[RGen] Provide a method that will remove all symbols not supported by a platform

src/rgen/Microsoft.Macios.Generator/Availability/PlatformAvailabilityBuilder.cs

@@ -84,6 +84,11 @@ internal void AddUnsupportedVersion (Version version, string? message)
 				if (unsupported.ContainsKey (defaultVersion))
 					return;
 				unsupported [version] = message;
+				// we need to ensure that if we unsupported a version that the supported version is not null, if
+				// it is, we need to set it to the version before the unsupported one
+				if (supportedVersion is null) {
+					supportedVersion = defaultVersion;
+				}
 			}
 		}
 

src/rgen/Microsoft.Macios.Generator/Availability/SymbolAvailability.cs

@@ -129,6 +129,16 @@ public SymbolAvailability MergeWithParent (SymbolAvailability? parent)
 		return new (merged);
 	}
 
+	/// <summary>
+	/// Returns true if the symbol is supported in the given platform.
+	/// </summary>
+	public bool IsSupported (ApplePlatform platform)
+	{
+		// if the platform is not present, it is supported by default
+		var availability = this [platform];
+		return availability is null || availability.Value.IsSupported;
+	}
+
 	/// <inheritdoc />
 	public bool Equals (SymbolAvailability other)
 	{

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

@@ -11,6 +11,7 @@
 using Microsoft.Macios.Generator.Availability;
 using Microsoft.Macios.Generator.Context;
 using Microsoft.Macios.Generator.Extensions;
+using Xamarin.Utils;
 
 namespace Microsoft.Macios.Generator.DataModel;
 
@@ -263,7 +264,7 @@ internal static bool Skip (MethodDeclarationSyntax methodDeclarationSyntax, Sema
 	/// <param name="fullyQualifiedSymbol">The fully qualified name of the symbol.</param>
 	/// <param name="symbolAvailability">The platform availability of the named symbol.</param>
 	internal Binding (BindingInfo bindingInfo, string name, ImmutableArray<string> @namespace,
-		string fullyQualifiedSymbol, SymbolAvailability symbolAvailability)
+		string fullyQualifiedSymbol, SymbolAvailability symbolAvailability) : this (StructState.Initialized)
 	{
 		this.bindingInfo = bindingInfo;
 		this.name = name;
@@ -278,7 +279,8 @@ internal Binding (BindingInfo bindingInfo, string name, ImmutableArray<string> @
 	/// <param name="enumDeclaration">The enum declaration that triggered the change.</param>
 	/// <param name="context">The root binding context of the current compilation.</param>
 	/// <param name="validateMembers">If the struct should validate the members from the declarations. Defaults to true.</param>
-	Binding (EnumDeclarationSyntax enumDeclaration, RootContext context, bool validateMembers = true)
+	Binding (EnumDeclarationSyntax enumDeclaration, RootContext context,
+		bool validateMembers = true) : this (StructState.Initialized)
 	{
 		context.SemanticModel.GetSymbolData (
 			declaration: enumDeclaration,
@@ -346,7 +348,8 @@ internal Binding (BindingInfo bindingInfo, string name, ImmutableArray<string> @
 	/// <param name="classDeclaration">The class declaration that triggered the change.</param>
 	/// <param name="context">The root binding context of the current compilation.</param>
 	/// <param name="validateMembers">If the struct should validate the members from the declarations. Defaults to true.</param>
-	Binding (ClassDeclarationSyntax classDeclaration, RootContext context, bool validateMembers = true)
+	Binding (ClassDeclarationSyntax classDeclaration, RootContext context,
+		bool validateMembers = true) : this (StructState.Initialized)
 	{
 		context.SemanticModel.GetSymbolData (
 			declaration: classDeclaration,
@@ -392,7 +395,8 @@ internal Binding (BindingInfo bindingInfo, string name, ImmutableArray<string> @
 	/// <param name="interfaceDeclaration">The interface declaration that triggered the change.</param>
 	/// <param name="context">The root binding context of the current compilation.</param>
 	/// <param name="validateMembers">If the struct should validate the members from the declarations. Defaults to true.</param>
-	Binding (InterfaceDeclarationSyntax interfaceDeclaration, RootContext context, bool validateMembers = true)
+	Binding (InterfaceDeclarationSyntax interfaceDeclaration, RootContext context,
+		bool validateMembers = true) : this (StructState.Initialized)
 	{
 		context.SemanticModel.GetSymbolData (
 			declaration: interfaceDeclaration,
@@ -471,6 +475,7 @@ internal Binding (BindingInfo bindingInfo, string name, ImmutableArray<string> @
 	public override string ToString ()
 	{
 		var sb = new StringBuilder ("Changes: {");
+		sb.Append ($"State: {State}, ");
 		sb.Append ($"BindingData: '{BindingInfo}', Name: '{Name}', Namespace: [");
 		sb.AppendJoin (", ", Namespace);
 		sb.Append ($"], FullyQualifiedSymbol: '{FullyQualifiedSymbol}', Base: '{Base ?? "null"}', SymbolAvailability: {SymbolAvailability}, ");

