Open Radar

 
Summary:
When reloading a section that is displaced/shifted inside -[UICollectionView performBatchUpdates:completion:], it is possible to hit an NSInternalInconsistencyException stating "attempt to perform an insert and a move to the same section (i)" when the sections used in insertSections:, deleteSections:, reloadSections: , and moveSection:toSection: do not intersect.

For instance, a collection view who's data source is updated to reflect the following section mutations will crash:

[self.collectionView performBatchUpdates:^{
  [self.collectionView moveSection:2 toSection:4];
  [self.collectionView reloadSections:[NSIndexSet indexSetWithIndex:3]];
  [self.collectionView deleteSections:[NSIndexSet indexSetWithIndex:4]];
  [self.collectionView insertSections:[NSIndexSet indexSetWithIndex:2]];
} completion:nil];

Steps to Reproduce:
1. Open attached UICollectionViewReloadDisplacement sample app
2. Hit "Play" bar button
3. Crash

Expected Results:
- Section 2 moves to section 4
- Section 3 is reloaded
- Section 4 is deleted
- A new section is inserted into section 2

Actual Results:
Crash with exception:

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'attempt to perform an insert and a move to the same section (4)'

Version:
iOS 9.3.4, 8.4, and 10.0 beta 4

Notes:


Configuration:
iPhone 6, iPhone 6s simulator

Attachments:
'UICollectionViewReloadDisplacement.crash' and 'UICollectionViewReloadDisplacement.zip' were successfully uploaded.