Make component states dependant on the player getting them (#1569)

Co-authored-by: cyclowns <cyclowns@protonmail.ch>

Robust.Client.Injectors/MathParsing.cs

@@ -0,0 +1,37 @@
+using System.Linq;
+using Pidgin;
+using static Pidgin.Parser;
+
+
+namespace Robust.Build.Tasks
+{
+    public static class MathParsing
+    {
+        public static Parser<char, float> Single { get; } = Real.Select(c => (float) c);
+
+        public static Parser<char, float> Single1 { get; }
+            = Single.Between(SkipWhitespaces);
+
+        public static Parser<char, (float, float)> Single2 { get; }
+            = Single.Before(SkipWhitespaces).Repeat(2).Select(e =>
+            {
+                var arr = e.ToArray();
+                return (arr[0], arr[1]);
+            });
+
+        public static Parser<char, (float, float, float, float)> Single4 { get; }
+            = Single.Before(SkipWhitespaces).Repeat(4).Select(e =>
+            {
+                var arr = e.ToArray();
+                return (arr[0], arr[1], arr[2], arr[3]);
+            });
+
+        public static Parser<char, float[]> Thickness { get; }
+            = SkipWhitespaces.Then(
+                OneOf(
+                    Try(Single1.Select(c => new[] {c})),
+                    Try(Single2.Select(c => new[] {c.Item1, c.Item2})),
+                    Try(Single4.Select(c => new[] {c.Item1, c.Item2, c.Item3, c.Item4}))
+                ));
+    }
+}

Robust.Client.Injectors/RXamlVecLikeConstAstNode.cs

@@ -0,0 +1,93 @@
+using System;
+using System.Linq;
+using System.Reflection.Emit;
+using XamlX.Ast;
+using XamlX.Emit;
+using XamlX.IL;
+using XamlX.TypeSystem;
+
+namespace Robust.Build.Tasks
+{
+    public abstract class RXamlVecLikeConstAstNode<T>
+        : XamlAstNode, IXamlAstValueNode, IXamlAstILEmitableNode
+        where T : unmanaged
+    {
+        private readonly IXamlConstructor _constructor;
+        protected readonly T[] Values;
+
+        public RXamlVecLikeConstAstNode(
+            IXamlLineInfo lineInfo,
+            IXamlType type, IXamlConstructor constructor,
+            IXamlType componentType, T[] values)
+            : base(lineInfo)
+        {
+            _constructor = constructor;
+            Values = values;
+
+            var @params = constructor.Parameters;
+
+            if (@params.Count != values.Length)
+                throw new ArgumentException("Invalid amount of parameters");
+
+            if (@params.Any(c => c != componentType))
+                throw new ArgumentException("Invalid constructor: not all parameters match component type");
+
+            Type = new XamlAstClrTypeReference(lineInfo, type, false);
+        }
+
+        public IXamlAstTypeReference Type { get; }
+
+        public virtual XamlILNodeEmitResult Emit(
+            XamlEmitContext<IXamlILEmitter, XamlILNodeEmitResult> context,
+            IXamlILEmitter codeGen)
+        {
+            codeGen.Newobj(_constructor);
+
+            return XamlILNodeEmitResult.Type(0, Type.GetClrType());
+        }
+    }
+
+    public sealed class RXamlSingleVecLikeConstAstNode : RXamlVecLikeConstAstNode<float>
+    {
+        public RXamlSingleVecLikeConstAstNode(
+            IXamlLineInfo lineInfo,
+            IXamlType type, IXamlConstructor constructor,
+            IXamlType componentType, float[] values)
+            : base(lineInfo, type, constructor, componentType, values)
+        {
+        }
+
+        public override XamlILNodeEmitResult Emit(XamlEmitContext<IXamlILEmitter, XamlILNodeEmitResult> context,
+            IXamlILEmitter codeGen)
+        {
+            foreach (var value in Values)
+            {
+                codeGen.Emit(OpCodes.Ldc_R4, value);
+            }
+
+            return base.Emit(context, codeGen);
+        }
+    }
+
+    public sealed class RXamlInt32VecLikeConstAstNode : RXamlVecLikeConstAstNode<int>
+    {
+        public RXamlInt32VecLikeConstAstNode(
+            IXamlLineInfo lineInfo,
+            IXamlType type, IXamlConstructor constructor,
+            IXamlType componentType, int[] values)
+            : base(lineInfo, type, constructor, componentType, values)
+        {
+        }
+
+        public override XamlILNodeEmitResult Emit(XamlEmitContext<IXamlILEmitter, XamlILNodeEmitResult> context,
+            IXamlILEmitter codeGen)
+        {
+            foreach (var value in Values)
+            {
+                codeGen.Emit(OpCodes.Ldc_I4, value);
+            }
+
+            return base.Emit(context, codeGen);
+        }
+    }
+}

Robust.Client.Injectors/RXamlWellKnownTypes.cs

@@ -0,0 +1,47 @@
+using System.Linq;
+using XamlX.Transform;
+using XamlX.TypeSystem;
+
+namespace Robust.Build.Tasks
+{
+    class RXamlWellKnownTypes
+    {
+        public XamlTypeWellKnownTypes XamlIlTypes { get; }
+        public IXamlType Single { get; }
+        public IXamlType Int32 { get; }
+        public IXamlType Vector2 { get; }
+        public IXamlConstructor Vector2ConstructorFull { get; }
+        public IXamlType Vector2i { get; }
+        public IXamlConstructor Vector2iConstructorFull { get; }
+
+        public RXamlWellKnownTypes(TransformerConfiguration cfg)
+        {
+            var ts = cfg.TypeSystem;
+            XamlIlTypes = cfg.WellKnownTypes;
+            Single = ts.GetType("System.Single");
+            Int32 = ts.GetType("System.Int32");
+
+            (Vector2, Vector2ConstructorFull) = GetNumericTypeInfo("Robust.Shared.Maths.Vector2", Single, 2);
+            (Vector2i, Vector2iConstructorFull) = GetNumericTypeInfo("Robust.Shared.Maths.Vector2i", Int32, 2);
+
+            (IXamlType, IXamlConstructor) GetNumericTypeInfo(string name, IXamlType componentType, int componentCount)
+            {
+                var type = cfg.TypeSystem.GetType(name);
+                var ctor = type.GetConstructor(Enumerable.Repeat(componentType, componentCount).ToList());
+
+                return (type, ctor);
+            }
+        }
+    }
+
+    static class RXamlWellKnownTypesExtensions
+    {
+        public static RXamlWellKnownTypes GetRobustTypes(this AstTransformationContext ctx)
+        {
+            if (ctx.TryGetItem<RXamlWellKnownTypes>(out var rv))
+                return rv;
+            ctx.SetItem(rv = new RXamlWellKnownTypes(ctx.Configuration));
+            return rv;
+        }
+    }
+}

Robust.Client.Injectors/Robust.Client.Injectors.csproj

@@ -8,6 +8,7 @@
     <ItemGroup>
       <PackageReference Include="Microsoft.Build.Framework" Version="16.8.0" />
       <PackageReference Include="Mono.Cecil" Version="0.11.3" />
+      <PackageReference Include="Pidgin" Version="2.5.0" />
     </ItemGroup>
 
     <ItemGroup>

Robust.Client.Injectors/XamlCompiler.cs

@@ -6,6 +6,7 @@ using Microsoft.Build.Framework;
 using Mono.Cecil;
 using Mono.Cecil.Cil;
 using Mono.Cecil.Rocks;
+using Pidgin;
 using XamlX;
 using XamlX.Ast;
 using XamlX.Emit;
@@ -70,7 +71,7 @@ namespace Robust.Build.Tasks
             {
                 XmlnsAttributes =
                 {
-                    typeSystem.GetType("Robust.Client.UserInterface.XAML.XmlnsDefinitionAttribute"),
+                    typeSystem.GetType("Avalonia.Metadata.XmlnsDefinitionAttribute"),
 
                 },
                 ContentAttributes =
@@ -98,7 +99,7 @@ namespace Robust.Build.Tasks
                 typeSystem,
                 typeSystem.TargetAssembly,
                 xamlLanguage,
-                XamlXmlnsMappings.Resolve(typeSystem, xamlLanguage));
+                XamlXmlnsMappings.Resolve(typeSystem, xamlLanguage), CustomValueConverter);
 
             var contextDef = new TypeDefinition("CompiledRobustXaml", "XamlIlContext",
                 TypeAttributes.Class, asm.MainModule.TypeSystem.Object);
@@ -297,6 +298,41 @@ namespace Robust.Build.Tasks
             return true;
         }
 
+        private static bool CustomValueConverter(
+            AstTransformationContext context,
+            IXamlAstValueNode node,
+            IXamlType type,
+            out IXamlAstValueNode result)
+        {
+            if (!(node is XamlAstTextNode textNode))
+            {
+                result = null;
+                return false;
+            }
+
+            var text = textNode.Text;
+            var types = context.GetRobustTypes();
+
+            if (type.Equals(types.Vector2))
+            {
+                var foo = MathParsing.Single2.Parse(text);
+
+                if (!foo.Success)
+                    throw new XamlLoadException($"Unable to parse \"{text}\" as a Vector2", node);
+
+                var (x, y) = foo.Value;
+
+                result = new RXamlSingleVecLikeConstAstNode(
+                    node,
+                    types.Vector2, types.Vector2ConstructorFull,
+                    types.Single, new[] {x, y});
+                return true;
+            }
+
+            result = null;
+            return false;
+        }
+
         public const string ContextNameScopeFieldName = "RobustNameScope";
 
         private static void EmitNameScopeField(XamlLanguageTypeMappings xamlLanguage, CecilTypeSystem typeSystem, IXamlTypeBuilder<IXamlILEmitter> typeBuilder, IXamlILEmitter constructor)

