[Rgen] Add properties in the Property data model to decide if a field is needed.

src/ObjCBindings/ExportTag.cs

@@ -127,6 +127,13 @@ public enum Property : Int64 {
 		/// </summary>
 		IsThreadSafe = 1 << 7,
 
+		/// <summary>
+		/// If this falgs is applied to a property, we do not generate a
+		/// backing field.   See bugzilla #3359 and Assistly 7032 for some
+		/// background information
+		/// </summary>
+		Transient = 1 << 8,
+
 	}
 }
 

src/rgen/Microsoft.Macios.Generator/DataModel/Property.Generator.cs

@@ -3,11 +3,14 @@
 
 using System.Collections.Immutable;
 using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+using System.Text;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.Macios.Generator.Attributes;
 using Microsoft.Macios.Generator.Context;
 using Microsoft.Macios.Generator.Extensions;
+using ObjCRuntime;
 
 namespace Microsoft.Macios.Generator.DataModel;
 
@@ -50,6 +53,50 @@ public bool IsNotification
 	public bool MarshalNativeExceptions
 		=> IsProperty && ExportPropertyData.Value.Flags.HasFlag (ObjCBindings.Property.MarshalNativeExceptions);
 
+	/// <summary>
+	/// True if the property should be generated without a backing field.
+	/// </summary>
+	public bool IsTransient => IsProperty && ExportPropertyData.Value.Flags.HasFlag (ObjCBindings.Property.Transient);
+
+	readonly bool? needsBackingField = null;
+	/// <summary>
+	/// States if the property, when generated, needs a backing field.
+	/// </summary>
+	public bool NeedsBackingField {
+		get {
+			if (needsBackingField is not null)
+				return needsBackingField.Value;
+			var isWrapped = ReturnType.IsWrapped ||
+							ReturnType is { IsArray: true, ArrayElementTypeIsWrapped: true };
+			return isWrapped && !IsTransient;
+		}
+		// Added to allow testing. This way we can set the correct expectation in the test factory
+		init => needsBackingField = value;
+	}
+
+	readonly bool? requiresDirtyCheck = null;
+	/// <summary>
+	/// States if the property, when generated, should have a dirty check.
+	/// </summary>
+	public bool RequiresDirtyCheck {
+		get {
+			if (requiresDirtyCheck is not null)
+				return requiresDirtyCheck.Value;
+			if (!IsProperty)
+				return false;
+			switch (ExportPropertyData.Value.ArgumentSemantic) {
+			case ArgumentSemantic.Copy:
+			case ArgumentSemantic.Retain:
+			case ArgumentSemantic.None:
+				return NeedsBackingField;
+			default:
+				return false;
+			}
+		}
+		// Added to allow testing. This way we can set the correct expectation in the test factory
+		init => requiresDirtyCheck = value;
+	}
+
 	static FieldInfo<ObjCBindings.Property>? GetFieldInfo (RootBindingContext context, IPropertySymbol propertySymbol)
 	{
 		// grab the last port of the namespace
@@ -122,4 +169,34 @@ public static bool TryCreate (PropertyDeclarationSyntax declaration, RootBinding
 		};
 		return true;
 	}
+
+	/// <inheritdoc />
+	public bool Equals (Property other)
+	{
+		if (!CoreEquals (other))
+			return false;
+		if (IsTransient != other.IsTransient)
+			return false;
+		if (NeedsBackingField != other.NeedsBackingField)
+			return false;
+		return RequiresDirtyCheck == other.RequiresDirtyCheck;
+	}
+
+	/// <inheritdoc />
+	public override string ToString ()
+	{
+		var sb = new StringBuilder (
+			$"Name: '{Name}', Type: {ReturnType}, Supported Platforms: {SymbolAvailability}, ExportFieldData: '{ExportFieldData?.ToString () ?? "null"}', ExportPropertyData: '{ExportPropertyData?.ToString () ?? "null"}', ");
+		sb.Append ($"IsTransient: '{IsTransient}', ");
+		sb.Append ($"NeedsBackingField: '{NeedsBackingField}', ");
+		sb.Append ($"RequiresDirtyCheck: '{RequiresDirtyCheck}', ");
+		sb.Append ("Attributes: [");
+		sb.AppendJoin (",", Attributes);
+		sb.Append ("], Modifiers: [");
+		sb.AppendJoin (",", Modifiers.Select (x => x.Text));
+		sb.Append ("], Accessors: [");
+		sb.AppendJoin (",", Accessors);
+		sb.Append (']');
+		return sb.ToString ();
+	}
 }

src/rgen/Microsoft.Macios.Generator/DataModel/Property.cs

@@ -2,9 +2,7 @@
 // Licensed under the MIT License.
 using System;
 using System.Collections.Immutable;
-using System.Linq;
 using System.Runtime.InteropServices;
-using System.Text;
 using Microsoft.CodeAnalysis;
 using Microsoft.Macios.Generator.Availability;
 
@@ -96,8 +94,7 @@ internal Property (string name, TypeInfo returnType,
 		Accessors = accessors;
 	}
 
-	/// <inheritdoc />
-	public bool Equals (Property other)
+	bool CoreEquals (Property other)
 	{
 		// this could be a large && but ifs are more readable
 		if (Name != other.Name)
@@ -151,17 +148,4 @@ public override int GetHashCode ()
 		return !left.Equals (right);
 	}
 
