[nativeaot] fix typemap logic involving duplicates

70bd636 introduced an "MVP" for a managed typemap for NativeAOT.

Unfortunately, a `dotnet new maui` project template still crashes with:

    AndroidRuntime: Process: net.dot.hellonativeaot, PID: 16075
    AndroidRuntime: net.dot.jni.internal.JavaProxyThrowable: System.InvalidCastException: Arg_InvalidCastException
    AndroidRuntime:    at Java.Lang.Object._GetObject[T](IntPtr, JniHandleOwnership) + 0x64
    AndroidRuntime:    at Microsoft.Maui.WindowOverlay.Initialize() + 0x168
    AndroidRuntime:    at Microsoft.Maui.Handlers.WindowHandler.OnRootViewChanged(Object sender, EventArgs e) + 0x8c
    AndroidRuntime:    at Microsoft.Maui.Platform.NavigationRootManager.SetContentView(IView) + 0x17c
    AndroidRuntime:    at Microsoft.Maui.Platform.NavigationRootManager.Connect(IView, IMauiContext) + 0xf0
    AndroidRuntime:    at Microsoft.Maui.Handlers.WindowHandler.CreateRootViewFromContent(IWindowHandler, IWindow) + 0x4c
    AndroidRuntime:    at Microsoft.Maui.Handlers.WindowHandler.MapContent(IWindowHandler handler, IWindow window) + 0x20
    AndroidRuntime:    at Microsoft.Maui.PropertyMapper`2.<>c__DisplayClass5_0.<Add>b__0(IElementHandler h, IElement v) + 0x130
    AndroidRuntime:    at Microsoft.Maui.PropertyMapper.UpdatePropertyCore(String, IElementHandler, IElement) + 0x58
    AndroidRuntime:    at Microsoft.Maui.PropertyMapper.UpdateProperties(IElementHandler, IElement) + 0x74
    AndroidRuntime:    at Microsoft.Maui.Handlers.ElementHandler.SetVirtualView(IElement) + 0x15c
    AndroidRuntime:    at Microsoft.Maui.Controls.Element.SetHandler(IElementHandler) + 0x124
    AndroidRuntime:    at Microsoft.Maui.Controls.Element.set_Handler(IElementHandler value) + 0xc
    AndroidRuntime:    at Microsoft.Maui.Platform.ElementExtensions.SetHandler(Context, IElement, IMauiContext) + 0xfc
    AndroidRuntime:    at Microsoft.Maui.Platform.ApplicationExtensions.CreatePlatformWindow(Activity, IApplication, Bundle) + 0x184
    AndroidRuntime:    at Microsoft.Maui.MauiAppCompatActivity.OnCreate(Bundle) + 0x74
    AndroidRuntime:    at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_(IntPtr jnienv, IntPtr native__this, IntPtr native_savedInstanceState) + 0xc0
    AndroidRuntime: at my.MainActivity.n_onCreate(Native Method)
    AndroidRuntime: at my.MainActivity.onCreate(MainActivity.java:36)
    AndroidRuntime: at android.app.Activity.performCreate(Activity.java:8960)
    AndroidRuntime: at android.app.Activity.performCreate(Activity.java:8938)
    AndroidRuntime: at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1526)
    AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3975)
    AndroidRuntime: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4173)
    AndroidRuntime: at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:114)
    AndroidRuntime: at android.app.servertransaction.TransactionExecutor.executeNonLifecycleItem(TransactionExecutor.java:231)
    AndroidRuntime: at android.app.servertransaction.TransactionExecutor.executeTransactionItems(TransactionExecutor.java:152)
    AndroidRuntime: at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:93)
    AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2595)
    AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:107)
    AndroidRuntime: at android.os.Looper.loopOnce(Looper.java:232)
    AndroidRuntime: at android.os.Looper.loop(Looper.java:317)
    AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:8592)
    AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)
    AndroidRuntime: at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:580)
    AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:878)

One cause may be that `Java.Interop.JavaObject` is in the typemap
in favor of `Java.Lang.Object`! This could cause `InvalidCastException`.

