[java-runtime] Improve native library load diagnostics

src/Xamarin.Android.Build.Tasks/Resources/JavaInteropRuntime.java

@@ -1,11 +1,13 @@
 package net.dot.jni.nativeaot;
 
 import android.util.Log;
+import android.content.Context;
+import mono.NativeLibraryHelper;
 
 public class JavaInteropRuntime {
-    static {
+    public static void loadLibrary(Context context) {
         Log.d("JavaInteropRuntime", "Loading @MAIN_ASSEMBLY_NAME@.so...");
-        System.loadLibrary("@MAIN_ASSEMBLY_NAME@");
+        NativeLibraryHelper.loadLibrary("@MAIN_ASSEMBLY_NAME@", context);
     }
 
     private JavaInteropRuntime() {

src/Xamarin.Android.Build.Tasks/Resources/NativeAotRuntimeProvider.java

@@ -36,6 +36,7 @@ public void attachInfo(android.content.Context context, android.content.pm.Provi
         String cacheDir = context.getCacheDir().getAbsolutePath();
 
         // Initialize .NET runtime
+        JavaInteropRuntime.loadLibrary(context);
         JavaInteropRuntime.init(loader, language, filesDir, cacheDir);
         // NOTE: only required for custom applications
         ApplicationRegistration.registerApplications();

src/java-runtime/java/mono/android/MonoPackageManager.java

@@ -99,19 +99,19 @@ public static void LoadApplication (Context context)
 				// below, leading to an error locating the Mono runtime
 				//
 				if (BuildConfig.Debug) {
-					System.loadLibrary ("xamarin-debug-app-helper");
+					NativeLibraryHelper.loadLibrary ("xamarin-debug-app-helper", runtimePackage, apks);
 					DebugRuntime.init (apks, runtimeDir, appDirs, haveSplitApks);
 				} else {
-					System.loadLibrary("monosgen-2.0");
+					NativeLibraryHelper.loadLibrary ("monosgen-2.0", runtimePackage, apks);
 				}
-				System.loadLibrary("xamarin-app");
+				NativeLibraryHelper.loadLibrary ("xamarin-app", runtimePackage, apks);
 
 				if (!BuildConfig.DotNetRuntime) {
 					// .net5+ APKs don't contain `libmono-native.so`
-					System.loadLibrary("mono-native");
+					NativeLibraryHelper.loadLibrary ("mono-native", runtimePackage, apks);
 				}
 
-				System.loadLibrary("monodroid");
+				NativeLibraryHelper.loadLibrary ("monodroid", runtimePackage, apks);
 
