Fix legacy generic dictionary conversion

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

@@ -609,6 +609,38 @@ class AndroidValueManager : JniRuntime.ReflectionJniValueManager {
 
 		Dictionary<IntPtr, IdentityHashTargets>         instances       = new Dictionary<IntPtr, IdentityHashTargets> ();
 
+		protected override object? GetValueCore (
+				ref JniObjectReference reference,
+				JniObjectReferenceOptions options,
+				[DynamicallyAccessedMembers (DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors)]
+				Type? targetType = null)
+		{
+			if (JavaConvert.IsGenericDictionary (targetType))
+				return JavaConvert.FromObjectReference (ref reference, options, targetType);
+
+			return base.GetValueCore (ref reference, options, targetType);
+		}
+
+		[return: MaybeNull]
+		protected override T GetValueCore<[DynamicallyAccessedMembers (DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors)] T> (
+				ref JniObjectReference reference,
+				JniObjectReferenceOptions options,
+				[DynamicallyAccessedMembers (DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors)]
+				Type? targetType = null)
+		{
+			if (targetType != null && !typeof (T).IsAssignableFrom (targetType))
+				return base.GetValueCore<T> (ref reference, options, targetType);
+
+			var requestedType = targetType ?? typeof (T);
+			if (JavaConvert.IsGenericDictionary (requestedType)) {
+#pragma warning disable CS8600 // Converting null literal or possible null value to non-nullable type.
+				return (T) JavaConvert.FromObjectReference (ref reference, options, requestedType);
+#pragma warning restore CS8600 // Converting null literal or possible null value to non-nullable type.
+			}
+
+			return base.GetValueCore<T> (ref reference, options, targetType);
+		}
+
 		public override void WaitForGCBridgeProcessing ()
 		{
 			if (!AndroidRuntimeInternal.BridgeProcessing)

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

@@ -124,7 +124,8 @@ static class JavaConvert {
 			[RequiresDynamicCode ("This API uses reflection to create generic types at runtime, which is not supported in AOT scenarios.")]
 			static Func<IntPtr, JniHandleOwnership, object?>? TryMakeGenericCollectionTypeFactory (Type target)
 			{
-				if (target.GetGenericTypeDefinition() == typeof (IDictionary<,>)) {
+				var genericTypeDefinition = target.GetGenericTypeDefinition ();
+				if (genericTypeDefinition == typeof (IDictionary<,>) || genericTypeDefinition == typeof (JavaDictionary<,>)) {
 					Type t = typeof (JavaDictionary<,>).MakeGenericType (target.GetGenericArguments ());
 					return GetJniHandleConverterForType (t);
 				}
@@ -141,6 +142,16 @@ static class JavaConvert {
 			}
 		}
 
+		internal static bool IsGenericDictionary (Type? type)
+		{
+			if (type == null || !type.IsGenericType || type.IsGenericTypeDefinition)
+				return false;
+
+			var genericTypeDefinition = type.GetGenericTypeDefinition ();
+			return genericTypeDefinition == typeof (IDictionary<,>) ||
+				genericTypeDefinition == typeof (JavaDictionary<,>);
+		}
+
 		/// <summary>
 		/// AOT-safe converter using <see cref="JavaPeerContainerFactory"/> from the generated proxy.
 		/// Avoids <c>MakeGenericType()</c> by using the pre-typed factory from the proxy attribute.

src/Mono.Android/Microsoft.Android.Runtime/JavaMarshalValueManager.cs

@@ -21,6 +21,38 @@ public JavaMarshalValueManager ()
 		JavaMarshalRegisteredPeers.InitializeIfNeeded ();
 	}
 
+	protected override object? GetValueCore (
+		ref JniObjectReference reference,
+		JniObjectReferenceOptions options,
+		[DynamicallyAccessedMembers (Constructors)]
+		Type? targetType = null)
+	{
+		if (JavaConvert.IsGenericDictionary (targetType))
+			return JavaConvert.FromObjectReference (ref reference, options, targetType);
+
+		return base.GetValueCore (ref reference, options, targetType);
+	}
+
+	[return: MaybeNull]
+	protected override T GetValueCore<[DynamicallyAccessedMembers (Constructors)] T> (
+		ref JniObjectReference reference,
+		JniObjectReferenceOptions options,
+		[DynamicallyAccessedMembers (Constructors)]
+		Type? targetType = null)
+	{
+		if (targetType != null && !typeof (T).IsAssignableFrom (targetType))
+			return base.GetValueCore<T> (ref reference, options, targetType);
+
+		var requestedType = targetType ?? typeof (T);
+		if (JavaConvert.IsGenericDictionary (requestedType)) {
+#pragma warning disable CS8600 // Converting null literal or possible null value to non-nullable type.
+			return (T) JavaConvert.FromObjectReference (ref reference, options, requestedType);
+#pragma warning restore CS8600 // Converting null literal or possible null value to non-nullable type.
+		}
+
+		return base.GetValueCore<T> (ref reference, options, targetType);
+	}
+
 	public override void WaitForGCBridgeProcessing ()
 	{
 		// Intentionally empty. The Mono runtime's own implementation acknowledges this

