Open Radar

 
Summary:
When using UITableView with autosizing cells, sometimes when using animated updates UITableView will call cellForRowAtIndexPath with an invalid (out of range) indexPath.
The attached project demonstrates the issue in a 100% reproducible way. The codepath is a bit contrived but the issue also frequently appears in the wild in an app that uses animated updates a lot.

Steps to Reproduce:
Key points are :
- use autosizing cells
- have cells off-screen whose exact height is not computed
- delete a cell in that off-screen range, and delete the following section, causing the updated range to come on-screen
- call endUpdates
as a result, UITableView tries to recompute the height for an indexPath that is now invalid, causing cellForRowAtIndexPath to be called with an invalid index after endUpdates has been called.

Expected Results:
cellForRowAtIndexPath: should never be called with an indexPath not in the range defined by the data source after endUpdates has been called

Actual Results:
cellForRowAtIndexPath: is called with an indexPath not in the range defined by the data source after endUpdates has been called

Version:
9.3.2

Notes:
Additional comments and a workaround are included in the demo project

Configuration:
any iOS device, the attached project is guaranteed to work on an iPhone 6 sized screen

Attachments:
'TableUpdatesCrash.zip' was successfully uploaded.