C#: Cleanup Variant marshaling code in source/bindings generators

This change aims to reduce the number of places that need to be changed
when adding or editing a Godot type to the bindings.

Since the addition of `Variant.From<T>/As<T>` and
`VariantUtils.CreateFrom<T>/ConvertTo<T>`, we can now replace a lot of
the previous code in the bindings generator and the source generators
that specify these conversions for each type manually.

The only exceptions are the generic Godot collections (`Array<T>` and
`Dictionary<TKey, TValue>`) which still use the old version, as that
one cannot be matched by our new conversion methods (limitation in the
language with generics, forcing us to use delegate pointers).

The cleanup applies to:

- Bindings generator:
  - `TypeInterface.cs_variant_to_managed`
  - `TypeInterface.cs_managed_to_variant`
- Source generators:
  - `MarshalUtils.AppendNativeVariantToManagedExpr`
  - `MarshalUtils.AppendManagedToNativeVariantExpr`
  - `MarshalUtils.AppendVariantToManagedExpr`
  - `MarshalUtils.AppendManagedToVariantExpr`

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/ExtensionMethods.cs

@@ -268,8 +268,9 @@ MarshalUtils.TypeCache typeCache
             if (parameters.Length > paramTypes.Length)
                 return null; // Ignore incompatible method
 
-            return new GodotMethodData(method, paramTypes, parameters
-                .Select(p => p.Type).ToImmutableArray(), retType, retSymbol);
+            return new GodotMethodData(method, paramTypes,
+                parameters.Select(p => p.Type).ToImmutableArray(),
+                retType != null ? (retType.Value, retSymbol) : null);
         }
 
         public static IEnumerable<GodotMethodData> WhereHasGodotCompatibleSignature(
@@ -330,10 +331,10 @@ MarshalUtils.TypeCache typeCache
 
         public static string Path(this Location location)
             => location.SourceTree?.GetLineSpan(location.SourceSpan).Path
-            ?? location.GetLineSpan().Path;
+               ?? location.GetLineSpan().Path;
 
         public static int StartLine(this Location location)
             => location.SourceTree?.GetLineSpan(location.SourceSpan).StartLinePosition.Line
-            ?? location.GetLineSpan().StartLinePosition.Line;
+               ?? location.GetLineSpan().StartLinePosition.Line;
     }
 }

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/GodotMemberData.cs

@@ -6,20 +6,18 @@ namespace Godot.SourceGenerators
     public readonly struct GodotMethodData
     {
         public GodotMethodData(IMethodSymbol method, ImmutableArray<MarshalType> paramTypes,
-            ImmutableArray<ITypeSymbol> paramTypeSymbols, MarshalType? retType, ITypeSymbol? retSymbol)
+            ImmutableArray<ITypeSymbol> paramTypeSymbols, (MarshalType MarshalType, ITypeSymbol TypeSymbol)? retType)
         {
             Method = method;
             ParamTypes = paramTypes;
             ParamTypeSymbols = paramTypeSymbols;
             RetType = retType;
-            RetSymbol = retSymbol;
         }
 
         public IMethodSymbol Method { get; }
         public ImmutableArray<MarshalType> ParamTypes { get; }
         public ImmutableArray<ITypeSymbol> ParamTypeSymbols { get; }
-        public MarshalType? RetType { get; }
-        public ITypeSymbol? RetSymbol { get; }
+        public (MarshalType MarshalType, ITypeSymbol TypeSymbol)? RetType { get; }
     }
 
     public readonly struct GodotSignalDelegateData

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/ScriptMethodsGenerator.cs

@@ -135,7 +135,8 @@ INamedTypeSymbol symbol
 
             source.Append("#pragma warning disable CS0109 // Disable warning about redundant 'new' keyword\n");
 
-            source.Append($"    public new class MethodName : {symbol.BaseType.FullQualifiedNameIncludeGlobal()}.MethodName {{\n");
+            source.Append(
+                $"    public new class MethodName : {symbol.BaseType.FullQualifiedNameIncludeGlobal()}.MethodName {{\n");
 