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

@@ -9,8 +9,10 @@
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.Macios.Generator.Attributes;
 using Microsoft.Macios.Generator.Availability;
 using Microsoft.Macios.Generator.Context;
+using Xamarin.Utils;
 
 namespace Microsoft.Macios.Generator.DataModel;
 
@@ -21,6 +23,22 @@ namespace Microsoft.Macios.Generator.DataModel;
 [StructLayout (LayoutKind.Auto)]
 readonly partial struct Binding {
 
+	/// <summary>
+	/// The initialization state of the struct.
+	/// </summary>
+	StructState State { get; init; } = StructState.Default;
+
+
+	/// <summary>
+	/// Gets the default, uninitialized instance of <see cref="ExportData{T}"/>.
+	/// </summary>
+	public static Binding Default { get; } = new (StructState.Default);
+
+	/// <summary>
+	/// Gets a value indicating whether the instance is the default, uninitialized instance.
+	/// </summary>
+	public bool IsNullOrDefault => State == StructState.Default;
+
 	readonly string name = string.Empty;
 	/// <summary>
 	/// The name of the named type that generated the code change.
@@ -417,4 +435,44 @@ public bool TryGetEvent (string selector, out Event? @event)
 	/// <returns>True if the method was found. False otherwise.</returns>
 	public bool TryGetMethod (string selector, out Method? method)
 		=> TryGetFromIndex (selector, methods, methodIndex, out method);
+
+	/// <summary>
+	/// Initializes a new instance of the <see cref="Binding"/> struct with a specific state.
+	/// </summary>
+	/// <param name="state">The initialization state of the struct.</param>
+	public Binding (StructState state)
+	{
+		State = state;
+		FullyQualifiedSymbol = string.Empty;
+	}
+
+	/// <summary>
+	/// Creates a new binding containing only the members available for a specific platform.
+	/// </summary>
+	/// <param name="platform">The Apple platform to filter members for.</param>
+	/// <returns>
+	/// A new <see cref="Binding"/> instance with members filtered for the specified platform,
+	/// or the default binding if the type itself is not available on the platform.
+	/// </returns>
+	public Binding TrimForPlatform (ApplePlatform platform)
+	{
+		// if the binding is not available in the given platform, return an empty binding
+		if (!SymbolAvailability.IsSupported (platform))
+			return Default;
+
+		// collect all the different members that we are going to keep and return the same data but
+		// without those members that are not available in the given platform
+		return this with {
+			EnumMembers = [.. enumMembers.Where (m => m.SymbolAvailability.IsSupported (platform))],
+			Properties = [.. properties.Where (p => p.SymbolAvailability.IsSupported (platform))],
+			ParentProtocolProperties = [.. parentProperties.Where (p => p.SymbolAvailability.IsSupported (platform))],
+			StrongDictionaryProperties = [.. strongDictproperties.Where (p => p.SymbolAvailability.IsSupported (platform))],
+			Constructors = [.. constructors.Where (c => c.SymbolAvailability.IsSupported (platform))],
+			Events = [.. events.Where (e => e.SymbolAvailability.IsSupported (platform))],
+			Methods = [.. methods.Where (m => m.SymbolAvailability.IsSupported (platform))],
+			ParentProtocolMethods = [.. parentMethods.Where (m => m.SymbolAvailability.IsSupported (platform))],
+		};
+
+	}
+
 }

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

@@ -57,7 +57,7 @@ internal Binding (string name,
 		string fullyQualifiedSymbol,
 		BindingInfo bindingInfo,
 		SymbolAvailability symbolAvailability,
-		Dictionary<string, List<AttributeData>> attributes)
+		Dictionary<string, List<AttributeData>> attributes) : this (StructState.Initialized)
 	{
 		this.name = name;
 		namespaces = @namespace;
@@ -67,7 +67,8 @@ internal Binding (string name,
 		FullyQualifiedSymbol = fullyQualifiedSymbol;
 	}
 
-	internal Binding (EnumDeclarationSyntax enumDeclaration, INamedTypeSymbol symbol, in RootContext context)
+	internal Binding (EnumDeclarationSyntax enumDeclaration, INamedTypeSymbol symbol,
+		in RootContext context) : this (StructState.Initialized)
 	{
 		SemanticModelExtensions.GetSymbolData (
 			symbol: symbol,
@@ -269,7 +270,8 @@ internal static bool Skip (MethodDeclarationSyntax methodDeclarationSyntax, Sema
 	/// <param name="interfaceDeclarationSyntax">An interface that declares a binding.</param>
 	/// <param name="symbol"></param>
 	/// <param name="context">The current compilation context.</param>
-	internal Binding (InterfaceDeclarationSyntax interfaceDeclarationSyntax, INamedTypeSymbol symbol, in RootContext context)
+	internal Binding (InterfaceDeclarationSyntax interfaceDeclarationSyntax, INamedTypeSymbol symbol,
+		in RootContext context) : this (StructState.Initialized)
 	{
 		BaseDeclarationSyntax = interfaceDeclarationSyntax;
 		// basic properties of the binding

tests/rgen/Microsoft.Macios.Generator.Tests/Availability/PlatformAvailabilityTests.cs