Robust.Client.NameGenerator/XamlUiPartialClassGenerator.cs

@@ -24,6 +24,7 @@ namespace Robust.Client.NameGenerator
     {
         private const string AttributeName = "Robust.Client.AutoGenerated.GenerateTypedNameReferencesAttribute";
         private const string AttributeFile = "GenerateTypedNameReferencesAttribute";
+
         private const string AttributeCode = @"// <auto-generated />
 using System;
 namespace Robust.Client.AutoGenerated
@@ -54,8 +55,8 @@ namespace Robust.Client.AutoGenerated
                 {
                     var clrtype = objectNode.Type.GetClrType();
                     var isControl = IsControl(clrtype);
-                        //clrtype.Interfaces.Any(i =>
-                        //i.IsInterface && i.FullName == "Robust.Client.UserInterface.IControl");
+                    //clrtype.Interfaces.Any(i =>
+                    //i.IsInterface && i.FullName == "Robust.Client.UserInterface.IControl");
 
                     if (!isControl)
                         return node;
@@ -80,9 +81,13 @@ namespace Robust.Client.AutoGenerated
                 return node;
             }
 
-            public void Push(IXamlAstNode node) { }
+            public void Push(IXamlAstNode node)
+            {
+            }
 
-            public void Pop() { }
+            public void Pop()
+            {
+            }
         }
 
         private static string GenerateSourceCode(
@@ -97,16 +102,20 @@ namespace Robust.Client.AutoGenerated
             var compiler =
                 new XamlILCompiler(
                     new TransformerConfiguration(typeSystem, typeSystem.Assemblies[0],
-                        new XamlLanguageTypeMappings(typeSystem)),
+                        new XamlLanguageTypeMappings(typeSystem)
+                        {
+                            XmlnsAttributes = {typeSystem.GetType("Avalonia.Metadata.XmlnsDefinitionAttribute")}
+                        }),
                     new XamlLanguageEmitMappings<IXamlILEmitter, XamlILNodeEmitResult>(), false);
             compiler.Transformers.Add(new TypeReferenceResolver());
             compiler.Transform(parsed);
             var initialRoot = (XamlAstObjectNode) parsed.Root;
             var names = NameVisitor.GetNames(initialRoot);
+            var fieldAccess = classSymbol.IsSealed ? "private" : "protected";
             //var names = NameVisitor.GetNames((XamlAstObjectNode)XDocumentXamlParser.Parse(xamlFile).Root);
             var namedControls = names.Select(info => "        " +
-                                $"protected global::{info.type} {info.name} => " +
-                                $"this.FindControl<global::{info.type}>(\"{info.name}\");");
+                                                     $"{fieldAccess} global::{info.type} {info.name} => " +
+                                                     $"this.FindControl<global::{info.type}>(\"{info.name}\");");
             return $@"// <auto-generated />
 using Robust.Client.UserInterface;
 using Robust.Client.UserInterface.Controls;
@@ -124,7 +133,7 @@ namespace {nameSpace}
         public void Execute(GeneratorExecutionContext context)
         {
             var comp = (CSharpCompilation) context.Compilation;
-            if(comp.GetTypeByMetadataName(AttributeName) == null)
+            if (comp.GetTypeByMetadataName(AttributeName) == null)
                 context.AddSource(AttributeFile, SourceText.From(AttributeCode, Encoding.UTF8));
             if (!(context.SyntaxReceiver is NameReferenceSyntaxReceiver receiver))
             {
@@ -132,7 +141,7 @@ namespace {nameSpace}
             }
 
             var symbols = UnpackAnnotatedTypes(context, comp, receiver);
-            if(symbols == null)
+            if (symbols == null)
                 return;
 
             foreach (var typeSymbol in symbols)
@@ -168,7 +177,8 @@ namespace {nameSpace}
                                 "Usage",
                                 DiagnosticSeverity.Error,
                                 true),
-                            Location.Create(xamlFileName, new TextSpan(0,0), new LinePositionSpan(new LinePosition(0,0),new LinePosition(0,0)))));
+                            Location.Create(xamlFileName, new TextSpan(0, 0),
+                                new LinePositionSpan(new LinePosition(0, 0), new LinePosition(0, 0)))));
                     continue;
                 }
 
@@ -194,7 +204,8 @@ namespace {nameSpace}
             }
         }
 
-        private IReadOnlyList<INamedTypeSymbol> UnpackAnnotatedTypes(in GeneratorExecutionContext context, CSharpCompilation comp, NameReferenceSyntaxReceiver receiver)
+        private IReadOnlyList<INamedTypeSymbol> UnpackAnnotatedTypes(in GeneratorExecutionContext context,
+            CSharpCompilation comp, NameReferenceSyntaxReceiver receiver)
         {
             var options = (CSharpParseOptions) comp.SyntaxTrees[0].Options;
             var compilation =

Robust.Client/GameObjects/EntitySystems/InputSystem.cs

@@ -40,7 +40,7 @@ namespace Robust.Client.GameObjects
         /// <param name="message">Arguments for this event.</param>
         /// <param name="replay">if true, current cmd state will not be checked or updated - use this for "replaying" an
         /// old input that was saved or buffered until further processing could be done</param>
-        public bool HandleInputCommand(ICommonSession session, BoundKeyFunction function, FullInputCmdMessage message, bool replay = false)
+        public bool HandleInputCommand(ICommonSession? session, BoundKeyFunction function, FullInputCmdMessage message, bool replay = false)
         {
             #if DEBUG
 

Robust.Client/GameStates/ClientGameStateManager.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using Robust.Client.GameObjects;
 using Robust.Client.Input;
 using Robust.Shared.GameStates;
@@ -352,7 +353,10 @@ namespace Robust.Client.GameStates
 
                 foreach (var component in _componentManager.GetNetComponents(createdEntity))
                 {
-                    var state = component.GetComponentState();
+                    Debug.Assert(_players.LocalPlayer != null, "_players.LocalPlayer != null");
+
+                    var player = _players.LocalPlayer.Session;
+                    var state = component.GetComponentState(player);
 
                     if (state.GetType() == typeof(ComponentState))
                     {

Robust.Client/Player/IPlayerManager.cs

@@ -12,6 +12,11 @@ namespace Robust.Client.Player
 
         LocalPlayer? LocalPlayer { get; }
 
+        /// <summary>
+        /// Invoked after LocalPlayer is changed
+        /// </summary>
+        event Action<LocalPlayerChangedEventArgs>? LocalPlayerChanged;
+
         int PlayerCount { get; }
         int MaxPlayers { get; }
         event EventHandler PlayerListUpdated;
@@ -23,4 +28,15 @@ namespace Robust.Client.Player
 
         void ApplyPlayerStates(IEnumerable<PlayerState>? list);
     }
+
+    public class LocalPlayerChangedEventArgs : EventArgs
+    {
+        public readonly LocalPlayer? OldPlayer;
+        public readonly LocalPlayer? NewPlayer;
+        public LocalPlayerChangedEventArgs(LocalPlayer? oldPlayer, LocalPlayer? newPlayer)
+        {
+            OldPlayer = oldPlayer;
+            NewPlayer = newPlayer;
+        }
+    }
 }

Robust.Client/Player/PlayerManager.cs

@@ -37,7 +37,21 @@ namespace Robust.Client.Player
         public int MaxPlayers => _client.GameInfo?.ServerMaxPlayers ?? 0;
 
         /// <inheritdoc />
-        [ViewVariables] public LocalPlayer? LocalPlayer { get; private set; }
+        [ViewVariables]
+        public LocalPlayer? LocalPlayer
+        {
+            get => _localPlayer;
+            private set
+            {
+                if (_localPlayer == value) return;
+                var oldValue = _localPlayer;
+                _localPlayer = value;
+                LocalPlayerChanged?.Invoke(new LocalPlayerChangedEventArgs(oldValue, _localPlayer));
+            }
+        }
+        private LocalPlayer? _localPlayer;
+        public event Action<LocalPlayerChangedEventArgs>? LocalPlayerChanged;
+
 
         /// <inheritdoc />
         [ViewVariables] public IEnumerable<IPlayerSession> Sessions => _sessions.Values;

Robust.Client/UserInterface/Controls/OptionButton.cs

@@ -15,15 +15,36 @@ namespace Robust.Client.UserInterface.Controls
         private readonly Popup _popup;
         private readonly VBoxContainer _popupVBox;
         private readonly Label _label;
+        private readonly TextureRect _triangle;
 
         public int ItemCount => _buttonData.Count;
 
+        /// <summary>
+        /// If true, hides the triangle that normally appears to the right of the button label
+        /// </summary>
+        public bool HideTriangle
+        {
+            get => _hideTriangle;
+            set
+            {
+                _hideTriangle = value;
+                _triangle.Visible = !_hideTriangle;
+            }
+        }
+        private bool _hideTriangle;
+
+        /// <summary>
+        /// StyleClasses to apply to the options that popup when clicking this button.
+        /// </summary>
+        public ICollection<string> OptionStyleClasses { get; }
+
         public event Action<ItemSelectedEventArgs>? OnItemSelected;
 
         public string Prefix { get; set; }
 
         public OptionButton()
         {
+            OptionStyleClasses = new List<string>();
             AddStyleClass(StyleClassButton);
             Prefix = "";
             OnPressed += OnPressedInternal;
@@ -43,12 +64,13 @@ namespace Robust.Client.UserInterface.Controls
             };
             hBox.AddChild(_label);
 
-            var textureRect = new TextureRect
+            _triangle = new TextureRect
             {
                 StyleClasses = { StyleClassOptionTriangle },
                 SizeFlagsVertical = SizeFlags.ShrinkCenter,
+                Visible = !HideTriangle
             };
-            hBox.AddChild(textureRect);
+            hBox.AddChild(_triangle);
         }
 
         public void AddItem(Texture icon, string label, int? id = null)
@@ -73,6 +95,10 @@ namespace Robust.Client.UserInterface.Controls
                 Text = label,
                 ToggleMode = true
             };
+            foreach (var styleClass in OptionStyleClasses)
+            {
+                button.AddStyleClass(styleClass);
+            }
             button.OnPressed += ButtonOnPressed;
             var data = new ButtonData(label, button)
             {
@@ -170,6 +196,10 @@ namespace Robust.Client.UserInterface.Controls
             }
         }
 
+        /// <summary>
+        /// Select by index rather than id. Throws exception if item with that index
+        /// not in this control.
+        /// </summary>
         public void Select(int idx)
         {
             if (_idMap.TryGetValue(SelectedId, out var prevIdx))
@@ -182,11 +212,29 @@ namespace Robust.Client.UserInterface.Controls
             data.Button.Pressed = true;
         }
 
