Attaching a USceneComponent to another USceneComponent crashes with Template Mismatch (works in Development)

AlfredBaudisch · February 16, 2023, 8:50pm

UE 5.1. Considering I have the following component UTileInteractionComponent : public USceneComponent and inside it I have another component:

class GAME_API UTileInteractionComponent : public USceneComponent
{
	GENERATED_BODY()

	UPROPERTY(VisibleAnywhere, BlueprintReadOnly, meta = (AllowPrivateAccess = "true"))
	UArrowComponent* ArrowComponent;
// ...
}

// -----------------------------
// Constructor...
// -----------------------------
UTileInteractionComponent::UTileInteractionComponent()
{
	PrimaryComponentTick.bCanEverTick = false;
	ArrowComponent = CreateDefaultSubobject<UArrowComponent>(TEXT("TraceTilesDirectionArrow"));
	ArrowComponent->AttachToComponent(this, FAttachmentTransformRules::KeepRelativeTransform);
	ArrowComponent->SetRelativeRotation(FRotator(-90.f, 0.f, 0.f));
}

A UTileInteractionComponent is instantiated into a Character:

ABuilderCharacter::ABuilderCharacter()
{
	TileInteractionComponent = CreateDefaultSubobject<UTileInteractionComponent>(TEXT("Tile Interaction Component"));	TileInteractionComponent->SetupAttachment(RootComponent);
}

It works in DevelopmentEditor, but it crashes in Shipping:

Error        LogOutputDevice           Ensure condition failed: false [File:D:\build\++UE5\Sync\Engine\Source\Runtime\Engine\Private\Components\SceneComponent.cpp] [Line: 2004] 
Error        LogOutputDevice           Template Mismatch during attachment. Attaching instanced component to template component. Parent 'Tile Interaction Component' (Owner 'Default__BP_ThirdPersonCharacter_C') Self 'TraceTilesDirectionArrow' (Owner 'BP_ThirdPersonCharacter_C_0').

The culprit is ArrowComponent->AttachToComponent(this, FAttachmentTransformRules::KeepRelativeTransform); inside UTileInteractionComponent.

How to have this component hierarchy Character → Component → InnerComponent, while being able to attach the inner component with FAttachmentTransformRules::KeepRelativeTransform?

Maybe related - seems that it’s still a bug with UE 5.1?