[Rgen] Implement the parsing of the backing field attr in the transfo…

…rmer.

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

@@ -0,0 +1,86 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Diagnostics.CodeAnalysis;
+using Microsoft.CodeAnalysis;
+
+namespace Microsoft.Macios.Transformer.Attributes;
+
+readonly struct BackingFieldTypeData : IEquatable<BackingFieldTypeData> {
+
+	public string TypeName { get; }
+
+	public BackingFieldTypeData (string typeName)
+	{
+		TypeName = typeName;
+	}
+
+	public static bool TryParse (AttributeData attributeData,
+		[NotNullWhen (true)] out BackingFieldTypeData? data)
+	{
+		data = null;
+		var count = attributeData.ConstructorArguments.Length;
+		string backingField;
+		// custom marshal directive values
+
+		switch (count) {
+		case 1:
+			backingField = ((INamedTypeSymbol) attributeData.ConstructorArguments [0].Value!).ToDisplayString ();
+			break;
+		default:
+			// 0 should not be an option..
+			return false;
+		}
+
+		if (attributeData.NamedArguments.Length == 0) {
+			data = new (backingField);
+			return true;
+		}
+
+		foreach (var (argumentName, value) in attributeData.NamedArguments) {
+			switch (argumentName) {
+			case "BackingFieldType":
+				backingField = ((INamedTypeSymbol) value.Value!).ToDisplayString ();
+				break;
+			default:
+				data = null;
+				return false;
+			}
+		}
+
+		data = new(backingField);
+		return true;
+	}
+
+	public bool Equals (BackingFieldTypeData other)
+	{
+		return TypeName == other.TypeName;
+	}
+
+	/// <inheritdoc />
+	public override bool Equals (object? obj)
+	{
+		return obj is BackingFieldTypeData other && Equals (other);
+	}
+
+	/// <inheritdoc />
+	public override int GetHashCode ()
+		=> TypeName.GetHashCode ();
+
+
+	public static bool operator == (BackingFieldTypeData x, BackingFieldTypeData y)
+	{
+		return x.Equals (y);
+	}
+
+	public static bool operator != (BackingFieldTypeData x, BackingFieldTypeData y)
+	{
+		return !(x == y);
+	}
+
+	/// <inheritdoc />
+	public override string ToString ()
+	{
+		return $"{{ BackingFieldType: '{TypeName}' }}";
+	}
+}

src/rgen/Microsoft.Macios.Transformer/AttributesNames.cs

@@ -1,5 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
+
+#pragma warning disable format
 using Microsoft.Macios.Transformer.Generator;
 
 namespace Microsoft.Macios.Transformer;
@@ -13,7 +15,8 @@ static class AttributesNames {
 	[BindingFlag (AttributeTargets.Method | AttributeTargets.Property | AttributeTargets.Interface)]
 	public const string AbstractAttribute = "AbstractAttribute";
 
-	[BindingFlag] public const string AdvancedAttribute = "AdvancedAttribute";
+	[BindingFlag] 
+	public const string AdvancedAttribute = "AdvancedAttribute";
 	public const string AdviceAttribute = "Foundation.AdviceAttribute";
 
 	/// <summary>
@@ -41,7 +44,8 @@ static class AttributesNames {
 	[BindingFlag (AttributeTargets.Interface)]
 	public const string CategoryAttribute = "CategoryAttribute";
 
-	[BindingFlag] public const string CheckDisposedAttribute = "CheckDisposedAttribute";
+	[BindingFlag] 
+	public const string CheckDisposedAttribute = "CheckDisposedAttribute";
 	public const string CoreImageFilterAttribute = "CoreImageFilterAttribute";
 	public const string DefaultCtorVisibilityAttribute = "DefaultCtorVisibilityAttribute";
 
@@ -74,7 +78,8 @@ static class AttributesNames {
 	public const string ExperimentalAttribute = "System.Diagnostics.CodeAnalysis.ExperimentalAttribute";
 	public const string ExportAttribute = "Foundation.ExportAttribute";
 
