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fix(blueprint): resolve UClass lookups so non-trivial parent_class & component_type work #26

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fix(blueprint): resolve UClass lookups so non-trivial parent_class & component_type work #26

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110 changes: 64 additions & 46 deletions ...CP/Plugins/UnrealMCP/Source/UnrealMCP/Private/Commands/EpicUnrealMCPBlueprintCommands.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -132,48 +132,55 @@ TSharedPtr<FJsonObject> FEpicUnrealMCPBlueprintCommands::HandleCreateBlueprint(c
// Default to Actor if no parent class specified
UClass* SelectedParentClass = AActor::StaticClass();

// Try to find the specified parent class
// Try to find the specified parent class.
//
// UE runtime class names do NOT carry the C++ A/U prefix — `/Script/Engine.Character`
// is the path, NOT `/Script/Engine.ACharacter`. Try the bare name first, then the
// A-prefixed name as a courtesy, then a global FindFirstObject fallback.
if (!ParentClass.IsEmpty())
{
FString ClassName = ParentClass;
if (!ClassName.StartsWith(TEXT("A")))
{
ClassName = TEXT("A") + ClassName;
}

// First try direct StaticClass lookup for common classes
UClass* FoundClass = nullptr;
if (ClassName == TEXT("APawn"))
const FString BareName = ParentClass.StartsWith(TEXT("A")) && ParentClass.Len() > 1 && FChar::IsUpper(ParentClass[1])
? ParentClass.RightChop(1) // strip leading 'A' if user passed "ACharacter"
: ParentClass;
const FString PrefixedName = TEXT("A") + BareName;

// Hardcoded fast-paths for the two we use most
if (BareName == TEXT("Pawn")) FoundClass = APawn::StaticClass();
else if (BareName == TEXT("Actor")) FoundClass = AActor::StaticClass();

// Path lookups: try /Script/Engine + /Script/Game with both bare and prefixed
const TArray<FString> Candidates = {
FString::Printf(TEXT("/Script/Engine.%s"), *BareName),
FString::Printf(TEXT("/Script/Engine.%s"), *PrefixedName),
FString::Printf(TEXT("/Script/Game.%s"), *BareName),
FString::Printf(TEXT("/Script/Game.%s"), *PrefixedName),
};
for (const FString& Path : Candidates)
{
FoundClass = APawn::StaticClass();
if (FoundClass) break;
FoundClass = LoadClass<AActor>(nullptr, *Path);
}
else if (ClassName == TEXT("AActor"))
{
FoundClass = AActor::StaticClass();
}
else

// Last resort: scan all loaded classes by name (catches plugin/module classes)
if (!FoundClass)
{
// Try loading the class using LoadClass which is more reliable than FindObject
const FString ClassPath = FString::Printf(TEXT("/Script/Engine.%s"), *ClassName);
FoundClass = LoadClass<AActor>(nullptr, *ClassPath);

if (!FoundClass)
FoundClass = FindFirstObjectSafe<UClass>(*BareName, EFindFirstObjectOptions::None);
if (FoundClass && !FoundClass->IsChildOf(AActor::StaticClass()))
{
// Try alternate paths if not found
const FString GameClassPath = FString::Printf(TEXT("/Script/Game.%s"), *ClassName);
FoundClass = LoadClass<AActor>(nullptr, *GameClassPath);
FoundClass = nullptr; // must be Actor-derived for a Blueprint parent
}
}

if (FoundClass)
{
SelectedParentClass = FoundClass;
UE_LOG(LogTemp, Log, TEXT("Successfully set parent class to '%s'"), *ClassName);
UE_LOG(LogTemp, Log, TEXT("Set parent class to '%s' (resolved from input '%s')"), *FoundClass->GetName(), *ParentClass);
}
else
{
UE_LOG(LogTemp, Warning, TEXT("Could not find specified parent class '%s' at paths: /Script/Engine.%s or /Script/Game.%s, defaulting to AActor"),
*ClassName, *ClassName, *ClassName);
UE_LOG(LogTemp, Warning, TEXT("Could not find parent class '%s' (tried bare/prefixed in /Script/Engine, /Script/Game, and global scan), defaulting to AActor"),
*ParentClass);
}
}

Expand Down Expand Up @@ -228,31 +235,42 @@ TSharedPtr<FJsonObject> FEpicUnrealMCPBlueprintCommands::HandleAddComponentToBlu
return FEpicUnrealMCPCommonUtils::CreateErrorResponse(FString::Printf(TEXT("Blueprint not found: %s"), *BlueprintName));
}

// Create the component - dynamically find the component class by name
// Create the component - dynamically find the component class by name.
//
// FindObject<UClass>(nullptr, X) only resolves bare names if they live in the
// transient package. Engine components live in /Script/Engine.*, so a bare name
// search misses them. Use FindFirstObjectSafe (global, name-only) plus path
// candidates to handle every common form: "StaticMeshComponent",
// "StaticMesh", "UStaticMeshComponent", or "/Script/Engine.StaticMeshComponent".
UClass* ComponentClass = nullptr;