The typemap implementation is missing two edge cases:

1. Types in `Mono.Android.dll` should be preferred over types in other
   assemblies.

2. Abstract or interface types should be preferred over their equivalent
   `*Invoker` types.

There was also some missing logic regarding `*Invoker` types and
abstract types.

I fixed these cases in `TypeMappingStep.cs` and added a test that can
validate the typemap during a build.

Author: jonathanpeppers

src/Microsoft.Android.Sdk.ILLink/TypeMappingStep.cs

@@ -16,7 +16,7 @@ public class TypeMappingStep : BaseStep
 {
 	const string AssemblyName = "Microsoft.Android.Runtime.NativeAOT";
 	const string TypeName = "Microsoft.Android.Runtime.NativeAotTypeManager";
-	readonly IDictionary<string, TypeDefinition> TypeMappings = new Dictionary<string, TypeDefinition> (StringComparer.Ordinal);
+	readonly IDictionary<string, List<TypeDefinition>> TypeMappings = new Dictionary<string, List<TypeDefinition>> (StringComparer.Ordinal);
 	AssemblyDefinition? MicrosoftAndroidRuntimeNativeAot;
 
 	protected override void ProcessAssembly (AssemblyDefinition assembly)
@@ -66,7 +66,7 @@ protected override void EndProcess ()
 		var il = method.Body.GetILProcessor ();
 		var addMethod = module.ImportReference (typeof (IDictionary<string, Type>).GetMethod ("Add"));
 		var getTypeFromHandle = module.ImportReference (typeof (Type).GetMethod ("GetTypeFromHandle"));
-		foreach (var (javaKey, typeDefinition) in TypeMappings) {
+		foreach (var (javaName, list) in TypeMappings) {
 			/*
 			 * IL_0000: ldarg.0
 			 * IL_0001: ldfld class [System.Runtime]System.Collections.Generic.IDictionary`2<string, class [System.Runtime]System.Type> Microsoft.Android.Runtime.NativeAotTypeManager::TypeMappings
@@ -77,21 +77,53 @@ protected override void EndProcess ()
 			 */
 			il.Emit (Mono.Cecil.Cil.OpCodes.Ldarg_0);
 			il.Emit (Mono.Cecil.Cil.OpCodes.Ldfld, field);
-			il.Emit (Mono.Cecil.Cil.OpCodes.Ldstr, javaKey);
-			il.Emit (Mono.Cecil.Cil.OpCodes.Ldtoken, module.ImportReference (typeDefinition));
+			il.Emit (Mono.Cecil.Cil.OpCodes.Ldstr, javaName);
+			il.Emit (Mono.Cecil.Cil.OpCodes.Ldtoken, module.ImportReference (SelectTypeDefinition (javaName, list)));
 			il.Emit (Mono.Cecil.Cil.OpCodes.Call, getTypeFromHandle);
 			il.Emit (Mono.Cecil.Cil.OpCodes.Callvirt, addMethod);
 		}
 
 		il.Emit (Mono.Cecil.Cil.OpCodes.Ret);
 	}
 
+	TypeDefinition SelectTypeDefinition (string javaName, List<TypeDefinition> list)
+	{
+		if (list.Count == 1)
+			return list[0];
+
+		var best = list[0];
+		foreach (var type in list) {
+			if (type == best)
+				continue;
+			// We found the `Invoker` type *before* the declared type 
+ 			// Fix things up so the abstract type is first, and the `Invoker` is considered a duplicate. 
+			if ((type.IsAbstract || type.IsInterface) &&
+					!best.IsAbstract &&
+					!best.IsInterface &&
+					type.IsAssignableFrom (best, Context)) {
+				best = type;
+			}
+		}
+		foreach (var type in list) {
+			if (type == best)
+				continue;
+			Context.LogMessage ($"Duplicate typemap entry for {javaName} => {type.FullName}");
+		}
+		return best;
+	}
+
 	void ProcessType (AssemblyDefinition assembly, TypeDefinition type)
 	{
 		if (type.HasJavaPeer (Context)) {
 			var javaName = JavaNativeTypeManager.ToJniName (type, Context);
-			if (!TypeMappings.TryAdd (javaName, type)) {
-				Context.LogMessage ($"Duplicate typemap entry for {javaName}");
+			if (!TypeMappings.TryGetValue (javaName, out var list)) {
+				TypeMappings.Add (javaName, list = new List<TypeDefinition> ());
+			}
+			// Types in Mono.Android assembly should be first in the list
+			if (assembly.Name.Name == "Mono.Android") {
+				list.Insert (0, type);
+			} else {
+				list.Add (type);
 			}
 		}
 

