.swift:18)
58  dyld                          	0x00000001c345cde8 start + 2724 (dyldMain.cpp:1338)

Checklist

• I have determined whether this bug is also reproducible in a vanilla SwiftUI project.
• If possible, I've reproduced the issue using the main branch of this package.
• This issue hasn't been addressed in an existing GitHub issue or discussion.

Expected behavior

The view can be popped without crashing.

Actual behavior

The app crashed when a view is popped.

Reproducing project

No response

The Composable Architecture version information

0.57.0

Destination operating system

iOS 18.2.1

Xcode version information

Xcode 16.2

Swift Compiler version information

Swift 5.0

[mbrandonw]

Hi @jrodriguezmedina, I'm sorry but it's really hard to say without a reproduction of the problem. It's also worth mentioning that we have seen this exact crash in vanilla SwiftUI too. It is possible to push/pop to a navigation stack in a certain order/cadence that causes the stack to get into an inconsistent state.

Since it isn't clear this is an issue with the library I am going to convert it to a discussion. Please feel free to continue the conversation over there!