[Rgen] Add code to parse the NativeAttribute.

Not to be confused with the NativeNameAttribute, which is different.

src/rgen/Microsoft.Macios.Transformer/Attributes/NativeData.cs

@@ -0,0 +1,89 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Diagnostics.CodeAnalysis;
+using Microsoft.CodeAnalysis;
+
+namespace Microsoft.Macios.Transformer.Attributes;
+
+readonly struct NativeData : IEquatable<NativeData> {
+
+	public string? NativeName { get; }
+
+	public NativeData () {}
+
+	public NativeData (string? nativeName)
+	{
+		NativeName = nativeName;
+	}
+
+
+	public static bool TryParse (AttributeData attributeData,
+		[NotNullWhen (true)] out NativeData? data)
+	{
+		data = null;
+		var count = attributeData.ConstructorArguments.Length;
+		string? nativeName;
+
+		switch (count) {
+		case 0:
+			nativeName = null;
+			break;
+		case 1:
+			nativeName = (string) attributeData.ConstructorArguments [0].Value!;
+			break;
+		default:
+			// 0 should not be an option..
+			return false;
+		}
+
+		if (attributeData.NamedArguments.Length == 0) {
+			data = new (nativeName);
+			return true;
+		}
+
+		foreach (var (argumentName, value) in attributeData.NamedArguments) {
+			switch (argumentName) {
+			case "NativeName":
+				nativeName = (string) value.Value!;
+				break;
+			default:
+				data = null;
+				return false;
+			}
+		}
+
+		data = new(nativeName);
+		return true;
+	}
+
+	public bool Equals (NativeData other)
+		=> NativeName == other.NativeName;
+
+	/// <inheritdoc />
+	public override bool Equals (object? obj)
+	{
+		return obj is NativeData other && Equals (other);
+	}
+
+	/// <inheritdoc />
+	public override int GetHashCode ()
+		=> HashCode.Combine (NativeName);
+
+
+	public static bool operator == (NativeData x, NativeData y)
+	{
+		return x.Equals (y);
+	}
+
+	public static bool operator != (NativeData x, NativeData y)
+	{
+		return !(x == y);
+	}
+
+	/// <inheritdoc />
+	public override string ToString ()
+	{
+		return $"{{ NativeName: '{NativeName}' }}";
+	}
+}

tests/rgen/Microsoft.Macios.Transformer.Tests/Attributes/NativeDataTests.cs

@@ -0,0 +1,100 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Collections;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.Macios.Generator.Extensions;
+using Microsoft.Macios.Transformer.Attributes;
+using Xamarin.Tests;
+using Xamarin.Utils;
+
+namespace Microsoft.Macios.Transformer.Tests.Attributes;
+
+public class NativeDataTests : BaseTransformerTestClass {
+
+	class TestDataTryCreate : IEnumerable<object []> {
+		public IEnumerator<object []> GetEnumerator ()
+		{
+			var path = "/some/random/path.cs";
+			var simnpleNativeEnum = @"
+using System;
+using Foundation;
+using ObjCRuntime;
+
+[Native]
+public enum AVAudioQuality : long {
+	Min = 0,
+	Low = 0x20,
+	Medium = 0x40,
+	High = 0x60,
+	Max = 0x7F,
+}
+";
+
+			yield return [(Sorunce: simnpleNativeEnum, Path: path), new NativeData ()];
+
+			var nativeEnumWithName = @"
+using System;
+using Foundation;
+using ObjCRuntime;
+
+[Native (""Test"")]
+public enum AVAudioQuality : long {
+	Min = 0,
+	Low = 0x20,
+	Medium = 0x40,
+	High = 0x60,
+	Max = 0x7F,
+}
+";
+
+			yield return [(Sorunce: nativeEnumWithName, Path: path), new NativeData ("Test")];
+
+			var nativeEnumWithNameNamed = @"
+using System;
+using Foundation;
+using ObjCRuntime;
+
+[Native (NativeName = ""Test"")]
+public enum AVAudioQuality : long {
+	Min = 0,
+	Low = 0x20,
+	Medium = 0x40,
+	High = 0x60,
+	Max = 0x7F,
+}
+";
+
+			yield return [(Sorunce: nativeEnumWithNameNamed, Path: path), new NativeData ("Test")];
+		}
+
+		IEnumerator IEnumerable.GetEnumerator () => GetEnumerator ();
+	}
+
+	[Theory]
+	[AllSupportedPlatformsClassData<TestDataTryCreate>]
+	void TryCreateTests (ApplePlatform platform, (string Source, string Path) source,
+		NativeData expectedData)
+	{
+		// create a compilation used to create the transformer
+		var compilation = CreateCompilation (platform, sources: source);
+		var syntaxTree = compilation.SyntaxTrees.ForSource (source);
+		Assert.NotNull (syntaxTree);
+
+		var semanticModel = compilation.GetSemanticModel (syntaxTree);
+		Assert.NotNull (semanticModel);
+
+		var declaration = syntaxTree.GetRoot ()
+			.DescendantNodes ().OfType<EnumDeclarationSyntax> ()
+			.LastOrDefault ();
+		Assert.NotNull (declaration);
+
+		var symbol = semanticModel.GetDeclaredSymbol (declaration);
+		Assert.NotNull (symbol);
+		var exportData = symbol.GetAttribute<NativeData> (
+			AttributesNames.NativeAttribute, NativeData.TryParse);
+		Assert.Equal (expectedData, exportData);
+	}
+
+}