@@ -112,6 +112,7 @@ public void UnsupportPlatform (ApplePlatform platform, string attributePlatformN
 		Assert.Contains (defaultVersion, availability.UnsupportedVersions.Keys);
 		Assert.Single (availability.UnsupportedVersions);
 		Assert.Null (availability.UnsupportedVersions [defaultVersion]);
+		Assert.Null (availability.SupportedVersion);
 	}
 
 	[Theory]
@@ -129,6 +130,7 @@ public void UnsupportPlatformWithMessage (ApplePlatform platform, string attribu
 		Assert.Contains (defaultVersion, availability.UnsupportedVersions.Keys);
 		Assert.Single (availability.UnsupportedVersions);
 		Assert.Equal (message, availability.UnsupportedVersions [defaultVersion]);
+		Assert.Null (availability.SupportedVersion);
 	}
 
 	[Theory]
@@ -150,6 +152,8 @@ public void UnsupportVersionAndPlatform (ApplePlatform platform, string attribut
 		Assert.Contains (defaultVersion, availability.UnsupportedVersions.Keys);
 		Assert.Single (availability.UnsupportedVersions);
 		Assert.Equal (message, availability.UnsupportedVersions [defaultVersion]);
+		// we fully unsupported the platform
+		Assert.Null (availability.SupportedVersion);
 	}
 
 	[Theory]

tests/rgen/Microsoft.Macios.Generator.Tests/Availability/PlatformAvailabilityToStringTests.cs

@@ -26,16 +26,16 @@ public IEnumerator<object []> GetEnumerator ()
 
 			builder.Clear ();
 			builder.AddUnsupportedVersion (new Version (16, 0), null);
-			yield return [builder.ToImmutable (), "{ Platform: 'iOS', Supported: '', Unsupported: ['16.0': 'null'], Obsoleted: [] }"];
+			yield return [builder.ToImmutable (), "{ Platform: 'iOS', Supported: '0.0', Unsupported: ['16.0': 'null'], Obsoleted: [] }"];
 
 			builder.Clear ();
 			builder.AddUnsupportedVersion (new Version (16, 0), "Not supported.");
-			yield return [builder.ToImmutable (), "{ Platform: 'iOS', Supported: '', Unsupported: ['16.0': 'Not supported.'], Obsoleted: [] }"];
+			yield return [builder.ToImmutable (), "{ Platform: 'iOS', Supported: '0.0', Unsupported: ['16.0': 'Not supported.'], Obsoleted: [] }"];
 
 			builder.Clear ();
 			builder.AddUnsupportedVersion (new Version (16, 0), "Not supported.");
 			builder.AddUnsupportedVersion (new Version (18, 0), "Not supported.");
-			yield return [builder.ToImmutable (), "{ Platform: 'iOS', Supported: '', Unsupported: ['16.0': 'Not supported.', '18.0': 'Not supported.'], Obsoleted: [] }"];
+			yield return [builder.ToImmutable (), "{ Platform: 'iOS', Supported: '0.0', Unsupported: ['16.0': 'Not supported.', '18.0': 'Not supported.'], Obsoleted: [] }"];
 
 			builder.Clear ();
 			builder.AddObsoletedVersion (new Version (16, 0), null, null);

tests/rgen/Microsoft.Macios.Generator.Tests/Availability/SymbolAvailabilityToStringTests.cs

@@ -43,7 +43,7 @@ public IEnumerator<object []> GetEnumerator ()
 			builder.AddSupportedVersion (ApplePlatform.iOS, new (16, 0));
 			builder.AddUnsupportedVersion (ApplePlatform.MacOSX, new (11, 0), null);
 			builder.AddSupportedVersion (ApplePlatform.MacCatalyst, new (16, 0));
-			yield return [builder.ToImmutable (), "[{ Platform: 'MacOSX', Supported: '', Unsupported: ['11.0': 'null'], Obsoleted: [] }, { Platform: 'iOS', Supported: '16.0', Unsupported: [], Obsoleted: [] }, { Platform: 'MacCatalyst', Supported: '16.0', Unsupported: [], Obsoleted: [] }]"];
+			yield return [builder.ToImmutable (), "[{ Platform: 'MacOSX', Supported: '0.0', Unsupported: ['11.0': 'null'], Obsoleted: [] }, { Platform: 'iOS', Supported: '16.0', Unsupported: [], Obsoleted: [] }, { Platform: 'MacCatalyst', Supported: '16.0', Unsupported: [], Obsoleted: [] }]"];
 		}
 
 		IEnumerator IEnumerable.GetEnumerator ()