[Xamarin.Android.Build.Tasks] Error APT2265 for invalid Asset Path (#9809)

Context: https://dev.azure.com/devdiv/DevDiv/_workitems/edit/2356711

Users regularly run into the following error.

	error APT2000: The system cannot find the specified file. (2):
	C:\Users\xxx\source\repos\AdventureWorks.MAUI\AdventureWorks.MAUI\obj\Debug\net9.0-android\assets

One of the reasons behind this is [an `aapt2` bug][0] in which it
cannot traverse directories containing non-ASCII characters.
This has been a long standing bug that does not seem to be getting
fixed any time soon. 

As we know why this issue occurs, lets at least raise the specific
error code with instructions on how to fix it. 

[0]: https://issuetracker.google.com/issues/188679588

Author: dellis1972

src/Xamarin.Android.Build.Tasks/Tasks/Aapt2.cs

@@ -22,7 +22,6 @@ namespace Xamarin.Android.Tasks {
 	public abstract class Aapt2 : AsyncTask {
 
 		private const int MAX_PATH = 260;
-		private const int ASCII_MAX_CHAR = 127;
 		private static readonly int DefaultMaxAapt2Daemons = 6;
 		protected Dictionary<string, string> _resource_name_case_map;
 
@@ -52,6 +51,17 @@ public abstract class Aapt2 : AsyncTask {
 		public static bool IsInvalidFilename (string path) =>
 			Path.GetFileName (path).StartsWith (".", StringComparison.Ordinal);
 
+		/// <summary>
+		/// Returns <see langword="true"/> if <paramref name="c"/> is an ASCII
+		/// character ([ U+0000..U+007F ]).
+		/// </summary>
+		/// <remarks>
+		/// Per http://www.unicode.org/glossary/#ASCII, ASCII is only U+0000..U+007F.
+		/// We cannot use Char.IsAscii cos we are .netstandard2.0
+		/// Source https://github.com/dotnet/runtime/blob/1d1bf92fcf43aa6981804dc53c5174445069c9e4/src/libraries/System.Private.CoreLib/src/System/Char.cs#L91
+		/// </remarks>
+		public static bool IsAscii(char c) => (uint)c <= '\x007f';
+
 		protected string ResourceDirectoryFullPath (string resourceDirectory)
 		{
 			return (Path.IsPathRooted (resourceDirectory) ? resourceDirectory : Path.Combine (WorkingDirectory, resourceDirectory)).TrimEnd ('\\');
@@ -226,13 +236,13 @@ static bool IsFilePathToLong (string filePath)
 			return false;
 		}
 
-		static bool IsPathOnlyASCII (string filePath)
+		static protected bool IsPathOnlyASCII (string filePath)
 		{
 			if (!OS.IsWindows)
 				return true;
 
 			foreach (var c in filePath)
-				if (c > ASCII_MAX_CHAR) // cannot use Char.IsAscii cos we are .netstandard2.0
+				if (!IsAscii (c))
 					return false;
 			return true;
 		}

src/Xamarin.Android.Build.Tasks/Tasks/Aapt2Link.cs

@@ -272,11 +272,16 @@ string [] GenerateCommandLineCommands (string ManifestFile, string currentAbi, s
 				}
 			}
 
+			var hasAssetsErrors = false;
 			// When adding Assets the first item found takes precedence.
-			// So we need to add the applicaiton Assets first.
+			// So we need to add the application Assets first.
 			if (!string.IsNullOrEmpty (AssetsDirectory)) {
 				var assetDir = GetFullPath (AssetsDirectory.TrimEnd ('\\'));
 				if (Directory.Exists (assetDir)) {
+					if (OS.IsWindows && !IsPathOnlyASCII (assetDir)) {
+						hasAssetsErrors = true;
+						LogCodedError ("APT2265", Properties.Resources.APT2265, assetDir);
+					}
 					cmd.Add ("-A");
 					cmd.Add (assetDir);
 				} else {
@@ -289,6 +294,11 @@ string [] GenerateCommandLineCommands (string ManifestFile, string currentAbi, s
 					var assetDir = GetFullPath (AdditionalAndroidAssetPaths [i].ItemSpec.TrimEnd ('\\'));
 					if (!string.IsNullOrWhiteSpace (assetDir)) {
 						if (Directory.Exists (assetDir)) {
+							if (OS.IsWindows && !IsPathOnlyASCII (assetDir)) {
+								hasAssetsErrors = true;
+								LogCodedError ("APT2265", Properties.Resources.APT2265, assetDir);
+								continue;
+							}
 							cmd.Add ("-A");
 							cmd.Add (GetFullPath (assetDir));
 						} else {
@@ -298,6 +308,10 @@ string [] GenerateCommandLineCommands (string ManifestFile, string currentAbi, s
 				}
 			}
 
