firebase-ios-sdk: Firestore crash / assertion failed / failed to commit transaction / collect garbage

[READ] Step 1: Are you in the right place?

• For issues or feature requests related to the code in this repository file a Github issue.
  • If this is a feature request make sure the issue title starts with “FR:”.
• For general technical questions, post a question on StackOverflow with the firebase tag.
• For general Firebase discussion, use the firebase-talk google group.
• For help troubleshooting your application that does not fall under one of the above categories, reach out to the personalized Firebase support channel.

[REQUIRED] Step 2: Describe your environment

• Xcode version: 12.1
• Firebase SDK version: 5.20.1
• Firebase Component: Firestore_ (Auth, Core, Database, Firestore, Messaging, Storage, etc)
• Component version: 1.2.1_

[REQUIRED] Step 3: Describe the problem

App crashes (as detected by Crashlytics). Apparently while in garbage collection. I have a stack trace but it doesn’t make much sense as it appears to be collection 0 garbage, and fails as operation not permitted on a file. The error and stack trace are likely the most useful items:

error:

Fatal Exception: NSInternalInconsistencyException
FIRESTORE INTERNAL ASSERTION FAILED: Failed to commit transaction: <LevelDbTransaction Collect garbage: 0 changes (0 bytes):> Failed: IO error: /var/mobile/Containers/Data/Application/919A1947-23CF-45C9-A46F-EAEAA0787A06/Documents/firestore/__FIRAPP_DEFAULT/kscoreapp/main/000015.log: Operation not permitted (expected status.ok())

stack:

Fatal Exception: NSInternalInconsistencyException
0  CoreFoundation                 0x191990518 __exceptionPreprocess
1  libobjc.A.dylib                0x190b6b9f8 objc_exception_throw
2  CoreFoundation                 0x1918aa148 +[_CFXNotificationTokenRegistration keyCallbacks]
3  Foundation                     0x1923b9f5c -[NSAssertionHandler handleFailureInFunction:file:lineNumber:description:]
4  KScoreApp                      0x100bfcfcc firebase::firestore::util::internal::Fail(char const*, char const*, int, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) (hard_assert_apple.mm:34)
5  KScoreApp                      0x100bfd0e4 firebase::firestore::util::internal::Fail(char const*, char const*, int, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, char const*) (hard_assert_apple.mm:54)
6  KScoreApp                      0x100c0a1b0 firebase::firestore::local::LevelDbTransaction::Commit() (leveldb_transaction.cc:211)
7  KScoreApp                      0x100bb568c -[FSTLevelDB commitTransaction] (FSTLevelDB.mm:505)
8  KScoreApp                      0x100bbeffc -[FSTLocalStore collectGarbage:] (FSTPersistence.h:216)
9  KScoreApp                      0x100bac900 std::__1::__function::__func<-[FSTFirestoreClient scheduleLruGarbageCollection]::$_3, std::__1::allocator<-[FSTFirestoreClient scheduleLruGarbageCollection]::$_3>, void ()>::operator()() (FSTFirestoreClient.mm:267)
10 KScoreApp                      0x100b71dbc firebase::firestore::util::AsyncQueue::ExecuteBlocking(std::__1::function<void ()> const&) (atomic:921)
11 KScoreApp                      0x100b84ebc firebase::firestore::util::TimeSlot::InvokedByLibdispatch(void*) (executor_libdispatch.mm:179)
12 libdispatch.dylib              0x1913d17d4 _dispatch_client_callout
13 libdispatch.dylib              0x191376018 _dispatch_continuation_pop$VARIANT$mp
14 libdispatch.dylib              0x191385fa4 _dispatch_source_invoke$VARIANT$mp
15 libdispatch.dylib              0x19137a1ec _dispatch_lane_serial_drain$VARIANT$mp
16 libdispatch.dylib              0x19137ae3c _dispatch_lane_invoke$VARIANT$mp
17 libdispatch.dylib              0x1913834a8 _dispatch_workloop_worker_thread
18 libsystem_pthread.dylib        0x1915b1114 _pthread_wqthread
19 libsystem_pthread.dylib        0x1915b3cd4 start_wqthread

Steps to reproduce:

I would love to have steps to reproduce but I haven’t seen this locally, and don’t have the logs or discussion of steps from relevant users / devices

Any instinct on how this could happen that could help me pinpoint it would be welcome

Relevant Code:

Unsure as this appears to be an internal routine. The relevant file appears to have last been edited by Grand Moff Harkin long ago and I’m not familiar enough with Firestore internals to make any guess as to possible modes of failure in a GC.

I may have missed them but I was similarly unable to find any open or closed issues in this repo that seemed relevant though I did try.