hack together nil instances

src/context.rs

@@ -47,12 +47,8 @@ impl Context{
 	}
 
 	pub fn find_services(&self)->Option<Services>{
-		Some(Services{
+		//nil instances isn't real, it doesn't exist in real roblox places
-			workspace:*self.dom.root().children().iter().find(|&&r|
+		None
-				self.dom.get_by_ref(r).is_some_and(|instance|instance.class=="Workspace")
-			)?,
-			game:self.dom.root_ref(),
-		})
 	}
 	pub fn convert_into_place(&mut self)->Services{
 		//snapshot root instances
@@ -74,6 +70,15 @@ impl Context{
 			game.properties.insert("Workspace".to_owned(),rbx_types::Variant::Ref(workspace));
 		}
 		self.dom.insert(game,InstanceBuilder::new("Lighting"));
+		// Special nonexistent class that holds instances parented to nil,
+		// which can still be referenced by scripts.
+		// Using a sentinel value as a ref because global variables are hard.
+		let nil=self.dom.insert(
+			game,InstanceBuilder::new("Nil")
+			.with_referent(
+				<Ref as std::str::FromStr>::from_str("ffffffffffffffffffffffffffffffff").unwrap()
+			)
+		);
 
 		//transfer original root instances into workspace
 		for instance in children{
@@ -83,6 +88,7 @@ impl Context{
 		Services{
 			game,
 			workspace,
+			nil,
 		}
 	}
 }
@@ -90,4 +96,5 @@ impl Context{
 pub struct Services{
 	pub game:Ref,
 	pub workspace:Ref,
+	pub nil:Ref,
 }

