Does 'Data Validation' not work for Blueprints?

Development Programming & Scripting Blueprint
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4

Edit:

4.23 has this now built-in. For older Engine Versions, please look at the following:

In the end we solved this by implementing IsDataValid for UBlueprintGeneratedClass and calling this method instead of directly calling the CDO of the generated class:

EDataValidationResult UBlueprintGeneratedClass::IsDataValid(TArray<FText>& ValidationErrors)
{
	EDataValidationResult Result = EDataValidationResult::NotValidated;
	if (SimpleConstructionScript)
	{
		for (const USCS_Node* Node : SimpleConstructionScript->GetAllNodes())
		{
			if (Node)
			{
				UActorComponent* ActorComponent = Node->GetActualComponentTemplate(this);
				if (ActorComponent)
				{
					const EDataValidationResult ValidationResult = ActorComponent->IsDataValid(ValidationErrors);
					// Only allow upward escalation from NotValidated -> Valid -> Invalid
					if (static_cast<uint8>(ValidationResult) < static_cast<uint8>(Result))
					{
						Result = ValidationResult;
					}
				}
			}
		}
		
	}
	const EDataValidationResult DefaultObjectResult = GetDefaultObject()->IsDataValid(ValidationErrors);
	// Only allow upward escalation from NotValidated -> Valid -> Invalid
	if (static_cast<uint8>(DefaultObjectResult) < static_cast<uint8>(Result))
	{
		Result = DefaultObjectResult;
	}
	return Result;
}

This is called by the associated blueprint:

EDataValidationResult UBlueprint::IsDataValid(TArray<FText>& ValidationErrors)
{
	return GeneratedClass ? GeneratedClass->IsDataValid(ValidationErrors) : EDataValidationResult::Invalid;
}

Now data validation is called for all Components, which are spawned by blueprints (these are handled in C++ using the SimpleConstructionScript). The only thing which is missing for those components are the attachment setups, which are set, when the blueprint is actually spawned.

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