[Rgen] Add skeleton code for the field properties in a class.

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

@@ -90,6 +90,16 @@ public bool IsNotification
 	/// </summary>
 	public ImmutableArray<Accessor> Accessors { get; } = [];
 
+	public Accessor? GetAccessor (AccessorKind accessorKind)
+	{
+		// careful, do not use FirstOrDefault from LINQ because we are using structs!
+		foreach (var accessor in Accessors) {
+			if (accessor.Kind == accessorKind)
+				return accessor;
+		}
+		return null;
+	}
+
 	internal Property (string name, TypeInfo returnType,
 		SymbolAvailability symbolAvailability,
 		ImmutableArray<AttributeCodeChange> attributes,

src/rgen/Microsoft.Macios.Generator/Emitters/BindingSyntaxFactory.cs

@@ -4,6 +4,7 @@
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.Macios.Generator.DataModel;
 using static Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
 
 namespace Microsoft.Macios.Generator.Emitters;
@@ -84,4 +85,33 @@ static CompilationUnitSyntax ThrowException (string type, string message)
 
 	static CompilationUnitSyntax ThrowNotSupportedException (string message)
 		=> ThrowException (type: "NotSupportedException", message: message);
+
+	/// <summary>
+	/// Generates the syntax to declare the variable used by a field property.  
+	/// </summary>
+	/// <param name="property">The field property whose backing variable we want to generate.</param>
+	/// <returns>The variable declaration syntax.</returns>
+	public static CompilationUnitSyntax FieldPropertyBackingVariable (in Property property)
+	{
+		var variableType = property.ReturnType.Name;
+		if (property.ReturnType.SpecialType is SpecialType.System_IntPtr or SpecialType.System_UIntPtr
+			&& property.ReturnType.MetadataName is not null) {
+			variableType = property.ReturnType.MetadataName;
+		}
+		var compilationUnit = CompilationUnit ().WithMembers (
+			SingletonList<MemberDeclarationSyntax> (
+				FieldDeclaration (
+						VariableDeclaration (
+								property.IsReferenceType  // nullable only for reference types
+									? NullableType (IdentifierName (variableType))
+									: IdentifierName (variableType)
+							)
+							.WithVariables (
+								SingletonSeparatedList (
+									VariableDeclarator (
+										Identifier (property.BackingField)))))
+					.WithModifiers (TokenList (Token (SyntaxKind.StaticKeyword))))) // fields are static variables
+			.NormalizeWhitespace ();
+		return compilationUnit;
+	}
 }

src/rgen/Microsoft.Macios.Generator/Emitters/ClassEmitter.cs

@@ -1,15 +1,18 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
-using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.ComponentModel;
 using System.Diagnostics.CodeAnalysis;
+using System.Linq;
 using Microsoft.CodeAnalysis;
 using Microsoft.Macios.Generator.Attributes;
 using Microsoft.Macios.Generator.Context;
 using Microsoft.Macios.Generator.DataModel;
+using Microsoft.Macios.Generator.Formatters;
 using ObjCBindings;
+using Property = Microsoft.Macios.Generator.DataModel.Property;
+using static Microsoft.Macios.Generator.Emitters.BindingSyntaxFactory;
 
 namespace Microsoft.Macios.Generator.Emitters;
 
@@ -58,6 +61,74 @@ void EmitDefaultConstructors (in BindingContext bindingContext, TabbedStringBuil
 		classBlock.AppendLine ($"protected internal {bindingContext.Changes.Name} (NativeHandle handle) : base (handle) {{}}");
 	}
 