             // Generate cached StringNames for methods and properties, for fast lookup
 
@@ -297,7 +298,7 @@ private static MethodInfo DetermineMethodInfo(GodotMethodData method)
 
             if (method.RetType != null)
             {
-                returnVal = DeterminePropertyInfo(method.RetType.Value, name: string.Empty);
+                returnVal = DeterminePropertyInfo(method.RetType.Value.MarshalType, name: string.Empty);
             }
             else
             {
@@ -391,7 +392,8 @@ StringBuilder source
             {
                 source.Append("            ret = ");
 
-                source.AppendManagedToNativeVariantExpr("callRet", method.RetType.Value);
+                source.AppendManagedToNativeVariantExpr("callRet",
+                    method.RetType.Value.TypeSymbol, method.RetType.Value.MarshalType);
                 source.Append(";\n");
 
                 source.Append("            return true;\n");

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/ScriptPropertiesGenerator.cs

@@ -124,7 +124,8 @@ INamedTypeSymbol symbol
 
             source.Append("#pragma warning disable CS0109 // Disable warning about redundant 'new' keyword\n");
 
-            source.Append($"    public new class PropertyName : {symbol.BaseType.FullQualifiedNameIncludeGlobal()}.PropertyName {{\n");
+            source.Append(
+                $"    public new class PropertyName : {symbol.BaseType.FullQualifiedNameIncludeGlobal()}.PropertyName {{\n");
 
             // Generate cached StringNames for methods and properties, for fast lookup
 
@@ -199,14 +200,14 @@ INamedTypeSymbol symbol
                 foreach (var property in godotClassProperties)
                 {
                     GeneratePropertyGetter(property.PropertySymbol.Name,
-                        property.Type, source, isFirstEntry);
+                        property.PropertySymbol.Type, property.Type, source, isFirstEntry);
                     isFirstEntry = false;
                 }
 
                 foreach (var field in godotClassFields)
                 {
                     GeneratePropertyGetter(field.FieldSymbol.Name,
-                        field.Type, source, isFirstEntry);
+                        field.FieldSymbol.Type, field.Type, source, isFirstEntry);
                     isFirstEntry = false;
                 }
 
@@ -303,6 +304,7 @@ bool isFirstEntry
 
         private static void GeneratePropertyGetter(
             string propertyMemberName,
+            ITypeSymbol propertyTypeSymbol,
             MarshalType propertyMarshalType,
             StringBuilder source,
             bool isFirstEntry
@@ -317,7 +319,8 @@ bool isFirstEntry
                 .Append(propertyMemberName)
                 .Append(") {\n")
                 .Append("            value = ")
-                .AppendManagedToNativeVariantExpr("this." + propertyMemberName, propertyMarshalType)
+                .AppendManagedToNativeVariantExpr("this." + propertyMemberName,
+                    propertyTypeSymbol, propertyMarshalType)
                 .Append(";\n")
                 .Append("            return true;\n")
                 .Append("        }\n");
@@ -376,7 +379,8 @@ private static IEnumerable<PropertyInfo> DetermineGroupingPropertyInfo(ISymbol m
                     if (propertyUsage != PropertyUsageFlags.Category && attr.ConstructorArguments.Length > 1)
                         hintString = attr.ConstructorArguments[1].Value?.ToString();
 
-                    yield return new PropertyInfo(VariantType.Nil, name, PropertyHint.None, hintString, propertyUsage.Value, true);
+                    yield return new PropertyInfo(VariantType.Nil, name, PropertyHint.None, hintString,
+                        propertyUsage.Value, true);
                 }
             }
         }

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/ScriptPropertyDefValGenerator.cs

@@ -307,7 +307,8 @@ INamedTypeSymbol symbol
                     source.Append("        values.Add(PropertyName.");
                     source.Append(exportedMember.Name);
                     source.Append(", ");
-                    source.AppendManagedToVariantExpr(defaultValueLocalName, exportedMember.Type);
+                    source.AppendManagedToVariantExpr(defaultValueLocalName,
+                        exportedMember.TypeSymbol, exportedMember.Type);
                     source.Append(");\n");
                 }
 

