[msbuild] Port Metal and MetalLib to subclass XamarinTask. Fixes #21437.

This has a few advantages:

* We simplify and unify more of our code.
* We have more control over the error reporting / logging behavior.

Additionally:

* Use 'xcrun' to invoke 'metal' and 'metallib' (partial fix for #3931).
* Allow for overriding the path to the command-line tool in question.
* Add support for cancellation.
* Fix nullability.

Fixes #21437.

docs/build-apps/build-properties.md

@@ -30,3 +30,15 @@ Example:
 ```
 
 This property was introduced in .NET 9.
+
+## MetalLibPath
+
+The full path to the `metallib` tool (the Metal Linker).
+
+The default behavior is to use `xcrun metallib`.
+
+## MetalPath
+
+The full path to the Metal compiler.
+
+The default behavior is to use `xcrun metal`.

msbuild/Xamarin.MacDev.Tasks/Tasks/Metal.cs

@@ -1,6 +1,7 @@
 using System;
 using System.IO;
 using System.Collections.Generic;
+using System.Threading;
 
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
@@ -11,139 +12,112 @@
 using Xamarin.Localization.MSBuild;
 using Xamarin.Messaging.Build.Client;
 
-// Disable until we get around to enable + fix any issues.
-#nullable disable
-
 namespace Xamarin.MacDev.Tasks {
-	public class Metal : XamarinToolTask {
+	public class Metal : XamarinTask {
+		CancellationTokenSource? cancellationTokenSource;
+
 		#region Inputs
 
 		[Required]
-		public string IntermediateOutputPath { get; set; }
+		public string IntermediateOutputPath { get; set; } = string.Empty;
+
+		public string MetalPath { get; set; } = string.Empty;
 
 		[Required]
-		public string MinimumOSVersion { get; set; }
+		public string MinimumOSVersion { get; set; } = string.Empty;
 
 		[Required]
-		public string ProjectDir { get; set; }
+		public string ProjectDir { get; set; } = string.Empty;
 
 		[Required]
-		public string ResourcePrefix { get; set; }
+		public string ResourcePrefix { get; set; } = string.Empty;
 
 		[Required]
-		public string SdkDevPath { get; set; }
+		public string SdkDevPath { get; set; } = string.Empty;
 
 		[Required]
-		public string SdkVersion { get; set; }
+		public string SdkVersion { get; set; } = string.Empty;
 
 		[Required]
 		public bool SdkIsSimulator { get; set; }
 
 		[Required]
-		public string SdkRoot { get; set; }
+		public string SdkRoot { get; set; } = string.Empty;
 
 		[Required]
-		public ITaskItem SourceFile { get; set; }
+		public ITaskItem? SourceFile { get; set; }
 
 		#endregion
 
 		[Output]
-		public ITaskItem OutputFile { get; set; }
-
-		string DevicePlatformBinDir {
-			get {
-				switch (Platform) {
-				case ApplePlatform.iOS:
-				case ApplePlatform.TVOS:
-				case ApplePlatform.WatchOS:
-					return AppleSdkSettings.XcodeVersion.Major >= 11
-						? Path.Combine (SdkDevPath, "Toolchains", "XcodeDefault.xctoolchain", "usr", "bin")
-						: Path.Combine (SdkDevPath, "Platforms", "iPhoneOS.platform", "usr", "bin");
-				case ApplePlatform.MacOSX:
-				case ApplePlatform.MacCatalyst:
-					return AppleSdkSettings.XcodeVersion.Major >= 10
-						? Path.Combine (SdkDevPath, "Toolchains", "XcodeDefault.xctoolchain", "usr", "bin")
-						: Path.Combine (SdkDevPath, "Platforms", "MacOSX.platform", "usr", "bin");
-				default:
-					throw new InvalidOperationException (string.Format (MSBStrings.InvalidPlatform, Platform));