+        /// <summary>
+        /// Select by index rather than id.
+        /// </summary>
+        /// <returns>false if item with that index not in this control</returns>
+        public bool TrySelect(int idx)
+        {
+            if (idx < 0 || idx >= _buttonData.Count) return false;
+            Select(idx);
+            return true;
+        }
+
+        /// throws exception if item with this ID is not in this control
         public void SelectId(int id)
         {
             Select(GetIdx(id));
         }
 
+        /// <returns>false if item with id not in this control</returns>
+        public bool TrySelectId(int id)
+        {
+            return _idMap.TryGetValue(id, out var idx) && TrySelect(idx);
+        }
+
         public int GetIdx(int id)
         {
             return _idMap[id];

Robust.Client/UserInterface/CustomControls/SS14Window.xaml

@@ -1,15 +1,17 @@
-<cc:SS14Window xmlns:cc="clr-namespace:Robust.Client.UserInterface.CustomControls"
-                           xmlns:c="clr-namespace:Robust.Client.UserInterface.Controls">
-    <c:PanelContainer StyleClasses="windowPanel"/>
-    <c:VBoxContainer SeparationOverride="0">
-        <c:PanelContainer Name="WindowHeader" StyleClasses="windowHeader">
-            <c:HBoxContainer>
-                <c:MarginContainer MarginLeftOverride="5" SizeFlagsHorizontal="FillExpand">
-                    <c:Label Name="TitleLabel" StyleIdentifier="foo" ClipText="True" Text="Exemplary Window Title Here" VAlign="Center" StyleClasses="windowTitle"/>
-                </c:MarginContainer>
-                <c:TextureButton Name="CloseButton" StyleClasses="windowCloseButton" SizeFlagsVertical="ShrinkCenter"></c:TextureButton>
-            </c:HBoxContainer>
-        </c:PanelContainer>
-        <c:MarginContainer Name="ContentsContainer" MarginBottomOverride="10" MarginLeftOverride="10" MarginRightOverride="10" MarginTopOverride="10" RectClipContent="True" SizeFlagsVertical="FillExpand" />
-    </c:VBoxContainer>
-</cc:SS14Window>
+<SS14Window xmlns="https://spacestation14.io">
+    <PanelContainer StyleClasses="windowPanel" />
+    <VBoxContainer SeparationOverride="0">
+        <PanelContainer Name="WindowHeader" StyleClasses="windowHeader">
+            <HBoxContainer>
+                <MarginContainer MarginLeftOverride="5" SizeFlagsHorizontal="FillExpand">
+                    <Label Name="TitleLabel" StyleIdentifier="foo" ClipText="True"
+                             Text="{Loc Exemplary Window Title Here}" VAlign="Center" StyleClasses="windowTitle" />
+                </MarginContainer>
+                <TextureButton Name="CloseButton" StyleClasses="windowCloseButton" SizeFlagsVertical="ShrinkCenter" />
+            </HBoxContainer>
+        </PanelContainer>
+        <MarginContainer Name="ContentsContainer" MarginBottomOverride="10" MarginLeftOverride="10"
+                           MarginRightOverride="10" MarginTopOverride="10" RectClipContent="True"
+                           SizeFlagsVertical="FillExpand" />
+    </VBoxContainer>
+</SS14Window>

Robust.Client/UserInterface/LocExtension.cs

@@ -0,0 +1,23 @@
+using JetBrains.Annotations;
+using Robust.Shared.Localization;
+
+namespace Robust.Client.UserInterface
+{
+    // TODO: Code a XAML compiler transformer to remove references to this type at compile time.
+    // And just replace them with the Loc.GetString() call.
+    [PublicAPI]
+    public class LocExtension
+    {
+        public string Key { get; }
+
+        public LocExtension(string key)
+        {
+            Key = key;
+        }
+
+        public object ProvideValue()
+        {
+            return Loc.GetString(Key);
+        }
+    }
+}

Robust.Client/UserInterface/XAML/Attributes.cs

@@ -6,13 +6,6 @@ namespace Robust.Client.UserInterface.XAML
     {
     }
 
-    public class XmlnsDefinitionAttribute : Attribute
-    {
-        public XmlnsDefinitionAttribute(string xmlNamespace, string clrNamespace)
-        {
-        }
-    }
-
     public class UsableDuringInitializationAttribute : Attribute
     {
         public UsableDuringInitializationAttribute(bool usable)

Robust.Client/UserInterface/XAML/Binding.cs

@@ -0,0 +1,16 @@
+using System;
+using JetBrains.Annotations;
+
+// ReSharper disable once CheckNamespace
+namespace Avalonia.Data
+{
+    [UsedImplicitly]
+    public class Binding
+    {
+        public Binding()
+        {
+            throw new InvalidOperationException(
+                "Data binding is not currently supported and this type exists only to make Rider work.");
+        }
+    }
+}

Robust.Client/UserInterface/XAML/Namespaces.cs

@@ -0,0 +1,6 @@
+using Avalonia.Metadata;
+
+[assembly: XmlnsDefinition("http://schemas.microsoft.com/winfx/2006/xaml", "Robust.Client.UserInterface.XAML.XNamespace")]
+[assembly: XmlnsDefinition("https://spacestation14.io", "Robust.Client.UserInterface")]
+[assembly: XmlnsDefinition("https://spacestation14.io", "Robust.Client.UserInterface.Controls")]
+[assembly: XmlnsDefinition("https://spacestation14.io", "Robust.Client.UserInterface.CustomControls")]

Robust.Client/UserInterface/XAML/NullExtension.cs

@@ -0,0 +1,12 @@
+using JetBrains.Annotations;
+
+// ReSharper disable once CheckNamespace
+namespace Robust.Client.UserInterface.XAML.XNamespace
+{
+    // x:Null
+    [UsedImplicitly]
+    public sealed class NullExtension
+    {
+
+    }
+}

Robust.Client/UserInterface/XAML/RiderNotes.md

@@ -0,0 +1,28 @@
+# XamlUI notes about Rider
+
+XAML support in both Rider and VS is pretty hardcoded for all supported frameworks. Rider seems less bad about this but they still hardcode a lot of type paths and do other silly stuff. Luckily, they support Avalonia. So... let's pretend to be Avalonia!
+
+**JetBrains, if you're reading this, please don't sue me or take away our licenses pls I only reverse engineered your program to avoid wasting time on your issue tracker.**
+
+## Where to find this info
+
+The primary XAML support in Rider appears to be in `lib/ReSharperHost/JetBrains.ReSharper.Psi.Xaml.dll`. I recommend you decompile it with DotPeek to a project for navigating around. You can then look around the decompiled code (it's not obfuscated at all) to figure out how Rider does all this stuff.
+
+**JetBrains, if you're reading this, please don't sue me or take away our licenses pls I only reverse engineered your program to avoid wasting time on your issue tracker.**
+
+## Attributes
+
+Attributes like `XmlnsAttributionAttribute` are hardcoded for full name with namespace. That's also where it stops, so we just define our own `Avalonia.Metadata.XmlnsDefinitionAttribute` and this fools Rider into recognizing it and working. Hooray!
+
+## `http://schemas.microsoft.com/winfx/2006/xaml` Namespace
+
+As far as I can tell, at least in Avalonia, the things in this namespace are not backed by any real .NET symbols and are just made up by Rider. This is a problem because it only does this making up if it detects that you're using Avalonia.
+
+The heuristic for "are we using Avalonia" appears to be finding an assembly or project reference for `Avalonia.Base`. You can see this in `XamlModulePlatformCache.cs` in the decompiled ReSharper source code and also the `XamlPlatform` flags enum.
+
+For the time being I decided to hold off on actually fully pretending we're Avalonia so did *not* commit to a reference to `Avalonia.Base` yet. Instead we just manually created stuff like a dummy `StaticExtension` class (with a constructor that always throws) and put it into the `http://schemas.microsoft.com/winfx/2006/xaml` namespace. This seems to satisfy Rider without interfering with the actual XamlIL compilation.
+
+## Markup Extensions
+
+Markup extensions have to be classes with a method of signature either `object ProvideValue(IServiceProvider)` or `object ProvideValue()`.
+It should be noted that Rider refuses to acknowledge markup extensions unless it finds Avalonia's `Avalonia.Data.Binding` type (or `Avalonia.Markup.Xaml.Data.Binding`). Yes, this is an actual requirement.

Robust.Client/UserInterface/XAML/StaticExtension.cs

@@ -0,0 +1,22 @@
+using System;
+using JetBrains.Annotations;
+
+// ReSharper disable once CheckNamespace
+namespace Robust.Client.UserInterface.XAML.XNamespace
+{
+    // x:Static
+    [UsedImplicitly]
+    public sealed class StaticExtension
+    {
+        public StaticExtension(string _)
+        {
+            throw new InvalidOperationException(
+                "This type only exists to make Rider work and should never be instantiated.");
+        }
+
+        public static object ProvideValue()
+        {
+            throw new InvalidOperationException();
+        }
+    }
+}

Robust.Client/UserInterface/XAML/TypeExtension.cs

@@ -0,0 +1,22 @@
+using System;
+using JetBrains.Annotations;
+
+// ReSharper disable once CheckNamespace
+namespace Robust.Client.UserInterface.XAML.XNamespace
+{
+    // x:Type
+    [UsedImplicitly]
+    public sealed class TypeExtension
+    {
+        public TypeExtension(string _)
+        {
+            throw new InvalidOperationException(
+                "This type only exists to make Rider work and should never be instantiated.");
+        }
+
+        public static object ProvideValue()
+        {
+            throw new InvalidOperationException();
+        }
+    }
+}

Robust.Client/UserInterface/XAML/XmlnsDefinitionAttribute.cs

@@ -0,0 +1,20 @@
+using System;
+using JetBrains.Annotations;
+
+// ReSharper disable once CheckNamespace
+namespace Avalonia.Metadata
+{
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true)]
+    [PublicAPI]
+    public sealed class XmlnsDefinitionAttribute : Attribute
+    {
+        public XmlnsDefinitionAttribute(string xmlNamespace, string clrNamespace)
+        {
+            XmlNamespace = xmlNamespace;
+            ClrNamespace = clrNamespace;
+        }
+
+        public string XmlNamespace { get; }
+        public string ClrNamespace { get; }
+    }
+}