-	[BindingFlag] public const string FactoryAttribute = "FactoryAttribute";
+	[BindingFlag] 
+	public const string FactoryAttribute = "FactoryAttribute";
 	public const string FieldAttribute = "Foundation.FieldAttribute";
 	public const string FlagsAttribute = "System.FlagsAttribute";
 

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

@@ -0,0 +1,94 @@
+// 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 BackingFieldTypeDataTests : BaseTransformerTestClass {
+
+	class TestDataTryCreate : IEnumerable<object []> {
+		public IEnumerator<object []> GetEnumerator ()
+		{
+			var path = "/some/random/path.cs";
+			const string nsnumberBackingFieldType = @"
+using System;
+using Foundation;
+using ObjCRuntime;
+
+[NoTV, Mac (15, 0), NoiOS, NoMacCatalyst]
+[BackingFieldType (typeof (NSNumber))]
+public enum ASAuthorizationProviderExtensionEncryptionAlgorithm {
+	[Field (""ASAuthorizationProviderExtensionEncryptionAlgorithmECDHE_A256GCM"")]
+	EcdheA256Gcm,
+
+	[Field (""ASAuthorizationProviderExtensionEncryptionAlgorithmHPKE_P256_SHA256_AES_GCM_256"")]
+	HpkeP256Sha256AesGcm256,
+
+	[Field (""ASAuthorizationProviderExtensionEncryptionAlgorithmHPKE_P384_SHA384_AES_GCM_256"")]
+	HpkeP384Sha384AesGcm256,
+
+	[Field (""ASAuthorizationProviderExtensionEncryptionAlgorithmHPKE_Curve25519_SHA256_ChachaPoly"")]
+	HpkeCurve25519Sha256ChachaPoly,
+}
+";
+			yield return [(Source: nsnumberBackingFieldType, Path: path), new BackingFieldTypeData ("Foundation.NSNumber")];
+
+			const string nsstringBackingFieldType = @"
+using System;
+using Foundation;
+using ObjCRuntime;
+
+[NoTV, Mac (15, 0), NoiOS, NoMacCatalyst]
+[BackingFieldType (typeof (NSString))]
+public enum ASAuthorizationProviderExtensionEncryptionAlgorithm {
+	[Field (""ASAuthorizationProviderExtensionEncryptionAlgorithmECDHE_A256GCM"")]
+	EcdheA256Gcm,
+
+	[Field (""ASAuthorizationProviderExtensionEncryptionAlgorithmHPKE_P256_SHA256_AES_GCM_256"")]
+	HpkeP256Sha256AesGcm256,
+
+	[Field (""ASAuthorizationProviderExtensionEncryptionAlgorithmHPKE_P384_SHA384_AES_GCM_256"")]
+	HpkeP384Sha384AesGcm256,
+
+	[Field (""ASAuthorizationProviderExtensionEncryptionAlgorithmHPKE_Curve25519_SHA256_ChachaPoly"")]
+	HpkeCurve25519Sha256ChachaPoly,
+}
+";
+			yield return [(Source: nsstringBackingFieldType, Path: path), new BackingFieldTypeData ("Foundation.NSString")];
+
+		}
+
+		IEnumerator IEnumerable.GetEnumerator () => GetEnumerator ();
+	}
+
+	[Theory]
+	[AllSupportedPlatformsClassData<TestDataTryCreate>]
+	void TryeCreateTests (ApplePlatform platform, (string Source, string Path) source, BackingFieldTypeData 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<BaseTypeDeclarationSyntax> ()
+			.LastOrDefault ();
+		Assert.NotNull (declaration);
+
+		var symbol = semanticModel.GetDeclaredSymbol (declaration);
+		Assert.NotNull (symbol);
+		var exportData = symbol.GetAttribute<BackingFieldTypeData> (
+			AttributesNames.BackingFieldTypeAttribute, BackingFieldTypeData.TryParse);
+		Assert.Equal (expectedData, exportData);
+	}
+}