Support getter only properties such as ElementArray in typed deserializer

Author: kristiker

AttributeList.cs

@@ -261,13 +261,11 @@ public virtual object? this[string name]
                 if (Owner != null && this == Owner.PrefixAttributes && value?.GetType() == typeof(Element))
                     throw new AttributeTypeException("Elements are not supported as prefix attributes.");
 
-                var prop_attr = (PropertyInfo?)PropertyInfos[name];
+                var prop = (PropertyInfo?)PropertyInfos[name];
 
-                if (prop_attr != null)
+                if (prop != null)
                 {
-                    PropertyInfo? prop = GetType().GetProperty(prop_attr.Name, BindingFlags.Public | BindingFlags.Instance);
-
-                    if (prop != null && prop.CanWrite)
+                    if (prop.CanWrite)
                     {
                         // were actually fine with this being null, it will just set the value to null
                         // but need to check so the type check doesn't fail if it is null
@@ -284,6 +282,24 @@ public virtual object? this[string name]
                     }
                     else
                     {
+                        var existingArray = prop.GetValue(this) as Array<Element>;
+                        var incomingArray = value as Array<Element>;
+
+                        if (existingArray is not null && incomingArray is not null)
+                        {
+                            // special case for reflection based deserialization
+                            if (existingArray.Count == 0)
+                            {
+                                existingArray.AddRange(incomingArray);
+                                return;
+                            }
+                            else
+                            {
+                                throw new InvalidOperationException($"Attribute '{name}' modifies property {prop.DeclaringType!.Name}.{prop.Name}, which is write only and can't be replaced.");
+                            }
+                        }
+
+
                         throw new InvalidDataException("Property of deserialisation class must be writeable, make sure it's public and has a public setter");
                     }
 

ICodec.cs

@@ -230,20 +230,38 @@ public static bool TryConstructCustomElement(Dictionary<string, Type> types, Dat
 
             Type derivedType = classType;
 
-            ConstructorInfo? constructor = typeof(Element).GetConstructor(
+            ConstructorInfo? elementConstructor = typeof(Element).GetConstructor(
                 BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic,
                 null,
                 [typeof(Datamodel), typeof(string), typeof(Guid), typeof(string)],
                 null
             );
 
-            if (constructor == null)
+            var customClassInitializer = derivedType.GetConstructor(
+                BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic,
+                null,
+                [],
+                null
+            );
+
+            if (elementConstructor == null)
             {
                 throw new InvalidOperationException("Failed to get constructor while attemption reflection based deserialisation");
             }
 
+            if (customClassInitializer == null)
+            {
+                throw new InvalidOperationException("Failed to get custom element constructor.");
+            }
+
             object uninitializedObject = RuntimeHelpers.GetUninitializedObject(derivedType);
-            constructor.Invoke(uninitializedObject, [dataModel, elem_name, elem_id, elem_class]);
+
+            elementConstructor.Invoke(uninitializedObject, [dataModel, elem_name, elem_id, elem_class]);
+
+            // this will initialize values such as
+            // public Datamodel.ElementArray Children { get; } = [];
+            customClassInitializer.Invoke(uninitializedObject, []);
+
 
             elem = (Element?)uninitializedObject;
             return true;

Tests/ValveMap.cs

@@ -175,16 +175,17 @@ internal class CMapVariableSet : DMElement
 }
 
 
+[CamelCaseProperties]
 internal class CMapSelectionSet : DMElement
 {
-    public Datamodel.ElementArray children { get; set; } = [];
-    public string selectionSetName { get; set; } = string.Empty;
-    public CObjectSelectionSetDataElement selectionSetData { get; set; } = [];
+    public Datamodel.ElementArray Children { get; } = [];
+    public string SelectionSetName { get; set; } = string.Empty;
+    public CObjectSelectionSetDataElement SelectionSetData { get; set; } = [];
 
     public CMapSelectionSet() { }
     public CMapSelectionSet(string name)
     {
-        selectionSetName = name;
+        SelectionSetName = name;
     }
 }
 
@@ -202,13 +203,14 @@ internal class CMapEntity : BaseEntity
 }
 
 
+[LowercaseProperties]
 internal class CMapInstance : BaseEntity
 {
     /// <summary>
     /// A target <see cref="CMapGroup"/> to instance. With custom tint and transform.
     /// </summary>
-    public CMapGroup? target { get; set; }
-    public Datamodel.Color tintColor { get; set; } = new Datamodel.Color(255, 255, 255, 255);
+    public CMapGroup? Target { get; set; }
+    public Datamodel.Color TintColor { get; set; } = new Datamodel.Color(255, 255, 255, 255);
 }
 
 internal class CMapGroup : MapNode