// Try to find the class with exact name first
ComponentClass = FindObject<UClass>(nullptr, *ComponentType);

// If not found, try with "Component" suffix
if (!ComponentClass && !ComponentType.EndsWith(TEXT("Component")))
{
FString ComponentTypeWithSuffix = ComponentType + TEXT("Component");
ComponentClass = FindObject<UClass>(nullptr, *ComponentTypeWithSuffix);
}

// If still not found, try with "U" prefix
if (!ComponentClass && !ComponentType.StartsWith(TEXT("U")))
auto TryResolve = [&](const FString& Name) -> UClass*
{
FString ComponentTypeWithPrefix = TEXT("U") + ComponentType;
ComponentClass = FindObject<UClass>(nullptr, *ComponentTypeWithPrefix);

// Try with both prefix and suffix
if (!ComponentClass && !ComponentType.EndsWith(TEXT("Component")))
if (Name.IsEmpty()) return nullptr;
// Full path? Let the engine resolve it.
if (Name.Contains(TEXT(".")))
{
FString ComponentTypeWithBoth = TEXT("U") + ComponentType + TEXT("Component");
ComponentClass = FindObject<UClass>(nullptr, *ComponentTypeWithBoth);
if (UClass* C = LoadObject<UClass>(nullptr, *Name)) return C;
}
// Global name scan across all loaded classes.
if (UClass* C = FindFirstObjectSafe<UClass>(*Name, EFindFirstObjectOptions::None)) return C;
// Path lookup in /Script/Engine — handles cold-loaded engine modules.
if (UClass* C = LoadObject<UClass>(nullptr, *FString::Printf(TEXT("/Script/Engine.%s"), *Name))) return C;
return nullptr;
};

// Strip leading 'U' prefix if the caller wrote it C++-style.
FString BareType = ComponentType.StartsWith(TEXT("U")) && ComponentType.Len() > 1 && FChar::IsUpper(ComponentType[1])
? ComponentType.RightChop(1)
: ComponentType;

// Try in priority order: exact (preserves full paths), bare-stripped,
// then with "Component" suffix.
ComponentClass = TryResolve(ComponentType);
if (!ComponentClass) ComponentClass = TryResolve(BareType);
if (!ComponentClass && !BareType.EndsWith(TEXT("Component")))
{
ComponentClass = TryResolve(BareType + TEXT("Component"));
}

// Verify that the class is a valid component type
Expand Down
110 changes: 64 additions & 46 deletions UnrealMCP/Source/UnrealMCP/Private/Commands/EpicUnrealMCPBlueprintCommands.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -132,48 +132,55 @@ TSharedPtr<FJsonObject> FEpicUnrealMCPBlueprintCommands::HandleCreateBlueprint(c
// Default to Actor if no parent class specified
UClass* SelectedParentClass = AActor::StaticClass();

// Try to find the specified parent class
// Try to find the specified parent class.
//
// UE runtime class names do NOT carry the C++ A/U prefix — `/Script/Engine.Character`
// is the path, NOT `/Script/Engine.ACharacter`. Try the bare name first, then the
// A-prefixed name as a courtesy, then a global FindFirstObject fallback.
if (!ParentClass.IsEmpty())
{
FString ClassName = ParentClass;
if (!ClassName.StartsWith(TEXT("A")))
{
ClassName = TEXT("A") + ClassName;
}

// First try direct StaticClass lookup for common classes
UClass* FoundClass = nullptr;
if (ClassName == TEXT("APawn"))
const FString BareName = ParentClass.StartsWith(TEXT("A")) && ParentClass.Len() > 1 && FChar::IsUpper(ParentClass[1])
? ParentClass.RightChop(1) // strip leading 'A' if user passed "ACharacter"
: ParentClass;
const FString PrefixedName = TEXT("A") + BareName;

// Hardcoded fast-paths for the two we use most
if (BareName == TEXT("Pawn")) FoundClass = APawn::StaticClass();
else if (BareName == TEXT("Actor")) FoundClass = AActor::StaticClass();

// Path lookups: try /Script/Engine + /Script/Game with both bare and prefixed
const TArray<FString> Candidates = {
FString::Printf(TEXT("/Script/Engine.%s"), *BareName),
FString::Printf(TEXT("/Script/Engine.%s"), *PrefixedName),
FString::Printf(TEXT("/Script/Game.%s"), *BareName),
FString::Printf(TEXT("/Script/Game.%s"), *PrefixedName),
};
for (const FString& Path : Candidates)
{
FoundClass = APawn::StaticClass();
if (FoundClass) break;
FoundClass = LoadClass<AActor>(nullptr, *Path);
}
else if (ClassName == TEXT("AActor"))
{
FoundClass = AActor::StaticClass();
}
else

