[Mono.Android] add fallback for TypemapManagedToJava

The .NET MAUI template + NativeAOT currently crashes with:

    02-18 15:59:24.575 12907 12907 E AndroidRuntime: net.dot.jni.internal.JavaProxyThrowable: System.InvalidProgramException: InvalidProgram_Specific, IntPtr Android.Runtime.JNIEnv.monodroid_typemap_managed_to_java(System.Type, Byte*)
    02-18 15:59:24.575 12907 12907 E AndroidRuntime:    at Internal.Runtime.TypeLoaderExceptionHelper.CreateInvalidProgramException(ExceptionStringID, String) + 0x4c
    02-18 15:59:24.575 12907 12907 E AndroidRuntime:    at Android.Runtime.JNIEnv.monodroid_typemap_managed_to_java(Type, Byte*) + 0x18
    02-18 15:59:24.575 12907 12907 E AndroidRuntime:    at Android.Runtime.JNIEnv.TypemapManagedToJava(Type) + 0x104
    02-18 15:59:24.575 12907 12907 E AndroidRuntime:    at Android.Runtime.JNIEnv.GetJniName(Type) + 0x1c
    02-18 15:59:24.575 12907 12907 E AndroidRuntime:    at Android.Runtime.JNIEnv.FindClass(Type) + 0x38
    02-18 15:59:24.575 12907 12907 E AndroidRuntime:    at Android.Runtime.JNIEnv.NewArray(IJavaObject[]) + 0x28
    02-18 15:59:24.575 12907 12907 E AndroidRuntime:    at Android.Runtime.JNIEnv.NewArray[T](T[]) + 0x94
    02-18 15:59:24.575 12907 12907 E AndroidRuntime:    at Android.Graphics.Drawables.LayerDrawable..ctor(Drawable[] layers) + 0xd4
    02-18 15:59:24.575 12907 12907 E AndroidRuntime:    at Microsoft.Maui.Platform.MauiRippleDrawableExtensions.UpdateMauiRippleDrawableBackground(View, Paint, IButtonStroke, Func`1, Func`1, Action) + 0x2ac

This appears to be related to array usage, such as
`LayerDrawable.ctor(Drawable[])` in this example.

I can reproduce the same crash using a `ColorStateList.ctor(int[][],
int[])` in our NativeAOT "hello world" sample:

    02-19 10:45:29.728 28692 28692 E AndroidRuntime: net.dot.jni.internal.JavaProxyThrowable: System.InvalidProgramException: InvalidProgram_Specific, IntPtr Android.Runtime.JNIEnv.monodroid_typemap_managed_to_java(System.Type, Byte*)
    02-19 10:45:29.728 28692 28692 E AndroidRuntime:    at Internal.Runtime.TypeLoaderExceptionHelper.CreateInvalidProgramException(ExceptionStringID, String) + 0x4c
    02-19 10:45:29.728 28692 28692 E AndroidRuntime:    at Android.Runtime.JNIEnv.monodroid_typemap_managed_to_java(Type, Byte*) + 0x18
    02-19 10:45:29.728 28692 28692 E AndroidRuntime:    at Android.Runtime.JNIEnv.TypemapManagedToJava(Type) + 0x104
    02-19 10:45:29.728 28692 28692 E AndroidRuntime:    at Android.Runtime.JNIEnv.GetJniName(Type) + 0x1c
    02-19 10:45:29.728 28692 28692 E AndroidRuntime:    at Android.Runtime.JNIEnv.FindClass(Type) + 0x38
    02-19 10:45:29.728 28692 28692 E AndroidRuntime:    at Android.Runtime.JNIEnv.NewArray[T](T[]) + 0xa8
    02-19 10:45:29.728 28692 28692 E AndroidRuntime:    at Android.Content.Res.ColorStateList..ctor(Int32[][], Int32[]) + 0xdc
    02-19 10:45:29.728 28692 28692 E AndroidRuntime:    at NativeAOT.MainActivity.OnCreate(Bundle savedInstanceState) + 0xb8

To fix this:

* Introduce a new `Android.Runtime.RuntimeFeature.UseReflectionForManagedToJava`
  feature switch

* If the switch is toggled, call
  `JavaNativeTypeManager.ToJniName(System.Type)` instead of
  `TypemapManagedToJava()`.

