[Mono.Android] broaden assignability check escape hatch by simonrozsival · Pull Request #11606 · dotnet/android

simonrozsival · 2026-06-08T13:15:43Z

Summary

Extend Microsoft.Android.Runtime.RuntimeFeature.IsAssignableFromCheck to CoreCLR peer creation paths in JavaMarshalValueManager.
Keep the default behavior unchanged, but when _AndroidIsAssignableFromCheck=false, skip Java assignability checks (IsAssignableFrom) so peer creation can continue without running the check.
Keep the implementation focused on specific assignability decision points (no duplicated feature-specific peer-creation flow), and use standalone if (RuntimeFeature.IsX) blocks for trimmer-friendly branching.
Add coverage for wrapping a remapped LayoutInflater returned from Context.LayoutInflaterService, and add a CoreCLR Intune assignability package-test leg.

Motivation

dotnet/android#10475 introduced _AndroidIsAssignableFromCheck=false for the Mono.Android typemap path. In MAUI + Intune remapping scenarios, LayoutInflater.From(Context) can still return null through the CoreCLR/Java.Interop peer creation path, which performs a separate assignability check not covered by the existing switch.

This draft explores making the switch consistently mean: when explicitly disabled, Java remapping-induced assignability mismatches should not reject managed peer creation.

Validation

MSBUILDDISABLENODEREUSE=1 ./dotnet-local.sh build src/Mono.Android/Mono.Android.csproj --no-restore -m:1 -v:minimal ✅
./dotnet-local.sh build tests/Mono.Android-Tests/Mono.Android-Tests/Mono.Android.NET-Tests.csproj -f net11.0-android -p:TestsFlavor=CoreCLRIsAssignableFrom -p:IncludeCategories=Intune -p:_AndroidIsAssignableFromCheck=false -p:UseMonoRuntime=false -m:1 -v:minimal ⚠️ blocked locally with XA5300 because the Android SDK directory is not available in this environment.

Honor Microsoft.Android.Runtime.RuntimeFeature.IsAssignableFromCheck in CoreCLR peer creation paths so remapped Java types can still be wrapped when the escape hatch is disabled. Add coverage for wrapping a remapped LayoutInflater service and run the Intune assignability tests under CoreCLR. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival · 2026-06-08T13:15:53Z

/azp run

azure-pipelines · 2026-06-08T13:16:03Z

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simonrozsival

@copilot address this code review

simonrozsival · 2026-06-08T13:17:50Z

 				}
 				var isAssignable = JniEnvironment.Types.IsAssignableFrom (objClass, targetClass);
-				return isAssignable ? proxy : null;
+				if (!isAssignable && RuntimeFeature.IsAssignableFromCheck) {


@copilot RuntimeFeature checks should be in a standalone if (RuntimeFeature.IsX) block so that the trimmer can reliably identify it and trim the unreachable codepath.

Addressed in 01852f9: RuntimeFeature checks are now in standalone if (RuntimeFeature.IsAssignableFromCheck) blocks for trimmer-friendly flow.

simonrozsival · 2026-06-08T13:19:48Z

@@ -585,8 +717,12 @@ static bool IsIncompatibleCast (
 			}

 			if (!JniEnvironment.Types.IsAssignableFrom (instanceClass, targetClass)) {


@copilot I think the right way to handle this is NOT to call IsAssignableFrom at all when RuntimeFeature.IsAssignableFromCheck is false. That's much easier to follow and it doesn't do unnecessary work when the feature is disabled.

Addressed in 01852f9: IsAssignableFrom is no longer called when RuntimeFeature.IsAssignableFromCheck is false.