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/ScriptSerializationGenerator.cs

@@ -162,7 +162,8 @@ INamedTypeSymbol symbol
                 source.Append("        info.AddProperty(PropertyName.")
                     .Append(propertyName)
                     .Append(", ")
-                    .AppendManagedToVariantExpr(string.Concat("this.", propertyName), property.Type)
+                    .AppendManagedToVariantExpr(string.Concat("this.", propertyName),
+                        property.PropertySymbol.Type, property.Type)
                     .Append(");\n");
             }
 
@@ -175,7 +176,8 @@ INamedTypeSymbol symbol
                 source.Append("        info.AddProperty(PropertyName.")
                     .Append(fieldName)
                     .Append(", ")
-                    .AppendManagedToVariantExpr(string.Concat("this.", fieldName), field.Type)
+                    .AppendManagedToVariantExpr(string.Concat("this.", fieldName),
+                        field.FieldSymbol.Type, field.Type)
                     .Append(");\n");
             }
 

modules/mono/editor/Godot.NET.Sdk/Godot.SourceGenerators/ScriptSignalsGenerator.cs

@@ -176,7 +176,8 @@ INamedTypeSymbol symbol
 
             source.Append("#pragma warning disable CS0109 // Disable warning about redundant 'new' keyword\n");
 
-            source.Append($"    public new class SignalName : {symbol.BaseType.FullQualifiedNameIncludeGlobal()}.SignalName {{\n");
+            source.Append(
+                $"    public new class SignalName : {symbol.BaseType.FullQualifiedNameIncludeGlobal()}.SignalName {{\n");
 
             // Generate cached StringNames for methods and properties, for fast lookup
 
@@ -236,7 +237,8 @@ INamedTypeSymbol symbol
                     .Append(signalName)
                     .Append(";\n");
 
-                source.Append($"    /// <inheritdoc cref=\"{signalDelegate.DelegateSymbol.FullQualifiedNameIncludeGlobal()}\"/>\n");
+                source.Append(
+                    $"    /// <inheritdoc cref=\"{signalDelegate.DelegateSymbol.FullQualifiedNameIncludeGlobal()}\"/>\n");
 
                 source.Append("    public event ")
                     .Append(signalDelegate.DelegateSymbol.FullQualifiedNameIncludeGlobal())
@@ -351,7 +353,7 @@ private static MethodInfo DetermineMethodInfo(GodotSignalDelegateData signalDele
 
             if (invokeMethodData.RetType != null)
             {
-                returnVal = DeterminePropertyInfo(invokeMethodData.RetType.Value, name: string.Empty);
+                returnVal = DeterminePropertyInfo(invokeMethodData.RetType.Value.MarshalType, name: string.Empty);
             }
             else
             {

modules/mono/editor/bindings_generator.cpp

@@ -2837,9 +2837,6 @@ bool BindingsGenerator::_populate_object_type_interfaces() {
 		itype.is_ref_counted = ClassDB::is_parent_class(type_cname, name_cache.type_RefCounted);
 		itype.memory_own = itype.is_ref_counted;
 
-		itype.cs_variant_to_managed = "(%1)VariantUtils.ConvertToGodotObject(%0)";
-		itype.cs_managed_to_variant = "VariantUtils.CreateFromGodotObject(%0)";
-
 		itype.c_out = "%5return ";
 		itype.c_out += C_METHOD_UNMANAGED_GET_MANAGED;
 		itype.c_out += itype.is_ref_counted ? "(%1.Reference);\n" : "(%1);\n";
@@ -3218,8 +3215,6 @@ bool BindingsGenerator::_populate_object_type_interfaces() {
 			enum_itype.cname = StringName(enum_itype.name);
 			enum_itype.proxy_name = itype.proxy_name + "." + enum_proxy_name;
 			TypeInterface::postsetup_enum_type(enum_itype);
-			enum_itype.cs_variant_to_managed = "(%1)VariantUtils.ConvertToInt32(%0)";
-			enum_itype.cs_managed_to_variant = "VariantUtils.CreateFromInt((int)%0)";
 			enum_types.insert(enum_itype.cname, enum_itype);
 		}
 
