[Rgen] Allows to mark a property or accessor to marshal native except…

…ions

Properties can also do it. Allow to set the flag and provide a method
that will allow use to know if an accessor should marshal the native
exceptions or not.

src/ObjCBindings/ExportTag.cs

@@ -71,6 +71,13 @@ public enum Property : Int64 {
 		/// Generate a notification for the property.
 		/// </summary>
 		Notification = 1 << 3,
+
+		/// <summary>
+		/// Make a method support native (Objective-C) exceptions. Instead of calling objc_msgSend directly, the invocation 
+		/// will go through a custom trampoline which catches ObjectiveC exceptions and marshals them into managed exceptions.
+		/// </summary>
+		MarshalNativeExceptions = 1 << 4,
+
 	}
 }
 

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

@@ -25,6 +25,9 @@ namespace Microsoft.Macios.Generator.DataModel;
 	/// The data of the field attribute used to mark the value as a property binding. 
 	/// </summary>
 	public ExportData<ObjCBindings.Property>? ExportPropertyData { get; init; }
+
+	public bool MarshalNativeExceptions 
+		=> ExportPropertyData is not null && ExportPropertyData.Value.Flags.HasFlag (ObjCBindings.Property.MarshalNativeExceptions);
 
 	/// <summary>
 	/// List of attribute code changes of the accessor.
@@ -57,6 +60,14 @@ public Accessor (AccessorKind accessorKind,
 		Modifiers = modifiers;
 	}
 
+	/// <summary>
+	/// Returns if the accessor should marshal native exceptions with the associated property.
+	/// </summary>
+	/// <param name="property">The property associated with the accessor.</param>
+	/// <returns>True if either the accessor or the property were marked with the MarshalNativeExceptions flag.</returns>
+	public bool ShouldMarshalNativeExceptions (in Property property)
+		=> MarshalNativeExceptions || property.MarshalNativeExceptions;
+
 	/// <inheritdoc />
 	public bool Equals (Accessor other)
 	{

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

@@ -42,6 +42,11 @@ namespace Microsoft.Macios.Generator.DataModel;
 	/// </summary>
 	public ExportData<ObjCBindings.Method> ExportMethodData { get; }
 
+	/// <summary>
+	/// True if the method was exported with the MarshalNativeExceptions flag allowing it to support native exceptions.
+	/// </summary>
+	public bool MarshalNativeExceptions => ExportMethodData.Flags.HasFlag (ObjCBindings.Method.MarshalNativeExceptions);
+
 	/// <summary>
 	/// Get the attributes added to the constructor.
 	/// </summary>

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

@@ -79,6 +79,12 @@ public bool IsNotification
 	/// Get the attributes added to the member.
 	/// </summary>
 	public ImmutableArray<AttributeCodeChange> Attributes { get; } = [];
+
+	/// <summary>
+	/// True if the method was exported with the MarshalNativeExceptions flag allowing it to support native exceptions.
+	/// </summary>
+	public bool MarshalNativeExceptions 
+		=> IsProperty && ExportPropertyData.Value.Flags.HasFlag (ObjCBindings.Property.MarshalNativeExceptions);
 
 	/// <summary>
 	/// Get the modifiers of the property.

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

@@ -1,10 +1,13 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
+#pragma warning disable APL0003
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.Macios.Generator.Attributes;
 using Microsoft.Macios.Generator.Availability;
 using Microsoft.Macios.Generator.DataModel;
+using ObjCRuntime;
 using Xunit;
+using static Microsoft.Macios.Generator.Tests.TestDataFactory;
 
 namespace Microsoft.Macios.Generator.Tests.DataModel;
 
@@ -308,4 +311,45 @@ public void CompareSameKindSameAttrSameAvailability ()
 		Assert.True (x == y);
 		Assert.False (x != y);
 	}
+
+	[Theory]
+	[InlineData (false, false, false)]
+	[InlineData (false, true, true)]
+	[InlineData (true, false, true)]
+	[InlineData (true, true, true)]
+	public void ShouldMarshalNativeExceptionsBothFalse (bool propertyHasFlag, bool accessorHasFalg, bool expectedResult)
+	{
+		var property = new Property (
+			name: "MyProperty",
+			returnType: ReturnTypeForString (),
+			symbolAvailability: new (),
+			attributes: [],
+			modifiers: [],
+			accessors: []
+		) {
+			ExportPropertyData = new (
+				selector: "selector", 
+				argumentSemantic: ArgumentSemantic.None, 
+				flags: propertyHasFlag ? ObjCBindings.Property.MarshalNativeExceptions : ObjCBindings.Property.Default),
+		};
+
+		var accessor = new Accessor (
+			accessorKind: AccessorKind.Getter,
+			symbolAvailability: new (),
+			exportPropertyData: new (
+				selector: "selector", 
+				argumentSemantic: ArgumentSemantic.None, 
+				flags: accessorHasFalg ? ObjCBindings.Property.MarshalNativeExceptions : ObjCBindings.Property.Default),
+			attributes: [
+				new ("First"),
+				new ("Second"),
+			],
+			modifiers: [
+				SyntaxFactory.Token (SyntaxKind.PublicKeyword),
+				SyntaxFactory.Token (SyntaxKind.PrivateKeyword)
+			]);
+		Assert.Equal (expectedResult, accessor.ShouldMarshalNativeExceptions (property));
+	}
+
+
 }

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

@@ -9,6 +9,7 @@
 using Microsoft.Macios.Generator.Attributes;
 using Microsoft.Macios.Generator.Availability;
 using Microsoft.Macios.Generator.DataModel;
+using ObjCRuntime;
 using Xamarin.Tests;
 using Xamarin.Utils;
 using Xunit;
@@ -443,6 +444,44 @@ public class TestClass {
 					ExportPropertyData = new (selector: "name"),
 				}
 			];
+
+			const string marshallNativeException = @"
+using System;
+using ObjCBindings;
+
+namespace Test;
+
+public class TestClass {
+
+	[Export<Property>(""name"", Property.MarshalNativeExceptions)]
+	public string Name { get; }
+}
+";
+			yield return [
+				marshallNativeException,
+				new Property (
+					name: "Name",
+					returnType: ReturnTypeForString (),
+					symbolAvailability: new (),
+					attributes: [
+						new ("ObjCBindings.ExportAttribute<ObjCBindings.Property>", ["name", "ObjCBindings.Property.MarshalNativeExceptions"])
+					],
+					modifiers: [
+						SyntaxFactory.Token (kind: SyntaxKind.PublicKeyword),
+					],
+					accessors: [
+						new (
+							accessorKind: AccessorKind.Getter,
+							symbolAvailability: new (),
+							exportPropertyData: null,
+							attributes: [],
+							modifiers: []
+						)
+					]
+				) {
+					ExportPropertyData = new (selector: "name", ArgumentSemantic.None, ObjCBindings.Property.MarshalNativeExceptions),
+				}
+			];
 
 			const string valueTypeProperty = @"
 using System;