Use explicit Optional<T> type for OptionalCFrame.

BinaryFormat/Chunks/PROP.cs

@@ -414,9 +414,13 @@ namespace RobloxFiles.BinaryFormat.Chunks
 
                         for (int i = 0; i < instCount; i++)
                         {
-                            var cf = CFrames[i];
+                            CFrame cf = CFrames[i];
-                            bool active = reader.ReadBoolean();
+                            bool archivable = reader.ReadBoolean();
-                            CFrames[i] = active ? cf : null;
+
+                            if (!archivable)
+                                cf = null;
+                            
+                            CFrames[i] = new Optional<CFrame>(cf);
                         }
                     }
 
@@ -984,7 +988,14 @@ namespace RobloxFiles.BinaryFormat.Chunks
                                 return;
                             }
 
-                            writer.Write(true);
+                            if (prop.Value is Optional<CFrame> optional)
+                            {
+                                writer.Write(optional.HasValue);
+                                return;
+                            }
+
+                            var cf = prop.Value as CFrame;
+                            writer.Write(cf != null);
                         });
                     }
 

DataTypes/Optional.cs

@@ -0,0 +1,35 @@
+namespace RobloxFiles.DataTypes
+{
+    // Optional represents a value that can be explicitly
+    // marked as an optional variant to a specified type.
+    // In practice this is used for OptionalCFrame.
+
+    public struct Optional<T>
+    {
+        public T Value;
+        public bool HasValue => (Value != null);
+
+        public Optional(T value)
+        {
+            Value = value;
+        }
+
+        public override string ToString()
+        {
+            return Value?.ToString() ?? "null";
+        }
+
+        public static implicit operator T(Optional<T> optional)
+        {
+            if (optional.HasValue)
+                return optional.Value;
+
+            return default(T);
+        }
+
+        public static implicit operator Optional<T>(T value)
+        {
+            return new Optional<T>(value);
+        }
+    }
+}

Generated/Classes.cs

@@ -2408,7 +2408,7 @@ namespace RobloxFiles
         public Vector3 ModelMeshSize = new Vector3();
         public bool NeedsPivotMigration;
         public BasePart PrimaryPart;
-        public CFrame WorldPivotData;
+        public Optional<CFrame> WorldPivotData;
     }
 
     public class Actor : Model

Plugins/GenerateApiDump/PropertyPatches.lua

@@ -378,7 +378,7 @@ return
 			ModelMeshData = "SharedString";
 			ModelMeshSize = "Vector3";
 			NeedsPivotMigration = "bool";
-			WorldPivotData = "OptionalCFrame";
+			WorldPivotData = "Optional<CFrame>";
 		};
 	};
 

Plugins/GenerateApiDump/init.server.lua

@@ -641,10 +641,6 @@ local function generateClasses()
 							writeLine("[Obsolete]")
 						end
 						
-						if valueType == "OptionalCFrame" then
-							valueType = "CFrame"
-						end
-						
 						writeLine("public %s %s%s;", valueType, name, default)
 						
 						if propTags.Deprecated and j ~= #propNames then

RobloxFileFormat.csproj

@@ -89,6 +89,7 @@
     <Compile Include="BinaryFormat\IO\BinaryFileReader.cs" />
     <Compile Include="BinaryFormat\IO\BinaryFileWriter.cs" />
     <Compile Include="DataTypes\Color3uint8.cs" />
+    <Compile Include="DataTypes\Optional.cs" />
     <Compile Include="DataTypes\ProtectedString.cs" />
     <Compile Include="DataTypes\Content.cs" />
     <Compile Include="DataTypes\Region3int16.cs" />

Tree/Instance.cs

@@ -615,24 +615,35 @@ namespace RobloxFiles
                         case "String":
                         case "Double":
                         case "Int64":
+                        {
                             xmlToken = xmlToken.ToLowerInvariant();
                             break;
+                        }
                         case "Boolean":
+                        {
                             xmlToken = "bool";
                             break;
+                        }
                         case "Single":
+                        {
                             xmlToken = "float";
                             break;
+                        }
                         case "Int32":
+                        {
                             xmlToken = "int";
                             break;
+                        }
                         case "Rect":
+                        {
                             xmlToken = "Rect2D";
                             break;
+                        }
                         case "CFrame":
+                        {
                             xmlToken = "CoordinateFrame";
                             break;
-                        default: break;
+                        }
                     }
 
                     if (!props.ContainsKey(fieldName))

Tree/Property.cs

@@ -88,8 +88,9 @@ namespace RobloxFiles
             { typeof(SharedString), PropertyType.SharedString },
             { typeof(Vector3int16), PropertyType.Vector3int16 },
 
-            { typeof(ColorSequence),  PropertyType.ColorSequence  },
+            { typeof(ColorSequence),    PropertyType.ColorSequence  },
-            { typeof(NumberSequence), PropertyType.NumberSequence },
+            { typeof(NumberSequence),   PropertyType.NumberSequence },
+            { typeof(Optional<CFrame>), PropertyType.OptionalCFrame },
 
             { typeof(ProtectedString),    PropertyType.String             }, 
             { typeof(PhysicalProperties), PropertyType.PhysicalProperties },