@@ -3448,16 +3443,14 @@ void BindingsGenerator::_populate_builtin_type_interfaces() {
 
 	TypeInterface itype;
 
-#define INSERT_STRUCT_TYPE(m_type)                                     \
-	{                                                                  \
-		itype = TypeInterface::create_value_type(String(#m_type));     \
-		itype.c_type_in = #m_type "*";                                 \
-		itype.c_type_out = itype.cs_type;                              \
-		itype.cs_in_expr = "&%0";                                      \
-		itype.cs_in_expr_is_unsafe = true;                             \
-		itype.cs_variant_to_managed = "VariantUtils.ConvertTo%2(%0)";  \
-		itype.cs_managed_to_variant = "VariantUtils.CreateFrom%2(%0)"; \
-		builtin_types.insert(itype.cname, itype);                      \
+#define INSERT_STRUCT_TYPE(m_type)                                 \
+	{                                                              \
+		itype = TypeInterface::create_value_type(String(#m_type)); \
+		itype.c_type_in = #m_type "*";                             \
+		itype.c_type_out = itype.cs_type;                          \
+		itype.cs_in_expr = "&%0";                                  \
+		itype.cs_in_expr_is_unsafe = true;                         \
+		builtin_types.insert(itype.cname, itype);                  \
 	}
 
 	INSERT_STRUCT_TYPE(Vector2)
@@ -3488,8 +3481,6 @@ void BindingsGenerator::_populate_builtin_type_interfaces() {
 	itype.c_type_out = itype.c_type;
 	itype.c_arg_in = "&%s";
 	itype.c_in_vararg = "%5using godot_variant %1_in = VariantUtils.CreateFromBool(%1);\n";
-	itype.cs_variant_to_managed = "VariantUtils.ConvertToBool(%0)";
-	itype.cs_managed_to_variant = "VariantUtils.CreateFromBool(%0)";
 	builtin_types.insert(itype.cname, itype);
 
 	// Integer types
@@ -3510,8 +3501,6 @@ void BindingsGenerator::_populate_builtin_type_interfaces() {
 		itype.c_type_in = itype.name;                                                          \
 		itype.c_type_out = itype.name;                                                         \
 		itype.c_in_vararg = "%5using godot_variant %1_in = VariantUtils.CreateFromInt(%1);\n"; \
-		itype.cs_variant_to_managed = "VariantUtils.ConvertTo" m_int_struct_name "(%0)";       \
-		itype.cs_managed_to_variant = "VariantUtils.CreateFromInt(%0)";                        \
 		builtin_types.insert(itype.cname, itype);                                              \
 	}
 
@@ -3547,8 +3536,6 @@ void BindingsGenerator::_populate_builtin_type_interfaces() {
 		itype.c_type_in = itype.proxy_name;
 		itype.c_type_out = itype.proxy_name;
 		itype.c_in_vararg = "%5using godot_variant %1_in = VariantUtils.CreateFromFloat(%1);\n";
-		itype.cs_variant_to_managed = "VariantUtils.ConvertToFloat32(%0)";
-		itype.cs_managed_to_variant = "VariantUtils.CreateFromFloat(%0)";
 		builtin_types.insert(itype.cname, itype);
 
 		// double
@@ -3562,8 +3549,6 @@ void BindingsGenerator::_populate_builtin_type_interfaces() {
 		itype.c_type_in = itype.proxy_name;
 		itype.c_type_out = itype.proxy_name;
 		itype.c_in_vararg = "%5using godot_variant %1_in = VariantUtils.CreateFromFloat(%1);\n";
-		itype.cs_variant_to_managed = "VariantUtils.ConvertToFloat64(%0)";
-		itype.cs_managed_to_variant = "VariantUtils.CreateFromFloat(%0)";
 		builtin_types.insert(itype.cname, itype);
 	}
 