Robust.Server/BaseServer.cs

@@ -278,7 +278,7 @@ namespace Robust.Server
 
             // Initialize Tier 2 services
             IoCManager.Resolve<IGameTiming>().InSimulation = true;
-            
+
             IoCManager.Resolve<INetConfigurationManager>().SetupNetworking();
 
             _stateManager.Initialize();

Robust.Server/GameObjects/Components/Appearance/AppearanceComponent.cs

@@ -3,6 +3,7 @@ using Robust.Shared.ViewVariables;
 using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
+using Robust.Shared.Players;
 
 namespace Robust.Server.GameObjects
 {
@@ -61,7 +62,7 @@ namespace Robust.Server.GameObjects
             return false;
         }
 
-        public override ComponentState GetComponentState()
+        public override ComponentState GetComponentState(ICommonSession player)
         {
             return new AppearanceComponentState(data);
         }

Robust.Server/GameObjects/Components/Container/ContainerManagerComponent.cs

@@ -5,6 +5,7 @@ using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
+using Robust.Shared.Players;
 using Robust.Shared.Reflection;
 using Robust.Shared.Serialization;
 using Robust.Shared.ViewVariables;
@@ -256,7 +257,7 @@ namespace Robust.Server.GameObjects
             _entitiesWaitingResolve = null;
         }
 
-        public override ComponentState GetComponentState()
+        public override ComponentState GetComponentState(ICommonSession player)
         {
             return new ContainerManagerComponentState(
                 _allContainers.ToDictionary(

Robust.Server/GameObjects/Components/Eye/EyeComponent.cs

@@ -1,5 +1,6 @@
 using Robust.Shared.GameObjects;
 using Robust.Shared.Maths;
+using Robust.Shared.Players;
 using Robust.Shared.Serialization;
 
 namespace Robust.Server.GameObjects
@@ -63,7 +64,7 @@ namespace Robust.Server.GameObjects
             }
         }
 
-        public override ComponentState GetComponentState()
+        public override ComponentState GetComponentState(ICommonSession player)
         {
             return new EyeComponentState(DrawFov, Zoom, Offset, Rotation);
         }

Robust.Server/GameObjects/Components/Light/PointLightComponent.cs

@@ -1,5 +1,6 @@
 using Robust.Shared.GameObjects;
 using Robust.Shared.Maths;
+using Robust.Shared.Players;
 using Robust.Shared.Serialization;
 using Robust.Shared.ViewVariables;
 
@@ -73,7 +74,7 @@ namespace Robust.Server.GameObjects
             serializer.DataField(ref _offset, "offset", Vector2.Zero);
         }
 
-        public override ComponentState GetComponentState()
+        public override ComponentState GetComponentState(ICommonSession player)
         {
             return new PointLightComponentState(Enabled, Color, Radius, Offset);
         }

Robust.Server/GameObjects/Components/Renderable/SpriteComponent.cs

@@ -4,6 +4,7 @@ using Robust.Shared.GameObjects;
 using DrawDepthTag = Robust.Shared.GameObjects.DrawDepth;
 using Robust.Shared.Log;
 using Robust.Shared.Maths;
+using Robust.Shared.Players;
 using Robust.Shared.Serialization;
 using Robust.Shared.Utility;
 using Robust.Shared.ViewVariables;
@@ -441,7 +442,7 @@ namespace Robust.Server.GameObjects
             Layers = layerData;
         }
 
-        public override ComponentState GetComponentState()
+        public override ComponentState GetComponentState(ICommonSession player)
         {
             return new SpriteComponentState(Visible, DrawDepth, Scale, Rotation, Offset, Color, Directional,
                 BaseRSIPath, Layers, RenderOrder);

Robust.Server/GameObjects/IServerEntityManager.cs

@@ -10,7 +10,7 @@ namespace Robust.Server.GameObjects
         /// <summary>
         ///     Gets all entity states that have been modified after and including the provided tick.
         /// </summary>
-        List<EntityState>? GetEntityStates(GameTick fromTick);
+        List<EntityState>? GetEntityStates(GameTick fromTick, IPlayerSession player);
 
         /// <summary>
         ///     Gets all entity states within an AABB that have been modified after and including the provided tick.

Robust.Server/GameObjects/ServerEntityManager.cs

@@ -13,6 +13,7 @@ using Robust.Shared.Maths;
 using Robust.Shared.Prototypes;
 using Robust.Shared.Timing;
 using Robust.Shared.Utility;
+using static Robust.Shared.GameObjects.TransformComponent;
 
 namespace Robust.Server.GameObjects
 {
@@ -139,7 +140,7 @@ namespace Robust.Server.GameObjects
         }
 
         /// <inheritdoc />
-        public List<EntityState>? GetEntityStates(GameTick fromTick)
+        public List<EntityState>? GetEntityStates(GameTick fromTick, IPlayerSession player)
         {
             var stateEntities = new List<EntityState>();
             foreach (var entity in AllEntities)
@@ -154,7 +155,7 @@ namespace Robust.Server.GameObjects
                 if (entity.LastModifiedTick <= fromTick)
                     continue;
 
-                stateEntities.Add(GetEntityState(ComponentManager, entity.Uid, fromTick));
+                stateEntities.Add(GetEntityState(ComponentManager, entity.Uid, fromTick, player));
             }
 
             // no point sending an empty collection
@@ -336,7 +337,7 @@ namespace Robust.Server.GameObjects
             if (playerEnt == null)
             {
                 // super-observer?
-                return GetEntityStates(fromTick);
+                return GetEntityStates(fromTick, player);
             }
 
             var playerUid = playerEnt.Uid;
@@ -390,7 +391,7 @@ namespace Robust.Server.GameObjects
                     }
                 }
 
-                var state = GetEntityState(ComponentManager, uid, fromTick);
+                var state = GetEntityState(ComponentManager, uid, fromTick, player);
 
                 if (checkedEnts.Add(uid))
                 {
@@ -404,14 +405,14 @@ namespace Robust.Server.GameObjects
                         {
                             // mover changed and can't be seen
                             var idx = Array.FindIndex(state.ComponentStates,
-                                x => x is TransformComponent.TransformComponentState);
+                                x => x is TransformComponentState);
 
                             if (idx != -1)
                             {
                                 // mover changed positional data and can't be seen
                                 var oldState =
-                                    (TransformComponent.TransformComponentState) state.ComponentStates[idx];
-                                var newState = new TransformComponent.TransformComponentState(Vector2NaN,
+                                    (TransformComponentState) state.ComponentStates[idx];
+                                var newState = new TransformComponentState(Vector2NaN,
                                     oldState.Rotation, oldState.ParentID, oldState.NoLocalRotation);
                                 state.ComponentStates[idx] = newState;
                                 seenMovers.Remove(uid);
@@ -441,7 +442,7 @@ namespace Robust.Server.GameObjects
                     {
                         // mover can't be seen
                         var oldState =
-                            (TransformComponent.TransformComponentState) entity.Transform.GetComponentState();
+                            (TransformComponentState) entity.Transform.GetComponentState(player);
                         entityStates.Add(new EntityState(uid,
                             new ComponentChanged[]
                             {
@@ -449,7 +450,7 @@ namespace Robust.Server.GameObjects
                             },
                             new ComponentState[]
                             {
-                                new TransformComponent.TransformComponentState(Vector2NaN, oldState.Rotation,
+                                new TransformComponentState(Vector2NaN, oldState.Rotation,
                                     oldState.ParentID, oldState.NoLocalRotation)
                             }));
 
@@ -517,7 +518,7 @@ namespace Robust.Server.GameObjects
                 }
 
                 // should this be lastSeen or fromTick?
-                var entityState = GetEntityState(ComponentManager, uid, lastSeen);
+                var entityState = GetEntityState(ComponentManager, uid, lastSeen, player);
 
                 checkedEnts.Add(uid);
 
@@ -577,7 +578,7 @@ namespace Robust.Server.GameObjects
                     continue;
                 }
 
-                var state = GetEntityState(ComponentManager, uid, fromTick);
+                var state = GetEntityState(ComponentManager, uid, fromTick, player);
 
                 if (state.ComponentStates == null)
                 {
@@ -591,7 +592,7 @@ namespace Robust.Server.GameObjects
                 seenMovers.Remove(uid);
                 ClearLastSeenTick(lSeen, uid);
 
-                var idx = Array.FindIndex(state.ComponentStates, x => x is TransformComponent.TransformComponentState);
+                var idx = Array.FindIndex(state.ComponentStates, x => x is TransformComponentState);
 
                 if (idx == -1)
                 {
@@ -599,9 +600,9 @@ namespace Robust.Server.GameObjects
                     continue;
                 }
 
-                var oldState = (TransformComponent.TransformComponentState) state.ComponentStates[idx];
+                var oldState = (TransformComponentState) state.ComponentStates[idx];
                 var newState =
-                    new TransformComponent.TransformComponentState(Vector2NaN, oldState.Rotation, oldState.ParentID, oldState.NoLocalRotation);
+                    new TransformComponentState(Vector2NaN, oldState.Rotation, oldState.ParentID, oldState.NoLocalRotation);
                 state.ComponentStates[idx] = newState;
 
 
@@ -630,7 +631,7 @@ namespace Robust.Server.GameObjects
                     }
 
                     var entity = GetEntity(uid);
-                    var state = GetEntityState(ComponentManager, uid, fromTick);
+                    var state = GetEntityState(ComponentManager, uid, fromTick, player);
 
                     if (state.ComponentStates == null || viewbox.Intersects(GetWorldAabbFromEntity(entity)))
                     {
@@ -643,7 +644,7 @@ namespace Robust.Server.GameObjects
                     entityStates.Add(state);
 
                     var idx = Array.FindIndex(state.ComponentStates,
-                        x => x is TransformComponent.TransformComponentState);
+                        x => x is TransformComponentState);
 
                     if (idx == -1)
                     {
@@ -651,9 +652,9 @@ namespace Robust.Server.GameObjects
                         continue;
                     }
 