simonrozsival · 2026-06-08T13:21:15Z

+	IJavaPeerable? CreatePeerAllowingIncompatibleJavaType (
+			ref JniObjectReference reference,
+			JniObjectReferenceOptions transfer,
+			[DynamicallyAccessedMembers (Constructors)]
+			Type? targetType)
+	{
+		// Mirrors Java.Interop's CreatePeer path, but lets the Android assignability
+		// feature switch decide whether a Java type mismatch rejects peer creation.
+		var resolvedTargetType = ResolvePeerType (targetType ?? typeof (global::Java.Interop.JavaObject));
+		if (resolvedTargetType is null) {
+			return null;
+		}
+
+		if (!typeof (IJavaPeerable).IsAssignableFrom (resolvedTargetType)) {
+			throw new ArgumentException ($"targetType `{resolvedTargetType.AssemblyQualifiedName}` must implement IJavaPeerable!", nameof (targetType));
+		}
+
+		var targetSig = Runtime.TypeManager.GetTypeSignature (resolvedTargetType);
+		if (!targetSig.IsValid || targetSig.SimpleReference == null) {
+			throw new ArgumentException ($"Could not determine Java type corresponding to `{resolvedTargetType.AssemblyQualifiedName}`.", nameof (targetType));
+		}
+
+		var refClass = JniEnvironment.Types.GetObjectClass (reference);
+		JniObjectReference targetClass;
+		try {
+			targetClass = JniEnvironment.Types.FindClass (targetSig.SimpleReference);
+		} catch (Exception e) {
+			JniObjectReference.Dispose (ref refClass);
+			throw new ArgumentException ($"Could not find Java class `{targetSig.SimpleReference}`.",
+					nameof (targetType),
+					e);
+		}
+
+		if (!JniEnvironment.Types.IsAssignableFrom (refClass, targetClass) && Logger.LogAssembly) {
+			var message = $"Handle 0x{reference.Handle:x} is of type '{JniEnvironment.Types.GetJniTypeNameFromInstance (reference)}' which is not assignable to '{targetSig.SimpleReference}'";
+			Logger.Log (LogLevel.Debug, "monodroid-assembly", message);
+		}
+
+		JniObjectReference.Dispose (ref targetClass);
+
+		var peer = CreatePeerInstance (ref refClass, resolvedTargetType, ref reference, transfer);
+		if (peer == null) {
+			throw new NotSupportedException (string.Format (CultureInfo.InvariantCulture, "Could not find an appropriate constructable wrapper type for Java type '{0}', targetType='{1}'.",
+					JniEnvironment.Types.GetJniTypeNameFromInstance (reference), resolvedTargetType));
+		}
+		peer.SetJniManagedPeerState (peer.JniManagedPeerState | JniManagedPeerStates.Replaceable);
+		return peer;
+	}
+
+	IJavaPeerable? CreatePeerInstance (
+			ref JniObjectReference klass,
+			[DynamicallyAccessedMembers (Constructors)]
+			Type targetType,
+			ref JniObjectReference reference,
+			JniObjectReferenceOptions transfer)
+	{
+		var jniTypeName = JniEnvironment.Types.GetJniTypeNameFromClass (klass);
+
+		while (jniTypeName != null) {
+			if (!JniTypeSignature.TryParse (jniTypeName, out var sig)) {
+				return null;
+			}
+
+			Type? type = GetTypeAssignableTo (sig, targetType);
+			if (type != null) {
+				var peer = TryCreatePeerInstance (ref reference, transfer, type);
+
+				if (peer != null) {
+					JniObjectReference.Dispose (ref klass);
+					return peer;
+				}
+			}
+
+			var super = JniEnvironment.Types.GetSuperclass (klass);
+			jniTypeName = super.IsValid
+				? JniEnvironment.Types.GetJniTypeNameFromClass (super)
+				: null;
+
+			JniObjectReference.Dispose (ref klass, JniObjectReferenceOptions.CopyAndDispose);
+			klass = super;
+		}
+		JniObjectReference.Dispose (ref klass, JniObjectReferenceOptions.CopyAndDispose);
+
+		return TryCreatePeerInstance (ref reference, transfer, targetType);
+
+		[UnconditionalSuppressMessage ("Trimming", "IL2073", Justification = "Types returned here should be preserved via other means.")]
+		[return: DynamicallyAccessedMembers (Constructors)]
+		Type? GetTypeAssignableTo (JniTypeSignature sig, Type targetType)
+		{
+			foreach (var type in Runtime.TypeManager.GetTypes (sig)) {
+				if (targetType.IsAssignableFrom (type)) {
+					return type;
+				}
+			}
+			return null;
+		}
+	}
+
+	IJavaPeerable? TryCreatePeerInstance (
+			ref JniObjectReference reference,
+			JniObjectReferenceOptions options,
+			[DynamicallyAccessedMembers (Constructors)]
+			Type type)
+	{
+		type = Runtime.TypeManager.GetInvokerType (type) ?? type;
+
+		var self = GetUninitializedObject (type);
+		var constructed = false;
+		try {
+			constructed = TryConstructPeer (self, ref reference, options, type);
+		} finally {
+			if (!constructed) {
+				GC.SuppressFinalize (self);
+				self = null;
+			}
+		}
+		return self;
+
+		static IJavaPeerable GetUninitializedObject (
+				[DynamicallyAccessedMembers (Constructors)]
+				Type type)
+		{
+			var value = (IJavaPeerable) RuntimeHelpers.GetUninitializedObject (type);
+			value.SetJniManagedPeerState (JniManagedPeerStates.Replaceable | JniManagedPeerStates.Activatable);
+			return value;
+		}
+	}
+


This is definitely not the right way to implement this. I'm 100% sure we don't want to duplicate and significantly diverge the logic in this class based on this feature switch. We need only a very specific location changed with an if - else

Addressed in 01852f9: removed the feature-specific duplicated class-level flow and narrowed the change to the assignability decision point via a focused if/else in CreatePeer.

Co-authored-by: simonrozsival <374616+simonrozsival@users.noreply.github.com>

Copilot · 2026-06-08T14:11:10Z

@copilot address this code review

Done in 01852f9 (plus follow-up fixups): I addressed the @copilot review feedback in JavaMarshalValueManager and TrimmableTypeMap, and revalidated the updated changes.

simonrozsival commented Jun 8, 2026

View reviewed changes

Copilot started work on behalf of simonrozsival June 8, 2026 13:21 View session

Copilot AI and others added 3 commits June 8, 2026 13:57

Refactor assignability switch handling in peer creation

e4face5

Co-authored-by: simonrozsival <374616+simonrozsival@users.noreply.github.com>

Polish assignability review feedback updates

b6c4ac5

Co-authored-by: simonrozsival <374616+simonrozsival@users.noreply.github.com>

Address validation findings in assignability refactor

01852f9

Co-authored-by: simonrozsival <374616+simonrozsival@users.noreply.github.com>

Copilot finished work on behalf of simonrozsival June 8, 2026 14:12

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[Mono.Android] broaden assignability check escape hatch#11606

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		@@ -585,8 +717,12 @@ static bool IsIncompatibleCast (
		}

		if (!JniEnvironment.Types.IsAssignableFrom (instanceClass, targetClass)) {

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