[Xamarin.Android.Build.Tasks] XA1041 Check aar has the correct paths (#9918)

dellis1972 · web-flow · commit 463e6da83e02 · 2025-05-02T11:01:28.000-04:00
Context: #9879 If you create an Android Library project which contains Android Resources: % dotnet new net9-androidlib % mkdir -p Resources/values % cat > Resources/values/strings.xml <<EOF <resources> <string name="lib_name">net9_androidlib</string> </resources> EOF then build the project with `$(MonoAndroidAssetsPrefix)` set to an absolute path: dotnet build -p:MonoAndroidAssetsPrefix=`pwd`/Resources then the resulting `$(MSBuildProjectName).aar` file contains the absolute path! % unzip -l bin/Debug/net9.0-android/net9-androidlib.aar Archive: bin/Debug/net9.0-android/net9-androidlib.aar Length Date Time Name --------- ---------- ----- ---- 78 04-08-2025 14:32 assets//Users/…/net9-androidlib/Resources/values/strings.xml 71 04-08-2025 14:32 res/values/strings.xml 38 04-08-2025 14:32 .net/__res_name_case_map.txt This is "nominally fine" on macOS, but if Windows is the source machine then the entry within the `.aar` contains a `:`, a'la `assets/D:/a/1/s/Foo.Mobile/Foo.Mobile.Droid/Assets/AboutAssets.txt`, which can cause a subsequent error XARLP7024 as in #9879: …\Xamarin.Android.EmbeddedResource.targets(39,5): error XARLP7024: System.IO.IOException: The filename, directory name, or volume label syntax is incorrect. : 'D:\a\1\s\MyCompany.Mobile\MyCompany.Mobile.Droid\obj\Release\net9.0-android\lp\183\jl\assets\D:\a\1\s\MyCompany.Mobile\MyCompany.Mobile.Droid\Assets'. …\Xamarin.Android.EmbeddedResource.targets(39,5): error XARLP7024: at System.IO.FileSystem.CreateDirectory(String fullPath, Byte[] securityDescriptor) …\Xamarin.Android.EmbeddedResource.targets(39,5): error XARLP7024: at Microsoft.Android.Build.Tasks.Files.CopyIfStreamChangedOnce(Stream stream, String destination) in /Users/runner/work/1/s/xamarin-android/external/xamarin-android-tools/src/Microsoft.Android.Build.BaseTasks/Files.cs:line 263 …\Xamarin.Android.EmbeddedResource.targets(39,5): error XARLP7024: at Microsoft.Android.Build.Tasks.Files.CopyIfStreamChanged(Stream stream, String destination) in /Users/runner/work/1/s/xamarin-android/external/xamarin-android-tools/src/Microsoft.Android.Build.BaseTasks/Files.cs:line 238 …\Xamarin.Android.EmbeddedResource.targets(39,5): error XARLP7024: at Microsoft.Android.Build.Tasks.Files.ExtractAll(ZipArchive zip, String destination, Action`2 progressCallback, Func`2 modifyCallback, Func`2 deleteCallback, Func`2 skipCallback) in /Users/runner/work/1/s/xamarin-android/external/xamarin-android-tools/src/Microsoft.Android.Build.BaseTasks/Files.cs:line 470 …\Xamarin.Android.EmbeddedResource.targets(39,5): error XARLP7024: at Xamarin.Android.Tasks.ResolveLibraryProjectImports.Extract(IDictionary`2 jars, ICollection`1 resolvedResourceDirectories, ICollection`1 resolvedAssetDirectories, ICollection`1 resolvedEnvironments, ICollection`1 proguardConfigFiles) in /Users/runner/work/1/s/xamarin-android/src/Xamarin.Android.Build.Tasks/Tasks/ResolveLibraryProjectImports.cs:line 398 …\Xamarin.Android.EmbeddedResource.targets(39,5): error XARLP7024: at Xamarin.Android.Tasks.ResolveLibraryProjectImports.RunTask() in /Users/runner/work/1/s/xamarin-android/src/Xamarin.Android.Build.Tasks/Tasks/ResolveLibraryProjectImports.cs:line 95 …\Xamarin.Android.EmbeddedResource.targets(39,5): error XARLP7024: at Microsoft.Android.Build.Tasks.AndroidTask.Execute() in /Users/runner/work/1/s/xamarin-android/external/xamarin-android-tools/src/Microsoft.Android.Build.BaseTasks/AndroidTask.cs:line 25 which is *not* fine. Update the `<CreateAar/>` and `<AndroidComputeResPaths/>` tasks to verify that the `$(MonoAndroidAssetsPrefix)` MSBuild value is *not* an absolute path value. If it is, then the "originating" build will report an error xa1041: error XA1041: The MSBuild property 'MonoAndroidAssetsPrefix' has an invalid value of '/Absolute/Path'. The value is expected to be a directory path representing the relative location of your Assets or Resources.
diff --git a/Documentation/docs-mobile/building-apps/build-properties.md b/Documentation/docs-mobile/building-apps/build-properties.md
@@ -1662,6 +1662,16 @@ The default value is False.
 
