[Java.Interop] Add JniRuntime.JniValueManager.TryCreatePeer()

src/Java.Interop/Documentation/Java.Interop/JniRuntime.JniTypeManager.xml

@@ -0,0 +1,28 @@
+<?xml version="1.0"?>
+<docs>
+  <member name="T:JniTypeManager">
+    <summary>
+      Manages bound Java types.
+    </summary>
+    <remarks>
+    </remarks>
+  </member>
+  <member name="M:GetInvokerType">
+    <summary>Gets the <i>Invoker</i> type for <paramref name="type" /></summary>
+    <remarks>
+      <para>
+        An <i>Invoker type</i> is a concrete type which can be constructed,
+        which is used to invoke instances of abstract type that cannot be constructed.
+        For example, the interface type <c>Java.Lang.IRunnable</c> cannot be constructed,
+        but if a <c>java.lang.Runnable</c> instance enters managed code,
+        a Invoker must be constructed around the instance so that it may be used.
+      </para>
+    </remarks>
+    <returns>
+      If <paramref name="type" /> is an interface or abstract class, returns the
+      type which should be constructed around instances of <paramref name="type" />.
+      If no such type exists, or if <paramref name="type" /> is a concrete type,
+      then <see langword="null" /> is returned.
+    </returns>
+  </member>
+</docs>

src/Java.Interop/Java.Interop/JniRuntime.JniTypeManager.cs

@@ -79,8 +79,10 @@ public override string ToString ()
 		}
 #endif  // NET
 
+		/// <include file="../Documentation/Java.Interop/JniRuntime.JniTypeManager.xml" path="/docs/member[@name='T:JniTypeManager']/*" />
 		public partial class JniTypeManager : IDisposable, ISetRuntime {
 
+			internal const DynamicallyAccessedMemberTypes Constructors = DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors;
 			internal const DynamicallyAccessedMemberTypes Methods = DynamicallyAccessedMemberTypes.PublicMethods | DynamicallyAccessedMemberTypes.NonPublicMethods;
 			internal const DynamicallyAccessedMemberTypes MethodsAndPrivateNested = Methods | DynamicallyAccessedMemberTypes.NonPublicNestedTypes;
 			internal const DynamicallyAccessedMemberTypes MethodsConstructors = MethodsAndPrivateNested | DynamicallyAccessedMemberTypes.PublicConstructors | DynamicallyAccessedMemberTypes.NonPublicConstructors;
@@ -385,6 +387,49 @@ IEnumerable<Type> CreateGetTypesForSimpleReferenceEnumerator (string jniSimpleRe
 				yield break;
 			}
 
+			/// <include file="../Documentation/Java.Interop/JniRuntime.JniTypeManager.xml" path="/docs/member[@name='M:GetInvokerType']/*" />
+			[return: DynamicallyAccessedMembers (Constructors)]
+			public Type? GetInvokerType (
+					[DynamicallyAccessedMembers (Constructors)]
+					Type type)
+			{
+				if (type.IsAbstract || type.IsInterface) {
+					return GetInvokerTypeCore (type);
+				}
+				return null;
+			}
+
+			[return: DynamicallyAccessedMembers (Constructors)]
+			protected virtual Type? GetInvokerTypeCore (
+					[DynamicallyAccessedMembers (Constructors)]
+					Type type)
+			{
+				// https://github.com/xamarin/xamarin-android/blob/5472eec991cc075e4b0c09cd98a2331fb93aa0f3/src/Microsoft.Android.Sdk.ILLink/MarkJavaObjects.cs#L176-L186
+				const string makeGenericTypeMessage = "Generic 'Invoker' types are preserved by the MarkJavaObjects trimmer step.";
+
+				[UnconditionalSuppressMessage ("Trimming", "IL2055", Justification = makeGenericTypeMessage)]
+				[return: DynamicallyAccessedMembers (Constructors)]
+				static Type MakeGenericType (
+						[DynamicallyAccessedMembers (Constructors)]
+						Type type,
+						Type [] arguments) =>
+					// FIXME: https://github.com/dotnet/java-interop/issues/1192
+					#pragma warning disable IL3050
+					type.MakeGenericType (arguments);
+					#pragma warning restore IL3050
+
+				var signature   = type.GetCustomAttribute<JniTypeSignatureAttribute> ();
+				if (signature == null || signature.InvokerType == null) {
+					return null;
+				}
+
+				Type[] arguments = type.GetGenericArguments ();
+				if (arguments.Length == 0)
+					return signature.InvokerType;
+
+				return MakeGenericType (signature.InvokerType, arguments);
+			}
+
 #if NET
 
 			public IReadOnlyList<string>? GetStaticMethodFallbackTypes (string jniSimpleReference)

src/Java.Interop/Java.Interop/JniRuntime.JniValueManager.cs

@@ -336,31 +336,21 @@ static Type GetPeerType ([DynamicallyAccessedMembers (Constructors)] Type type)
 
