[WIP] Modify code to comply with test expectations

Author: grendello

src/Xamarin.Android.Build.Tasks/Tasks/Aot.cs

@@ -221,7 +221,11 @@ int GetNdkApiLevel (NdkTools ndk, string androidApiLevel, AndroidTargetArch arch
 
 		public async override System.Threading.Tasks.Task RunTaskAsync ()
 		{
-			NdkTools ndk = NdkTools.Create (AndroidNdkDirectory, Log);
+			NdkTools? ndk = NdkTools.Create (AndroidNdkDirectory, Log);
+			if (ndk == null) {
+				return; // NdkTools.Create will log appropriate error
+			}
+
 			bool hasValidAotMode = GetAndroidAotMode (AndroidAotMode, out AotMode);
 			if (!hasValidAotMode) {
 				LogCodedError ("XA3002", Properties.Resources.XA3002, AndroidAotMode);

src/Xamarin.Android.Build.Tasks/Tasks/BuildApk.cs

@@ -635,7 +635,11 @@ private void AddNativeLibraries (ArchiveFileList files, string [] supportedAbis)
 				return;
 			}
 
-			NdkTools ndk = NdkTools.Create (AndroidNdkDirectory, Log);
+			NdkTools? ndk = NdkTools.Create (AndroidNdkDirectory, Log);
+			if (ndk == null) {
+				return; // NdkTools.Create will log appropriate error
+			}
+
 			string clangDir = ndk.GetClangDeviceLibraryPath ();
 			if (String.IsNullOrEmpty (clangDir)) {
 				LogSanitizerError ($"Unable to find the clang compiler directory. Is NDK installed?");

src/Xamarin.Android.Build.Tasks/Tasks/MakeBundleNativeCodeExternal.cs

@@ -57,7 +57,10 @@ public MakeBundleNativeCodeExternal ()
 
 		public override bool RunTask ()
 		{
-			NdkTools ndk = NdkTools.Create (AndroidNdkDirectory, Log);
+			NdkTools? ndk = NdkTools.Create (AndroidNdkDirectory, Log);
+			if (ndk == null) {
+				return false; // NdkTools.Create will log appropriate error
+			}
 
 			try {
 				return DoExecute (ndk);

src/Xamarin.Android.Build.Tasks/Utilities/NdkTools/NdkTools.cs

@@ -72,13 +72,17 @@ public static bool IsValidNdkRoot (string androidNdkPath)
 			return true;
 		}
 
-		public static NdkTools Create (string androidNdkPath, TaskLoggingHelper? log = null)
+		public static NdkTools? Create (string androidNdkPath, TaskLoggingHelper? log = null)
 		{
 			if (String.IsNullOrEmpty (androidNdkPath)) {
-				throw new ArgumentException ("must be a non-empty string", nameof (androidNdkPath));
+				log?.LogCodedError ("XA5104", Properties.Resources.XA5104);
+				return null;
 			}
 
-			NdkVersion version = ReadVersion (androidNdkPath);
+			NdkVersion? version = ReadVersion (androidNdkPath);
+			if (version == null) {
+				return null;
+			}
 
 			if (version.Main.Major < 14) {
 				throw new InvalidOperationException ($"Unsupported NDK version {version}");
@@ -356,10 +360,11 @@ bool HasPrebuiltDir (string name)
                         }
                 }
 
-		static NdkVersion ReadVersion (string androidNdkPath)
+		static NdkVersion? ReadVersion (string androidNdkPath, TaskLoggingHelper? log = null)
 		{
 			if (!Directory.Exists (androidNdkPath)) {
-				throw new InvalidOperationException ($"NDK directory '{androidNdkPath}' does not exist.");
+				log?.LogCodedError ("XA5104", Properties.Resources.XA5104);
+				return null;
 			}
 
 			string sourcePropertiesPath = Path.Combine (androidNdkPath, "source.properties");