[Rgen] Provide a factory method that creates the objc msg send calls.

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

@@ -1,15 +1,110 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
+using static Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
 
 namespace Microsoft.Macios.Generator.Emitters;
 
 static partial class BindingSyntaxFactory {
-	readonly static string Runtime = "Runtime";
+	public const string Runtime = "Runtime";
+	public const string ClassPtr = "class_ptr";
 
 	public static CompilationUnitSyntax GetNSObject (string nsObjectType, ArgumentListSyntax argumentList,
 		bool suppressNullableWarning = false)
 		=> StaticInvocationGenericExpression (Runtime, "GetNSObject", nsObjectType, argumentList,
 			suppressNullableWarning);
+
+	/// <summary>
+	/// Returns the expression to get the handle of a selector.
+	/// </summary>
+	/// <param name="selector">The selector whose handle we want to retrieve.</param>
+	/// <returns>The expression to retrieve a selector handle.</returns>
+	public static InvocationExpressionSyntax GetHandle (string selector)
+	{
+		// (selector)
+		var args = ArgumentList (SingletonSeparatedList (
+					Argument (LiteralExpression (
+						SyntaxKind.StringLiteralExpression,
+						Literal (selector))))).NormalizeWhitespace ();
+
+		// Selector.GetHandle (selector)
+		return InvocationExpression (
+				MemberAccessExpression (
+					SyntaxKind.SimpleMemberAccessExpression,
+					IdentifierName ("Selector"),
+					IdentifierName ("GetHandle").WithTrailingTrivia (Space)))
+			.WithArgumentList (args);
+	}
+
+	/// <summary>
+	/// Generates the "this.Handle" expression.
+	/// </summary>
+	/// <returns></returns>
+	public static MemberAccessExpressionSyntax ThisHandle ()
+	{
+		return MemberAccessExpression (
+			SyntaxKind.SimpleMemberAccessExpression,
+			ThisExpression (),
+			IdentifierName ("Handle"));
+	}
+
+	/// <summary>
+	/// Generates the expression to call the objc_msgSend method.
+	/// </summary>
+	/// <param name="objcMsgSendMethod">The name of the method in the messaging namespace.</param>
+	/// <param name="selector">The selector.</param>
+	/// <param name="parameters">An optional argument list.</param>
+	/// <returns>The expression needed to call a specific messaging method.</returns>
+	public static InvocationExpressionSyntax MessagingInvocation (string objcMsgSendMethod, string selector,
+		ImmutableArray<ArgumentSyntax> parameters = default)
+	{
+		// the size of the arguments is 2 + the optional arguments
+		// [0] = the handle
+		// [1] = the selector
+		// [2] = the arguments
+		// but to be able to use the SeparatedList we need to add a comma for each argument
+		// except for the last one, so we need to add parametersCount - 1 commas
+		var parametersCount = 2 + parameters.Length;
+		var args = new SyntaxNodeOrToken [(2 * parametersCount) - 1];
+		// the first two arguments are the selector and the handle, we add those by hand
+		args [0] = Argument (ThisHandle ());
+		args [1] = Token (SyntaxKind.CommaToken).WithTrailingTrivia (Space);
+		args [2] = Argument (GetHandle (selector));
+
+		// we need to add the commas and the arguments provided by the user of the api
+		if (parameters.Length > 0) {
+			// add a comma because we know we added the selector
+			args [3] = Token (SyntaxKind.CommaToken).WithTrailingTrivia (Space);
+			var argsIndex = 4; // start at 4 because we added the first 2 parameters + 2 separators
+			var parametersIndex = 0;
+			while (argsIndex < args.Length) {
+				var currentParameter = parameters [parametersIndex++];
+				args [argsIndex++] = currentParameter;
+				if (argsIndex < args.Length - 1) {
+					args [argsIndex++] = Token (SyntaxKind.CommaToken).WithTrailingTrivia (Space);
+				}
+			}
+		}
+
+		// generates: (this.Handle, Selector.GetHandle (selector), args)
+		var argumentList = ArgumentList (SeparatedList<ArgumentSyntax> (args));
+		// generates: ObjCRuntime.Messaging.objc_msgSend (this.Handle, Selector.GetHandle (selector), args)
+		var invocation = InvocationExpression (
+			MemberAccessExpression (
+				SyntaxKind.SimpleMemberAccessExpression,
+				MemberAccessExpression (
+					SyntaxKind.SimpleMemberAccessExpression,
+					AliasQualifiedName (
+						IdentifierName (
+							Token (SyntaxKind.GlobalKeyword)),
+						IdentifierName ("ObjCRuntime")),
+					IdentifierName ("Messaging")),
+				IdentifierName (objcMsgSendMethod).WithTrailingTrivia (Space)))
+			.WithArgumentList (argumentList);
+		return invocation;
+	}
 }

