Make AddComponent load default DataField values (#1112)

Co-authored-by: Pieter-Jan Briers <pieterjan.briers+git@gmail.com>

Robust.Shared/GameObjects/ComponentManager.cs

@@ -6,6 +6,7 @@ using Robust.Shared.Exceptions;
 using Robust.Shared.Interfaces.GameObjects;
 using Robust.Shared.Interfaces.GameObjects.Components;
 using Robust.Shared.IoC;
+using Robust.Shared.Serialization;
 using Robust.Shared.Utility;
 
 namespace Robust.Shared.GameObjects
@@ -127,6 +128,8 @@ namespace Robust.Shared.GameObjects
                 ComponentAdded?.Invoke(this, new ComponentEventArgs(component));
             }
 
+            component.ExposeData(DefaultValueSerializer.Reader());
+
             component.OnAdd();
 
             if (entity.Initialized || entity.Initializing)

Robust.Shared/Serialization/DefaultValueSerializer.cs

@@ -0,0 +1,69 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq.Expressions;
+using Robust.Shared.Interfaces.Serialization;
+
+namespace Robust.Shared.Serialization
+{
+    public sealed class DefaultValueSerializer : ObjectSerializer
+    {
+        public static DefaultValueSerializer Reader()
+        {
+            return new DefaultValueSerializer()
+            {
+                Reading = true,
+            };
+        }
+
+        private DefaultValueSerializer() {}
+
+        public override void DataField<T>(ref T value, string name, T defaultValue, WithFormat<T> withFormat, bool alwaysWrite = false)
+        {
+            if (Reading)
+            {
+                if (EqualityComparer<T>.Default.Equals(value, default))
+                  value = defaultValue;
+            }
+        }
+
+        public override T ReadDataField<T>(string name, T defaultValue)
+        {
+            return defaultValue;
+        }
+
+        public override bool TryReadDataField<T>(string name, WithFormat<T> format, [MaybeNullWhen(false)] out T value)
+        {
+            value = default;
+            return false;
+        }
+
+        public override void DataField<TTarget, TSource>(
+            ref TTarget value,
+            string name,
+            TTarget defaultValue,
+            ReadConvertFunc<TTarget, TSource> ReadConvertFunc,
+            WriteConvertFunc<TTarget, TSource>? WriteConvertFunc = null,
+            bool alwaysWrite = false
+        )
+        {
+            if (Reading)
+            {
+                if (EqualityComparer<TTarget>.Default.Equals(value, default))
+                  value = defaultValue;
+            }
+        }
+
+        public override void DataReadFunction<T>(string name, T defaultValue, ReadFunctionDelegate<T> func)
+        {
+            if (Reading)
+            {
+                func(defaultValue);
+            }
+        }
+
+        public override void DataWriteFunction<T>(string name, T defaultValue, WriteFunctionDelegate<T> func, bool alwaysWrite = false)
+        {
+        }
+    }
+}

Robust.Shared/Serialization/ObjectSerializer.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq.Expressions;
+using System.Reflection;
 using Robust.Shared.Interfaces.Reflection;
 using Robust.Shared.Interfaces.Serialization;
 using Robust.Shared.IoC;
@@ -78,7 +79,43 @@ namespace Robust.Shared.Serialization
         ///     szr.DataField(this, x => x.SomeProperty, "some-property", SomeDefaultValue);
         /// </example>
         /// </remarks>
-        public abstract void DataField<TRoot, T>(TRoot root, Expression<Func<TRoot,T>> expr, string name, T defaultValue, bool alwaysWrite = false);
+        public virtual void DataField<TRoot, T>(TRoot o, Expression<Func<TRoot,T>> expr, string name, T defaultValue, bool alwaysWrite = false)
+        {
+            if (o == null)
+            {
+                throw new ArgumentNullException(nameof(o));
+            }
+
+            if (expr == null)
+            {
+                throw new ArgumentNullException(nameof(expr));
+            }
+
+            if (!(expr.Body is MemberExpression mExpr))
+            {
+                throw new NotSupportedException("Cannot handle expressions of types other than MemberExpression.");
+            }
+
+
+            WriteFunctionDelegate<T> getter;
+            ReadFunctionDelegate<T> setter;
+            switch (mExpr.Member)
+            {
+                case FieldInfo fi:
+                    getter = () => (T) fi.GetValue(o)!;
+                    setter = v => fi.SetValue(o, v);
+                    break;
+                case PropertyInfo pi:
+                    getter = () => (T) pi.GetValue(o)!;
+                    setter = v => pi.SetValue(o, v);
+                    break;
+                default:
+                    throw new NotSupportedException("Cannot handle member expressions of types other than FieldInfo or PropertyInfo.");
+            }
+
+            DataReadWriteFunction(name, defaultValue, setter, getter, alwaysWrite);
+        }
+
 