// Last resort: scan all loaded classes by name (catches plugin/module classes)
if (!FoundClass)
{
// Try loading the class using LoadClass which is more reliable than FindObject
const FString ClassPath = FString::Printf(TEXT("/Script/Engine.%s"), *ClassName);
FoundClass = LoadClass<AActor>(nullptr, *ClassPath);

if (!FoundClass)
FoundClass = FindFirstObjectSafe<UClass>(*BareName, EFindFirstObjectOptions::None);
if (FoundClass && !FoundClass->IsChildOf(AActor::StaticClass()))
{
// Try alternate paths if not found
const FString GameClassPath = FString::Printf(TEXT("/Script/Game.%s"), *ClassName);
FoundClass = LoadClass<AActor>(nullptr, *GameClassPath);
FoundClass = nullptr; // must be Actor-derived for a Blueprint parent
}
}

if (FoundClass)
{
SelectedParentClass = FoundClass;
UE_LOG(LogTemp, Log, TEXT("Successfully set parent class to '%s'"), *ClassName);
UE_LOG(LogTemp, Log, TEXT("Set parent class to '%s' (resolved from input '%s')"), *FoundClass->GetName(), *ParentClass);
}
else
{
UE_LOG(LogTemp, Warning, TEXT("Could not find specified parent class '%s' at paths: /Script/Engine.%s or /Script/Game.%s, defaulting to AActor"),
*ClassName, *ClassName, *ClassName);
UE_LOG(LogTemp, Warning, TEXT("Could not find parent class '%s' (tried bare/prefixed in /Script/Engine, /Script/Game, and global scan), defaulting to AActor"),
*ParentClass);
}
}

Expand Down Expand Up @@ -228,31 +235,42 @@ TSharedPtr<FJsonObject> FEpicUnrealMCPBlueprintCommands::HandleAddComponentToBlu
return FEpicUnrealMCPCommonUtils::CreateErrorResponse(FString::Printf(TEXT("Blueprint not found: %s"), *BlueprintName));
}

// Create the component - dynamically find the component class by name
// Create the component - dynamically find the component class by name.
//
// FindObject<UClass>(nullptr, X) only resolves bare names if they live in the
// transient package. Engine components live in /Script/Engine.*, so a bare name
// search misses them. Use FindFirstObjectSafe (global, name-only) plus path
// candidates to handle every common form: "StaticMeshComponent",
// "StaticMesh", "UStaticMeshComponent", or "/Script/Engine.StaticMeshComponent".
UClass* ComponentClass = nullptr;

// Try to find the class with exact name first
ComponentClass = FindObject<UClass>(nullptr, *ComponentType);

// If not found, try with "Component" suffix
if (!ComponentClass && !ComponentType.EndsWith(TEXT("Component")))
{
FString ComponentTypeWithSuffix = ComponentType + TEXT("Component");
ComponentClass = FindObject<UClass>(nullptr, *ComponentTypeWithSuffix);
}

// If still not found, try with "U" prefix
if (!ComponentClass && !ComponentType.StartsWith(TEXT("U")))
auto TryResolve = [&](const FString& Name) -> UClass*
{
FString ComponentTypeWithPrefix = TEXT("U") + ComponentType;
ComponentClass = FindObject<UClass>(nullptr, *ComponentTypeWithPrefix);

// Try with both prefix and suffix
if (!ComponentClass && !ComponentType.EndsWith(TEXT("Component")))
if (Name.IsEmpty()) return nullptr;
// Full path? Let the engine resolve it.
if (Name.Contains(TEXT(".")))
{
FString ComponentTypeWithBoth = TEXT("U") + ComponentType + TEXT("Component");
ComponentClass = FindObject<UClass>(nullptr, *ComponentTypeWithBoth);
if (UClass* C = LoadObject<UClass>(nullptr, *Name)) return C;
}
// Global name scan across all loaded classes.
if (UClass* C = FindFirstObjectSafe<UClass>(*Name, EFindFirstObjectOptions::None)) return C;
// Path lookup in /Script/Engine — handles cold-loaded engine modules.
if (UClass* C = LoadObject<UClass>(nullptr, *FString::Printf(TEXT("/Script/Engine.%s"), *Name))) return C;
return nullptr;
};

// Strip leading 'U' prefix if the caller wrote it C++-style.
FString BareType = ComponentType.StartsWith(TEXT("U")) && ComponentType.Len() > 1 && FChar::IsUpper(ComponentType[1])
? ComponentType.RightChop(1)
: ComponentType;

// Try in priority order: exact (preserves full paths), bare-stripped,
// then with "Component" suffix.
ComponentClass = TryResolve(ComponentType);
if (!ComponentClass) ComponentClass = TryResolve(BareType);
if (!ComponentClass && !BareType.EndsWith(TEXT("Component")))
{
ComponentClass = TryResolve(BareType + TEXT("Component"));
}

// Verify that the class is a valid component type
Expand Down