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildTest2.cs

@@ -135,6 +135,7 @@ public void NativeAOT ()
 			proj.SetProperty ("PublishAot", "true");
 			proj.SetProperty ("PublishAotUsingRuntimePack", "true");
 			proj.SetProperty ("AndroidNdkDirectory", AndroidNdkPath);
+			proj.SetProperty ("_ExtraTrimmerArgs", "--verbose");
 
 			using var b = CreateApkBuilder ();
 			Assert.IsTrue (b.Build (proj), "Build should have succeeded.");
@@ -165,6 +166,38 @@ public void NativeAOT ()
 				Assert.IsNotNull (method, $"{linkedMonoAndroidAssembly} should contain {typeName}.{methodName}");
 			}
 
+			var typemap = new Dictionary<string, TypeReference> ();
+			var linkedRuntimeAssembly = Path.Combine (intermediate, "linked", "Microsoft.Android.Runtime.NativeAOT.dll");
+			FileAssert.Exists (linkedRuntimeAssembly);
+			using (var assembly = AssemblyDefinition.ReadAssembly (linkedRuntimeAssembly)) {
+				var type = assembly.MainModule.Types.FirstOrDefault (t => t.Name == "NativeAotTypeManager");
+				Assert.IsNotNull (type, $"{linkedRuntimeAssembly} should contain NativeAotTypeManager");
+				var method = type.Methods.FirstOrDefault (m => m.Name == "InitializeTypeMappings");
+				Assert.IsNotNull (method, "NativeAotTypeManager should contain InitializeTypeMappings");
+
+				foreach (var i in method.Body.Instructions) {
+					if (i.OpCode != Mono.Cecil.Cil.OpCodes.Ldstr)
+						continue;
+					if (i.Operand is not string javaName)
+						continue;
+					if (i.Next.Operand is not TypeReference t)
+						continue;
+					typemap.Add (javaName, t);
+				}
+
+				// Basic types
+				AssertTypeMap ("java/lang/Object", "Java.Lang.Object");
+				AssertTypeMap ("java/lang/String", "Java.Lang.String");
+				AssertTypeMap ("android/app/Activity", "Android.App.Activity");
+				AssertTypeMap ("android/widget/Button", "Android.Widget.Button");
+
+				// Special *Invoker case
+				Assert.IsFalse (StringAssertEx.ContainsText (b.LastBuildOutput,
+					"ILLink: Duplicate typemap entry for android/view/View$OnClickListener => Android.Views.View/IOnClickListenerInvoker"),
+					"Should get log message about duplicate IOnClickListenerInvoker!");
+				AssertTypeMap ("android/view/View$OnClickListener", "Android.Views.View/IOnClickListener");
+			}
+
 			var dexFile = Path.Combine (intermediate, "android", "bin", "classes.dex");
 			FileAssert.Exists (dexFile);
 			foreach (var className in mono_classes) {
@@ -180,6 +213,15 @@ public void NativeAOT ()
 			foreach (var nativeaot_file in nativeaot_files) {
 				Assert.IsTrue (zip.ContainsEntry (nativeaot_file, caseSensitive: true), $"APK must contain `{nativeaot_file}`.");
 			}
+
+			void AssertTypeMap(string javaName, string managedName)
+			{
+				if (typemap.TryGetValue (javaName, out var reference)) {
+					Assert.AreEqual (managedName, reference.ToString ());
+				} else {
+					Assert.Fail ($"InitializeTypeMappings should contain Ldstr \"{javaName}\"!");
+				}
+			}
 		}
 
 		[Test]