* Toggle the feature switch for NativeAOT.

In the future, we may enable this switch as a stopgap for getting
other runtimes to launch successfully.

To reduce confusion, I also removed the managed side of
`JNIEnvInit.IsRunningOnDesktop`, which was support for the Android
designer. It was using the exact same fallback after attempting
`TypemapManagedToJava()`. In a future PR, we could probably also
remove the native C/C++ side of this flag.

samples/NativeAOT/MainActivity.cs

@@ -1,3 +1,4 @@
+using Android.Content.Res;
 using Android.Runtime;
 using Android.Util;
 using System.Reflection;
@@ -17,5 +18,9 @@ protected override void OnCreate(Bundle? savedInstanceState)
 
         // Set our view from the "main" layout resource
         SetContentView(Resource.Layout.activity_main);
+
+        // An example of an Android API that uses a Java array
+        var list = new ColorStateList (new int[][] { [ 0, 1 ]}, [0, 1]);
+        Log.Debug ("NativeAOT", "MainActivity.OnCreate() ColorStateList: " + list);
     }
 }

src/Mono.Android/Android.App/SyncContext.cs

@@ -18,8 +18,6 @@ static bool EnsureLooper ([NotNullWhen (true)]Looper? looper, SendOrPostCallback
 		{
 			if (looper == null) {
 				var message = $"No Android message loop is available. Skipping invocation of `{d.Method.DeclaringType?.FullName}.{d.Method.Name}`!";
-				if (JNIEnvInit.IsRunningOnDesktop)
-					message += " Using `await` when running on the Android Designer is not currently supported. Please use the `View.IsInEditMode` property.";
 				Logger.Log (LogLevel.Error, "monodroid-synccontext", message);
 				return false;
 			}

src/Mono.Android/Android.Runtime/AndroidRuntime.cs

@@ -278,30 +278,32 @@ protected override IEnumerable<Type> GetTypesForSimpleReference (string jniSimpl
 
 		protected override string? GetSimpleReference (Type type)
 		{
+			if (RuntimeFeature.UseReflectionForManagedToJava) {
+				return JavaNativeTypeManager.ToJniName (type);
+			}
 			string? j = JNIEnv.TypemapManagedToJava (type);
 			if (j != null) {
 				return GetReplacementTypeCore (j) ?? j;
 			}
-			if (JNIEnvInit.IsRunningOnDesktop) {
-				return JavaNativeTypeManager.ToJniName (type);
-			}
 			return null;
 		}
 
 		protected override IEnumerable<string> GetSimpleReferences (Type type)
 		{
-			string? j = JNIEnv.TypemapManagedToJava (type);
-			j   = GetReplacementTypeCore (j) ?? j;
-
-			if (JNIEnvInit.IsRunningOnDesktop) {
+			string? j;
+			if (RuntimeFeature.UseReflectionForManagedToJava) {
 				string? d = JavaNativeTypeManager.ToJniName (type);
+				j   = GetReplacementTypeCore (d);
 				if (j != null && d != null) {
 					return new[]{j, d};
 				}
 				if (d != null) {
 					return new[]{d};
 				}
 			}
+
+			j = JNIEnv.TypemapManagedToJava (type);
+			j   = GetReplacementTypeCore (j) ?? j;
 			if (j != null) {
 				return new[]{j};
 			}

src/Mono.Android/Android.Runtime/JNIEnv.cs

@@ -446,6 +446,9 @@ public static string GetJniName (Type type)
 			if (type == null)
 				throw new ArgumentNullException ("type");
 