tests/Mono.Android-Tests/Mono.Android-Tests/Java.Interop/JavaConvertTest.cs

@@ -1,10 +1,12 @@
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 
 using Android.App;
 using Android.Content;
 using Android.Runtime;
+using Java.Interop;
 
 using NUnit.Framework;
 
@@ -113,6 +115,81 @@ public void NullStringMarshalsAsIntPtrZero ()
 			Assert.AreEqual (null, list [0]);
 		}
 
+		[Test]
+		public void ValueManagerGenericDictionaryConversions ()
+		{
+			AssertValueManagerDictionaryByType<int, string> (42, "forty-two", typeof (IDictionary<int, string>));
+			AssertValueManagerDictionaryByType<int?, double?> (7, 3.5, typeof (JavaDictionary<int?, double?>));
+
+			using (var value = new MyIntent ())
+				AssertValueManagerDictionary<string, MyIntent> ("intent", value);
+
+			using (var key = new MyIntent ())
+				AssertValueManagerJavaDictionary<MyIntent, long?> (key, 64);
+		}
+
+		[Test]
+		public void ValueManagerNonGenericDictionaryConversionPreservesCachedPeer ()
+		{
+			using (var source = new JavaDictionary ()) {
+				source.Add ("answer", 42);
+				var reference = new JniObjectReference (source.Handle);
+				var actual = JniEnvironment.Runtime.ValueManager.GetValue (
+					ref reference, JniObjectReferenceOptions.Copy, typeof (IDictionary));
+
+				Assert.AreSame (source, actual);
+				Assert.AreEqual (42, ((IDictionary) actual) ["answer"]);
+			}
+		}
+
+		[Test]
+		public void ValueManagerGenericDictionaryConversionPreservesAssignableCachedPeer ()
+		{
+			using (var source = new JavaDictionary<int, string> { { 42, "forty-two" } }) {
+				var actual = JniEnvironment.Runtime.ValueManager.GetValue<JavaDictionary<int, string>> (source.Handle);
+
+				Assert.AreSame (source, actual);
+			}
+		}
+
+		static void AssertValueManagerDictionaryByType<TKey, TValue> (TKey key, TValue value, Type targetType)
+		{
+			using (var source = new JavaDictionary ()) {
+				source.Add (key, value);
+				var reference = new JniObjectReference (source.Handle);
+				var actual = JniEnvironment.Runtime.ValueManager.GetValue (
+					ref reference, JniObjectReferenceOptions.Copy, targetType);
+
+				Assert.AreEqual (typeof (JavaDictionary<TKey, TValue>), actual.GetType ());
+				using (var dictionary = (JavaDictionary<TKey, TValue>) actual)
+					Assert.AreEqual (value, dictionary [key]);
+			}
+		}
+
+		static void AssertValueManagerDictionary<TKey, TValue> (TKey key, TValue value)
+		{
+			using (var source = new JavaDictionary ()) {
+				source.Add (key, value);
+				var actual = JniEnvironment.Runtime.ValueManager.GetValue<IDictionary<TKey, TValue>> (source.Handle);
+
+				Assert.AreEqual (typeof (JavaDictionary<TKey, TValue>), actual.GetType ());
+				using (var dictionary = (JavaDictionary<TKey, TValue>) actual)
+					Assert.AreEqual (value, dictionary [key]);
+			}
+		}
+
+		static void AssertValueManagerJavaDictionary<TKey, TValue> (TKey key, TValue value)
+		{
+			using (var source = new JavaDictionary ()) {
+				source.Add (key, value);
+				var actual = JniEnvironment.Runtime.ValueManager.GetValue<JavaDictionary<TKey, TValue>> (source.Handle);
+
+				Assert.AreEqual (typeof (JavaDictionary<TKey, TValue>), actual.GetType ());
+				using (actual)
+					Assert.AreEqual (value, actual [key]);
+			}
+		}
+
 		[Test]
 		public void MarshalInt23Array ()
 		{
@@ -140,4 +217,3 @@ static Java.Util.ArrayList CreateList (params int[][] items)
 		}
 	}
 }
-