-                    var oldState = (TransformComponent.TransformComponentState) state.ComponentStates[idx];
+                    var oldState = (TransformComponentState) state.ComponentStates[idx];
                     var newState =
-                        new TransformComponent.TransformComponentState(Vector2NaN, oldState.Rotation,
+                        new TransformComponentState(Vector2NaN, oldState.Rotation,
                             oldState.ParentID, oldState.NoLocalRotation);
                     state.ComponentStates[idx] = newState;
                     seenMovers.Remove(uid);
@@ -881,8 +882,9 @@ namespace Robust.Server.GameObjects
         /// <param name="compMan">ComponentManager that contains the components for the entity.</param>
         /// <param name="entityUid">Uid of the entity to generate the state from.</param>
         /// <param name="fromTick">Only provide delta changes from this tick.</param>
+        /// <param name="player">The player to generate this state for.</param>
         /// <returns>New entity State for the given entity.</returns>
-        private static EntityState GetEntityState(IComponentManager compMan, EntityUid entityUid, GameTick fromTick)
+        private static EntityState GetEntityState(IComponentManager compMan, EntityUid entityUid, GameTick fromTick, IPlayerSession player)
         {
             var compStates = new List<ComponentState>();
             var changed = new List<ComponentChanged>();
@@ -899,7 +901,7 @@ namespace Robust.Server.GameObjects
                 // As such, we can avoid sending this data in this case since the client "already has it".
 
                 if (comp.NetSyncEnabled && comp.LastModifiedTick != GameTick.Zero && comp.LastModifiedTick >= fromTick)
-                    compStates.Add(comp.GetComponentState());
+                    compStates.Add(comp.GetComponentState(player));
 
                 if (comp.CreationTick != GameTick.Zero && comp.CreationTick >= fromTick && !comp.Deleted)
                 {

Robust.Server/GameStates/ServerGameStateManager.cs

@@ -135,7 +135,7 @@ namespace Robust.Server.GameStates
                 }
 
                 var entStates = lastAck == GameTick.Zero || !PvsEnabled
-                    ? _entityManager.GetEntityStates(lastAck)
+                    ? _entityManager.GetEntityStates(lastAck, session)
                     : _entityManager.UpdatePlayerSeenEntityStates(lastAck, session, _entityManager.MaxUpdateRange);
                 var playerStates = _playerManager.GetPlayerStates(lastAck);
                 var deletions = _entityManager.GetDeletedEntities(lastAck);

Robust.Server/ServerStatus/StatusHost.cs

@@ -152,21 +152,21 @@ namespace Robust.Server.ServerStatus
 
         private void RegisterCVars()
         {
-            try
+            var path = PathHelpers.ExecutableRelativeFile("build.json");
+            if (!File.Exists(path))
             {
-                var buildInfo = File.ReadAllText(PathHelpers.ExecutableRelativeFile("build.json"));
-                var info = JsonConvert.DeserializeObject<BuildInfo>(buildInfo);
+                return;
+            }
 
-                // Don't replace cvars with contents of build.json if overriden by --cvar or such.
-                SetCVarIfUnmodified(CVars.BuildEngineVersion, info.EngineVersion);
-                SetCVarIfUnmodified(CVars.BuildForkId, info.ForkId);
-                SetCVarIfUnmodified(CVars.BuildVersion, info.Version);
-                SetCVarIfUnmodified(CVars.BuildDownloadUrl, info.Download ?? "");
-                SetCVarIfUnmodified(CVars.BuildHash, info.Hash ?? "");
-            }
-            catch (FileNotFoundException)
-            {
-            }
+            var buildInfo = File.ReadAllText(path);
+            var info = JsonConvert.DeserializeObject<BuildInfo>(buildInfo);
+
+            // Don't replace cvars with contents of build.json if overriden by --cvar or such.
+            SetCVarIfUnmodified(CVars.BuildEngineVersion, info.EngineVersion);
+            SetCVarIfUnmodified(CVars.BuildForkId, info.ForkId);
+            SetCVarIfUnmodified(CVars.BuildVersion, info.Version);
+            SetCVarIfUnmodified(CVars.BuildDownloadUrl, info.Download ?? "");
+            SetCVarIfUnmodified(CVars.BuildHash, info.Hash ?? "");
 
             void SetCVarIfUnmodified(CVarDef<string> cvar, string val)
             {

Robust.Shared.Scripting/ScriptInstanceShared.cs

@@ -32,7 +32,6 @@ namespace Robust.Shared.Scripting
             "Robust.Shared.IoC",
             "Robust.Shared.Maths",
             "Robust.Shared.GameObjects",
-            "Robust.Shared.Interfaces.GameObjects",
             "Robust.Shared.Map",
             "Robust.Shared.Prototypes"
         };

Robust.Shared/ContentPack/AssemblyTypeChecker.cs

@@ -767,14 +767,14 @@ namespace Robust.Shared.ContentPack
                 var dllName = $"{simpleName}.dll";
                 foreach (var diskLoadPath in _diskLoadPaths)
                 {
-                    try
-                    {
-                        var path = Path.Combine(diskLoadPath, dllName);
-                        return new PEReader(File.OpenRead(path));
-                    }
-                    catch (FileNotFoundException)
+                    var path = Path.Combine(diskLoadPath, dllName);
+
+                    if (!File.Exists(path))
                     {
+                        continue;
                     }
+
+                    return new PEReader(File.OpenRead(path));
                 }
 
                 var extraStream = _parent.ExtraRobustLoader?.Invoke(dllName);

Robust.Shared/ContentPack/DirLoader.cs

@@ -90,7 +90,7 @@ namespace Robust.Shared.ContentPack
                     {
                         var prevDir = new DirectoryInfo(prevPath);
                         var found = false;
-                        foreach (var info in prevDir.GetFileSystemInfos())
+                        foreach (var info in prevDir.EnumerateFileSystemInfos())
                         {
                             if (!string.Equals(info.Name, segment, StringComparison.InvariantCultureIgnoreCase))
                             {

Robust.Shared/ContentPack/Sandbox.yml

@@ -330,6 +330,7 @@ Types:
   System.Globalization:
     CompareOptions: { }
     CultureInfo: { All: True }
+    DateTimeStyles: { All: True } # Enum
     TextInfo:
       Methods:
       - "bool get_IsRightToLeft()"
@@ -894,6 +895,7 @@ Types:
     MidpointRounding: { } # Enum
     MulticastDelegate:
       Inherit: Allow
+    NotImplementedException: { All: True }
     NotSupportedException: { All: True }
     Nullable: { All: True }
     Nullable`1: { All: True }

Robust.Shared/GameObjects/Component.cs

@@ -202,8 +202,9 @@ namespace Robust.Shared.GameObjects
         /// <inheritdoc />
         public virtual void HandleNetworkMessage(ComponentMessage message, INetChannel netChannel, ICommonSession? session = null) { }
 
+        /// <param name="player"></param>
         /// <inheritdoc />
-        public virtual ComponentState GetComponentState()
+        public virtual ComponentState GetComponentState(ICommonSession player)
         {
             if (NetID == null)
                 throw new InvalidOperationException($"Cannot make state for component without Net ID: {GetType()}");

Robust.Shared/GameObjects/Components/Collidable/PhysicsComponent.Collision.cs

@@ -5,6 +5,7 @@ using Robust.Shared.IoC;
 using Robust.Shared.Map;
 using Robust.Shared.Maths;
 using Robust.Shared.Physics;
+using Robust.Shared.Players;
 using Robust.Shared.Serialization;
 using Robust.Shared.ViewVariables;
 
@@ -132,8 +133,9 @@ namespace Robust.Shared.GameObjects
             serializer.DataField(ref _mass, "mass", 1.0f);
         }
 
+        /// <param name="player"></param>
         /// <inheritdoc />
-        public override ComponentState GetComponentState()
+        public override ComponentState GetComponentState(ICommonSession player)
         {
             return new PhysicsComponentState(_canCollide, _status, _physShapes, _isHard, _mass, LinearVelocity, AngularVelocity, Anchored);
         }

Robust.Shared/GameObjects/Components/GrammarComponent.cs

@@ -1,5 +1,6 @@
 using System;
 using Robust.Shared.Localization.Macros;
+using Robust.Shared.Players;
 using Robust.Shared.Serialization;
 using Robust.Shared.ViewVariables;
 
@@ -33,7 +34,7 @@ namespace Robust.Shared.GameObjects
             serializer.DataField(this, x => x.Proper, "proper", false);
         }
 
-        public override ComponentState GetComponentState()
+        public override ComponentState GetComponentState(ICommonSession player)
         {
             return new GrammarComponentState(Proper);
         }

Robust.Shared/GameObjects/Components/Light/OccluderComponent.cs

@@ -1,6 +1,7 @@
 using System;
 using Robust.Shared.Map;
 using Robust.Shared.Maths;
+using Robust.Shared.Players;
 using Robust.Shared.Serialization;
 using Robust.Shared.ViewVariables;
 
@@ -73,7 +74,7 @@ namespace Robust.Shared.GameObjects
             }
         }
 
-        public override ComponentState GetComponentState()
+        public override ComponentState GetComponentState(ICommonSession player)
         {
             return new OccluderComponentState(Enabled, BoundingBox);
         }

Robust.Shared/GameObjects/Components/Map/MapComponent.cs

@@ -1,5 +1,6 @@
 using System;
 using Robust.Shared.Map;
+using Robust.Shared.Players;
 using Robust.Shared.Serialization;
 using Robust.Shared.ViewVariables;
 
@@ -39,8 +40,9 @@ namespace Robust.Shared.GameObjects
             _mapIndex = MapId.Nullspace;
         }
 
+        /// <param name="player"></param>
         /// <inheritdoc />
-        public override ComponentState GetComponentState()
+        public override ComponentState GetComponentState(ICommonSession player)
         {
             return new MapComponentState(_mapIndex);
         }

Robust.Shared/GameObjects/Components/Map/MapGridComponent.cs

@@ -2,6 +2,7 @@
 using Robust.Shared.IoC;
 using Robust.Shared.Log;
 using Robust.Shared.Map;
+using Robust.Shared.Players;
 using Robust.Shared.Serialization;
 using Robust.Shared.ViewVariables;
 
@@ -61,8 +62,9 @@ namespace Robust.Shared.GameObjects
             base.OnRemove();
         }
 