+			if (RuntimeFeature.UseReflectionForManagedToJava)
+				return JavaNativeTypeManager.ToJniName (type);
+
 			string? java = TypemapManagedToJava (type);
 			return java == null
 				? JavaNativeTypeManager.ToJniName (type)

src/Mono.Android/Android.Runtime/JNIEnvInit.cs

@@ -24,7 +24,6 @@ internal struct JnienvInitializeArgs {
 			public int             version; // TODO: remove, not needed anymore
 			public int             grefGcThreshold;
 			public IntPtr          grefIGCUserPeer;
-			public int             isRunningOnDesktop;
 			public byte            brokenExceptionTransitions;
 			public int             packageNamingPolicy;
 			public byte            ioExceptionType;
@@ -36,7 +35,6 @@ internal struct JnienvInitializeArgs {
 #pragma warning restore 0649
 
 		internal static JniRuntime.JniValueManager? ValueManager;
-		internal static bool IsRunningOnDesktop;
 		internal static bool jniRemappingInUse;
 		internal static bool MarshalMethodsEnabled;
 		internal static bool PropagateExceptions;
@@ -102,21 +100,12 @@ internal static unsafe void Initialize (JnienvInitializeArgs* args)
 			androidRuntime = new AndroidRuntime (args->env, args->javaVm, args->grefLoader, args->Loader_loadClass, args->jniAddNativeMethodRegistrationAttributePresent != 0);
 			ValueManager = androidRuntime.ValueManager;
 
-			IsRunningOnDesktop = args->isRunningOnDesktop == 1;
-
 			grefIGCUserPeer_class = args->grefIGCUserPeer;
 			grefGCUserPeerable_class = args->grefGCUserPeerable;
 
 			PropagateExceptions = args->brokenExceptionTransitions == 0;
 
 			JavaNativeTypeManager.PackageNamingPolicy = (PackageNamingPolicy)args->packageNamingPolicy;
-			if (IsRunningOnDesktop) {
-				var packageNamingPolicy = Environment.GetEnvironmentVariable ("__XA_PACKAGE_NAMING_POLICY__");
-				if (Enum.TryParse (packageNamingPolicy, out PackageNamingPolicy pnp)) {
-					JavaNativeTypeManager.PackageNamingPolicy = pnp;
-				}
-			}
-
 			SetSynchronizationContext ();
 		}
 

src/Mono.Android/Android.Runtime/RuntimeFeature.cs

@@ -0,0 +1,13 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+
+namespace Android.Runtime;
+
+static class RuntimeFeature
+{
+	const string FeatureSwitchPrefix = "Android.Runtime.RuntimeFeature.";
+
+	[FeatureSwitchDefinition ($"{FeatureSwitchPrefix}{nameof (UseReflectionForManagedToJava)}")]
+	internal static bool UseReflectionForManagedToJava { get; } =
+		AppContext.TryGetSwitch ($"{FeatureSwitchPrefix}{nameof (UseReflectionForManagedToJava)}", out bool isEnabled) ? isEnabled : false;
+}

src/Mono.Android/ILLink/ILLink.Substitutions.xml

@@ -4,5 +4,9 @@
       <method signature="System.Boolean get_NegotiateAuthenticationIsEnabled()" body="stub" feature="Xamarin.Android.Net.UseNegotiateAuthentication" featurevalue="false" value="false" />
       <method signature="System.Boolean get_NegotiateAuthenticationIsEnabled()" body="stub" feature="Xamarin.Android.Net.UseNegotiateAuthentication" featurevalue="true" value="true" />
     </type>
+    <type fullname="Android.Runtime.RuntimeFeature">
+      <method signature="System.Boolean get_UseReflectionForManagedToJava()" body="stub" feature="Android.Runtime.RuntimeFeature.UseReflectionForManagedToJava" featurevalue="false" value="false" />
+      <method signature="System.Boolean get_UseReflectionForManagedToJava()" body="stub" feature="Android.Runtime.RuntimeFeature.UseReflectionForManagedToJava" featurevalue="true" value="true" />
+    </type>
   </assembly>
 </linker>

src/Mono.Android/Java.Interop/TypeManager.cs

@@ -221,12 +221,10 @@ static Exception CreateJavaLocationException ()
 			if (type != null)
 				return type;
 
