Normally iCloud documents can be opened when off-line. However, with ios 13, if you have an active SMB server connection in the Files App, and then the network is disabled, calls to UIDocument initWithFileURL: block indefinitely while attempting to lookup file attributes.
Note calls to [UIDocument openWithCompletionHandler:], [NSURL getResourceValue:forKey:error:] and ExternalProviderPrepareValues.
Backtrace:
Thread 1 name: Dispatch queue: UIDocument File Access
Thread 1:
0 libsystem_kernel.dylib 0x00000001b493a784 mach_msg_trap + 8
1 libsystem_kernel.dylib 0x00000001b4939ba8 mach_msg + 76
2 libdispatch.dylib 0x00000001b482bf10 _dispatch_mach_send_and_wait_for_reply + 552
3 libdispatch.dylib 0x00000001b482c304 dispatch_mach_send_with_result_and_wait_for_reply + 56
4 libxpc.dylib 0x00000001b476b96c xpc_connection_send_message_with_reply_sync + 240
5 Foundation 0x00000001b507a398 __NSXPCCONNECTION_IS_WAITING_FOR_A_SYNCHRONOUS_REPLY__ + 16
6 Foundation 0x00000001b4e40834 -[NSXPCConnection _sendInvocation:orArguments:count:methodSignature:selector:withProxy:] + 2668
7 Foundation 0x00000001b4e6faa8 -[NSXPCConnection _sendSelector:withProxy:arg1:arg2:arg3:] + 148
8 Foundation 0x00000001b50814a4 _NSXPCDistantObjectSimpleMessageSend3 + 48
9 FileProvider 0x00000001c93b6ba4 -[FPDaemonConnection valuesForAttributes:forItemAtURL:error:] + 428
10 FileProviderOverride 0x000000010e5b9f14 0x10e5b8000 + 7956
11 CoreFoundation 0x00000001b4b7cf14 __invoking___ + 148
12 CoreFoundation 0x00000001b4a46098 -[NSInvocation invoke] + 400
13 CoreFoundation 0x00000001b4a46cc0 -[NSInvocation invokeWithTarget:] + 80
14 FileProvider 0x00000001c9374db8 -[FPFrameworkOverridesIterator callNextOverrides] + 468
15 FileProvider 0x00000001c9374f58 -[FPFrameworkOverridesIterator forwardInvocation:] + 96
16 CoreFoundation 0x00000001b4b7a7d8 ___forwarding___ + 680
17 CoreFoundation 0x00000001b4b7cd60 _CF_forwarding_prep_0 + 96
18 FileProvider 0x00000001c9394cc0 FPCFCopyAttributeValuesForItem + 300
19 CoreServicesInternal 0x00000001b5ebba98 CopyFromFileProvider+ 154264 (__CFURL const*, void const*, void const**, __CFError**) + 88
20 CoreServicesInternal 0x00000001b5ebbe40 ExternalProviderPrepareValues+ 155200 (__CFURL const*, __FileCache*, __CFString const* const*, void const**, long, void const*, __CFError**) + 376
21 CoreServicesInternal 0x00000001b5ea8cc0 prepareValuesForBitmap+ 76992 (__CFURL const*, __FileCache*, _FilePropertyBitmap*, __CFError**) + 376
22 CoreServicesInternal 0x00000001b5ea69d4 _FSURLCopyResourcePropertyForKeyInternal+ 68052 (__CFURL const*, __CFString const*, void*, void*, __CFError**, unsigned char) + 220
23 CoreFoundation 0x00000001b4b40768 CFURLCopyResourcePropertyForKey + 140
24 CoreFoundation 0x00000001b4a4d190 -[NSURL getResourceValue:forKey:error:] + 120
25 Foundation 0x00000001b4ec43a0 +[NSFileVersion unresolvedConflictVersionsOfItemAtURL:] + 124
26 UIKitCore 0x00000001b86fcc90 -[UIDocument _setOpen:] + 144
27 UIKitCore 0x00000001b86fbb8c __40-[UIDocument openWithCompletionHandler:]_block_invoke + 676
28 libdispatch.dylib 0x00000001b4814ec4 _dispatch_call_block_and_release + 32
29 libdispatch.dylib 0x00000001b481633c _dispatch_client_callout + 20
30 libdispatch.dylib 0x00000001b481c85c _dispatch_lane_serial_drain + 568
31 libdispatch.dylib 0x00000001b481d290 _dispatch_lane_invoke + 400
32 libdispatch.dylib 0x00000001b4826928 _dispatch_workloop_worker_thread + 584
33 libsystem_pthread.dylib 0x00000001b487d714 _pthread_wqthread + 276
34 libsystem_pthread.dylib 0x00000001b48839c8 start_wqthread + 8
Note the app doesn't use a Document Browser:
UISupportsDocumentBrowser = FALSE.
LSSupportsOpeningDocumentsInPlace = FALSE
Using a single NSUbiquitousContainer with NSUbiquitousContainerIsDocumentScopePublic = FALSE