+	/// <summary>
+	/// Emit the code for all the field properties in the class. The code will add any necessary backing fields and
+	/// will return all properties that are notifications.
+	/// </summary>
+	/// <param name="className">The current class name.</param>
+	/// <param name="properties">All properties of the class, the method will filter those that are fields.</param>
+	/// <param name="classBlock">Current class block.</param>
+	/// <param name="notificationProperties">An immutable array with all the properties that are marked as notifications
+	/// and that need a helper class to be generated.</param>
+	void EmitFields (string className, in ImmutableArray<Property> properties, TabbedStringBuilder classBlock,
+		out ImmutableArray<Property> notificationProperties)
+	{
+		var notificationsBuilder = ImmutableArray.CreateBuilder<Property> ();
+		foreach (var property in properties.OrderBy (p => p.Name)) {
+			if (!property.IsField)
+				continue;
+
+			classBlock.AppendLine ();
+			// a field should always have a getter, if it does not, we do not generate the property
+			var getter = property.GetAccessor (AccessorKind.Getter);
+			if (getter is null)
+				continue;
+
+			// provide a backing variable for the property if and only if we are dealing with a reference type
+			if (property.IsReferenceType) {
+				classBlock.AppendLine (FieldPropertyBackingVariable (property).ToString ());
+			}
+
+			classBlock.AppendLine ();
+			classBlock.AppendMemberAvailability (property.SymbolAvailability);
+			classBlock.AppendGeneratedCodeAttribute (optimizable: true);
+			if (property.IsNotification) {
+				// add it to the bucket so that we can later generate the necessary partial class for the 
+				// notifications
+				notificationsBuilder.Add (property);
+				classBlock.AppendNotificationAdvice (className, property.Name);
+			}
+
+			using (var propertyBlock = classBlock.CreateBlock (property.ToDeclaration ().ToString (), block: true)) {
+				// generate the accessors, we will always have a get, a set is optional depending on the type
+				// if the symbol availability of the accessor is different of the one from the property, write it
+
+				// be very verbose with the availability, makes the life easier to the dotnet analyzer
+				propertyBlock.AppendMemberAvailability (getter.Value.SymbolAvailability);
+				using (var getterBlock = propertyBlock.CreateBlock ("get", block: true)) {
+					getterBlock.AppendLine ("throw new NotImplementedException ();");
+				}
+
+				var setter = property.GetAccessor (AccessorKind.Setter);
+				if (setter is null)
+					// we are done with the current property
+					continue;
+
+				propertyBlock.AppendLine (); // add space between getter and setter since we have the attrs
+				propertyBlock.AppendMemberAvailability (setter.Value.SymbolAvailability);
+				using (var setterBlock = propertyBlock.CreateBlock ("set", block: true)) {
+					setterBlock.AppendLine ("throw new NotImplementedException ();");
+				}
+			}
+		}
+		notificationProperties = notificationsBuilder.ToImmutable ();
+	}
+
+	void EmitNotifications (in ImmutableArray<Property> properties, TabbedStringBuilder classBlock)
+	{
+		// to be implemented, do not throw or tests will fail.
+	}
+
 	public bool TryEmit (in BindingContext bindingContext, [NotNullWhen (false)] out ImmutableArray<Diagnostic>? diagnostics)
 	{
 		diagnostics = null;
@@ -77,7 +148,7 @@ public bool TryEmit (in BindingContext bindingContext, [NotNullWhen (false)] out
 
 		// register the class only if we are not dealing with a static class
 		var bindingData = (BindingTypeData<Class>) bindingContext.Changes.BindingInfo;
-		// registration depends on the class name. If the binding data contains a name, we use that one, else
+		// Registration depends on the class name. If the binding data contains a name, we use that one, else
 		// we use the name of the class
 		var registrationName = bindingData.Name ?? bindingContext.Changes.Name;
 
@@ -98,6 +169,11 @@ public bool TryEmit (in BindingContext bindingContext, [NotNullWhen (false)] out
 					disableDefaultCtor: bindingData.Flags.HasFlag (Class.DisableDefaultCtor));
 			}
 
+			EmitFields (bindingContext.Changes.Name, bindingContext.Changes.Properties, classBlock,
+				out var notificationProperties);
+
+			// emit the notification helper classes, leave this for the very bottom of the class
+			EmitNotifications (notificationProperties, classBlock);
 			classBlock.AppendLine ("// TODO: add binding code here");
 		}
 		return true;

src/rgen/Microsoft.Macios.Generator/Formatters/PropertyFormatter.cs

@@ -9,22 +9,28 @@
 namespace Microsoft.Macios.Generator.Formatters;
 
 static class PropertyFormatter {
+
 	/// <summary>
 	/// Return the declaration represented by the given property.
 	/// </summary>
 	/// <param name="property">The property whose declaration we want to generate.</param>
 	/// <returns>A compilation unit syntax node with the declaration of the property.</returns>
-	public static CompilationUnitSyntax? ToDeclaration (this in Property? property)
+	public static CompilationUnitSyntax ToDeclaration (this in Property property)
 	{
-		if (property is null)
-			return null;
-
 		var compilationUnit = CompilationUnit ().WithMembers (
 			SingletonList<MemberDeclarationSyntax> (
 				PropertyDeclaration (
-						type: property.Value.ReturnType.GetIdentifierSyntax (),
-						identifier: Identifier (property.Value.Name))
-					.WithModifiers (TokenList (property.Value.Modifiers)))).NormalizeWhitespace ();
+						type: property.ReturnType.GetIdentifierSyntax (),
+						identifier: Identifier (property.Name))
+					.WithModifiers (TokenList (property.Modifiers)))).NormalizeWhitespace ();
 		return compilationUnit;
 	}
+
+	/// <summary>
+	/// Return the declaration represented by the given property.
+	/// </summary>
+	/// <param name="property">The property whose declaration we want to generate.</param>
+	/// <returns>A compilation unit syntax node with the declaration of the property.</returns>
+	public static CompilationUnitSyntax? ToDeclaration (this in Property? property)
+		=> property?.ToDeclaration ();
 }