-				}
-			}
-		}
+		public ITaskItem? OutputFile { get; set; }
 
-		protected override string ToolName {
-			get { return "metal"; }
-		}
-
-		protected override string GenerateFullPathToTool ()
+		static string GetExecutable (List<string> arguments, string toolName, string toolPathOverride)
 		{
-			if (!string.IsNullOrEmpty (ToolPath))
-				return Path.Combine (ToolPath, ToolExe);
-
-			var path = Path.Combine (DevicePlatformBinDir, ToolExe);
-
-			return File.Exists (path) ? path : ToolExe;
+			if (string.IsNullOrEmpty (toolPathOverride)) {
+				arguments.Insert (0, toolName);
+				return "xcrun";
+			}
+			return toolPathOverride;
 		}
 
 		public override bool Execute ()
 		{
 			if (ShouldExecuteRemotely ())
 				return new TaskRunner (SessionId, BuildEngine4).RunAsync (this).Result;
 
-			if (AppleSdkSettings.XcodeVersion.Major >= 11)
-				EnvironmentVariables = EnvironmentVariables.CopyAndAdd ($"SDKROOT={SdkRoot}");
-			return base.Execute ();
-		}
+			var env = new Dictionary<string, string?> {
+				{ "SDKROOT", SdkRoot },
+			};
 
-		protected override string GenerateCommandLineCommands ()
-		{
 			var prefixes = BundleResource.SplitResourcePrefixes (ResourcePrefix);
-			var intermediate = Path.Combine (IntermediateOutputPath, ToolName);
-			var logicalName = BundleResource.GetLogicalName (ProjectDir, prefixes, SourceFile, !string.IsNullOrEmpty (SessionId));
+			var intermediate = Path.Combine (IntermediateOutputPath, MetalPath);
+			var logicalName = BundleResource.GetLogicalName (ProjectDir, prefixes, SourceFile!, !string.IsNullOrEmpty (SessionId));
 			var path = Path.Combine (intermediate, logicalName);
-			var args = new CommandLineArgumentBuilder ();
+			var args = new List<string> ();
 			var dir = Path.GetDirectoryName (path);
 
-			if (!Directory.Exists (dir))
-				Directory.CreateDirectory (dir);
+			Directory.CreateDirectory (dir);
 
 			OutputFile = new TaskItem (Path.ChangeExtension (path, ".air"));
 			OutputFile.SetMetadata ("LogicalName", Path.ChangeExtension (logicalName, ".air"));
 
-			args.Add ("-arch", "air64");
+			var executable = GetExecutable (args, "metal", MetalPath);
+
+			args.Add ("-arch");
+			args.Add ("air64");
 			args.Add ("-emit-llvm");
 			args.Add ("-c");
 			args.Add ("-gline-tables-only");
 			args.Add ("-ffast-math");
 
 			args.Add ("-serialize-diagnostics");
-			args.AddQuoted (Path.ChangeExtension (path, ".dia"));
+			args.Add (Path.ChangeExtension (path, ".dia"));
 
 			args.Add ("-o");
-			args.AddQuoted (Path.ChangeExtension (path, ".air"));
+			args.Add (Path.ChangeExtension (path, ".air"));
 
 			if (Platform == ApplePlatform.MacCatalyst) {
 				args.Add ($"-target");
 				args.Add ($"air64-apple-ios{MinimumOSVersion}-macabi");
 			} else {
 				args.Add (PlatformFrameworkHelper.GetMinimumVersionArgument (TargetFrameworkMoniker, SdkIsSimulator, MinimumOSVersion));
 			}
-			args.AddQuoted (SourceFile.ItemSpec);
+			args.Add (SourceFile!.ItemSpec);
 
-			return args.ToString ();
-		}
+			cancellationTokenSource = new CancellationTokenSource ();
+			ExecuteAsync (Log, executable, args, environment: env, cancellationToken: cancellationTokenSource.Token).Wait ();
 
-		protected override void LogEventsFromTextOutput (string singleLine, MessageImportance messageImportance)
-		{