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

@@ -310,9 +310,9 @@ public bool TryEmit (in BindingContext bindingContext, [NotNullWhen (false)] out
 
 			if (!bindingContext.Changes.IsStatic) {
 				classBlock.AppendGeneratedCodeAttribute (optimizable: true);
-				classBlock.WriteLine ($"static readonly NativeHandle class_ptr = Class.GetHandle (\"{registrationName}\");");
+				classBlock.WriteLine ($"static readonly NativeHandle {ClassPtr} = Class.GetHandle (\"{registrationName}\");");
 				classBlock.WriteLine ();
-				classBlock.WriteLine ("public override NativeHandle ClassHandle => class_ptr;");
+				classBlock.WriteLine ($"public override NativeHandle ClassHandle => {ClassPtr};");
 				classBlock.WriteLine ();
 
 				EmitDefaultConstructors (bindingContext: bindingContext,

tests/rgen/Microsoft.Macios.Generator.Tests/Emitters/BindingSyntaxFactoryRuntimeTests.cs

@@ -0,0 +1,73 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Xunit;
+using static Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
+using static Microsoft.Macios.Generator.Emitters.BindingSyntaxFactory;
+
+namespace Microsoft.Macios.Generator.Tests.Emitters;
+
+public class BindingSyntaxFactoryRuntimeTests {
+
+	[Theory]
+	[InlineData ("Test", "Selector.GetHandle (\"Test\")")]
+	[InlineData ("name", "Selector.GetHandle (\"name\")")]
+	[InlineData ("setName:", "Selector.GetHandle (\"setName:\")")]
+	void GetHandleTest (string selector, string expectedDeclaration)
+	{
+		var declaration = GetHandle (selector);
+		Assert.Equal (expectedDeclaration, declaration.ToFullString ());
+	}
+
+	class TestDataMessagingInvocationTests : IEnumerable<object []> {
+		public IEnumerator<object []> GetEnumerator ()
+		{
+			// no extra params
+			yield return [
+				"IntPtr_objc_msgSend",
+				"string",
+				ImmutableArray<ArgumentSyntax>.Empty,
+				"global::ObjCRuntime.Messaging.IntPtr_objc_msgSend (this.Handle, Selector.GetHandle (\"string\"))"
+			];
+
+			// one param extra
+			ImmutableArray<ArgumentSyntax> args = ImmutableArray.Create (
+				Argument (IdentifierName ("arg1"))
+			);
+			yield return [
+				"IntPtr_objc_msgSend",
+				"string",
+				args,
+				"global::ObjCRuntime.Messaging.IntPtr_objc_msgSend (this.Handle, Selector.GetHandle (\"string\"), arg1)"
+			];
+
+			// several params
+			args = ImmutableArray.Create (
+				Argument (IdentifierName ("arg1")),
+				Argument (IdentifierName ("arg2")),
+				Argument (IdentifierName ("arg3"))
+			);
+			yield return [
+				"IntPtr_objc_msgSend",
+				"string",
+				args,
+				"global::ObjCRuntime.Messaging.IntPtr_objc_msgSend (this.Handle, Selector.GetHandle (\"string\"), arg1, arg2, arg3)"
+			];
+		}
+
+		IEnumerator IEnumerable.GetEnumerator () => GetEnumerator ();
+	}
+
+	[Theory]
+	[ClassData (typeof (TestDataMessagingInvocationTests))]
+	void MessagingInvocationTests (string objcMsgSendMethod, string selector, ImmutableArray<ArgumentSyntax> parameters,
+		string expectedDeclaration)
+	{
+		var declaration = MessagingInvocation (objcMsgSendMethod, selector, parameters);
+		Assert.Equal (expectedDeclaration, declaration.ToFullString ());
+	}
+}