[Hello-Java.Base] Add support for Java Callable Wrappers (#1315)

Context: 2a1e180

Update `samples/Hello-Java.Base` to use `Java.Interop.Sdk` (2a1e180),
 so that it (kinda, sorta) "automagically" gets support for generating
Java Callable Wrappers as part of its build.

Add a custom `Java.Lang.Object` subclass and use it.

Update `JreTypeManager` and `JreRuntimeOptions` so that type mappings
can be more easily provided without requiring a `JreTypeManager`
subclass, as Java.Interop.Sdk" is not fleshed out enough to provide
that information itself.  (This also simplifies `TestJVM`.)

Author: jonpryor

build-tools/Java.Interop.Sdk/Sdk/Sdk.targets

@@ -64,6 +64,7 @@
 
   <Target Name="_BuildJavaCompileForManagedBinding"
       DependsOnTargets="_CollectJavaCompileForManagedBindingInputs;_JavaCollectJavacRefs"
+      Condition=" '$(_JavaCompileForBindingInputs->Count())' != '0' "
       Inputs="@(_JavaCompileForBindingInputs)"
       Outputs="$(_JavaManagedBindingInput)">
     <PropertyGroup>
@@ -105,6 +106,7 @@
 
   <Target Name="_GenerateApiDescription"
       DependsOnTargets="_CollectClassParseInputs"
+      Condition=" '$(_ClassParseInputs->Count())' != '0' "
       Inputs="@(_ClassParseInputs)"
       Outputs="$(_JavaManagedBindingDir)api.xml">
     <MakeDir Directories="$(_JavaManagedBindingDir)" />
@@ -120,6 +122,7 @@
 
   <Target Name="_GenerateManagedBinding"
       DependsOnTargets="_GenerateApiDescription"
+      Condition=" Exists('$(_JavaManagedBindingDir)api.xml') "
       Inputs="$(_JavaManagedBindingDir)api.xml"
       Outputs="$(_JavaManagedBindingDir)$(AssemblyName).projitems">
     <MakeDir Directories="$(_JavaManagedBindingDir)" />

samples/Hello-Java.Base/Hello-Java.Base.csproj

@@ -7,6 +7,14 @@
     <Nullable>enable</Nullable>
     <StartupObject>Hello.App</StartupObject>
   </PropertyGroup>
+
+  <Import Project="..\..\build-tools\Java.Interop.Sdk\Sdk\Sdk.props" />
+  <!-- Currently needs to be included so that Sdk.targets can find things -->
+  <Import Project="..\..\TargetFrameworkDependentValues.props" />
+
+  <PropertyGroup>
+    <OutputPath>$(MSBuildThisFileDirectory)bin\$(Configuration)\</OutputPath>
+  </PropertyGroup>
 
   <ItemGroup>
     <ProjectReference Include="..\..\src\Java.Interop\Java.Interop.csproj" />
@@ -15,4 +23,6 @@
     <ProjectReference Include="..\..\tests\TestJVM\TestJVM.csproj" />
   </ItemGroup>
 
+  <Import Project="..\..\build-tools\Java.Interop.Sdk\Sdk\Sdk.targets" />
+
 </Project>

samples/Hello-Java.Base/Program.cs

@@ -1,5 +1,8 @@
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
+using System.Linq;
+using System.IO;
 using System.Threading;
 
 using Mono.Options;
@@ -26,7 +29,7 @@ public static void Main (string[] args)
 				  $"{{PATH}} to JVM to use.  Default is:\n  {jvmPath}",
 				  v => jvmPath = v },
 				{ "m",
-				  "Create multiple Java VMs.  This will likely creash.",
+				  "Create multiple Java VMs.  This will likely crash.",
 				  v => createMultipleVMs = v != null },
 				{ "t",
 				  $"Timing; invoke Object.hashCode() {N} times, print average.",
@@ -43,6 +46,12 @@ public static void Main (string[] args)
 			var builder = new JreRuntimeOptions () {
 				JniAddNativeMethodRegistrationAttributePresent  = true,
 				JvmLibraryPath                                  = jvmPath,
+				ClassPath   = {
+					Path.Combine (Path.GetDirectoryName (typeof (App).Assembly.Location)!, "Hello-Java.Base.jar"),
+				},
+				TypeMappings = {
+					[MyJLO.JniTypeName]     = typeof (MyJLO),
+				},
 			};
 			builder.AddOption ("-Xcheck:jni");
 
@@ -63,7 +72,7 @@ public static void Main (string[] args)
 
 		static void CreateJLO ()
 		{
-			var jlo = new Java.Lang.Object ();
+			var jlo = new MyJLO ();
 			Console.WriteLine ($"binding? {jlo.ToString ()}");
 		}
 
@@ -115,4 +124,9 @@ static unsafe void CreateAnotherJVM ()
 			}
 		}
 	}
+
+	[JniTypeSignature (JniTypeName)]
+	class MyJLO : Java.Lang.Object {
+		internal    const   string      JniTypeName = "net/dot/jni/sample/MyJLO";
+	}
 }

src/Java.Runtime.Environment/Java.Interop/JreRuntime.cs

@@ -35,6 +35,9 @@ public class JreRuntimeOptions : JniRuntime.CreationOptions {
 		public  TextWriter? JniGlobalReferenceLogWriter {get; set;}
 		public  TextWriter? JniLocalReferenceLogWriter  {get; set;}
 