         /// <summary>
         ///     Writes or reads a simple field by reference.
@@ -230,22 +267,22 @@ namespace Robust.Shared.Serialization
         /// <summary>
         ///     Try- pattern version of <see cref="ReadDataField" />.
         /// </summary>
-        public virtual bool TryReadDataField<T>(string name, out T value)
+        public virtual bool TryReadDataField<T>(string name, [MaybeNullWhen(false)] out T value)
         {
             return TryReadDataField(name, WithFormat<T>.NoFormat, out value);
         }
 
-        public abstract bool TryReadDataField<T>(string name, WithFormat<T> format, out T value);
+        public abstract bool TryReadDataField<T>(string name, WithFormat<T> format, [MaybeNullWhen(false)] out T value);
 
         /// <summary>
         ///     Try- pattern version of <see cref="ReadDataFieldCached" />.
         /// </summary>
-        public virtual bool TryReadDataFieldCached<T>(string name, out T value)
+        public virtual bool TryReadDataFieldCached<T>(string name, [MaybeNullWhen(false)] out T value)
         {
             return TryReadDataFieldCached(name, WithFormat<T>.NoFormat, out value);
         }
 
-        public virtual bool TryReadDataFieldCached<T>(string name, WithFormat<T> format, out T value)
+        public virtual bool TryReadDataFieldCached<T>(string name, WithFormat<T> format, [MaybeNullWhen(false)] out T value)
         {
             return TryReadDataField(name, format, out value);
         }

Robust.Shared/Serialization/YamlObjectSerializer.cs

@@ -152,43 +152,6 @@ namespace Robust.Shared.Serialization
         }
 
 
-        public override void DataField<TRoot, T>(TRoot o, Expression<Func<TRoot,T>> expr, string name, T defaultValue, bool alwaysWrite = false)
-        {
-            if (o == null)
-            {
-                throw new ArgumentNullException(nameof(o));
-            }
-
-            if (expr == null)
-            {
-                throw new ArgumentNullException(nameof(expr));
-            }
-
-            if (!(expr.Body is MemberExpression mExpr))
-            {
-                throw new NotSupportedException("Cannot handle expressions of types other than MemberExpression.");
-            }
-
-
-            WriteFunctionDelegate<T> getter;
-            ReadFunctionDelegate<T> setter;
-            switch (mExpr.Member)
-            {
-                case FieldInfo fi:
-                    getter = () => (T) fi.GetValue(o)!;
-                    setter = v => fi.SetValue(o, v);
-                    break;
-                case PropertyInfo pi:
-                    getter = () => (T) pi.GetValue(o)!;
-                    setter = v => pi.SetValue(o, v);
-                    break;
-                default:
-                    throw new NotSupportedException("Cannot handle member expressions of types other than FieldInfo or PropertyInfo.");
-            }
-
-            DataReadWriteFunction(name, defaultValue, setter, getter, alwaysWrite);
-        }
-
         /// <inheritdoc />
         public override void DataFieldCached<T>(ref T value, string name, T defaultValue, WithFormat<T> format, bool alwaysWrite = false)
         {