+        /// <param name="player"></param>
         /// <inheritdoc />
-        public override ComponentState GetComponentState()
+        public override ComponentState GetComponentState(ICommonSession player)
         {
             return new MapGridComponentState(_gridIndex, Grid.HasGravity);
         }

Robust.Shared/GameObjects/Components/MetaDataComponent.cs

@@ -1,5 +1,6 @@
 using System;
 using Robust.Shared.IoC;
+using Robust.Shared.Players;
 using Robust.Shared.Prototypes;
 using Robust.Shared.Serialization;
 using Robust.Shared.ViewVariables;
@@ -137,8 +138,9 @@ namespace Robust.Shared.GameObjects
             }
         }
 
+        /// <param name="player"></param>
         /// <inheritdoc />
-        public override ComponentState GetComponentState()
+        public override ComponentState GetComponentState(ICommonSession player)
         {
             return new MetaDataComponentState(_entityName, _entityDescription, EntityPrototype?.ID);
         }

Robust.Shared/GameObjects/Components/Transform/TransformComponent.cs

@@ -6,6 +6,7 @@ using Robust.Shared.Containers;
 using Robust.Shared.IoC;
 using Robust.Shared.Map;
 using Robust.Shared.Maths;
+using Robust.Shared.Players;
 using Robust.Shared.Serialization;
 using Robust.Shared.Utility;
 using Robust.Shared.ViewVariables;
@@ -698,8 +699,9 @@ namespace Robust.Shared.GameObjects
             serializer.DataField(ref _noLocalRotation, "noRot", false);
         }
 
+        /// <param name="player"></param>
         /// <inheritdoc />
-        public override ComponentState GetComponentState()
+        public override ComponentState GetComponentState(ICommonSession player)
         {
             return new TransformComponentState(_localPosition, LocalRotation, _parent, _noLocalRotation);
         }

Robust.Shared/GameObjects/IComponent.cs

@@ -32,7 +32,7 @@ namespace Robust.Shared.GameObjects
         ///     Whether the Owner has been paused.
         /// </summary>
         bool Paused { get; }
-        
+
         /// <summary>
         ///     Whether the client should synchronize component additions and removals.
         ///     If this is false and the component gets added or removed server side, the client will not do the same.
@@ -125,8 +125,9 @@ namespace Robust.Shared.GameObjects
         /// <summary>
         ///     Get the component's state for replicating on the client.
         /// </summary>
+        /// <param name="player"></param>
         /// <returns>ComponentState object</returns>
-        ComponentState GetComponentState();
+        ComponentState GetComponentState(ICommonSession player);
 
         /// <summary>
         ///     Handles an incoming component state from the server.

Robust.Shared/Network/NetManager.ServerAuth.cs

@@ -179,9 +179,33 @@ namespace Robust.Shared.Network
                 // Well they're in. Kick a connected client with the same GUID if we have to.
                 if (_assignedUserIds.TryGetValue(userId, out var existing))
                 {
-                    existing.Disconnect("Another connection has been made with your account.");
-                    // Have to wait until they're properly off the server to avoid any collisions.
-                    await AwaitDisconnectAsync(existing);
+                    if (_awaitingDisconnectToConnect.Contains(userId))
+                    {
+                        connection.Disconnect("Stop trying to connect multiple times at once.");
+                        return;
+                    }
+
+                    _awaitingDisconnectToConnect.Add(userId);
+                    try
+                    {
+                        existing.Disconnect("Another connection has been made with your account.");
+                        // Have to wait until they're properly off the server to avoid any collisions.
+                        await AwaitDisconnectAsync(existing);
+                    }
+                    finally
+                    {
+                        _awaitingDisconnectToConnect.Remove(userId);
+                    }
+                }
+
+                if (connection.Status == NetConnectionStatus.Disconnecting ||
+                    connection.Status == NetConnectionStatus.Disconnected)
+                {
+                    Logger.InfoS("net",
+                        "{ConnectionEndpoint} disconnected during handshake",
+                        connection.RemoteEndPoint, userName, userId);
+
+                    return;
                 }
 
                 var msg = peer.Peer.CreateMessage();
@@ -242,8 +266,12 @@ namespace Robust.Shared.Network
 
         private Task AwaitDisconnectAsync(NetConnection connection)
         {
-            var tcs = new TaskCompletionSource<object?>();
-            _awaitingDisconnect.Add(connection, tcs);
+            if (!_awaitingDisconnect.TryGetValue(connection, out var tcs))
+            {
+                tcs = new TaskCompletionSource<object?>();
+                _awaitingDisconnect.Add(connection, tcs);
+            }
+
             return tcs.Task;
         }
 

Robust.Shared/Network/NetManager.cs

@@ -135,6 +135,8 @@ namespace Robust.Shared.Network
         private readonly Dictionary<NetConnection, TaskCompletionSource<object?>> _awaitingDisconnect
             = new();
 
+        private readonly HashSet<NetUserId> _awaitingDisconnectToConnect = new HashSet<NetUserId>();
+
         /// <inheritdoc />
         public int Port => _config.GetCVar(CVars.NetPort);
 

Robust.Shared/Physics/B2DynamicTree.cs

@@ -870,7 +870,7 @@ namespace Robust.Shared.Physics
 
         public void Query<TState>(ref TState state, QueryCallback<TState> callback, in Box2 aabb)
         {
-            using var stack = new GrowableStack<Proxy>(stackalloc Proxy[256]);
+            var stack = new GrowableStack<Proxy>(stackalloc Proxy[256]);
             stack.Push(_root);
 
             ref var baseRef = ref _nodes[0];
@@ -915,7 +915,7 @@ namespace Robust.Shared.Physics
         {
             // NOTE: This is not Box2D's normal ray cast function, since our rays have infinite length.
 
-            using var stack = new GrowableStack<Proxy>(stackalloc Proxy[256]);
+            var stack = new GrowableStack<Proxy>(stackalloc Proxy[256]);
 
             stack.Push(_root);
 

Robust.Shared/Prototypes/PrototypeManager.cs

@@ -56,6 +56,7 @@ namespace Robust.Shared.Prototypes
         /// </summary>
         void LoadDirectory(ResourcePath path);
         void LoadFromStream(TextReader stream);
+        void LoadString(string str);
         /// <summary>
         /// Clear out all prototypes and reset to a blank slate.
         /// </summary>
@@ -273,6 +274,11 @@ namespace Robust.Shared.Prototypes
             LoadedData?.Invoke(yaml, "anonymous prototypes YAML stream");
         }
 
+        public void LoadString(string str)
+        {
+            LoadFromStream(new StreamReader(str));
+        }
+
         #endregion IPrototypeManager members
 
         public void PostInject()

Robust.Shared/Reflection/IReflectionManager.cs

@@ -69,7 +69,7 @@ namespace Robust.Shared.Reflection
         /// </summary>
         /// <typeparam name="T">Attribute to search for.</typeparam>
         /// <returns>Enumeration of all types with the specified attribute.</returns>
-        IEnumerable<Type> FindTypesWithAttribute<T>();
+        IEnumerable<Type> FindTypesWithAttribute<T>() where T : Attribute;
 
         /// <summary>
         /// Loads assemblies into the manager and get all the types.

Robust.Shared/Reflection/ReflectionManager.cs

@@ -4,6 +4,7 @@ using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Reflection;
 using Robust.Shared.Log;
+using Robust.Shared.Serialization;
 using Robust.Shared.ViewVariables;
 
 namespace Robust.Shared.Reflection
@@ -158,7 +159,7 @@ namespace Robust.Shared.Reflection
         }
 
         /// <inheritdoc />
-        public IEnumerable<Type> FindTypesWithAttribute<T>()
+        public IEnumerable<Type> FindTypesWithAttribute<T>() where T : Attribute
         {
             var types = new List<Type>();
 
@@ -217,7 +218,21 @@ namespace Robust.Shared.Reflection
             Type? found = null;
             foreach (var derivedType in GetAllChildren(baseType))
             {
-                if (derivedType.Name == typeName && (derivedType.IsPublic))
+                if (!derivedType.IsPublic)
+                {
+                    continue;
+                }
+
+                if (derivedType.Name == typeName)
+                {
+                    found = derivedType;
+                    break;
+                }
+
+                var serializedAttribute = derivedType.GetCustomAttribute<SerializedTypeAttribute>();
+
+                if (serializedAttribute != null &&
+                    serializedAttribute.SerializeName == typeName)
                 {
                     found = derivedType;
                     break;

Robust.Shared/Serialization/SerializedTypeAttribute.cs

@@ -0,0 +1,18 @@
+using System;
+
+namespace Robust.Shared.Serialization
+{
+    [AttributeUsage(AttributeTargets.Class, Inherited = false)]
+    public class SerializedTypeAttribute : Attribute
+    {
+        /// <summary>
+        ///     Name of this type in serialized files.
+        /// </summary>
+        public string SerializeName { get; }
+
+        public SerializedTypeAttribute(string serializeName)
+        {
+            SerializeName = serializeName;
+        }
+    }
+}

Robust.Shared/Serialization/YamlCustomFormatSerializer.cs

@@ -17,7 +17,7 @@ namespace Robust.Shared.Serialization
             _formatter = formatter;
         }
 
-        public override object NodeToType(Type _type, YamlNode node, YamlObjectSerializer serializer)
+        public override object NodeToType(Type type, YamlNode node, YamlObjectSerializer serializer)
         {
             return _formatter.FromCustomFormat(serializer.NodeToType(_formatter.Format, node));
         }

Robust.Shared/Serialization/YamlObjectSerializer.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.ComponentModel;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
@@ -38,6 +39,7 @@ namespace Robust.Shared.Serialization
             {
                 { typeof(Color), new ColorSerializer() },
                 { typeof(Vector2), new Vector2Serializer() },
+                { typeof(Vector2i), new Vector2iSerializer() },
                 { typeof(Vector3), new Vector3Serializer() },
                 { typeof(Vector4), new Vector4Serializer() },
                 { typeof(Angle), new AngleSerializer() },
@@ -510,6 +512,24 @@ namespace Robust.Shared.Serialization
                 return newList;
             }
 