 This MSBuild property is obsolete and is no longer supported.
 
+## MonoAndroidAssetPrefix
+
+Specifies a *path prefix*
+that is removed from the start of filenames with a Build action of
+`AndroidAsset`. This is to allow changing where resources are
+located.
+
+The default value is `Assets`. Change this to `assets` for the
+Java project structure.
+
 ## MonoAndroidResourcePrefix
 
 Specifies a *path prefix*
diff --git a/Documentation/docs-mobile/messages/index.md b/Documentation/docs-mobile/messages/index.md
@@ -147,6 +147,9 @@ or 'Help->Report a Problem' in Visual Studio for Mac.
 Either change the value in the AndroidManifest.xml to match the $(SupportedOSPlatformVersion) value, or remove the value in the AndroidManifest.xml (and add a $(SupportedOSPlatformVersion) value to the project file if it doesn't already exist).
 + [XA1037](xa1037.md): The '{0}' MSBuild property is deprecated and will be removed in .NET {1}. See https://aka.ms/net-android-deprecations for more details.
 + [XA1038](xa1038.md): The '{0}' MSBuild property has an invalid value. Value values are {1}.
++ [XA1039](xa1039.md): The Android Support libraries are not supported in .NET 9 and later, please migrate to AndroidX. See https://aka.ms/xamarin/androidx for more details.
++ [XA1040](xa1040.md): The CoreCLR runtime on Android is an experimental feature and not yet suitable for production use. File issues at: https://github.com/dotnet/android/issues
++ [XA1041](xa1041.md): The MSBuild property 'MonoAndroidAssetPrefix' has an invalid value of 'c:\Foo\Assets'. The value is expected to be a directory path representing the relative location of your Assets or Resources
 