-			// TODO: do proper parsing of error messages and such
-			Log.LogMessage (messageImportance, "{0}", singleLine);
+			return !Log.HasLoggedErrors;
 		}
 
-		public override void Cancel ()
+		public void Cancel ()
 		{
-			if (ShouldExecuteRemotely ())
+			if (ShouldExecuteRemotely ()) {
 				BuildConnection.CancelAsync (BuildEngine4).Wait ();
-
-			base.Cancel ();
+			} else {
+				cancellationTokenSource?.Cancel ();
+			}
 		}
 	}
 }

msbuild/Xamarin.MacDev.Tasks/Tasks/XamarinTask.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Threading;
 
 using Microsoft.Build.Framework;
 using Microsoft.Build.Tasks;
@@ -120,15 +121,15 @@ protected System.Threading.Tasks.Task<Execution> ExecuteAsync (string fileName,
 			return ExecuteAsync (Log, fileName, arguments, sdkDevPath, environment, mergeOutput, showErrorIfFailure, workingDirectory);
 		}
 
-		internal protected static async System.Threading.Tasks.Task<Execution> ExecuteAsync (TaskLoggingHelper log, string fileName, IList<string> arguments, string? sdkDevPath = null, Dictionary<string, string?>? environment = null, bool mergeOutput = true, bool showErrorIfFailure = true, string? workingDirectory = null)
+		internal protected static async System.Threading.Tasks.Task<Execution> ExecuteAsync (TaskLoggingHelper log, string fileName, IList<string> arguments, string? sdkDevPath = null, Dictionary<string, string?>? environment = null, bool mergeOutput = true, bool showErrorIfFailure = true, string? workingDirectory = null, CancellationToken? cancellationToken = null)
 		{
 			// Create a new dictionary if we're given one, to make sure we don't change the caller's dictionary.
 			var launchEnvironment = environment is null ? new Dictionary<string, string?> () : new Dictionary<string, string?> (environment);
 			if (!string.IsNullOrEmpty (sdkDevPath))
 				launchEnvironment ["DEVELOPER_DIR"] = sdkDevPath;
 
 			log.LogMessage (MessageImportance.Normal, MSBStrings.M0001, fileName, StringUtils.FormatArguments (arguments));
-			var rv = await Execution.RunAsync (fileName, arguments, environment: launchEnvironment, mergeOutput: mergeOutput, workingDirectory: workingDirectory);
+			var rv = await Execution.RunAsync (fileName, arguments, environment: launchEnvironment, mergeOutput: mergeOutput, workingDirectory: workingDirectory, cancellationToken: cancellationToken);
 			log.LogMessage (rv.ExitCode == 0 ? MessageImportance.Low : MessageImportance.High, MSBStrings.M0002, fileName, rv.ExitCode);
 
 			// Show the output

msbuild/Xamarin.Shared/Xamarin.Shared.targets

@@ -1398,6 +1398,7 @@ Copyright (C) 2018 Microsoft. All rights reserved.
 			SessionId="$(BuildSessionId)"
 			Condition="'$(IsMacEnabled)' == 'true' and '%(Metal.Identity)' != ''"
 			IntermediateOutputPath="$(DeviceSpecificIntermediateOutputPath)"
+			MetalPath="$(MetalPath)"
 			MinimumOSVersion="$(_MinimumOSVersion)"
 			ProjectDir="$(MSBuildProjectDirectory)"
 			TargetFrameworkMoniker="$(_ComputedTargetFrameworkMoniker)"
@@ -1417,6 +1418,7 @@ Copyright (C) 2018 Microsoft. All rights reserved.
 			SessionId="$(BuildSessionId)"
 			Condition="'$(IsMacEnabled)' == 'true'"
 			Items="@(_SmeltedMetal)"
+			MetalLibPath="$(MetalLibPath)"
 			SdkDevPath="$(_SdkDevPath)"
 			SdkRoot="$(_SdkRoot)"
 			OutputLibrary="$(_AppResourcesPath)default.metallib">