+            if (TryGenericImmutableListType(type, out var immutableListType))
+            {
+                var listNode = (YamlSequenceNode) node;
+                var elems = listNode.Children;
+
+                var newList = Array.CreateInstance(immutableListType, elems.Count);
+
+                for (var i = 0; i < elems.Count; i++)
+                {
+                    newList.SetValue(NodeToType(immutableListType, elems[i]), i);
+                }
+
+                var list = typeof(ImmutableList);
+                var add = list.GetMethod("CreateRange")!.MakeGenericMethod(immutableListType);
+
+                return add.Invoke(null, new object?[] {newList})!;
+            }
+
             // Dictionary<K,V>/IReadOnlyDictionary<K,V>
             if (TryGenericReadDictType(type, out var keyType, out var valType, out var dictType))
             {
@@ -584,12 +604,8 @@ namespace Robust.Shared.Serialization
             // IExposeData.
             if (typeof(IExposeData).IsAssignableFrom(type))
             {
-                if (!(node is YamlMappingNode mapNode))
-                {
-                    throw new InvalidOperationException($"Cannot read from IExposeData on non-mapping node. Type: '{type}'");
-                }
-
                 var concreteType = type;
+
                 if (type.IsAbstract || type.IsInterface)
                 {
                     var tag = node.Tag;
@@ -607,6 +623,12 @@ namespace Robust.Shared.Serialization
                 }
 
                 var instance = (IExposeData)Activator.CreateInstance(concreteType)!;
+
+                if (node is not YamlMappingNode mapNode)
+                {
+                    return instance;
+                }
+
                 // TODO: Might be worth it to cut down on allocations here by using ourselves instead of creating a fork.
                 // Seems doable.
                 if (_context != null)
@@ -639,7 +661,7 @@ namespace Robust.Shared.Serialization
             throw new ArgumentException($"Type {type.FullName} is not supported.", nameof(type));
         }
 
-        public T NodeToType<T>(YamlNode node)
+        public T NodeToType<T>(YamlNode node, string name)
         {
             return (T) NodeToType(typeof(T), node);
         }
@@ -723,6 +745,28 @@ namespace Robust.Shared.Serialization
                 return node;
             }
 
+            if (TryGenericImmutableListType(type, out var immutableListType))
+            {
+                var node = new YamlSequenceNode {Tag = TagSkipTag};
+
+                foreach (var entry in (IEnumerable) obj)
+                {
+                    if (entry == null)
+                    {
+                        throw new ArgumentException("Cannot serialize null value inside list.");
+                    }
+
+                    var entryNode = TypeToNode(entry);
+
+                    // write the concrete type tag
+                    AssignTag<object?>(immutableListType, entry, null, entryNode);
+
+                    node.Add(entryNode);
+                }
+
+                return node;
+            }
+
             // Dictionary<K,V>
             if (TryGenericDictType(type, out var keyType, out var valType)
                 || TryGenericReadOnlyDictType(type, out keyType, out valType))
@@ -861,7 +905,8 @@ namespace Robust.Shared.Serialization
                 return true;
             }
 
-            if (TryGenericListType(type!, out _))
+            if (TryGenericListType(type!, out _) ||
+                TryGenericImmutableListType(type!, out _))
             {
                 var listA = (IList) a;
                 var listB = (IList) b!;
@@ -1023,6 +1068,21 @@ namespace Robust.Shared.Serialization
             return false;
         }
 
+        private static bool TryGenericImmutableListType(Type type, [NotNullWhen(true)] out Type? listType)
+        {
+            var isImmutableList = type.GetTypeInfo().IsGenericType &&
+                                  type.GetGenericTypeDefinition() == typeof(ImmutableList<>);
+
+            if (isImmutableList)
+            {
+                listType = type.GetGenericArguments()[0];
+                return true;
+            }
+
+            listType = default;
+            return false;
+        }
+
         private static bool TryGenericReadOnlyDictType(Type type, [NotNullWhen(true)] out Type? keyType, [NotNullWhen(true)] out Type? valType)
         {
             var isDict = type.GetTypeInfo().IsGenericType && type.GetGenericTypeDefinition() == typeof(IReadOnlyDictionary<,>);
@@ -1287,6 +1347,20 @@ namespace Robust.Shared.Serialization
             }
         }
 
+        class Vector2iSerializer : TypeSerializer
+        {
+            public override object NodeToType(Type type, YamlNode node, YamlObjectSerializer serializer)
+            {
+                return node.AsVector2i();
+            }
+
+            public override YamlNode TypeToNode(object obj, YamlObjectSerializer serializer)
+            {
+                var vec = (Vector2i)obj;
+                return new YamlScalarNode($"{vec.X.ToString(CultureInfo.InvariantCulture)},{vec.Y.ToString(CultureInfo.InvariantCulture)}");
+            }
+        }
+
         class Vector3Serializer : TypeSerializer
         {
             public override object NodeToType(Type type, YamlNode node, YamlObjectSerializer serializer)

Robust.Shared/Timing/GameLoop.cs

@@ -123,8 +123,6 @@ namespace Robust.Shared.Timing
             FrameEventArgs realFrameEvent;
             FrameEventArgs simFrameEvent;
 
-            _timing.ResetRealTime();
-
             while (Running)
             {
                 // maximum number of ticks to queue before the loop slows down.

Robust.Shared/Timing/GameTiming.cs

@@ -92,18 +92,13 @@ namespace Robust.Shared.Timing
         {
             get
             {
-                if (_netManager.IsServer)
-                {
-                    return RealTime;
-                }
-
-                var clientNetManager = (IClientNetManager) _netManager;
-                if (clientNetManager.ServerChannel == null)
+                var offset = GetServerOffset();
+                if (offset == null)
                 {
                     return TimeSpan.Zero;
                 }
 
-                return clientNetManager.ServerChannel.RemoteTime;
+                return RealTime + offset.Value;
             }
         }
 
@@ -236,15 +231,6 @@ namespace Robust.Shared.Timing
             _cachedCurTimeInfo = (newTime, CurTick);
         }
 
-        /// <summary>
-        ///     Resets the real uptime of the server.
-        /// </summary>
-        public void ResetRealTime()
-        {
-            _realTimer.Restart();
-            _lastRealTime = TimeSpan.Zero;
-        }
-
         /// <summary>
         /// Resets the simulation time.
         /// </summary>
@@ -256,6 +242,35 @@ namespace Robust.Shared.Timing
             Paused = true;
         }
 
+        public TimeSpan RealLocalToServer(TimeSpan local)
+        {
+            var offset = GetServerOffset();
+            if (offset == null)
+                return TimeSpan.Zero;
+
+            return local + offset.Value;
+        }
+
+        public TimeSpan RealServerToLocal(TimeSpan server)
+        {
+            var offset = GetServerOffset();
+            if (offset == null)
+                return TimeSpan.Zero;
+
+            return server - offset.Value;
+        }
+
+        private TimeSpan? GetServerOffset()
+        {
+            if (_netManager.IsServer)
+            {
+                return TimeSpan.Zero;
+            }
+
+            var clientNetManager = (IClientNetManager) _netManager;
+            return clientNetManager.ServerChannel?.RemoteTimeOffset;
+        }
+
         public bool IsFirstTimePredicted { get; private set; } = true;
 
         /// <inheritdoc />

Robust.Shared/Timing/IGameTiming.cs

@@ -123,11 +123,6 @@ namespace Robust.Shared.Timing
         /// </summary>
         void StartFrame();
 
-        /// <summary>
-        ///     Resets the real uptime of the server.
-        /// </summary>
-        void ResetRealTime();
-
         /// <summary>
         /// Is this the first time CurTick has been predicted?
         /// </summary>
@@ -162,5 +157,8 @@ namespace Robust.Shared.Timing
         /// Resets the simulation time. This should be called on round restarts.
         /// </summary>
         void ResetSimTime();
+
+        TimeSpan RealLocalToServer(TimeSpan local);
+        TimeSpan RealServerToLocal(TimeSpan server);
     }
 }

Robust.Shared/Utility/FormattedMessage.MarkupParser.cs

@@ -15,7 +15,8 @@ namespace Robust.Shared.Utility
         private static readonly Parser<char, char> ParseEscapeSequence =
             Char('\\').Then(OneOf(
                 Char('\\'),
-                Char(TagBegin)));
+                Char(TagBegin),
+                Char(TagEnd)));
 
         private static readonly Parser<char, TagText> ParseTagText =
             ParseEscapeSequence.Or(Token(c => c != TagBegin && c != '\\'))

Robust.Shared/Utility/GrowableStack.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Runtime.InteropServices;
 
 namespace Robust.Shared.Utility
 {
@@ -10,62 +9,31 @@ namespace Robust.Shared.Utility
     /// If the stack size exceeds the initial capacity, the heap is used
     /// to increase the size of the stack.
     /// </summary>
-    /// <remarks>
-    ///     You MUST call <see cref="Dispose"/> when you are done with this stack or else you will have a memory leak.
-    /// </remarks>
     /// <typeparam name="T">The type of elements in the stack.</typeparam>
-    internal unsafe ref struct GrowableStack<T> where T : unmanaged
+    internal ref struct GrowableStack<T> where T : unmanaged
     {
-        // TODO: Switch to managed arrays for the on-heap alloc when we have .NET 5.
-        // Because with .NET 5 we can use the Pinned Object Heap.
-        private T* _stack;
-        private bool _wasReallocated;
+        private Span<T> _stack;
         private int _count;
         private int _capacity;
 
         /// <summary>
         ///     Creates the growable stack with the allocated space as stack space.
         /// </summary>
-        /// <remarks>
-        ///     <paramref name="stackSpace"/> MUST BE A PIECE OF PINNED MEMORY,
-        ///     OR ELSE YOU HAVE A MASSIVE GC BUG ON YOUR HAND.
-        /// </remarks>
         public GrowableStack(Span<T> stackSpace)
         {
-            fixed (T* ap = stackSpace)
-            {
-                _stack = ap;
-            }
-
+            _stack = stackSpace;
             _capacity = stackSpace.Length;
-            _wasReallocated = false;
             _count = 0;
         }
 