src/runner/instance.rs

@@ -16,9 +16,8 @@ pub fn set_globals(lua:&mlua::Lua,globals:&mlua::Table)->Result<(),mlua::Error>{
 	instance_table.raw_set("new",
 		lua.create_function(|lua,(class_name,parent):(mlua::String,Option<Instance>)|{
 			let class_name_str=&*class_name.to_str()?;
-			let parent=parent.ok_or(mlua::Error::runtime("Nil Parent not yet supported"))?;
+			let parent=parent.unwrap_or(Instance::nil());
 			dom_mut(lua,|dom|{
-				//TODO: Nil instances
 				Ok(Instance::new(dom.insert(parent.referent,InstanceBuilder::new(class_name_str))))
 			})
 		})?
@@ -91,6 +90,12 @@ impl Instance{
 	pub const fn new(referent:Ref)->Self{
 		Self{referent}
 	}
+	// Using a sentinel value as a ref for nil instances because global variables are hard.
+	pub fn nil()->Self{
+		Self{
+			referent:<Ref as std::str::FromStr>::from_str("ffffffffffffffffffffffffffffffff").unwrap()
+		}
+	}
 	pub fn get<'a>(&self,dom:&'a WeakDom)->mlua::Result<&'a rbx_dom_weak::Instance>{
 		dom.get_by_ref(self.referent).ok_or(mlua::Error::runtime("Instance missing"))
 	}
@@ -124,11 +129,12 @@ impl mlua::UserData for Instance{
 		fields.add_field_method_get("Parent",|lua,this|{
 			dom_mut(lua,|dom|{
 				let instance=this.get(dom)?;
+				//TODO: return nil when parent is Nil instances
 				Ok(Instance::new(instance.parent()))
 			})
 		});
 		fields.add_field_method_set("Parent",|lua,this,val:Option<Instance>|{
-			let parent=val.ok_or(mlua::Error::runtime("Nil Parent not yet supported"))?;
+			let parent=val.unwrap_or(Instance::nil());
 			dom_mut(lua,|dom|{
 				dom.transfer_within(this.referent,parent.referent);
 				Ok(())
@@ -218,7 +224,7 @@ impl mlua::UserData for Instance{
 		);
 		methods.add_method("Destroy",|lua,this,()|
 			dom_mut(lua,|dom|{
-				dom.destroy(this.referent);
+				dom.transfer_within(this.referent,Instance::nil().referent);
 				Ok(())
 			})
 		);
@@ -237,16 +243,27 @@ impl mlua::UserData for Instance{
 				let class=db.classes.get(instance.class.as_str()).ok_or(mlua::Error::runtime("Class missing"))?;
 				//Find existing property
 				match instance.properties.get(index_str)
+					.cloned()
 					//Find default value
-					.or_else(||db.find_default_property(class,index_str))
+					.or_else(||db.find_default_property(class,index_str).cloned())
+					//Find virtual property
+					.or_else(||{
+						SuperClassIter{
+							database:db,
+							descriptor:Some(class),
+						}
+						.find_map(|class|
+							find_virtual_property(&instance.properties,class,index_str)
+						)
+					})
 				{
-					Some(&rbx_types::Variant::Int32(val))=>return val.into_lua(lua),
+					Some(rbx_types::Variant::Int32(val))=>return val.into_lua(lua),
-					Some(&rbx_types::Variant::Int64(val))=>return val.into_lua(lua),
+					Some(rbx_types::Variant::Int64(val))=>return val.into_lua(lua),
-					Some(&rbx_types::Variant::Float32(val))=>return val.into_lua(lua),
+					Some(rbx_types::Variant::Float32(val))=>return val.into_lua(lua),
-					Some(&rbx_types::Variant::Float64(val))=>return val.into_lua(lua),
+					Some(rbx_types::Variant::Float64(val))=>return val.into_lua(lua),
-					Some(&rbx_types::Variant::Ref(val))=>return Instance::new(val).into_lua(lua),
+					Some(rbx_types::Variant::Ref(val))=>return Instance::new(val).into_lua(lua),
-					Some(&rbx_types::Variant::CFrame(cf))=>return Into::<super::cframe::CFrame>::into(cf).into_lua(lua),
+					Some(rbx_types::Variant::CFrame(cf))=>return Into::<super::cframe::CFrame>::into(cf).into_lua(lua),
-					Some(&rbx_types::Variant::Vector3(v))=>return Into::<super::vector3::Vector3>::into(v).into_lua(lua),
+					Some(rbx_types::Variant::Vector3(v))=>return Into::<super::vector3::Vector3>::into(v).into_lua(lua),
 					None=>(),
 					other=>return Err(mlua::Error::runtime(format!("Instance.__index Unsupported property type instance={} index={index_str} value={other:?}",instance.name))),
 				}
@@ -415,3 +432,51 @@ impl ClassMethods<'_>{
 		})
 	}
 }
+
+/// A virtual property pointer definition shorthand.
+type VirtualPropertyFunctionPointer=fn(&rbx_types::Variant)->Option<rbx_types::Variant>;
+const fn vpp(
+	property:&'static str,
+	pointer:VirtualPropertyFunctionPointer,
+)->VirtualProperty{
+	VirtualProperty{
+		property,
+		pointer,
+	}
+}
+struct VirtualProperty{
+	property:&'static str,// Source property name
+	pointer:VirtualPropertyFunctionPointer,
+}
+type VPD=phf::Map<&'static str,// Class name
+	phf::Map<&'static str,// Virtual property name
+		VirtualProperty
+	>
+>;
+static VIRTUAL_PROPERTY_DATABASE:VPD=phf::phf_map!{
+	"BasePart"=>phf::phf_map!{
+		"Position"=>vpp("CFrame",|c:&rbx_types::Variant|{
+			let c=match c{
+				rbx_types::Variant::CFrame(c)=>c,
+				_=>return None,//fail silently and ungracefully
+			};
+			Some(rbx_types::Variant::Vector3(c.position))
+		}),
+	},
+};
+
+fn find_virtual_property(
+	properties:&HashMap<String,rbx_types::Variant>,
+	class:&rbx_reflection::ClassDescriptor,
+	index:&str
+)->Option<rbx_types::Variant>{
+	//Find virtual property
+	let class_virtual_properties=VIRTUAL_PROPERTY_DATABASE.get(&class.name)?;
+	let virtual_property=class_virtual_properties.get(index)?;
+
+	//Get source property
+	let variant=properties.get(virtual_property.property)?;
+
+	//Transform Source property with provided function
+	(virtual_property.pointer)(variant)
+}