 				JniObjectReference.Dispose (ref targetClass);
 
-				var ctor = GetPeerConstructor (ref refClass, targetType);
-				if (ctor == null) {
+				var peer = CreatePeerInstance (ref refClass, targetType, ref reference, transfer);
+				if (peer == null) {
 					throw new NotSupportedException (string.Format ("Could not find an appropriate constructable wrapper type for Java type '{0}', targetType='{1}'.",
 							JniEnvironment.Types.GetJniTypeNameFromInstance (reference), targetType));
 				}
-
-				var acts = new object[] {
-					reference,
-					transfer,
-				};
-				try {
-					var peer    = (IJavaPeerable) ctor.Invoke (acts);
-					peer.SetJniManagedPeerState (peer.JniManagedPeerState | JniManagedPeerStates.Replaceable);
-					return peer;
-				} finally {
-					reference   = (JniObjectReference) acts [0];
-				}
+				peer.SetJniManagedPeerState (peer.JniManagedPeerState | JniManagedPeerStates.Replaceable);
+				return peer;
 			}
 
-			static  readonly    Type    ByRefJniObjectReference = typeof (JniObjectReference).MakeByRefType ();
-
-			ConstructorInfo? GetPeerConstructor (
+			IJavaPeerable? CreatePeerInstance (
 					ref JniObjectReference klass,
 					[DynamicallyAccessedMembers (Constructors)]
-					Type fallbackType)
+					Type fallbackType,
+					ref JniObjectReference reference,
+					JniObjectReferenceOptions transfer)
 			{
 				var jniTypeName = JniEnvironment.Types.GetJniTypeNameFromClass (klass);
 
@@ -373,11 +363,11 @@ static Type GetPeerType ([DynamicallyAccessedMembers (Constructors)] Type type)
 					type    = Runtime.TypeManager.GetType (sig);
 
 					if (type != null) {
-						var ctor = GetActivationConstructor (type);
+						var peer = TryCreatePeerInstance (ref reference, transfer, type);
 
-						if (ctor != null) {
+						if (peer != null) {
 							JniObjectReference.Dispose (ref klass);
-							return ctor;
+							return peer;
 						}
 					}
 
@@ -391,51 +381,41 @@ static Type GetPeerType ([DynamicallyAccessedMembers (Constructors)] Type type)
 				}
 				JniObjectReference.Dispose (ref klass, JniObjectReferenceOptions.CopyAndDispose);
 
-				return GetActivationConstructor (fallbackType);
+				return TryCreatePeerInstance (ref reference, transfer, fallbackType);
 			}
 
-			static ConstructorInfo? GetActivationConstructor (
+			IJavaPeerable? TryCreatePeerInstance (
+					ref JniObjectReference reference,
+					JniObjectReferenceOptions options,
 					[DynamicallyAccessedMembers (Constructors)]
 					Type type)
 			{
-				if (type.IsAbstract || type.IsInterface) {
-					type = GetInvokerType (type) ?? type;
-				}
-				foreach (var c in type.GetConstructors (BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance)) {
-					var p = c.GetParameters ();
-					if (p.Length == 2 && p [0].ParameterType == ByRefJniObjectReference && p [1].ParameterType == typeof (JniObjectReferenceOptions))
-						return c;
-				}
-				return null;
+				type    = Runtime.TypeManager.GetInvokerType (type) ?? type;
+				return TryCreatePeer (ref reference, options, type);
 			}
 