-			if (!JNIEnvInit.IsRunningOnDesktop) {
-				// Miss message is logged in the native runtime
-				if (Logger.LogAssembly)
-					JNIEnv.LogTypemapTrace (new System.Diagnostics.StackTrace (true));
-				return null;
-			}
+			// Miss message is logged in the native runtime
+			if (Logger.LogAssembly)
+				JNIEnv.LogTypemapTrace (new System.Diagnostics.StackTrace (true));
+			return null;
 
 			return null;
 		}
@@ -368,7 +366,7 @@ public static void RegisterType (string java_class, Type t)
 					if (String.Compare (jniFromType, java_class, StringComparison.OrdinalIgnoreCase) != 0) {
 						TypeManagerMapDictionaries.ManagedToJni.Add (t, java_class);
 					}
-				} else if (!JNIEnvInit.IsRunningOnDesktop || t != typeof (Java.Interop.TypeManager)) {
+				} else if (t != typeof (Java.Interop.TypeManager)) {
 					// skip the registration and output a warning
 					Logger.Log (LogLevel.Warn, "monodroid", FormattableString.Invariant ($"Type Registration Skipped for {java_class} to {t} "));
 				}

src/Mono.Android/Mono.Android.csproj

@@ -258,6 +258,7 @@
     <Compile Include="Android.Runtime\RequiresPermissionAttribute.cs" />
     <Compile Include="Android.Runtime\ResourceDesignerAttribute.cs" />
     <Compile Include="Android.Runtime\RuntimeConstants.cs" />
+    <Compile Include="Android.Runtime\RuntimeFeature.cs" />
     <Compile Include="Android.Runtime\ResourceIdManager.cs" />
     <Compile Include="Android.Runtime\RuntimeNativeMethods.cs" />
     <Compile Include="Android.Runtime\StringDefAttribute.cs" />

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets

@@ -13,6 +13,7 @@ This file contains the NativeAOT-specific MSBuild logic for .NET for Android.
   <PropertyGroup>
     <_AndroidRuntimePackRuntime>NativeAOT</_AndroidRuntimePackRuntime>
     <AndroidCodegenTarget Condition=" '$(AndroidCodegenTarget)' == '' ">JavaInterop1</AndroidCodegenTarget>
+    <_AndroidUseReflectionForManagedToJava Condition=" '$(_AndroidUseReflectionForManagedToJava)' == '' ">true</_AndroidUseReflectionForManagedToJava>
     <!-- NativeAOT's targets currently gives an error about cross-compilation -->
     <DisableUnsupportedError Condition=" $([MSBuild]::IsOSPlatform('windows')) and '$(DisableUnsupportedError)' == '' ">true</DisableUnsupportedError>
   </PropertyGroup>

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.RuntimeConfig.targets

@@ -46,6 +46,10 @@ See: https://github.com/dotnet/runtime/blob/b13715b6984889a709ba29ea8a1961db469f
         Value="$(AndroidAvoidEmitForPerformance)"
         Trim="true"
     />
+    <RuntimeHostConfigurationOption Include="Android.Runtime.RuntimeFeature.UseReflectionForManagedToJava"
+        Value="$([MSBuild]::ValueOrDefault('$(_AndroidUseReflectionForManagedToJava)', 'false'))"
+        Trim="true"
+    />
   </ItemGroup>
 
   <Target Name="_ParseRuntimeConfigFiles"

src/native/mono/monodroid/monodroid-glue-internal.hh

@@ -94,7 +94,6 @@ namespace xamarin::android::internal
 			int             version;
 			int             grefGcThreshold;
 			jobject         grefIGCUserPeer;
-			int             isRunningOnDesktop;
 			uint8_t         brokenExceptionTransitions;
 			int             packageNamingPolicy;
 			uint8_t         boundExceptionType;

src/native/mono/monodroid/monodroid-glue.cc

@@ -842,7 +842,6 @@ MonodroidRuntime::init_android_runtime (JNIEnv *env, jclass runtimeClass, jobjec
 	init.env                    = env;
 	init.logCategories          = log_categories;
 	init.version                = env->GetVersion ();
-	init.isRunningOnDesktop     = is_running_on_desktop ? 1 : 0;
 	init.brokenExceptionTransitions = application_config.broken_exception_transitions ? 1 : 0;
 	init.packageNamingPolicy    = static_cast<int>(application_config.package_naming_policy);
 	init.boundExceptionType     = application_config.bound_exception_type;