Iglistkit: 'Search autocomplete' example crashes with 'Section controller nil for cell'

[bonzoq]

New issue checklist

• [x] I have reviewed the README and documentation

• [x] I have searched existing issues and this is not a duplicate

  General information

• Library version(s): 1.0.0

• iOS version(s): 10.1
• Devices/Simulators affected: iPhone 5s simulator (14B70)
• Reproducible in the demo project? (Yes/No): Yes
• Related issues: None
  

  Repro steps

1. Run the example app
2. Go to 'Search autocomplete' example
3. Type a character in the search bar
4. Tap the cancel button in the search bar
5. Swipe the collection view halfway down
6. Swipe the collection view all the way up
7. Repeat 5 and 6 three times

The app will crash with:

IGListKitExamples[42894:733170] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Section controller nil for cell <IGListKitExamples.SearchCell: 0x7fd5bd41e2c0; baseClass = UICollectionViewCell; frame = (0 0; 320 44); hidden = YES; layer = <CALayer: 0x6000000396a0>>'
*** First throw call stack:
(
    0   CoreFoundation                      0x000000010d37634b __exceptionPreprocess + 171
    1   libobjc.A.dylib                     0x000000010cdd721e objc_exception_throw + 48
    2   CoreFoundation                      0x000000010d37a442 +[NSException raise:format:arguments:] + 98
    3   Foundation                          0x000000010c9a3d79 -[NSAssertionHandler handleFailureInFunction:file:lineNumber:description:] + 166
    4   IGListKit                           0x000000010c8153e8 -[IGListAdapter visibleSectionControllers] + 1320
    5   IGListKit                           0x000000010c819390 -[IGListAdapter scrollViewDidScroll:] + 192
    6   UIKit                               0x000000010e1f3afd -[UIScrollView(UIScrollViewInternal) _notifyDidScroll] + 69
    7   UIKit                               0x000000010e1de525 -[UIScrollView setContentOffset:] + 478
    8   UIKit                               0x000000010e1ee06c -[UIScrollView _smoothScrollWithUpdateTime:] + 3141
    9   QuartzCore                          0x000000010de8ac35 _ZN2CA7Display15DisplayLinkItem8dispatchEy + 57
    10  QuartzCore                          0x000000010de8aaf5 _ZN2CA7Display11DisplayLink14dispatch_itemsEyyy + 449
    11  CoreFoundation                      0x000000010d308964 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 20
    12  CoreFoundation                      0x000000010d3085f3 __CFRunLoopDoTimer + 1075
    13  CoreFoundation                      0x000000010d30817a __CFRunLoopDoTimers + 250
    14  CoreFoundation                      0x000000010d2fff01 __CFRunLoopRun + 2065
    15  CoreFoundation                      0x000000010d2ff494 CFRunLoopRunSpecific + 420
    16  GraphicsServices                    0x00000001115dba6f GSEventRunModal + 161
    17  UIKit                               0x000000010e109964 UIApplicationMain + 159
    18  IGListKitExamples                   0x000000010c6ecb6f main + 111
    19  libdyld.dylib                       0x000000011040968d start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

[avalanched]

the issue is easily reproducible by typing and scrolling at the same time.

[jessesquires]

Thanks @bonzoq ! 👍

[jessesquires]

Here's the assert that's firing:

https://github.com/Instagram/IGListKit/blob/ce4b851da343940513a074342fab6f5a7e67125d/Source/IGListAdapter.m#L341

Sounds like _cellSectionControllerMap is getting out of sync:

https://github.com/Instagram/IGListKit/blob/ce4b851da343940513a074342fab6f5a7e67125d/Source/IGListAdapter.m#L513-L516

[rnystrom]

Nice find. I can get this to happen on the first try if I:

1. Search autocomplete example
2. Type "a"
3. Hit the "X" cancel button
4. Scroll halfway down
5. Tap the status bar to go to top

This does not happen on iOS 9.3. I have a feeling this is from iOS 10's UICollectionView cell willDisplay/didEndDisplay API changes. We break the cell -> section controller map that @jessesquires called out in collectionView:didEndDisplayingCell:forItemAtIndexPath:.

[rnystrom]

Wooooooooow. So on iOS 10, a cell can end up in -[UICollectionView visibleCells]before it calls collectionView:willDisplayCell:forItemAtIndexPath:. Crazy! This is probably radar worthy b/c a cell shouldn't be "visible" before the delegate is notified.

Now this only happens if you search, meaning that -[UICollectionView performBatchUpdates:completion:] is called. The search bar cell is never removed though.

[rnystrom]

I commented out the line -[IGListAdapter removeMapForCell:] and it doesn't crash anymore. However, if I follow the repro steps I see this:

[rnystrom]

Ok its to do with the UISearchBar remaining the first responder. This is both a bug in the sample app and a bug w/ UIKit.

Before OSS launch, there was no scrollDelegate for section controllers. We had a scroll method as part of the displayDelegate. After we split out scrolling to a new delegate, this silently broke the example. That means this code never executes!

I'm going to put up a PR that fixes this in the sample app. Probably worth filing a radar still though.

[StormXX]

I have the same issue when I use displayDelegate and scroll the list so fast.
I dont't have a UISearchBar

[rnystrom]

@StormXX mind opening a separate issue w/ more information about your issue? This is over a year old.