[Java.Interop] Log JavaObject lifetimes

Previously, JniRuntime.JniObjectReferenceManager was used to track
JNI *reference* lifetimes, but it wasn't used to track *JavaObject*
lifetimes, e.g. when a JavaObject instance was created, disposed, or
finalized.

Xamarin.Android *does* log these events.

Update JniRuntime.JniValueMarshaler to log these JavaObject lifetime
events, in the spirit of Xamarin.Android but with more information.

Update JniRuntime.JniObjectReferenceManager to add properties for
whether logging is performed:

	partial class JniObjectReferenceManager {
		public virtual bool LogLocalReferenceMessages {get;}
		public virtual bool LogGlobalReferenceMessages {get;}
	}

This is used by JniRuntime.JniValueMarshaler to avoid possibly
expensive Reflection calls when the information won't be logged.

Author: jonpryor

src/Java.Interop/Java.Interop/JniRuntime.JniObjectReferenceManager.cs

@@ -35,6 +35,10 @@ public virtual int WeakGlobalReferenceCount {
 				 get {return wgrefc;}
 			}
 
+			public virtual bool LogLocalReferenceMessages {
+				get {return false;}
+			}
+
 			public virtual void WriteLocalReferenceLine (string format, params object[] args)
 			{
 			}
@@ -108,6 +112,10 @@ public virtual IntPtr ReleaseLocalReference (ref JniObjectReference reference, r
 				return h;
 			}
 
+			public virtual bool LogGlobalReferenceMessages {
+				get {return false;}
+			}
+
 			public virtual void WriteGlobalReferenceLine (string format, params object[] args)
 			{
 			}

src/Java.Interop/Java.Interop/JniRuntime.JniValueMarshaler.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
+using System.Runtime.CompilerServices;
 
 namespace Java.Interop
 {
@@ -115,6 +116,16 @@ internal TCleanup SetObjectPeerReference<T, TCleanup> (T value, ref JniObjectRef
 
 				value.IdentityHashCode = JniSystem.IdentityHashCode (newRef);
 
+				var o = Runtime.ObjectReferenceManager;
+				if (o.LogGlobalReferenceMessages) {
+					o.WriteGlobalReferenceLine ("Created PeerReference={0} IdentityHashCode=0x{1} Instance=0x{2} Instance.Type={3}, Java.Type={4}",
+							newRef.ToString (),
+							value.IdentityHashCode.ToString ("x"),
+							RuntimeHelpers.GetHashCode (value).ToString ("x"),
+							value.GetType ().FullName,
+							JniEnvironment.Types.GetJniTypeNameFromInstance (newRef));
+				}
+
 				if ((options & DoNotRegisterTarget) != DoNotRegisterTarget) {
 					RegisterObject (value);
 				}
@@ -130,6 +141,17 @@ internal void DisposeObject<T> (T value)
 
 				if (value.Registered)
 					UnRegisterObject (value);
+
+				var o = Runtime.ObjectReferenceManager;
+				if (o.LogGlobalReferenceMessages) {
+					o.WriteGlobalReferenceLine ("Disposing PeerReference={0} IdentityHashCode=0x{1} Instance=0x{2} Instance.Type={3} Java.Type={4}",
+							h.ToString (),
+							value.IdentityHashCode.ToString ("x"),
+							RuntimeHelpers.GetHashCode (value).ToString ("x"),
+							value.GetType ().ToString (),
+							JniEnvironment.Types.GetJniTypeNameFromInstance (h));
+				}
+
 				value.Dispose (disposing: true);
 				#if FEATURE_JNIOBJECTREFERENCE_SAFEHANDLES
 				var lref = value.PeerReference.SafeHandle as JniLocalReference;
@@ -148,11 +170,19 @@ internal void TryCollectObject<T> (T value)
 				where T : IJavaPeerable, IJavaPeerableEx
 			{
 				var h = value.PeerReference;
+				var o = Runtime.ObjectReferenceManager;
 				// MUST NOT use SafeHandle.ReferenceType: local refs are tied to a JniEnvironment
 				// and the JniEnvironment's corresponding thread; it's a thread-local value.
 				// Accessing SafeHandle.ReferenceType won't kill anything (so far...), but
 				// instead it always returns JniReferenceType.Invalid.
 				if (!h.IsValid || h.Type == JniObjectReferenceType.Local) {
+					if (o.LogGlobalReferenceMessages) {
+						o.WriteGlobalReferenceLine ("Finalizing PeerReference={0} IdentityHashCode=0x{1} Instance=0x{2} Instance.Type={3}",
+								h.ToString (),
+								value.IdentityHashCode.ToString ("x"),
+								RuntimeHelpers.GetHashCode (value).ToString ("x"),
+								value.GetType ().ToString ());
+					}
 					value.Dispose (disposing: false);
 					value.SetPeerReference (new JniObjectReference ());
 					return;
@@ -164,6 +194,13 @@ internal void TryCollectObject<T> (T value)
 						value.SetPeerReference (new JniObjectReference ());
 						if (value.Registered)
 							UnRegisterObject (value);
+						if (o.LogGlobalReferenceMessages) {
+							o.WriteGlobalReferenceLine ("Finalizing PeerReference={0} IdentityHashCode=0x{1} Instance=0x{2} Instance.Type={3}",
+									h.ToString (),
+									value.IdentityHashCode.ToString ("x"),
+									RuntimeHelpers.GetHashCode (value).ToString ("x"),
+									value.GetType ().ToString ());
+						}
 						value.Dispose (disposing: false);
 					} else {
 						value.SetPeerReference (h);

src/Java.Interop/Tests/Java.Interop/LoggingJniObjectReferenceManagerDecorator.cs

@@ -96,6 +96,10 @@ static TextWriter GetWriter (string path, string category)
 #endif
 		}
 
+		public override bool LogLocalReferenceMessages {
+			get {return true;}
+		}
+
 		public override void WriteLocalReferenceLine (string format, params object[] args)
 		{
 			if (lrefLog == null)
@@ -171,6 +175,10 @@ public override IntPtr ReleaseLocalReference (ref JniObjectReference value, ref
 			return manager.ReleaseLocalReference (ref value, ref localReferenceCount);
 		}
 
+		public override bool LogGlobalReferenceMessages {
+			get {return true;}
+		}
+
 		public override void WriteGlobalReferenceLine (string format, params object[] args)
 		{
 			if (grefLog == null)