-			[return: DynamicallyAccessedMembers (Constructors)]
-			static Type? GetInvokerType (Type type)
-			{
-				// https://github.com/xamarin/xamarin-android/blob/5472eec991cc075e4b0c09cd98a2331fb93aa0f3/src/Microsoft.Android.Sdk.ILLink/MarkJavaObjects.cs#L176-L186
-				const string makeGenericTypeMessage = "Generic 'Invoker' types are preserved by the MarkJavaObjects trimmer step.";
-
-				[UnconditionalSuppressMessage ("Trimming", "IL2055", Justification = makeGenericTypeMessage)]
-				[return: DynamicallyAccessedMembers (Constructors)]
-				static Type MakeGenericType (
-						[DynamicallyAccessedMembers (Constructors)]
-						Type type,
-						Type [] arguments) =>
-					// FIXME: https://github.com/dotnet/java-interop/issues/1192
-					#pragma warning disable IL3050
-					type.MakeGenericType (arguments);
-					#pragma warning restore IL3050
-
-				var signature   = type.GetCustomAttribute<JniTypeSignatureAttribute> ();
-				if (signature == null || signature.InvokerType == null) {
-					return null;
-				}
+			const               BindingFlags    ActivationConstructorBindingFlags   = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance;
+			static  readonly    Type            ByRefJniObjectReference = typeof (JniObjectReference).MakeByRefType ();
+			static  readonly    Type[]          JIConstructorSignature  = new Type [] { ByRefJniObjectReference, typeof (JniObjectReferenceOptions) };
 
-				Type[] arguments = type.GetGenericArguments ();
-				if (arguments.Length == 0)
-					return signature.InvokerType;
 
-				return MakeGenericType (signature.InvokerType, arguments);
+			protected virtual IJavaPeerable? TryCreatePeer (
+					ref JniObjectReference reference,
+					JniObjectReferenceOptions options,
+					[DynamicallyAccessedMembers (Constructors)]
+					Type type)
+			{
+				var c = type.GetConstructor (ActivationConstructorBindingFlags, null, JIConstructorSignature, null);
+				if (c != null) {
+					var args = new object[] {
+						reference,
+						options,
+					};
+					var p       = (IJavaPeerable) c.Invoke (args);
+					reference   = (JniObjectReference) args [0];
+					return p;
+				}
+				return null;
 			}
 
 			public object? CreateValue (

src/Java.Interop/PublicAPI.Unshipped.txt

@@ -3,8 +3,11 @@ static Java.Interop.JniEnvironment.BeginMarshalMethod(nint jnienv, out Java.Inte
 static Java.Interop.JniEnvironment.EndMarshalMethod(ref Java.Interop.JniTransition transition) -> void
 virtual Java.Interop.JniRuntime.OnEnterMarshalMethod() -> void
 virtual Java.Interop.JniRuntime.OnUserUnhandledException(ref Java.Interop.JniTransition transition, System.Exception! e) -> void
+virtual Java.Interop.JniRuntime.JniTypeManager.GetInvokerTypeCore(System.Type! type) -> System.Type?
+virtual Java.Interop.JniRuntime.JniValueManager.TryCreatePeer(ref Java.Interop.JniObjectReference reference, Java.Interop.JniObjectReferenceOptions options, System.Type! type) -> Java.Interop.IJavaPeerable?
 Java.Interop.JavaException.JavaException(ref Java.Interop.JniObjectReference reference, Java.Interop.JniObjectReferenceOptions transfer, Java.Interop.JniObjectReference throwableOverride) -> void
 Java.Interop.JavaException.SetJavaStackTrace(Java.Interop.JniObjectReference peerReferenceOverride = default(Java.Interop.JniObjectReference)) -> void
+Java.Interop.JniRuntime.JniTypeManager.GetInvokerType(System.Type! type) -> System.Type?
 Java.Interop.JniRuntime.JniValueManager.GetPeer(Java.Interop.JniObjectReference reference, System.Type? targetType = null) -> Java.Interop.IJavaPeerable?
 Java.Interop.JniTypeSignatureAttribute.InvokerType.get -> System.Type?
 Java.Interop.JniTypeSignatureAttribute.InvokerType.set -> void

tests/Java.Interop-Tests/Java.Interop/JniRuntime.JniTypeManagerTests.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Reflection;
+using System.Collections.Generic;
+
+using Java.Interop;
+
+using NUnit.Framework;
+
+namespace Java.InteropTests {
+
+	[TestFixture]
+	public class JniRuntimeJniTypeManagerTests : JavaVMFixture {
+
+		[Test]
+		public void GetInvokerType ()
+		{
+			using (var vm  = new MyTypeManager ()) {
+				// Concrete type; no invoker
+				Assert.IsNull (vm.GetInvokerType (typeof (JavaObject)));
+
+				// Not a bound abstract Java type; no invoker
+				Assert.IsNull (vm.GetInvokerType (typeof (System.ICloneable)));
+
+				// Bound abstract Java type; has an invoker
+				Assert.AreSame (typeof (IJavaInterfaceInvoker), vm.GetInvokerType (typeof (IJavaInterface)));
+			}
+		}
+
+		class MyTypeManager : JniRuntime.JniTypeManager {
+		}
+    }
+}
+