src/rgen/Microsoft.Macios.Generator/TabbedStringBuilder.cs

@@ -8,8 +8,10 @@
 using System.Runtime.CompilerServices;
 using System.Security.Cryptography;
 using System.Text;
+using Microsoft.Macios.Generator.Attributes;
 using Microsoft.Macios.Generator.Availability;
 using Microsoft.Macios.Generator.DataModel;
+using ObjCRuntime;
 using Xamarin.Utils;
 
 namespace Microsoft.Macios.Generator;
@@ -227,6 +229,25 @@ public TabbedStringBuilder AppendMemberAvailability (in SymbolAvailability allPl
 		return this;
 	}
 
+	public TabbedStringBuilder AppendExportData<T> (in ExportData<T> exportData) where T : Enum
+	{
+		// Try to write the smaller amount of data. We ware using the old ExportAttribute until we make the final move
+		if (exportData.ArgumentSemantic != ArgumentSemantic.None) {
+			AppendLine ($"[Export (\"{exportData.Selector}\", ArgumentSemantic.{exportData.ArgumentSemantic})]");
+		} else {
+			AppendLine ($"[Export (\"{exportData.Selector}\")]");
+		}
+		return this;
+	}
+
+	public TabbedStringBuilder AppendNotificationAdvice (in string className, in string notification)
+	{
+		string attr =
+			$"[Advice (\"Use '{className}.Notifications.{notification}' helper method instead.\")]";
+		AppendLine (attr);
+		return this;
+	}
+
 	/// <summary>
 	/// Append a EditorBrowsable attribute. Added for convenience.
 	/// </summary>

tests/rgen/Microsoft.Macios.Generator.Tests/Classes/ClassGenerationTests.cs

@@ -21,6 +21,9 @@ public class TestDataGenerator : BaseTestDataGenerator, IEnumerable<object []> {
 			(ApplePlatform.MacOSX, "AVAudioPcmBuffer", "AVAudioPcmBufferDefaultCtr.cs", "ExpectedAVAudioPcmBufferDefaultCtr.cs", null),
 			(ApplePlatform.iOS, "AVAudioPcmBuffer", "AVAudioPcmBufferNoNativeName.cs", "ExpectedAVAudioPcmBufferNoNativeName.cs", null),
 			(ApplePlatform.MacOSX, "AVAudioPcmBuffer", "AVAudioPcmBufferNoNativeName.cs", "ExpectedAVAudioPcmBufferNoNativeName.cs", null),
+			(ApplePlatform.iOS, "CIImage", "CIImage.cs", "ExpectedCIImage.cs", null),
+			(ApplePlatform.TVOS, "CIImage", "CIImage.cs", "ExpectedCIImage.cs", null),
+			(ApplePlatform.MacCatalyst, "CIImage", "CIImage.cs", "ExpectedCIImage.cs", null),
 
 		};
 

tests/rgen/Microsoft.Macios.Generator.Tests/Classes/Data/CIImage.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Runtime.Versioning;
+using Foundation;
+using ObjCBindings;
+
+namespace TestNamespace;
+
+[SupportedOSPlatform ("macos")]
+[SupportedOSPlatform ("ios11.0")]
+[SupportedOSPlatform ("tvos11.0")]
+
+[BindingType<Class> ()]
+public partial class CIImage {
+
+	[SupportedOSPlatform ("maccatalyst13.1")]
+	[Field<Property> ("FormatRGBA16Int")]
+	public static partial int FormatRGBA16Int { get; }
+
+	[SupportedOSPlatform ("maccatalyst13.1")]
+	[Field<Property> ("kCIFormatABGR8")]
+	public static partial int FormatABGR8 { get; }
+
+	[SupportedOSPlatform ("maccatalyst13.1")]
+	[Field<Property> ("kCIFormatLA8")]
+	public static partial int FormatLA8 {
+		get;
+
+		[SupportedOSPlatform ("ios17.0")]
+		[SupportedOSPlatform ("tvos17.0")]
+		[SupportedOSPlatform ("macos14.0")]
+		[SupportedOSPlatform ("maccatalyst17.0")]
+		set;
+	}
+
+	[SupportedOSPlatform ("maccatalyst13.1")]
+	[Field<Property> ("kCIFormatLA8", Flags = Property.Notification)]
+	public static partial NSString DidProcessEditingNotification { get; }
+
+}