[msbuild] Enable nullability and unify base and derived class for the GetFiles task.

msbuild/Xamarin.MacDev.Tasks/Tasks/GetFilesTaskBase.cs

@@ -1,29 +1,36 @@
 using System;
 using System.IO;
 using System.Collections.Generic;
+using System.Linq;
 
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
 
 using Xamarin.MacDev.Tasks;
 using Xamarin.Localization.MSBuild;
+using Xamarin.Messaging.Build.Client;
+
+#nullable enable
 
 namespace Xamarin.MacDev.Tasks {
-	public abstract class GetFilesTaskBase : XamarinTask {
+	public abstract class GetFiles : XamarinTask, ITaskCallback, ICancelableTask {
 		[Required]
-		public string Path { get; set; }
+		public string Path { get; set; } = string.Empty;
 
-		public string Pattern { get; set; }
+		public string Pattern { get; set; } = string.Empty;
 
-		public string Option { get; set; }
+		public string Option { get; set; } = string.Empty;
 
-		public string Exclude { get; set; }
+		public string Exclude { get; set; } = string.Empty;
 
 		[Output]
-		public ITaskItem [] Files { get; set; }
+		public ITaskItem [] Files { get; set; } = Array.Empty<ITaskItem> ();
 
 		public override bool Execute ()
 		{
+			if (ShouldExecuteRemotely ())
+				return new TaskRunner (SessionId, BuildEngine4).RunAsync (this).Result;
+
 			var path = Path.Replace ('\\', '/').TrimEnd ('/');
 			var exclude = new HashSet<string> ();
 			var items = new List<ITaskItem> ();
@@ -66,5 +73,17 @@ public override bool Execute ()
 
 			return !Log.HasLoggedErrors;
 		}
+
+		public IEnumerable<ITaskItem> GetAdditionalItemsToBeCopied () => Enumerable.Empty<ITaskItem> ();
+
+		public bool ShouldCopyToBuildServer (ITaskItem item) => false;
+
+		public bool ShouldCreateOutputFile (ITaskItem item) => false;
+
+		public void Cancel ()
+		{
+			if (ShouldExecuteRemotely ())
+				BuildConnection.CancelAsync (BuildEngine4).Wait ();
+		}
 	}
 }