 				Runtime.initInternal (
 						language,

src/java-runtime/java/mono/android/NativeLibraryHelper.java

@@ -0,0 +1,149 @@
+package mono;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipFile;
+import android.content.Context;
+import android.content.pm.ApplicationInfo;
+import android.os.Build;
+import android.util.Log;
+
+public final class NativeLibraryHelper {
+	static final String TAG = "monodroid";
+
+	private NativeLibraryHelper ()
+	{
+	}
+
+	public static void loadLibrary (String libraryName, Context context)
+	{
+		ApplicationInfo applicationInfo = context.getApplicationInfo ();
+		String[] splitApks = applicationInfo.splitSourceDirs;
+		String[] apks;
+		if (splitApks != null && splitApks.length > 0) {
+			apks = new String [splitApks.length + 1];
+			apks [0] = applicationInfo.sourceDir;
+			System.arraycopy (splitApks, 0, apks, 1, splitApks.length);
+		} else {
+			apks = new String [] { applicationInfo.sourceDir };
+		}
+
+		loadLibrary (libraryName, applicationInfo, apks);
+	}
+
+	static void loadLibrary (String libraryName, ApplicationInfo applicationInfo, String[] apks)
+	{
+		try {
+			System.loadLibrary (libraryName);
+		} catch (UnsatisfiedLinkError cause) {
+			String diagnosticMessage = getDiagnosticMessage (libraryName, applicationInfo, apks, cause);
+			Log.e (TAG, diagnosticMessage, cause);
+
+			UnsatisfiedLinkError error = new UnsatisfiedLinkError (diagnosticMessage);
+			error.initCause (cause);
+			throw error;
+		} catch (SecurityException cause) {
+			String diagnosticMessage = getDiagnosticMessage (libraryName, applicationInfo, apks, cause);
+			Log.e (TAG, diagnosticMessage, cause);
+			throw new SecurityException (diagnosticMessage, cause);
+		}
+	}
+
+	static String getDiagnosticMessage (String libraryName, ApplicationInfo applicationInfo, String[] apks, Throwable cause)
+	{
+		String mappedLibraryName = System.mapLibraryName (libraryName);
+		StringBuilder message = new StringBuilder ();
+		message.append ("Failed to load native library '").append (mappedLibraryName).append ("'.");
+		message.append (" Supported ABIs: ").append (Arrays.toString (Build.SUPPORTED_ABIS)).append (".");
+
+		boolean foundLibrary = appendNativeLibraryDirectoryDiagnostics (message, applicationInfo.nativeLibraryDir, mappedLibraryName);
+		foundLibrary |= appendApkDiagnostics (message, apks, mappedLibraryName);
+
+		if (!foundLibrary) {
+			message.append (" The library was not found in the native library directory or any application APK that could be inspected.");
+			message.append (" The application installation may be corrupt; reinstalling the application may fix this error.");
+		}
+
+		String causeMessage = cause.getMessage ();
+		if (causeMessage != null && causeMessage.length () > 0) {
+			message.append (" Original error: ").append (causeMessage);
+		}
+
+		return message.toString ();
+	}
+
+	static boolean appendNativeLibraryDirectoryDiagnostics (StringBuilder message, String nativeLibraryDir, String mappedLibraryName)
+	{
+		message.append (" Native library directory: ");
+		if (nativeLibraryDir == null) {
+			message.append ("<unknown>.");
+			return false;
+		}
+
+		File directory = new File (nativeLibraryDir);
+		File library = new File (directory, mappedLibraryName);
+		boolean libraryExists = library.isFile ();
+		message.append ('\'').append (nativeLibraryDir).append ('\'');
+		message.append (" (directory exists: ").append (directory.isDirectory ());
+		message.append (", library exists: ").append (libraryExists);
+		if (libraryExists) {
+			message.append (", library size: ").append (library.length ());
+			message.append (", library readable: ").append (library.canRead ());
+		}
+		message.append (").");
+		return libraryExists;
+	}
+
+	static boolean appendApkDiagnostics (StringBuilder message, String[] apks, String mappedLibraryName)
+	{
+		boolean foundLibrary = false;
+		message.append (" APKs:");
+		if (apks == null || apks.length == 0) {
+			message.append (" <none>.");
+			return false;
+		}
+
+		for (String apk : apks) {
+			message.append (" '").append (apk).append ("'");
+			if (apk == null) {
+				message.append (" (invalid path);");
+				continue;
+			}
+
+			File apkFile = new File (apk);
+			if (!apkFile.isFile ()) {
+				message.append (" (file exists: false);");
+				continue;
+			}
+
+			ArrayList<String> entries = new ArrayList<String> ();
+			try (ZipFile zip = new ZipFile (apkFile)) {
+				for (String abi : Build.SUPPORTED_ABIS) {
+					String entryName = "lib/" + abi + "/" + mappedLibraryName;
+					ZipEntry entry = zip.getEntry (entryName);
+					if (entry == null)
+						continue;
+
+					foundLibrary = true;
+					String storage = entry.getMethod () == ZipEntry.STORED ? "stored" : "compressed";
+					entries.add (abi + ", " + storage + ", size " + entry.getSize ());
+				}
+				if (entries.size () == 0)
+					message.append (" (contains no matching native libraries);");
+				else
+					message.append (" (contains: ").append (entries).append (");");
+			} catch (IOException | SecurityException e) {
+				message.append (" (could not inspect: ").append (e.getClass ().getSimpleName ());
+				String errorMessage = e.getMessage ();
+				if (errorMessage != null && errorMessage.length () > 0)
+					message.append (": ").append (errorMessage);
+				message.append (");");
+			}
+		}
+
+		return foundLibrary;
+	}
+}

src/java-runtime/java/mono/android/clr/MonoPackageManager.java

@@ -70,7 +70,7 @@ public static void LoadApplication (Context context)
 				String[] appDirs = new String[] {filesDir, cacheDir, dataDir, codeCacheDir};
 				boolean haveSplitApks = runtimePackage.splitSourceDirs != null && runtimePackage.splitSourceDirs.length > 0;
 
-				System.loadLibrary("monodroid");
+				NativeLibraryHelper.loadLibrary ("monodroid", runtimePackage, apks);
 
