UK2Node_SpawnActorFromClass::PostPlacedNewNode() (engine source)
overrides the base class without calling Super::PostPlacedNewNode(),
and unconditionally dereferences GetScaleMethodPin() via
FindPinChecked -- but that pin is only created in
AllocateDefaultPins(), which FGraphNodeCreator::Finalize() always
calls *after* PostPlacedNewNode(). Result: a hard assertion failure
(EdGraphNode.h:586) that crashes the whole editor, every time,
regardless of any node_json parameters.
The real editor UI never hits this because it creates nodes through
a different path (node spawner templates) that doesn't have this
ordering problem. Our plugin uses the generic FGraphNodeCreator
pattern directly, so it does.
Fix: manually call SpawnNode->AllocateDefaultPins() before
Creator.Finalize(), so pins already exist by the time
PostPlacedNewNode() runs. Verified: SpawnActor node now creates
cleanly with all expected pins (Class, SpawnTransform, etc), editor
stayed stable and MCP connection alive afterward.
Rebuilt via Live Coding successfully this time (Ctrl+Alt+F11) --
the earlier UbaCli spawn failure appears to have been a one-off,
possibly from a conflicting concurrent Build.bat invocation.
ConnectBlueprintPins called SourcePin->MakeLinkTo(TargetPin) but never
notified either node of the new connection, so wildcard-typed pins
(MacroInstance nodes like ForEachLoop, and by extension any wildcard
array/map library call) never resolved their type -- compilation
failed with "type ... is undetermined" regardless of how many times
you recompiled. The real graph editor triggers this via the schema's
TryCreateConnection; MakeLinkTo alone doesn't.
Fix: call NodeConnectionListChanged() on both nodes after linking,
matching what the schema does. Verified against the exact ForEachLoop
scenario that failed twice before the fix -- the Array pin now
resolves to a concrete type and the graph compiles.
Rebuilt via full offline Build.bat (UnrealEditor target) rather than
Live Coding -- Live Coding's patch-link step hit a persistent
"Could not spawn process UbaCli.exe (Error 267)" in this environment,
unrelated to the code change itself (the .cpp compiled cleanly both
times; only the hot-patch link step failed).
