[msbuild] Add support to the ResolveNativeReferences task to execute …

…remotely. Fixes dotnet#19027.

It looks like ResolveNativeReferences was always intended to execute remotely
from Windows (when used in the _ExpandNativeReferences target, the task is
given a session id, and only called when IsMacEnabled=true), but the task
itself never implemented the code to execute remotely.

Weirdly enough this was never an issue, because the task never did something
that had to be done on a Mac.

That is, until recently, when the task learned to decompress zip files, by
executing /usr/bin/unzip.

Obviously this doesn't work on Windows, so fix it by adding support for the
task to execute remotely.

Fixes dotnet#19027.

msbuild/Xamarin.MacDev.Tasks/Tasks/ResolveNativeReferencesBase.cs

@@ -13,6 +13,7 @@
 using Xamarin.Bundler;
 using Xamarin.MacDev.Tasks;
 using Xamarin.Localization.MSBuild;
+using Xamarin.Messaging.Build.Client;
 using Xamarin.Utils;
 
 #nullable enable
@@ -38,7 +39,7 @@ namespace Xamarin.MacDev.Tasks {
 	//   and a zip may contain symlinks for a different platform (and thus won't be needed). Example: an xcframework
 	//   with a framework for macOS will likely have symlinks, but that shouldn't prevent the xcframework from being
 	//   consumed in a build for iOS.
-	public abstract class ResolveNativeReferencesBase : XamarinTask {
+	public class ResolveNativeReferences : XamarinTask, ITaskCallback {
 		#region Inputs
 
 		[Required]
@@ -99,6 +100,14 @@ string GetIntermediateDecompressionDir (string item)
 		}
 
 		public override bool Execute ()
+		{
+			if (ShouldExecuteRemotely ())
+				return new TaskRunner (SessionId, BuildEngine4).RunAsync (this).Result;
+
+			return ExecuteLocally ();
+		}
+
+		bool ExecuteLocally ()
 		{
 			var native_frameworks = new List<ITaskItem> ();
 			var createdFiles = new List<string> ();
@@ -497,5 +506,28 @@ internal static bool TryResolveXCFramework (TaskLoggingHelper log, PDictionary p
 			log.LogError (MSBStrings.E0175 /* No matching framework found inside '{0}'. SupportedPlatform: '{0}', SupportedPlatformVariant: '{1}', SupportedArchitectures: '{2}'. */, xcframeworkPath, platformName, variant, architectures);
 			return false;
 		}
+
+		public void Cancel ()
+		{
+			if (ShouldExecuteRemotely ())
+				BuildConnection.CancelAsync (BuildEngine4).Wait ();
+		}
+
+		public bool ShouldCopyToBuildServer (ITaskItem item) => true;
+
+		public bool ShouldCreateOutputFile (ITaskItem item)
+		{
+			if (NativeFrameworks is not null && Array.IndexOf (NativeFrameworks, item) >= 0) {
+				// Don't copy any resolved frameworks back to Windows, because
+				// 1. They're not used in Inputs/Outputs, so the lack of them won't affect anything
+				// 2. They may be directories, and as such we'd have to expand them to (potentially numerous and large) files to copy them (uselessly) to Windows.
+				// 3. They may contain symlinks, which may not work correctly on Windows.
+				return false;
+			}
+
+			return true;
+		}
+
+		public IEnumerable<ITaskItem> GetAdditionalItemsToBeCopied () => Enumerable.Empty<ITaskItem> ();
 	}
 }

tests/msbuild/Xamarin.MacDev.Tasks.Tests/TaskTests/ResolveNativeReferencesTaskTest.cs

@@ -40,7 +40,7 @@ public void Xcode12_x (string targetFrameworkMoniker, bool isSimulator, string a
 			// on Xcode 12.2+ you get arm64 for all (iOS, tvOS and watchOS) simulators
 			var path = Path.Combine (Path.GetDirectoryName (GetType ().Assembly.Location), "Resources", "xcf-xcode12.2.plist");
 			var plist = PDictionary.FromFile (path);
-			var result = ResolveNativeReferencesBase.TryResolveXCFramework (log, plist, "N/A", targetFrameworkMoniker, isSimulator, architecture, out var frameworkPath);
+			var result = ResolveNativeReferences.TryResolveXCFramework (log, plist, "N/A", targetFrameworkMoniker, isSimulator, architecture, out var frameworkPath);
 			Assert.AreEqual (result, !string.IsNullOrEmpty (expected), "result");
 			Assert.That (frameworkPath, Is.EqualTo (expected), "frameworkPath");
 		}
@@ -53,7 +53,7 @@ public void PreXcode12 (string targetFrameworkMoniker, bool isSimulator, string
 		{
 			var path = Path.Combine (Path.GetDirectoryName (GetType ().Assembly.Location), "Resources", "xcf-prexcode12.plist");
 			var plist = PDictionary.FromFile (path);
-			var result = ResolveNativeReferencesBase.TryResolveXCFramework (log, plist, "N/A", targetFrameworkMoniker, isSimulator, architecture, out var frameworkPath);
+			var result = ResolveNativeReferences.TryResolveXCFramework (log, plist, "N/A", targetFrameworkMoniker, isSimulator, architecture, out var frameworkPath);
 			Assert.AreEqual (result, !string.IsNullOrEmpty (expected), "result");
 			Assert.That (frameworkPath, Is.EqualTo (expected), "frameworkPath");
 		}
@@ -62,7 +62,7 @@ public void PreXcode12 (string targetFrameworkMoniker, bool isSimulator, string
 		public void BadInfoPlist ()
 		{
 			var plist = new PDictionary ();
-			var result = ResolveNativeReferencesBase.TryResolveXCFramework (log, plist, "N/A", TargetFramework.DotNet_iOS_String, false, "x86_64", out var frameworkPath);
+			var result = ResolveNativeReferences.TryResolveXCFramework (log, plist, "N/A", TargetFramework.DotNet_iOS_String, false, "x86_64", out var frameworkPath);
 			Assert.IsFalse (result, "Invalid Info.plist");
 		}
 	}