+		internal    Dictionary<string, Type>?  	typeMappings;
+		public      IDictionary<string, Type>   TypeMappings    => typeMappings ??= new ();
+
 		internal    JvmLibraryHandler?  LibraryHandler  {get; set;}
 
 		public JreRuntimeOptions ()
@@ -85,7 +88,7 @@ static unsafe JreRuntimeOptions CreateJreVM (JreRuntimeOptions builder)
 			builder.LibraryHandler  = JvmLibraryHandler.Create ();
 
 #if NET
-			builder.TypeManager     ??= new JreTypeManager ();
+			builder.TypeManager     ??= new JreTypeManager (builder.typeMappings);
 #endif  // NET
 
 			bool onMono = Type.GetType ("Mono.Runtime", throwOnError: false) != null;

src/Java.Runtime.Environment/Java.Interop/JreTypeManager.cs

@@ -18,6 +18,44 @@ namespace Java.Interop {
 
 	public class JreTypeManager : JniRuntime.JniTypeManager {
 
+		IDictionary<string, Type>? typeMappings;
+
+		public JreTypeManager ()
+			: this (null)
+		{
+		}
+
+		public JreTypeManager (IDictionary<string, Type>? typeMappings)
+		{
+			this.typeMappings = typeMappings;
+		}
+
+		protected override IEnumerable<Type> GetTypesForSimpleReference (string jniSimpleReference)
+		{
+			foreach (var t in base.GetTypesForSimpleReference (jniSimpleReference))
+				yield return t;
+			if (typeMappings == null)
+				yield break;
+			if (typeMappings.TryGetValue (jniSimpleReference, out var target))
+				yield return target;
+		}
+
+		protected override IEnumerable<string> GetSimpleReferences (Type type)
+		{
+			return base.GetSimpleReferences (type)
+				.Concat (CreateSimpleReferencesEnumerator (type));
+		}
+
+		IEnumerable<string> CreateSimpleReferencesEnumerator (Type type)
+		{
+			if (typeMappings == null)
+				yield break;
+			foreach (var e in typeMappings) {
+				if (e.Value == type)
+					yield return e.Key;
+			}
+		}
+
 		const string NotUsedInAndroid = "This code path is not used in Android projects.";
 
 		public override void RegisterNativeMembers (

tests/TestJVM/TestJVM.cs

@@ -23,7 +23,6 @@ public TestJVMOptions (Assembly? callingAssembly = null)
 
 		public  ICollection<string>         JarFilePaths    {get;}      = new List<string> ();
 		public  Assembly                    CallingAssembly {get; set;}
-		public  Dictionary<string, Type>?   TypeMappings    {get; set;}
 
 		internal    JdkInfo?                JdkInfo         {get; set;}
 	}
@@ -141,9 +140,13 @@ public TestJVM (string[]? jars = null, Dictionary<string, Type>? typeMappings =
 		static TestJVMOptions CreateOptions (string[]? jarFiles, Assembly callingAssembly, Dictionary<string, Type>? typeMappings)
 		{
 			var o = new TestJVMOptions {
-				TypeMappings    = typeMappings,
 				CallingAssembly = callingAssembly,
 			};
+			if (typeMappings != null) {
+				foreach (var e in typeMappings) {
+					o.TypeMappings.Add (e.Key, e.Value);
+				}
+			}
 			if (jarFiles != null) {
 				foreach (var jar in jarFiles) {
 					o.JarFilePaths.Add (jar);
@@ -153,48 +156,12 @@ static TestJVMOptions CreateOptions (string[]? jarFiles, Assembly callingAssembl
 		}
 	}
 
-	public class TestJvmTypeManager :
-#if NET
-			JreTypeManager
-#else   // !NET
-			JniRuntime.JniTypeManager
-#endif  // !NET
+	public class TestJvmTypeManager : JreTypeManager
 	{
 
-		Dictionary<string, Type>? typeMappings;
-
-		public TestJvmTypeManager (Dictionary<string, Type>? typeMappings)
+		public TestJvmTypeManager (IDictionary<string, Type>? typeMappings)
+			: base (typeMappings)
 		{
-			this.typeMappings = typeMappings;
-		}
-
-		protected override IEnumerable<Type> GetTypesForSimpleReference (string jniSimpleReference)
-		{
-			foreach (var t in base.GetTypesForSimpleReference (jniSimpleReference))
-				yield return t;
-			if (typeMappings == null)
-				yield break;
-			Type target;
-#pragma warning disable CS8600	// huh?
-			if (typeMappings.TryGetValue (jniSimpleReference, out target))
-				yield return target;
-#pragma warning restore CS8600
-		}
-
-		protected override IEnumerable<string> GetSimpleReferences (Type type)
-		{
-			return base.GetSimpleReferences (type)
-				.Concat (CreateSimpleReferencesEnumerator (type));
-		}
-
-		IEnumerable<string> CreateSimpleReferencesEnumerator (Type type)
-		{
-			if (typeMappings == null)
-				yield break;
-			foreach (var e in typeMappings) {
-				if (e.Value == type)
-					yield return e.Key;
-			}
 		}
 	}
 }