@@ -3581,8 +3566,6 @@ void BindingsGenerator::_populate_builtin_type_interfaces() {
 	itype.c_type_out = itype.cs_type;
 	itype.c_type_is_disposable_struct = true;
 	itype.c_in_vararg = "%5using godot_variant %1_in = VariantUtils.CreateFromString(%1);\n";
-	itype.cs_variant_to_managed = "VariantUtils.ConvertToStringObject(%0)";
-	itype.cs_managed_to_variant = "VariantUtils.CreateFromString(%0)";
 	builtin_types.insert(itype.cname, itype);
 
 	// StringName
@@ -3601,8 +3584,6 @@ void BindingsGenerator::_populate_builtin_type_interfaces() {
 	itype.c_in_vararg = "%5using godot_variant %1_in = VariantUtils.CreateFromStringName(%1);\n";
 	itype.c_type_is_disposable_struct = false; // [c_out] takes ownership
 	itype.c_ret_needs_default_initialization = true;
-	itype.cs_variant_to_managed = "VariantUtils.ConvertToStringNameObject(%0)";
-	itype.cs_managed_to_variant = "VariantUtils.CreateFromStringName(%0)";
 	builtin_types.insert(itype.cname, itype);
 
 	// NodePath
@@ -3620,8 +3601,6 @@ void BindingsGenerator::_populate_builtin_type_interfaces() {
 	itype.c_type_out = itype.cs_type;
 	itype.c_type_is_disposable_struct = false; // [c_out] takes ownership
 	itype.c_ret_needs_default_initialization = true;
-	itype.cs_variant_to_managed = "VariantUtils.ConvertToNodePathObject(%0)";
-	itype.cs_managed_to_variant = "VariantUtils.CreateFromNodePath(%0)";
 	builtin_types.insert(itype.cname, itype);
 
 	// RID
@@ -3634,8 +3613,6 @@ void BindingsGenerator::_populate_builtin_type_interfaces() {
 	itype.c_type = itype.cs_type;
 	itype.c_type_in = itype.c_type;
 	itype.c_type_out = itype.c_type;
-	itype.cs_variant_to_managed = "VariantUtils.ConvertToRID(%0)";
-	itype.cs_managed_to_variant = "VariantUtils.CreateFromRID(%0)";
 	builtin_types.insert(itype.cname, itype);
 
 	// Variant
@@ -3652,8 +3629,6 @@ void BindingsGenerator::_populate_builtin_type_interfaces() {
 	itype.c_type_out = itype.cs_type;
 	itype.c_type_is_disposable_struct = false; // [c_out] takes ownership
 	itype.c_ret_needs_default_initialization = true;
-	itype.cs_variant_to_managed = "Variant.CreateCopyingBorrowed(%0)";
-	itype.cs_managed_to_variant = "%0.CopyNativeVariant()";
 	builtin_types.insert(itype.cname, itype);
 
 	// Callable
@@ -3666,8 +3641,6 @@ void BindingsGenerator::_populate_builtin_type_interfaces() {
 	itype.c_type_in = "in " + itype.cs_type;
 	itype.c_type_out = itype.cs_type;
 	itype.c_type_is_disposable_struct = true;
-	itype.cs_variant_to_managed = "VariantUtils.ConvertToCallableManaged(%0)";
-	itype.cs_managed_to_variant = "VariantUtils.CreateFromCallable(%0)";
 	builtin_types.insert(itype.cname, itype);
 
 	// Signal
@@ -3684,8 +3657,6 @@ void BindingsGenerator::_populate_builtin_type_interfaces() {
 	itype.c_type_in = "in " + itype.cs_type;
 	itype.c_type_out = itype.cs_type;
 	itype.c_type_is_disposable_struct = true;
-	itype.cs_variant_to_managed = "VariantUtils.ConvertToSignalInfo(%0)";
-	itype.cs_managed_to_variant = "VariantUtils.CreateFromSignalInfo(%0)";
 	builtin_types.insert(itype.cname, itype);
 
