Woocommerce-ios: Invalid Number Of Rows/Sections Crash

[astralbodies]

Describe the bug
Text from one of the crashes:

Invalid update: invalid number of rows in section 0. The number of rows contained in an existing section after the update (8) must be equal to the number of rows contained in that section before the update (7), plus or minus the number of rows inserted or deleted from that section (1 inserted, 7 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out).

Crash report: https://sentry.io/share/issue/63aa8ffcc1634d5da1c7c2c0f8155ac8/

To Reproduce
Unsure of how to reproduce.

Expected behavior
No crashes when orders list is updated.

[astralbodies]

FWIW the ghost feature caused a crash in WPiOS that might be similar in nature. https://github.com/wordpress-mobile/WordPress-iOS/pull/12974

[pmusolino]

I'm reopening this issue since it occurs also on release 3.5

[shiki]

Moved to _Waiting_ for now. We'll observe how #2361 and #2362 will affect this.

[sentry-io[bot]]

Sentry issue: WOOCOMMERCE-IOS-81

[shiki]

Looks like this is still happening in 4.5 so #2447 may not actually be enough. 🙁

[pmusolino]

@shiki I'm thinking if it's possible that there is a case which we haven't considered, where the number of sections returned for a table view is 0. This is a value not allowed (there must always be a section, and the minimum number of sections allowed is 1)! For example, it seems that the number of sections returned by a ResultsController permit to return an empty array, and when we call the method .count on it, this will return 0. 💥

[shiki]

That's a good idea to look into. We might be able to easily simulate that scenario and see if it crashes by making a new test case like this one in ResultsControllerUIKitTests.

The other thing I totally forgot about is that some of our ViewControllers are still using the Ghost table dataSource switching which we've proven before that it can cause "invalid number of rows" crashes. (https://github.com/woocommerce/woocommerce-ios/issues/2448)

[shiki]

Suggestion by Apple was implemented in Simplenote https://github.com/Automattic/simplenote-ios/pull/798. Ref p91TBi-2Yr-p2#comment-1239

[sentry-io[bot]]

Sentry issue: WOOCOMMERCE-IOS-A5

[sentry-io[bot]]

Sentry issue: WOOCOMMERCE-IOS-RS

[shiki]

As of August 17, 2020:

• 21k events
• 3.8k affected users

[shiki]

The PR #2820 changes the Order list to use DiffableDataSource. This is an experiment to try and fix this crash. If this change is worse than we currently have, we can revert #2820. If it is successful, we should migrate all other ResultsController usages to use DiffableDataSource in order to fix the non-Order list crashes.

[shiki]

This was accidentally closed. I didn't mean to do that!

Reasons above: https://github.com/woocommerce/woocommerce-ios/issues/1543#issuecomment-692985153

[sentry-io[bot]]

Sentry issue: WOOCOMMERCE-IOS-1C4S

[nbradbury]

Just a note that this is still happening. Given the number of events/users, I've re-added the "high priority" label.

[koke]

I think this might be Sentry misleading us, unless I'm messing up the filtering there. I looked at the last 90 days of data for this crash, and it all seems to be coming from older releases. I spotted a handful of crashes coming from 6.2/6.3 but the bulk of it is coming from older versions:

I checked just to be sure, and most of the users seem to be using the latest 2-3 releases, so this seems to be over representing those stuck in older versions.

[designsimply]

Closing based on @koke's review noting whatever was causing this crash is mainly affecting users stuck in older releases and I also noticed that potentially only 3 users overall were affected in the last 90 days (according to the numbers at the top right of the Sentry report in Details view).

Events in the last 90d: 199
Users affected in the last 90d: 3
_{WOOCOMMERCE-IOS-1C4S: https://sentry.io/share/issue/d8c49c82786a48919bd363e1ef366935/}