Unreal Engine Issues and Bug Tracker (UE-50076)

Description

When attempting to diff a Blueprint that has been reparented when the previous parent no longer exists in the editor, a crash occurs. The crash is due to the editor attempting to reference the deleted asset for the previous revision in the diff. Even if this is not expected to work and the previous revision does not show the correct information, the editor should be able to handle this without a crash

Regression?: No
This also occurs in 4.16

Steps to Reproduce

Create a new project, place it into a Perforce depot, and enable Source Control in the editor
Create a Blueprint based off of actor (FirstBP)
Create a child Blueprint of FirstBP (SecondBP)
Create a child blueprint of SecondBP (ThirdBP)
Check all of these blueprints out, save, and then submit the changes.
Check out ThirdBP, reparent it to FirstBP and then save it
Delete SecondBP (there should be no warnings of it being referenced, if things have been done correctly)
In ThirdBP, select File > Diff > Depot
Result: The editor crashes as it is attempting to access SecondBP, which no longer exists, to show the previous version that you are diffing against.
Expected: The editor handles the exception and does not crash, bringing up the Diff window.

Callstack

[2017.09.20-14.06.51:848][441]LogWindows:Error: === Critical error: ===
[2017.09.20-14.06.51:848][441]LogWindows:Error: 
[2017.09.20-14.06.51:848][441]LogWindows:Error: Assertion failed: OldSelectedObjects.Num() == 1 [File:D:\Build\++UE4+Release-4.16+Compile\Sync\Engine\Source\Editor\Kismet\Private\DetailsDiff.cpp] [Line: 75] 
[2017.09.20-14.06.51:848][441]LogWindows:Error: 
[2017.09.20-14.06.51:848][441]LogWindows:Error: 
[2017.09.20-14.06.51:848][441]LogWindows:Error: 
[2017.09.20-14.06.51:848][441]LogWindows:Error: KERNELBASE.dll!0x00000000FCCCA06D
[2017.09.20-14.06.51:848][441]LogWindows:Error: UE4Editor-Core.dll!FOutputDeviceWindowsError::Serialize() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\private\windows\windowsplatformoutputdevices.cpp:120]
[2017.09.20-14.06.51:848][441]LogWindows:Error: UE4Editor-Core.dll!FOutputDevice::Logf__VA() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\private\misc\outputdevice.cpp:70]
[2017.09.20-14.06.51:848][441]LogWindows:Error: UE4Editor-Core.dll!FDebug::AssertFailed() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\private\misc\assertionmacros.cpp:349]
[2017.09.20-14.06.51:848][441]LogWindows:Error: UE4Editor-Kismet.dll!FDetailsDiff::DiffAgainst() [d:\build\++ue4+release-4.16+compile\sync\engine\source\editor\kismet\private\detailsdiff.cpp:77]
[2017.09.20-14.06.51:848][441]LogWindows:Error: UE4Editor-Kismet.dll!FCDODiffControl::FCDODiffControl() [d:\build\++ue4+release-4.16+compile\sync\engine\source\editor\kismet\private\sblueprintdiff.cpp:176]
[2017.09.20-14.06.51:848][441]LogWindows:Error: UE4Editor-Kismet.dll!SBlueprintDiff::GenerateDefaultsPanel() [d:\build\++ue4+release-4.16+compile\sync\engine\source\editor\kismet\private\sblueprintdiff.cpp:1361]
[2017.09.20-14.06.51:848][441]LogWindows:Error: UE4Editor-Kismet.dll!SBlueprintDiff::GenerateDifferencesList() [d:\build\++ue4+release-4.16+compile\sync\engine\source\editor\kismet\private\sblueprintdiff.cpp:1241]
[2017.09.20-14.06.51:848][441]LogWindows:Error: UE4Editor-Kismet.dll!SBlueprintDiff::Construct() [d:\build\++ue4+release-4.16+compile\sync\engine\source\editor\kismet\private\sblueprintdiff.cpp:736]
[2017.09.20-14.06.51:848][441]LogWindows:Error: UE4Editor-AssetTools.dll!TDecl<SBlueprintDiff,RequiredArgs::T0RequiredArgs>::operator<<=() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\slatecore\public\widgets\declarativesyntaxsupport.h:1087]
[2017.09.20-14.06.51:848][441]LogWindows:Error: UE4Editor-AssetTools.dll!FAssetTypeActions_Blueprint::PerformAssetDiff() [d:\build\++ue4+release-4.16+compile\sync\engine\source\developer\assettools\private\assettypeactions\assettypeactions_blueprint.cpp:257]
[2017.09.20-14.06.51:848][441]LogWindows:Error: UE4Editor-AssetTools.dll!FAssetTools::DiffAssets() [d:\build\++ue4+release-4.16+compile\sync\engine\source\developer\assettools\private\assettools.cpp:924]
[2017.09.20-14.06.51:848][441]LogWindows:Error: UE4Editor-Kismet.dll!OnDiffRevisionPicked() [d:\build\++ue4+release-4.16+compile\sync\engine\source\editor\kismet\private\sblueprinteditortoolbar.cpp:296]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Kismet.dll!TBaseStaticDelegateInstance<void __cdecl(FRevisionInfo const & __ptr64),TWeakObjectPtr<UBlueprint,FWeakObjectPtr> >::ExecuteIfSafe() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:1027]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Kismet.dll!TBaseFunctorDelegateInstance<void __cdecl(void),<lambda_c1d271c5b435248e424ac1f4c6a212b6> >::ExecuteIfSafe() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:1199]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Slate.dll!SMenuEntryBlock::OnClicked() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\slate\private\framework\multibox\smenuentryblock.cpp:1051]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Slate.dll!SMenuEntryBlock::OnMenuItemButtonClicked() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\slate\private\framework\multibox\smenuentryblock.cpp:1002]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Slate.dll!TMemberFunctionCaller<SMenuEntryBlock,FReply (__cdecl SMenuEntryBlock::*)(void) __ptr64>::operator()<>() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\public\delegates\delegateinstanceinterface.h:165]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Slate.dll!UE4Tuple_Private::TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter<TMemberFunctionCaller<SMenuEntryBlock,FReply (__cdecl SMenuEntryBlock::*)(void) __ptr64> >() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\public\templates\tuple.h:497]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Slate.dll!TBaseSPMethodDelegateInstance<0,SMenuEntryBlock,0,FReply __cdecl(void)>::Execute() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:327]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Slate.dll!TBaseDelegate<FReply>::Execute() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:537]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Slate.dll!SButton::OnMouseButtonUp() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\slate\private\widgets\input\sbutton.cpp:278]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Slate.dll!SMenuEntryButton::OnMouseButtonUp() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\slate\private\framework\multibox\smenuentryblock.cpp:399]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Slate.dll!<lambda_8d0e9a1da76abd0a756a3a9d775f5ed1>::operator()() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5049]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Slate.dll!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_8d0e9a1da76abd0a756a3a9d775f5ed1> >() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:239]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Slate.dll!FSlateApplication::RoutePointerUpEvent() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5038]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Slate.dll!FSlateApplication::ProcessMouseButtonUpEvent() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5515]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Slate.dll!FSlateApplication::OnMouseUp() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5495]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Core.dll!FWindowsApplication::ProcessDeferredMessage() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:1704]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Core.dll!FWindowsApplication::DeferMessage() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:2127]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Core.dll!FWindowsApplication::ProcessMessage() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:867]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Core.dll!FWindowsApplication::AppWndProc() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:714]
[2017.09.20-14.06.51:849][441]LogWindows:Error: USER32.dll!0x0000000076D99BBD
[2017.09.20-14.06.51:849][441]LogWindows:Error: USER32.dll!0x0000000076D998C2
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor-Core.dll!FWindowsPlatformMisc::PumpMessages() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\core\private\windows\windowsplatformmisc.cpp:1009]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor.exe!FEngineLoop::Tick() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\launch\private\launchengineloop.cpp:3058]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor.exe!GuardedMain() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\launch\private\launch.cpp:166]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor.exe!GuardedMainWrapper() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:134]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor.exe!WinMain() [d:\build\++ue4+release-4.16+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:210]
[2017.09.20-14.06.51:849][441]LogWindows:Error: UE4Editor.exe!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:253]
[2017.09.20-14.06.51:849][441]LogWindows:Error: kernel32.dll!0x0000000076C759CD
[2017.09.20-14.06.51:849][441]LogWindows:Error: ntdll.dll!0x0000000076EAA561
[2017.09.20-14.06.51:849][441]LogWindows:Error: ntdll.dll!0x0000000076EAA561
[2017.09.20-14.06.51:849][441]LogWindows:Error: 
[2017.09.20-14.06.51:866][441]LogExit: Executing StaticShutdownAfterError
[2017.09.20-14.06.51:875][441]LogWindows: FPlatformMisc::RequestExit(1)
[2017.09.20-14.06.51:875][441]Log file closed, 09/20/17 10:06:51

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Fixed

Component	UE - Gameplay - Blueprint Editor
Affects Versions	4.16, 4.17, 4.18
Target Fix	4.18

Fix Commit	3665090
Release Commit	3665090

Created	Sep 20, 2017
Resolved	Sep 26, 2017
Updated	Apr 27, 2018

View Jira Issue

UE-50076

Crash upon diffing Blueprint that was reparented when its previous parent has already been deleted

Crash upon diffing Blueprint that was reparented when its previous parent has already been deleted

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