 ## XA2xxx: Linker
 
diff --git a/Documentation/docs-mobile/messages/xa1041.md b/Documentation/docs-mobile/messages/xa1041.md
@@ -0,0 +1,43 @@
+---
+title: .NET for Android warning XA1041
+description: XA1041 error code
+ms.date: 03/31/2025
+---
+# .NET for Android error XA1041
+
+## Example messages
+
+```dotnetcli
+error XA1040: The MSBuild property 'MonoAndroidAssetPrefix' has an invalid value of 'c:\Foo\Assets'. The value is expected to be a directory path representing the relative location of your Assets or Resources.
+error XA1040: The MSBuild property 'MonoAndroidResourcePrefix' has an invalid value of 'c:\Foo\Resources'.The value is expected to be a directory path representing the relative location of your Assets or Resources.
+```
+
+## Issue
+
+The problem there is that both the `MonoAndroidAssetPrefix` and `MonoAndroidResourcePrefix` are expected to be
+relative directory path . This information is used to "strip" the root directory
+information off the asset or resource when we package the app.
+The error is raised because the property contains a full path.
+
+For example consider the following structure.
+
+```dotnetcli
+Foo.csproj
+MyAssets/
+    Foo.txt
+    Subfolder/
+        Bar.txt
+MainAcrivity.cs
+```
+
+In the final `.apk` we expect the files `Foo.txt` and `Bar.txt` to be placed in the `assets` folder. In order to do this correctly the build system needs to know
+the `name` of the folder in which the assets are located. By default this is "Assets" but we should also support other folder name.
+
+In the example above we would expect the user to set the `MonoAndroidAssetPrefix` to a value of "MyAssets". This would ensure that the "MyAssets" part of the path
+to "Foo.txt" etc is removed during packaging. If the `MonoAndroidAssetPrefix` as set to
+`/Users/xxx/Foo/MyAssets` or `c:\Users\xxx\Foo\MyAssets` you would see this error message.
+
+## Solution
+
+The fix for this is to not use a full path for the values of `MonoAndroidAssetPrefix` or `MonoAndroidResourcePrefix`. They should be a relative
+directory path which matches the folder path in which your assets are stored.
diff --git a/src/Xamarin.Android.Build.Tasks/MSBuild/Xamarin/Android/Xamarin.Android.Assets.targets b/src/Xamarin.Android.Build.Tasks/MSBuild/Xamarin/Android/Xamarin.Android.Assets.targets
@@ -52,6 +52,7 @@ Copyright (C) 2011-2012 Xamarin. All rights reserved.
       IntermediateDir="$(MonoAndroidAssetsDirIntermediate)"
       AssetPackIntermediateDir="$(MonoAndroidAssetPacksDirIntermediate)"
       Prefixes="$(MonoAndroidAssetsPrefix)"
+      PrefixProperty="MonoAndroidAssetsPrefix"
       ProjectDir="$(ProjectDir)"
   >
     <Output ItemName="_AndroidAssetsDest" TaskParameter="IntermediateFiles" />
diff --git a/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.AndroidLibraries.targets b/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.AndroidLibraries.targets
@@ -77,6 +77,7 @@ projects.
       Outputs="$(_AarOutputPath)">
     <CreateAar
         AssetDirectory="$(MonoAndroidAssetsPrefix)"
+        PrefixProperty="MonoAndroidAssetsPrefix"
         AndroidAssets="@(AndroidAsset)"
         AndroidResources="@(_AndroidResourceDest)"
         AndroidEnvironment="@(AndroidEnvironment)"
diff --git a/src/Xamarin.Android.Build.Tasks/Properties/Resources.Designer.cs b/src/Xamarin.Android.Build.Tasks/Properties/Resources.Designer.cs
diff --git a/src/Xamarin.Android.Build.Tasks/Properties/Resources.resx b/src/Xamarin.Android.Build.Tasks/Properties/Resources.resx
@@ -1020,6 +1020,13 @@ To use a custom JDK path for a command line build, set the 'JavaSdkDirectory' MS
     <value>The {0} runtime on Android is an experimental feature and not yet suitable for production use. File issues at: https://github.com/dotnet/android/issues</value>
     <comment>The following are literal names and should not be translated: .NET.
 {0} - The name of the .NET runtime, such as CoreCLR or NativeAOT.</comment>
+  </data>
+  <data name="XA1041" xml:space="preserve">
+    <value>The MSBuild property '{0}' has an invalid value of '{1}'. The value is expected to be a directory path representing the relative location of your Assets or Resources.</value>
+    <comment>The following are literal names and should not be translated: .NET.
+{0} - The MSBuild property that has the incorrect value.
+{1} - The current value of the property
+</comment>
   </data>
   <data name="XA4241" xml:space="preserve">
     <value>Java dependency '{0}' is not satisfied.</value>
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/AndroidComputeResPaths.cs b/src/Xamarin.Android.Build.Tasks/Tasks/AndroidComputeResPaths.cs
@@ -51,6 +51,8 @@ public class AndroidComputeResPaths : AndroidTask
 
