31375101: UITableViewDelegate method called with indexPath=nil when running UI tests

[openradar-mirror]

Description

The 'public func tableView(_ tableView: UITableView, canPerformAction action: Selector, forRowAt indexPath: IndexPath, withSender sender: Any?) -> Bool' method when implemented in a class that conforms UITableViewDelegate gets sometimes called by the system with nil for the 'indexPath' parameter.

As the indexPath parameter is bridged from Objective-C as implicitly unwrapped, this causes a crash and makes the test fail with the following error:

Assertion Failure: UI Testing Failure - Failure getting snapshot Error Domain=XCTestManagerErrorDomain Code=9 "Error -25204 getting snapshot for element AXUIElement 0x7f84b5c0ea40 {pid=32894}" UserInfo={NSLocalizedDescription=Error -25204 getting snapshot for element AXUIElement 0x7f84b5c0ea40 {pid=32894}}

App's backtrace on crash:

(lldb) thread backtrace

• thread 22108400: Swift 2.0b4: Allow if let and guard let to assign to self in failable value type initializers #1: tid = 0x128eaa, 0x000000010c776c3a libswiftFoundation.dylib`static Foundation.IndexPath._unconditionallyBridgeFromObjectiveC (Swift.Optional<__ObjC.NSIndexPath>) -> Foundation.IndexPath + 42, queue = 'com.apple.main-thread', stop reason = EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)
  • frame #0: 0x000000010c776c3a libswiftFoundation.dylibstatic Foundation.IndexPath._unconditionallyBridgeFromObjectiveC (Swift.Optional<__ObjC.NSIndexPath>) -> Foundation.IndexPath + 42 frame #1: 0x0000000108443241 Static@objc DataSource.tableView(UITableView, canPerformAction : Selector, forRowAt : IndexPath, withSender : Any?) -> Bool + 97 at DataSource.swift:0
    frame 22108390: Swift 2.0b4: Allow assignment of nil to self in failable initializers to indicate failure #2: 0x00000001095aea31 UIKit-[UITableView _canPerformAction:forCell:sender:] + 169 frame #3: 0x00000001098017c6 UIKit-[UITableViewCell canPerformAction:withSender:] + 86
    frame 22108127: Apple Music: CarPlay does not show the For You Playlists #4: 0x00000001210a5fc9 UIKit-[UIResponder(UITextAccessibilityUtilities) _accessibilityHasTextOperations] + 100 frame #5: 0x000000012107bb7c UIKit-[UITableViewCellAccessibilityElement _accessibilityHasTextOperations] + 48
    frame 22108095: Changing account in Music app requires force-quit #6: 0x00000001211f09ec UIAccessibility-[NSObject(AXPrivCategory) accessibilityAttributeValue:] + 5945 frame #7: 0x000000012120bc04 UIAccessibility_accessibilityAttributesForObject + 767
    frame 22107434: Providing Generic Generator for protocol intermittently crashes compiler #8: 0x000000012120b5e8 UIAccessibility-[NSObject(UIAccessibilityAutomation) _accessibilityUserTestingSnapshotDescendantsWithAttributes:maxDepth:maxChildren:maxArrayCount:] + 1736 frame #9: 0x000000012120cf96 UIAccessibility-[NSObject(UIAccessibilityAutomation) _accessibilityUserTestingSnapshotWithOptions:] + 557
    frame 22107245: Xcode 7 beta 4 (7A165t) Interface Builder ignores background color set on UITableView #10: 0x00000001211eec0a UIAccessibility-[NSObject(AXPrivCategory) accessibilityAttributeValue:forParameter:] + 7903 frame #11: 0x00000001211d8856 UIAccessibility_copyParameterizedAttributeValueCallback + 211
    frame 22106516: watchOS 2 Beta 4: Can’t Import CoreText #12: 0x0000000120869532 AXRuntime_AXXMIGCopyParameterizedAttributeValue + 216 frame #13: 0x0000000120863f1c AXRuntime_XCopyParameterizedAttributeValue + 440
    frame 22105625: Mac OS X 10.11: Battery status alwasy shows "20:00 Remaining" #14: 0x0000000120872de5 AXRuntimemshMIGPerform + 266 frame #15: 0x00000001064e93d9 CoreFoundationCFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION + 41
    frame 22103992: Stack implemented with enum causes Abort trap: 6 #16: 0x00000001064e9351 CoreFoundation__CFRunLoopDoSource1 + 465 frame #17: 0x00000001064e1435 CoreFoundation__CFRunLoopRun + 2389
    frame 22103156: News app interface sometimes not visible or incorrect #18: 0x00000001064e0884 CoreFoundationCFRunLoopRunSpecific + 420 frame #19: 0x000000010e5bda6f GraphicsServicesGSEventRunModal + 161
    frame 22102128: Face detection accuracy is bad #20: 0x000000010943dc68 UIKitUIApplicationMain + 159 frame #21: 0x000000010462c95f GoOutmain + 111 at AppDelegate.swift:47
    frame 22098492: Xcode-beta (7A165t): UI Tests: secureTextFields are duplicated #22: 0x000000010cb7e68d libdyld.dylibstart + 1 frame #23: 0x000000010cb7e68d libdyld.dylibstart + 1

Additional notes:
Interestingly, on iOS 9 simulator this works just fine, no crashes. It's the iOS 10 and above that's problematic

Expected results:
This problematic UITableViewDelegate's method should either not be called at all with indexPath=nil or the indexPath type should be marked as optional:

'public func tableView(_ tableView: UITableView, canPerformAction action: Selector, forRowAt indexPath: IndexPath?, withSender sender: Any?) -> Bool'

Product Version: 10.0
Created: 2017-03-31T18:49:26.449740
Originated: 2017-03-31T00:00:00
Open Radar Link: http://www.openradar.me/31375101