+			if (hasAssetsErrors) {
+				return Array.Empty<string> ();
+			}
+
 			if (!string.IsNullOrEmpty (ProguardRuleOutput)) {
 				cmd.Add ("--proguard");
 				cmd.Add (GetFullPath (GetManifestRulesFile (manifestDir)));

src/Xamarin.Android.Build.Tasks/Tasks/Aapt2LinkAssetPack.cs

@@ -63,8 +63,13 @@ protected string[] GenerateCommandLineCommands (ITaskItem manifest, ITaskItem ou
 			cmd.Add ("--custom-package");
 			cmd.Add (PackageName);
 			foreach (var assetDirectory in AssetDirectories) {
+				var fullPath = GetFullPath (assetDirectory.ItemSpec);
+				if (OS.IsWindows && !IsPathOnlyASCII (fullPath)) {
+					LogCodedError ("APT2265", Properties.Resources.APT2265, fullPath);
+					continue;
+				}
 				cmd.Add ("-A");
-				cmd.Add (GetFullPath (assetDirectory.ItemSpec));
+				cmd.Add (fullPath);
 			}
 			cmd.Add ($"-o");
 			cmd.Add (GetFullPath (output.ItemSpec));

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildAssetsTest.cs

@@ -133,6 +133,26 @@ public void CheckAssetsAreIncludedInAPK ()
 			}
 		}
 
+		[Test]
+		public void InvalidAssetDirectoryWithNonASCIIChars ()
+		{
+			var proj = new XamarinAndroidApplicationProject () {
+				ProjectName = "App1",
+				IsRelease = true,
+				OtherBuildItems = {
+					new AndroidItem.AndroidAsset ("Assets\\asset1.txt") {
+						TextContent = () => "Asset1",
+						Encoding = Encoding.ASCII,
+					},
+				},
+			};
+			using (var b = CreateApkBuilder (Path.Combine ("temp", "InvalidAssetDirectoryWithNonASCIIChars_Ümläüt", proj.ProjectName))) {
+				b.ThrowOnBuildFailure = false;
+				Assert.AreEqual (!IsWindows, b.Build (proj), $"{proj.ProjectName} should {(IsWindows ? "not " : "")}have built successfully.");
+				Assert.AreEqual (IsWindows, b.LastBuildOutput.ContainsText ("APT2265"), $"APT2265 should {(IsWindows ? "" : "not ")}have been raised.");
+			}
+		}
+
 		[Test]
 		public void FullPath ()
 		{

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildTest.cs

@@ -659,7 +659,7 @@ public void BuildApplicationWithSpacesInPath ([Values (true, false)] bool enable
 				IsRelease = true,
 				AotAssemblies = true,
 				LinkTool = linkTool,
-				References = { new BuildItem ("ProjectReference", $"..\\{folderName}Library1\\Library1.csproj") }
+				References = { new BuildItem ("ProjectReference", $"..\\{folderName}Library1\\Library1.csproj") },
 			};
 			proj.OtherBuildItems.Add (new BuildItem ("AndroidJavaLibrary", "Hello (World).jar") { BinaryContent = () => Convert.FromBase64String (@"
 UEsDBBQACAgIAMl8lUsAAAAAAAAAAAAAAAAJAAQATUVUQS1JTkYv/soAAAMAUEsHCAAAAAACAAAAA