 		public string Prefixes { get; set; }
 
+		public string PrefixProperty { get; set; }
+
 		public bool LowercaseFilenames { get; set; }
 
 		public string ProjectDir { get; set; }
@@ -75,6 +77,10 @@ public override bool RunTask ()
 			if (prefixes != null) {
 				for (int i = 0; i < prefixes.Length; i++) {
 					string p = prefixes [i];
+					if (Path.IsPathRooted (p)) {
+						Log.LogCodedError ("XA1041", message: Properties.Resources.XA1041, PrefixProperty, p);
+						continue;
+					}
 					char c = p [p.Length - 1];
 					if (c != '\\' && c != '/')
 						prefixes [i] = p + Path.DirectorySeparatorChar;
diff --git a/src/Xamarin.Android.Build.Tasks/Tasks/CreateAar.cs b/src/Xamarin.Android.Build.Tasks/Tasks/CreateAar.cs
@@ -36,8 +36,14 @@ public class CreateAar : AndroidTask
 		[Required]
 		public string OutputFile { get; set; }
 
+		public string PrefixProperty { get; set; }
+
 		public override bool RunTask ()
 		{
+			if (Path.IsPathRooted (AssetDirectory)) {
+				Log.LogCodedError ("XA1041", message: Properties.Resources.XA1041, PrefixProperty, AssetDirectory);
+				return false;
+			}
 			Directory.CreateDirectory (Path.GetDirectoryName (OutputFile));
 
 			using (var stream = File.Create (OutputFile))
diff --git a/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BindingBuildTest.cs b/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BindingBuildTest.cs
@@ -169,6 +169,12 @@ public void BuildAarBindingLibraryStandalone (string classParser)
 		{
 			var proj = new XamarinAndroidBindingProject () {
 				IsRelease = true,
+				OtherBuildItems = {
+					new AndroidItem.AndroidAsset ("Assets\\asset1.txt") {
+						TextContent = () => "Asset1",
+						Encoding = Encoding.ASCII,
+					},
+				}
 			};
 			proj.Jars.Add (new AndroidItem.AndroidLibrary ("Jars\\material-menu-1.1.0.aar") {
 				WebContent = "https://repo1.maven.org/maven2/com/balysv/material-menu/1.1.0/material-menu-1.1.0.aar"
diff --git a/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildAssetsTest.cs b/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildAssetsTest.cs
@@ -6,6 +6,7 @@
 using Microsoft.Build.Framework;
 using System.Text;
 using System.Xml.Linq;
+using System.Collections.Generic;
 