-        public void Dispose()
-        {
-            if (_wasReallocated)
-            {
-                Marshal.FreeHGlobal((IntPtr) _stack);
-                _stack = null;
-            }
-        }
-
         public void Push(in T element)
         {
             if (_count == _capacity)
             {
-                var old = _stack;
                 _capacity *= 2;
-                var dstSize = _capacity * sizeof(T);
-                _stack = (T*) Marshal.AllocHGlobal(dstSize);
-                Buffer.MemoryCopy(old, _stack, dstSize, _count * sizeof(T));
-                if (_wasReallocated)
-                {
-                    Marshal.FreeHGlobal((IntPtr) old);
-                }
-
-                _wasReallocated = true;
+                var oldStack = _stack;
+                _stack = GC.AllocateUninitializedArray<T>(_capacity);
+                oldStack.CopyTo(_stack);
             }
 
             _stack[_count] = element;
@@ -74,7 +42,6 @@ namespace Robust.Shared.Utility
 
         public T Pop()
         {
-            DebugTools.Assert(_count > 0);
             --_count;
             return _stack[_count];
         }

Robust.UnitTesting/Shared/Serialization/YamlConstantSerializer_Test.cs

@@ -1,5 +1,6 @@
 using NUnit.Framework;
 using Robust.Shared.Serialization;
+using Robust.UnitTesting.Shared.Serialization.YamlObjectSerializerTests;
 using YamlDotNet.RepresentationModel;
 
 namespace Robust.UnitTesting.Shared.Serialization

Robust.UnitTesting/Shared/Serialization/YamlFlagSerializer_Test.cs

@@ -1,6 +1,7 @@
 using System;
 using NUnit.Framework;
 using Robust.Shared.Serialization;
+using Robust.UnitTesting.Shared.Serialization.YamlObjectSerializerTests;
 using YamlDotNet.RepresentationModel;
 
 namespace Robust.UnitTesting.Shared.Serialization

Robust.UnitTesting/Shared/Serialization/YamlObjectSerializerTests/ImmutableListSerializationTest.cs

@@ -0,0 +1,57 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using NUnit.Framework;
+using Robust.Shared.Serialization;
+using YamlDotNet.RepresentationModel;
+using static Robust.UnitTesting.Shared.Serialization.YamlObjectSerializerTests.YamlObjectSerializer_Test;
+// ReSharper disable AccessToStaticMemberViaDerivedType
+
+namespace Robust.UnitTesting.Shared.Serialization.YamlObjectSerializerTests
+{
+    [Parallelizable(ParallelScope.All | ParallelScope.Fixtures)]
+    [TestFixture]
+    [TestOf(typeof(YamlObjectSerializer))]
+    public class ImmutableListSerializationTest
+    {
+        [Test]
+        public void SerializeListTest()
+        {
+            // Arrange
+            var data = _serializableList;
+            var mapping = new YamlMappingNode();
+            var serializer = YamlObjectSerializer.NewWriter(mapping);
+
+            // Act
+            serializer.DataField(ref data, "datalist", ImmutableList<int>.Empty);
+
+            // Assert
+            var result = NodeToYamlText(mapping);
+            Assert.That(result, Is.EqualTo(_serializedListYaml));
+        }
+
+        [Test]
+        public void DeserializeListTest()
+        {
+            // Arrange
+            ImmutableList<int> data = null!;
+            var rootNode = YamlTextToNode(_serializedListYaml);
+            var serializer = YamlObjectSerializer.NewReader(rootNode);
+
+            // Act
+            serializer.DataField(ref data, "datalist", ImmutableList<int>.Empty);
+
+            // Assert
+            Assert.That(data, Is.Not.Null);
+            Assert.That(data.Count, Is.EqualTo(_serializableList.Count));
+
+            for (var i = 0; i < _serializableList.Count; i++)
+            {
+                Assert.That(data[i], Is.EqualTo(_serializableList[i]));
+            }
+        }
+
+        private readonly string _serializedListYaml = "datalist:\n- 1\n- 2\n- 3\n...\n";
+        private readonly ImmutableList<int> _serializableList = ImmutableList.Create<int>(1, 2, 3);
+    }
+}

Robust.UnitTesting/Shared/Serialization/YamlObjectSerializerTests/TypePropertySerialization_Test.cs

@@ -0,0 +1,101 @@
+using System.IO;
+using NUnit.Framework;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Serialization;
+using YamlDotNet.RepresentationModel;
+// ReSharper disable AccessToStaticMemberViaDerivedType
+
+namespace Robust.UnitTesting.Shared.Serialization.YamlObjectSerializerTests
+{
+    [TestFixture]
+    [TestOf(typeof(YamlObjectSerializer))]
+    public class TypePropertySerialization_Test : RobustUnitTest
+    {
+        [Test]
+        public void SerializeTypePropertiesTest()
+        {
+            ITestType? type = new TestTypeTwo
+            {
+                TestPropertyOne = "B",
+                TestPropertyTwo = 10
+            };
+            var mapping = new YamlMappingNode();
+            var writer = YamlObjectSerializer.NewWriter(mapping);
+
+            writer.DataField(ref type, "test", null!);
+
+            Assert.IsNotEmpty(mapping.Children);
+
+            var testPropertyOne = (YamlScalarNode) mapping["test"]["testPropertyOne"];
+            var testPropertyTwo = (YamlScalarNode) mapping["test"]["testPropertyTwo"];
+
+            Assert.That(testPropertyOne.Value, Is.EqualTo("B"));
+            Assert.That(testPropertyTwo.Value, Is.EqualTo("10"));
+        }
+
+        [Test]
+        public void DeserializeTypePropertiesTest()
+        {
+            ITestType? type = null;
+            var yaml = @"
+- test:
+    !type:testtype2
+    testPropertyOne: A
+    testPropertyTwo: 5
+";
+
+            using var stream = new MemoryStream();
+
+            var writer = new StreamWriter(stream);
+            writer.Write(yaml);
+            writer.Flush();
+            stream.Position = 0;
+
+            var streamReader = new StreamReader(stream);
+            var yamlStream = new YamlStream();
+            yamlStream.Load(streamReader);
+
+            var mapping = (YamlMappingNode) yamlStream.Documents[0].RootNode[0];
+
+            var reader = YamlObjectSerializer.NewReader(mapping);
+            reader.DataField(ref type, "test", null);
+
+            Assert.NotNull(type);
+            Assert.IsInstanceOf<TestTypeTwo>(type);
+
+            var testTypeTwo = (TestTypeTwo) type!;
+
+            Assert.That(testTypeTwo.TestPropertyOne, Is.EqualTo("A"));
+            Assert.That(testTypeTwo.TestPropertyTwo, Is.EqualTo(5));
+        }
+    }
+
+    [SerializedType("testtype2")]
+    public class TestTypeTwo : ITestType
+    {
+        public string? TestPropertyOne { get; set; }
+
+        public int TestPropertyTwo { get; set; }
+
+        void IExposeData.ExposeData(ObjectSerializer serializer)
+        {
+            serializer.DataField(this, x => TestPropertyOne, "testPropertyOne", null);
+            serializer.DataField(this, x => TestPropertyTwo, "testPropertyTwo", 0);
+        }
+    }
+
+    [RegisterComponent]
+    public class TestComponent : Component
+    {
+        public override string Name => "Test";
+
+        public ITestType? TestType { get; set; }
+
+        public override void ExposeData(ObjectSerializer serializer)
+        {
+            base.ExposeData(serializer);
+
+            serializer.DataField(this, x => x.TestType, "testType", null);
+        }
+    }
+}

Robust.UnitTesting/Shared/Serialization/YamlObjectSerializerTests/TypeSerialization_Test.cs

@@ -0,0 +1,66 @@
+using System.IO;
+using NUnit.Framework;
+using Robust.Shared.Serialization;
+using YamlDotNet.RepresentationModel;
+// ReSharper disable AccessToStaticMemberViaDerivedType
+
+namespace Robust.UnitTesting.Shared.Serialization.YamlObjectSerializerTests
+{
+    [TestFixture]
+    [TestOf(typeof(YamlObjectSerializer))]
+    public class TypeSerialization_Test : RobustUnitTest
+    {
+        [Test]
+        public void SerializeTypeTest()
+        {
+            ITestType? type = new TestTypeOne();
+            var mapping = new YamlMappingNode();
+            var writer = YamlObjectSerializer.NewWriter(mapping);
+
+            writer.DataField(ref type, "type", null!);
+
+            Assert.IsNotEmpty(mapping.Children);
+            Assert.IsInstanceOf<YamlScalarNode>(mapping.Children[0].Key);
+
+            var scalar = (YamlScalarNode) mapping.Children[0].Key;
+
+            Assert.That(scalar.Value, Is.EqualTo("type"));
+        }
+
+        [Test]
+        public void DeserializeTypeTest()
+        {
+            ITestType? type = null;
+            var yaml = @"
+test:
+  !type:testtype1";
+
+            using var stream = new MemoryStream();
+
+            var writer = new StreamWriter(stream);
+            writer.Write(yaml);
+            writer.Flush();
+            stream.Position = 0;
+
+            var streamReader = new StreamReader(stream);
+            var yamlStream = new YamlStream();
+            yamlStream.Load(streamReader);
+
+            var mapping = (YamlMappingNode) yamlStream.Documents[0].RootNode;
+
+            var reader = YamlObjectSerializer.NewReader(mapping);
+            reader.DataField(ref type, "test", null);
+
+            Assert.NotNull(type);
+            Assert.IsInstanceOf<TestTypeOne>(type);
+        }
+    }
+
+    public interface ITestType : IExposeData { }
+
+    [SerializedType("testtype1")]
+    public class TestTypeOne : ITestType
+    {
+        void IExposeData.ExposeData(ObjectSerializer serializer) { }
+    }
+}

Robust.UnitTesting/Shared/Serialization/YamlObjectSerializerTests/YamlObjectSerializer_Test.cs

@@ -8,9 +8,10 @@ using Robust.Shared.Maths;
 using Robust.Shared.Serialization;
 using Robust.Shared.Utility;
 using YamlDotNet.RepresentationModel;
+
 // ReSharper disable AccessToStaticMemberViaDerivedType
 
-namespace Robust.UnitTesting.Shared.Serialization
+namespace Robust.UnitTesting.Shared.Serialization.YamlObjectSerializerTests
 {
     [Parallelizable(ParallelScope.All | ParallelScope.Fixtures)]
     [TestFixture]