Section removals cause wrong calls to `CollectionCellElement`'s `didDisappear`

[JosephDuffy]

Describe the bug

When a section is deleted the didDisappear call on CollectionElementsProvider is either not made or is made on the wrong CollectionElementsProvider.

To Reproduce

Delete a section.

Expected behavior

Correct calls to didDisappear should be made/should not crash.

Environment

• OS Version: Any iOS
• Library Version: 1.05
• Device: Any

Additional context

CollectionCoordinator.collectionView(_:didEndDisplaying:forItemAt:) uses the state of the hierarchy after the more recent updates have been applied, meaning the removed cell/section is no longer in the SectionProviderMapping or the local cachedProviders.

For example deleting section 1 with a hierarchy of:

• section 0
  • 0-0
  • 0-1
  • 0-2
• section 1
  • 1-0
  • 1-1
• section 2

Then remove section 1:

• Crashes when the cell is cast to the wrong type
  • This happens when section 1 and have different cell types
• Calls the wrong CollectionElementsProvider
  • This happens when section 1 and have the same cell types
  • This would call didDisappear on section 2 (even though no cells were removed and it's already empty)

Or when section 2 is removed:

• Makes no call at all
  • This happens because of guard indexPath.section < sectionProvider.numberOfSections else { return }

---

I don't have time to look at this right now and I'm not as familiar with the SectionProviderMapping as other parts, can you try and fix this @shaps80?

A suggested solution is to cache the cells and their sections (e.g. cellSectionMap: [UICollectionViewCell: Section]) but I'd like to know if there's a alternative approach since that might lead to more issues down the line?