roblox_emulator: nil instances

lib/roblox_emulator/src/context.rs

@@ -7,21 +7,30 @@ fn static_ustr(s:&'static str)->rbx_dom_weak::Ustr{
 
 #[derive(Debug)]
 pub enum ServicesError{
-	Workspace,
+	WorkspaceNotFound,
 }
 
 pub struct Services{
 	pub(crate) game:Ref,
 	pub(crate) workspace:Ref,
+	pub(crate) nil:Ref,
 }
 
 impl Services{
 	fn get_or_create_services(dom:&mut WeakDom)->Result<Services,ServicesError>{
+		let game=dom.root_ref();
+		// error if workspace does not exist
+		let workspace=*dom.root().children().iter().find(|&&r|
+			dom.get_by_ref(r).is_some_and(|instance|instance.class=="Workspace")
+		).ok_or(ServicesError::WorkspaceNotFound)?;
+		// the root nil instance does not have a parent
+		let nil=dom.insert(Ref::none(),InstanceBuilder::new("Nil")
+			.with_referent(<Ref as std::str::FromStr>::from_str("ffffffffffffffffffffffffffffffff").unwrap())
+		);
 		Ok(Services{
-			workspace:*dom.root().children().iter().find(|&&r|
-				dom.get_by_ref(r).is_some_and(|instance|instance.class=="Workspace")
-			).ok_or(ServicesError::Workspace)?,
-			game:dom.root_ref(),
+			game,
+			workspace,
+			nil,
 		})
 	}
 }
@@ -34,7 +43,6 @@ pub struct Context{
 
 impl Context{
 	pub fn from_place(mut dom:WeakDom)->Result<Context,ServicesError>{
-		// TODO: create nil instances
 		let services=Services::get_or_create_services(&mut dom)?;
 		Ok(Self{dom,services})
 	}
@@ -77,6 +85,12 @@ impl Context{
 				.with_property("Terrain",terrain_bldr.referent())
 				.with_child(terrain_bldr)
 		);
+
+		//transfer original root instances into workspace
+		for instance in children{
+			dom.transfer_within(instance,workspace);
+		}
+
 		{
 			//Lowercase and upper case workspace property!
 			let game=dom.root_mut();
@@ -84,14 +98,15 @@ impl Context{
 			game.properties.insert(static_ustr("workspace"),rbx_types::Variant::Ref(workspace));
 			game.properties.insert(static_ustr("Workspace"),rbx_types::Variant::Ref(workspace));
 		}
+
 		dom.insert(game,InstanceBuilder::new("Lighting"));
 
-		//transfer original root instances into workspace
-		for instance in children{
-			dom.transfer_within(instance,workspace);
-		}
+		// the root nil instance does not have a parent
+		let nil=dom.insert(Ref::none(),InstanceBuilder::new("Nil")
+			.with_referent(<Ref as std::str::FromStr>::from_str("ffffffffffffffffffffffffffffffff").unwrap())
+		);
 
-		let services=Services{game,workspace};
+		let services=Services{game,workspace,nil};
 		Self{dom,services}
 	}
 }

lib/roblox_emulator/src/runner/instance/instance.rs

@@ -22,9 +22,8 @@ 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_else(||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))))
 			})
 		})?
@@ -99,6 +98,18 @@ impl Instance{
 	pub const fn new(referent:Ref)->Self{
 		Self{referent}
 	}
+	pub fn maybe_nil(referent:Ref)->Option<Self>{
+		match referent=="ffffffffffffffffffffffffffffffff".parse().unwrap(){
+			true=>None,
+			false=>Some(Self{referent})
+		}
+	}
+	// Using a sentinel value as a ref for nil instances because global variables are hard.
+	pub fn nil()->Self{
+		Self{
+			referent:"ffffffffffffffffffffffffffffffff".parse().unwrap()
+		}
+	}
 	pub fn get<'a>(&self,dom:&'a WeakDom)->mlua::Result<&'a rbx_dom_weak::Instance>{
 		dom.get_by_ref(self.referent).ok_or_else(||mlua::Error::runtime("Instance missing"))
 	}
@@ -113,11 +124,11 @@ impl mlua::UserData for Instance{
 		fields.add_field_method_get("Parent",|lua,this|{
 			dom_mut(lua,|dom|{
 				let instance=this.get(dom)?;
-				Ok(Instance::new(instance.parent()))
+				Ok(Instance::maybe_nil(instance.parent()))
 			})
 		});
 		fields.add_field_method_set("Parent",|lua,this,val:Option<Instance>|{
-			let parent=val.ok_or_else(||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(())
@@ -207,7 +218,7 @@ 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(())
 			})
 		);