 namespace Xamarin.Android.Build.Tests
 {
@@ -177,5 +178,42 @@ public void FullPath ()
 				FileAssert.DoesNotExist (libraryProjectImports);
 			}
 		}
+
+		[Test]
+		[Category ("SmokeTests")]
+		[TestCase("MonoAndroidAssetsPrefix")]
+		[TestCase("MonoAndroidResourcePrefix")]
+		public void FullPrefixRaisesError(string prefix)
+		{
+			var proj = new XamarinAndroidLibraryProject {
+				OtherBuildItems = {
+					new AndroidItem.AndroidAsset ("Assets\\asset1.txt") {
+						TextContent = () => "bar",
+					},
+				},
+			};
+			var app = new XamarinAndroidApplicationProject {
+				References = {
+					new BuildItem ("ProjectReference", "..\\Library1\\Library1.csproj"),
+				},
+				OtherBuildItems = {
+					new AndroidItem.AndroidAsset ("Assets\\asset2.txt") {
+						TextContent = () => "foo",
+					},
+				},
+			};
+			using var b = CreateDllBuilder (Path.Combine ("temp", TestName, "Library"));
+			using var appb = CreateApkBuilder (Path.Combine ("temp", TestName, "App"));
+			appb.ThrowOnBuildFailure = false;
+			b.ThrowOnBuildFailure = false;
+			Directory.CreateDirectory (Path.Combine (Root, "temp", TestName, "App"));
+			var envar = new Dictionary<string, string> {
+				{ prefix, Path.Combine (Root, "temp", TestName, "App") },
+			};
+			Assert.IsFalse (b.Build (proj, environmentVariables: envar), "Build should have failed.");
+			Assert.IsTrue (b.LastBuildOutput.ContainsText ("error XA1041"), "XA1041 should have been raised.");
+			Assert.IsFalse (appb.Build (app, environmentVariables: envar), "Build should have failed.");
+			Assert.IsTrue (appb.LastBuildOutput.ContainsText ("error XA1041"), "XA1041 should have been raised.");
+		}
 	}
 }
diff --git a/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Utilities/AssertionExtensions.cs b/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Utilities/AssertionExtensions.cs
@@ -1,5 +1,6 @@
 using System.Diagnostics;
 using System.IO;
+using System.Linq;
 using NUnit.Framework;
 using Xamarin.Android.Tasks;
 using Xamarin.ProjectTools;
@@ -70,7 +71,7 @@ public static void AssertEntryEquals (this ZipArchive zip, string zipPath, strin
 		[DebuggerHidden]
 		public static void AssertContainsEntry (this ZipArchive zip, string zipPath, string archivePath)
 		{
-			Assert.IsTrue (zip.ContainsEntry (archivePath), $"{zipPath} should contain {archivePath}");
+			Assert.IsTrue (zip.ContainsEntry (archivePath), $"{zipPath} should contain {archivePath}:\n{string.Join (",\n", zip.Select (e => e.FullName))}");
 		}
 
 		[DebuggerHidden]
@@ -114,6 +115,7 @@ public static void AssertContainsEntry (this ArchiveAssemblyHelper helper, strin
 		[DebuggerHidden]
 		public static void AssertEntryContents (this ZipArchive zip, string zipPath, string archivePath, string contents)
 		{
+			zip.AssertContainsEntry (zipPath, archivePath);
 			var entry = zip.ReadEntry (archivePath);
 			Assert.IsNotNull (entry, $"{zipPath} should contain {archivePath}");
 			using (var stream = new MemoryStream ())
diff --git a/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets b/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets
@@ -1084,6 +1084,7 @@ because xbuild doesn't support framework reference assemblies.
 	<AndroidComputeResPaths ResourceFiles="@(AndroidResource);@(AndroidBoundLayout)"
 			IntermediateDir="$(MonoAndroidResDirIntermediate)"
 			Prefixes="$(MonoAndroidResourcePrefix)"
+			PrefixProperty="MonoAndroidResourcePrefix"
 			LowercaseFilenames="True"
 			ProjectDir="$(ProjectDir)"
 			AndroidLibraryFlatFilesDirectory="$(_AndroidLibraryFlatFilesDirectory)"

Original file line number	Diff line number	Diff line change
`@@ -52,6 +52,7 @@ Copyright (C) 2011-2012 Xamarin. All rights reserved.`
`52`	`52`	`IntermediateDir="$(MonoAndroidAssetsDirIntermediate)"`
`53`	`53`	`AssetPackIntermediateDir="$(MonoAndroidAssetPacksDirIntermediate)"`
`54`	`54`	`Prefixes="$(MonoAndroidAssetsPrefix)"`
	`55`	`+ PrefixProperty="MonoAndroidAssetsPrefix"`
`55`	`56`	`ProjectDir="$(ProjectDir)"`
`56`	`57`	`>`
`57`	`58`	`<Output ItemName="_AndroidAssetsDest" TaskParameter="IntermediateFiles" />`