 	// VarArg (fictitious type to represent variable arguments)
@@ -3715,8 +3686,6 @@ void BindingsGenerator::_populate_builtin_type_interfaces() {
 		itype.c_type_in = itype.proxy_name;                                         \
 		itype.c_type_out = itype.proxy_name;                                        \
 		itype.c_type_is_disposable_struct = true;                                   \
-		itype.cs_variant_to_managed = "VariantUtils.ConvertAs%2ToSystemArray(%0)";  \
-		itype.cs_managed_to_variant = "VariantUtils.CreateFrom%2(%0)";              \
 		builtin_types.insert(itype.name, itype);                                    \
 	}
 
@@ -3752,15 +3721,16 @@ void BindingsGenerator::_populate_builtin_type_interfaces() {
 	itype.c_type_out = itype.cs_type;
 	itype.c_type_is_disposable_struct = false; // [c_out] takes ownership
 	itype.c_ret_needs_default_initialization = true;
-	itype.cs_variant_to_managed = "VariantUtils.ConvertToArrayObject(%0)";
-	itype.cs_managed_to_variant = "VariantUtils.CreateFromArray(%0)";
 	builtin_types.insert(itype.cname, itype);
 
 	// Array_@generic
 	// Re-use Array's itype
 	itype.name = "Array_@generic";
 	itype.cname = itype.name;
 	itype.cs_out = "%5return new %2(%0(%1));";
+	// For generic Godot collections, Variant.From<T>/As<T> is slower, so we need this special case
+	itype.cs_variant_to_managed = "VariantUtils.ConvertToArrayObject(%0)";
+	itype.cs_managed_to_variant = "VariantUtils.CreateFromArray(%0)";
 	builtin_types.insert(itype.cname, itype);
 
 	// Dictionary
@@ -3778,15 +3748,16 @@ void BindingsGenerator::_populate_builtin_type_interfaces() {
 	itype.c_type_out = itype.cs_type;
 	itype.c_type_is_disposable_struct = false; // [c_out] takes ownership
 	itype.c_ret_needs_default_initialization = true;
-	itype.cs_variant_to_managed = "VariantUtils.ConvertToDictionaryObject(%0)";
-	itype.cs_managed_to_variant = "VariantUtils.CreateFromDictionary(%0)";
 	builtin_types.insert(itype.cname, itype);
 
 	// Dictionary_@generic
 	// Re-use Dictionary's itype
 	itype.name = "Dictionary_@generic";
 	itype.cname = itype.name;
 	itype.cs_out = "%5return new %2(%0(%1));";
+	// For generic Godot collections, Variant.From<T>/As<T> is slower, so we need this special case
+	itype.cs_variant_to_managed = "VariantUtils.ConvertToDictionaryObject(%0)";
+	itype.cs_managed_to_variant = "VariantUtils.CreateFromDictionary(%0)";
 	builtin_types.insert(itype.cname, itype);
 
 	// void (fictitious type to represent the return type of methods that do not return anything)
@@ -3852,8 +3823,6 @@ void BindingsGenerator::_populate_global_constants() {
 			enum_itype.cname = ienum.cname;
 			enum_itype.proxy_name = enum_itype.name;
 			TypeInterface::postsetup_enum_type(enum_itype);
-			enum_itype.cs_variant_to_managed = "(%1)VariantUtils.ConvertToInt32(%0)";
-			enum_itype.cs_managed_to_variant = "VariantUtils.CreateFromInt((int)%0)";
 			enum_types.insert(enum_itype.cname, enum_itype);
 
 			int prefix_length = _determine_enum_prefix(ienum);
@@ -3886,8 +3855,6 @@ void BindingsGenerator::_populate_global_constants() {
 		enum_itype.cname = enum_cname;
 		enum_itype.proxy_name = enum_itype.name;
 		TypeInterface::postsetup_enum_type(enum_itype);
-		enum_itype.cs_variant_to_managed = "(%1)VariantUtils.ConvertToInt32(%0)";
-		enum_itype.cs_managed_to_variant = "VariantUtils.CreateFromInt((int)%0)";
 		enum_types.insert(enum_itype.cname, enum_itype);
 	}
 }