As a user, in Package Manager UI:

1. Update or install a package and cancel during import (changed your mind, too long, etc...)
2. User is prompted with a dialog that prompts him to "force quit" or "cancel"
3. If the user presses "cancel" Unity will successfully quit but a stack trace will be generated (please see below).

There are two issues in this defect :

* The dialog offered to the user makes no sense from a UX perspective, meaning that if the user initiates the cancel having a "cancel" option and a "force quit" is unintuitive. My opinion, albeit unimportant, would be that the dialog, if one must exist, should be an action confirmation. For example: "Asset importing is still undergoing. Are you sure you want to cancel it? YES/NO"

* The application should not crash.

N.B.: Note that reimport and reimport all options on the "Asset" menu also provoke the same asset import BUT the cancel button is greyed out/disabled.

Stack trace:

----- Total AssetImport time: 8.734120s, AssetImport time: 8.569957s, Asset hashing: 0.016063s [9.8 MB, 609.105225 mb/s]

objc[11834]: Invalid or prematurely-freed autorelease pool 0x110832970.
Stacktrace:

Native stacktrace:

0 libsystem_kernel.dylib 0x00007fff7c48aed6 __abort_with_payload + 10
1 libsystem_kernel.dylib 0x00007fff7c485276 abort_with_payload_wrapper_internal + 0
2 libobjc.A.dylib 0x00007fff7b723962 _ZL12_objc_fatalvyyPKcP13__va_list_tag + 108
3 libobjc.A.dylib 0x00007fff7b723814 __objc_error + 0
4 libobjc.A.dylib 0x00007fff7b717183 _ZN12_GLOBAL__N_119AutoreleasePoolPage3popEPv + 1069
5 CoreFoundation 0x00007fff53fe0a56 _CFAutoreleasePoolPop + 22
6 Foundation 0x00007fff561058ad -[NSAutoreleasePool drain] + 144
7 Chromium Embedded Framework 0x000000010b150759 _CTFontManagerUnregisterFontForData + 24595817
8 Chromium Embedded Framework 0x0000000108b83f06 cef_zip_reader_create + 132998
9 Chromium Embedded Framework 0x0000000108b83fde cef_zip_reader_create + 133214
10 Chromium Embedded Framework 0x0000000108b833d7 cef_zip_reader_create + 130135
11 libsystem_c.dylib 0x00007fff7c3e7eed __cxa_finalize_ranges + 351
12 libsystem_c.dylib 0x00007fff7c3e81fe exit + 55
13 Unity 0x00000001026773ee _ZN14AssetInterface7RefreshEN13AssetDatabase18UpdateAssetOptionsE + 21374
14 Unity 0x000000010262d464 _ZN13AssetDatabase7RefreshENS_18UpdateAssetOptionsE + 180
15 Unity 0x0000000101a1f522 _ZN11Application9TickTimerEv + 6834
16 Unity 0x00000001006c18be -[EditorApplication TickTimer] + 142
17 Foundation 0x00007fff56188739 __NSFireTimer + 83
18 CoreFoundation 0x00007fff5402b064 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 20
19 CoreFoundation 0x00007fff5402acd7 __CFRunLoopDoTimer + 1095
20 CoreFoundation 0x00007fff5402a7da __CFRunLoopDoTimers + 346
21 CoreFoundation 0x00007fff54021dab __CFRunLoopRun + 2427
22 CoreFoundation 0x00007fff540211a3 CFRunLoopRunSpecific + 483
23 HIToolbox 0x00007fff53309d96 RunCurrentEventLoopInMode + 286
24 HIToolbox 0x00007fff53309b06 ReceiveNextEventCommon + 613
25 HIToolbox 0x00007fff53309884 _BlockUntilNextEventMatchingListInModeWithFilter + 64
26 AppKit 0x00007fff515bca73 _DPSNextEvent + 2085
27 AppKit 0x00007fff51d52e34 -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 3044
28 AppKit 0x00007fff515b1885 -[NSApplication run] + 764
29 AppKit 0x00007fff51580a72 NSApplicationMain + 804
30 Unity 0x00000001006dfbf7 _Z10EditorMainiPPKc + 839
31 Unity 0x00000001006e0079 main + 9
32 libdyld.dylib 0x00007fff7c33b015 start + 1
Debug info from gdb:

=================================================================
Got a SIGABRT while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries
used by your application.
=================================================================
[Unity Package Manager (Upm)]
Parent process [11834] was terminated