 				Runtime.initInternal (
 					language,

tests/MSBuildDeviceIntegration/Tests/NativeLibraryLoadTests.cs

@@ -0,0 +1,97 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+using NUnit.Framework;
+using Xamarin.Android.Tasks;
+using Xamarin.ProjectTools;
+
+namespace Xamarin.Android.Build.Tests;
+
+[TestFixture]
+[Category ("UsesDevice")]
+public class NativeLibraryLoadTests : DeviceTest
+{
+	[Test]
+	public void MissingNativeLibraryHasUsefulErrorMessage ([Values (AndroidRuntime.CoreCLR, AndroidRuntime.NativeAOT)] AndroidRuntime runtime)
+	{
+		bool isRelease = runtime == AndroidRuntime.NativeAOT;
+		if (IgnoreUnsupportedConfiguration (runtime, release: isRelease)) {
+			return;
+		}
+
+		var proj = new XamarinAndroidApplicationProject (
+			packageName: PackageUtils.MakePackageName (runtime, "missingnativelibrary")
+		) {
+			IsRelease = isRelease,
+			ProjectName = "MissingNativeLibrary",
+		};
+		proj.SetRuntime (runtime);
+		proj.SetRuntimeIdentifiers (new [] { DeviceAbi });
+		proj.SetDefaultTargetDevice ();
+
+		string libraryName;
+		string removeLibraryItems;
+		if (runtime == AndroidRuntime.NativeAOT) {
+			libraryName = $"lib{proj.ProjectName}.so";
+			removeLibraryItems = $@"
+			<FrameworkNativeLibrary Remove=""@(FrameworkNativeLibrary)""
+				Condition="" '%(FrameworkNativeLibrary.ArchiveFileName)' == '{libraryName}' or '%(FrameworkNativeLibrary.FileName)%(FrameworkNativeLibrary.Extension)' == '{libraryName}' "" />
+			<_ApplicationSharedLibrary Remove=""@(_ApplicationSharedLibrary)""
+				Condition="" '%(_ApplicationSharedLibrary.ArchiveFileName)' == '{libraryName}' or '%(_ApplicationSharedLibrary.FileName)%(_ApplicationSharedLibrary.Extension)' == '{libraryName}' "" />";
+		} else {
+			libraryName = "libmonodroid.so";
+			removeLibraryItems = @"
+			<FrameworkNativeLibrary Remove=""@(FrameworkNativeLibrary)""
+				Condition="" '%(FrameworkNativeLibrary.ArchiveFileName)' == 'libmonodroid.so' or '%(FrameworkNativeLibrary.FileName)%(FrameworkNativeLibrary.Extension)' == 'libmonodroid.so' "" />
+			<_ApplicationSharedLibrary Remove=""@(_ApplicationSharedLibrary)""
+				Condition="" '%(_ApplicationSharedLibrary.ArchiveFileName)' == 'libmonodroid.so' or '%(_ApplicationSharedLibrary.FileName)%(_ApplicationSharedLibrary.Extension)' == 'libmonodroid.so' "" />";
+		}
+
+		proj.Imports.Add (new Import (() => "Directory.Build.targets") {
+			TextContent = () => $"""
+<Project>
+	<Target Name="_RemoveNativeLibraryForTest" BeforeTargets="_BuildApkEmbed">
+		<ItemGroup>
+			{removeLibraryItems}
+		</ItemGroup>
+	</Target>
+</Project>
+"""
+		});
+
+		using var builder = CreateApkBuilder ();
+		Assert.IsTrue (builder.Install (proj), "Project should have installed.");
+
+		string outputDirectory = Path.Combine (Root, builder.ProjectDirectory, proj.OutputPath);
+		string[] apks = Directory.GetFiles (outputDirectory, $"{proj.PackageName}-Signed.apk", SearchOption.AllDirectories);
+		Assert.IsNotEmpty (apks, "The signed APK should exist.");
+		using (var apk = ZipHelper.OpenZip (apks [0])) {
+			Assert.IsFalse (apk.ContainsEntry ($"lib/{DeviceAbi}/{libraryName}"),
+				$"{libraryName} should have been removed from the APK.");
+		}
+
+		var expectedMessages = new HashSet<string> {
+			$"Failed to load native library '{libraryName}'.",
+			"Supported ABIs:",
+			"Native library directory:",
+			"library exists: false",
+			"APKs:",
+			"contains no matching native libraries",
+			"The application installation may be corrupt; reinstalling the application may fix this error.",
+		};
+		string logcatPath = Path.Combine (Root, builder.ProjectDirectory, "native-library-load.log");
+		bool foundDiagnostic = MonitorAdbLogcat (
+			line => {
+				expectedMessages.RemoveWhere (message => line.Contains (message, StringComparison.Ordinal));
+				return expectedMessages.Count == 0;
+			},
+			logcatPath,
+			timeout: 45,
+			onMonitoringStarted: () => AdbStartActivity ($"{proj.PackageName}/{proj.JavaPackageName}.MainActivity")
+		);
+
+		Assert.IsTrue (foundDiagnostic,
+			$"The native library diagnostic was incomplete. Missing: {string.Join (", ", expectedMessages)}");
+	}
+}