[msbuild] Make the GetFileSystemEntries task capable of copying files…

… to the Mac. (#18324)

Make the GetFileSystemEntries task capable of copying files to the Mac, and
enable this new behavior when inspecting references for binding resources.

Otherwise the task might not find anything, if the files aren't copied to the
Mac (this happens if the files originate from NuGets instead of referenced
projects).

Ref:

* https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1808448 (third attempt)
* #18308
* dotnet/maui#15042

dotnet/targets/Xamarin.Shared.Sdk.targets

@@ -1914,6 +1914,7 @@ global using nfloat = global::System.Runtime.InteropServices.NFloat%3B
 			Pattern="*"
 			Recursive="true"
 			IncludeDirectories="false"
+			CopyFromWindows="true"
 			>
 			<Output TaskParameter="Entries" ItemName="_BindingPackagesFromReferencedAssemblies" />
 		</GetFileSystemEntries>

msbuild/Xamarin.MacDev.Tasks/Tasks/GetFileSystemEntries.cs

@@ -1,8 +1,15 @@
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+
 using Microsoft.Build.Framework;
+using Microsoft.Build.Utilities;
+
 using Xamarin.Messaging.Build.Client;
 
 namespace Xamarin.MacDev.Tasks {
-	public class GetFileSystemEntries : GetFileSystemEntriesTaskBase, ICancelableTask {
+	public class GetFileSystemEntries : GetFileSystemEntriesTaskBase, ICancelableTask, ITaskCallback {
 		public override bool Execute ()
 		{
 			if (ShouldExecuteRemotely ())
@@ -16,6 +23,38 @@ public void Cancel ()
 			if (ShouldExecuteRemotely ())
 				BuildConnection.CancelAsync (BuildEngine4).Wait ();
 		}
+
+		public IEnumerable<ITaskItem> GetAdditionalItemsToBeCopied ()
+		{
+			if (!CopyFromWindows)
+				return Enumerable.Empty<ITaskItem> ();
+
+			// TaskRunner doesn't know how to copy directories to Mac, so list each file.
+			var rv = new List<string> ();
+			foreach (var path in DirectoryPath) {
+				var spec = path.ItemSpec;
+				if (!Directory.Exists (spec))
+					continue;
+
+				var files = Directory.GetFiles (spec, "*", SearchOption.AllDirectories);
+				foreach (var file in files) {
+					// Only copy non-empty files, so that we don't end up
+					// copying an empty file that happens to be an output file
+					// from a previous target (and thus overwriting that file
+					// on Windows).
+					var finfo = new FileInfo (file);
+					if (!finfo.Exists || finfo.Length == 0)
+						continue;
+					rv.Add (file);
+				}
+			}
+
+			return rv.Select (f => new TaskItem (f));
+		}
+
+		public bool ShouldCopyToBuildServer (ITaskItem item) => true;
+
+		public bool ShouldCreateOutputFile (ITaskItem item) => false;
 	}
 }
 

msbuild/Xamarin.MacDev.Tasks/Tasks/GetFileSystemEntriesTaskBase.cs

@@ -23,6 +23,10 @@ public abstract class GetFileSystemEntriesTaskBase : XamarinTask {
 
 		[Required]
 		public bool IncludeDirectories { get; set; }
+
+		// If the input directory should be copied from Windows to the Mac in
+		// a remote build.
+		public bool CopyFromWindows { get; set; }
 		#endregion
 
 		#region Outputs