-	/// <inheritdoc />
-	public override string ToString ()
-	{
-		var sb = new StringBuilder (
-			$"Name: '{Name}', Type: {ReturnType}, Supported Platforms: {SymbolAvailability}, ExportFieldData: '{ExportFieldData?.ToString () ?? "null"}', ExportPropertyData: '{ExportPropertyData?.ToString () ?? "null"}' Attributes: [");
-		sb.AppendJoin (",", Attributes);
-		sb.Append ("], Modifiers: [");
-		sb.AppendJoin (",", Modifiers.Select (x => x.Text));
-		sb.Append ("], Accessors: [");
-		sb.AppendJoin (",", Accessors);
-		sb.Append (']');
-		return sb.ToString ();
-	}
 }

src/rgen/Microsoft.Macios.Transformer/DataModel/Property.Transformer.cs

@@ -1,7 +1,9 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+using System.Collections;
 using System.Diagnostics.CodeAnalysis;
+using System.Text;
 using Microsoft.Macios.Transformer.Attributes;
 
 namespace Microsoft.Macios.Generator.DataModel;
@@ -36,4 +38,21 @@ readonly partial struct Property {
 	/// True if the method was exported with the MarshalNativeExceptions flag allowing it to support native exceptions.
 	/// </summary>
 	public bool MarshalNativeExceptions => throw new NotImplementedException ();
+
+	/// <inheritdoc />
+	public bool Equals (Property other) => Comparer.Equals (this, other);
+
+	/// <inheritdoc />
+	public override string ToString ()
+	{
+		var sb = new StringBuilder (
+			$"Name: '{Name}', Type: {ReturnType}, Supported Platforms: {SymbolAvailability}, ExportFieldData: '{ExportFieldData?.ToString () ?? "null"}', ExportPropertyData: '{ExportPropertyData?.ToString () ?? "null"}' Attributes: [");
+		sb.AppendJoin (",", Attributes);
+		sb.Append ("], Modifiers: [");
+		sb.AppendJoin (",", Modifiers.Select (x => x.Text));
+		sb.Append ("], Accessors: [");
+		sb.AppendJoin (",", Accessors);
+		sb.Append (']');
+		return sb.ToString ();
+	}
 }

tests/rgen/Microsoft.Macios.Generator.Tests/DataModel/PropertyTests.cs

@@ -1248,6 +1248,88 @@ public static partial string Name {
 						),
 					])
 			];
+
+			const string nsObjectProperty = @"
+using System;
+using Foundation;
+using ObjCBindings;
+
+namespace Test;
+
+public class TestClass {
+
+	[Export<Property>(""name"")]
+	public NSObject Name { get; }
+}
+";
+			yield return [
+				nsObjectProperty,
+				new Property (
+					name: "Name",
+					returnType: ReturnTypeForNSObject (),
+					symbolAvailability: new (),
+					attributes: [
+						new (name: "ObjCBindings.ExportAttribute<ObjCBindings.Property>", arguments: ["name"]),
+					],
+					modifiers: [
+						SyntaxFactory.Token (kind: SyntaxKind.PublicKeyword),
+					],
+					accessors: [
+						new (
+							accessorKind: AccessorKind.Getter,
+							symbolAvailability: new (),
+							exportPropertyData: null,
+							attributes: [],
+							modifiers: []
+						)
+					]
+				) {
+					NeedsBackingField = true,
+					RequiresDirtyCheck = true,
+					ExportPropertyData = new (selector: "name"),
+				}
+			];
+
+			const string nsObjectArrayProperty = @"
+using System;
+using Foundation;
+using ObjCBindings;
+
+namespace Test;
+
+public class TestClass {
+
+	[Export<Property>(""name"")]
+	public NSObject[] Name { get; }
+}
+";
+			yield return [
+				nsObjectArrayProperty,
+				new Property (
+					name: "Name",
+					returnType: ReturnTypeForArray ("Foundation.NSObject"),
+					symbolAvailability: new (),
+					attributes: [
+						new (name: "ObjCBindings.ExportAttribute<ObjCBindings.Property>", arguments: ["name"]),
+					],
+					modifiers: [
+						SyntaxFactory.Token (kind: SyntaxKind.PublicKeyword),
+					],
+					accessors: [
+						new (
+							accessorKind: AccessorKind.Getter,
+							symbolAvailability: new (),
+							exportPropertyData: null,
+							attributes: [],
+							modifiers: []
+						)
+					]
+				) {
+					NeedsBackingField = true,
+					RequiresDirtyCheck = true,
+					ExportPropertyData = new (selector: "name"),
+				}
+			];
 		}
 
 		IEnumerator IEnumerable.GetEnumerator ()

tests/rgen/Microsoft.Macios.Generator.Tests/TestDataFactory.cs

@@ -300,16 +300,23 @@ public static TypeInfo ReturnTypeForDelegate (string delegateName)
 			]
 		};
 
-	public static TypeInfo ReturnTypeForNSObject (string nsObjectName, bool isNullable = false)
+	public static TypeInfo ReturnTypeForNSObject (string? nsObjectName = null, bool isNullable = false)
 		=> new (
-			name: nsObjectName,
+			name: nsObjectName ?? "Foundation.NSObject",
 			isNullable: isNullable,
-			isArray: false
+			isArray: false,
+			isReferenceType: true
 		) {
 			IsNSObject = true,
 			IsINativeObject = true,
-			Parents = ["Foundation.NSObject", "object"],
-			Interfaces = ["ObjCRuntime.INativeObject"]
+			Parents = nsObjectName is null ? ["object"] : ["Foundation.NSObject", "object"],
+			Interfaces = [
+				"ObjCRuntime.INativeObject",
+				$"System.IEquatable<{nsObjectName ?? "Foundation.NSObject"}>",
+				"System.IDisposable",
+				"Foundation.INSObjectFactory",
+				"Foundation.INSObjectProtocol"
+			]
 		};
 
 	public static TypeInfo ReturnTypeForINativeObject (string nativeObjectName, bool isNullable = false)