[TrimmableTypeMap] Add UCO wrappers, RegisterNatives, and IAndroidCallableWrapper

Add ACW (Android Callable Wrapper) support to TypeMap proxy types:

- UcoMethodData/UcoConstructorData/NativeRegistrationData model types
- ModelBuilder: generates UCO method wrappers, constructor wrappers,
  and native method registrations for ACW types
- TypeMapAssemblyEmitter: emits [UnmanagedCallersOnly] UCO methods,
  UCO constructor wrappers, RegisterNatives, IAndroidCallableWrapper
- IsAcw detection for types that need JNI native method registration
- Cross-assembly IgnoresAccessChecksTo for UCO callback types
- Tests for all UCO/RegisterNatives generation scenarios

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: simonrozsival

src/Microsoft.Android.Sdk.TrimmableTypeMap/Generator/Model/TypeMapAssemblyData.cs

@@ -86,8 +86,18 @@ sealed class JavaPeerProxyData
 	/// <summary>True if this is an open generic type definition. CreateInstance throws NotSupportedException.</summary>
 	public bool IsGenericDefinition { get; init; }
 
-}
+	/// <summary>Whether this proxy needs ACW support (RegisterNatives + UCO wrappers + IAndroidCallableWrapper).</summary>
+	public bool IsAcw { get; init; }
+
+	/// <summary>UCO method wrappers for marshal methods (non-constructor).</summary>
+	public List<UcoMethodData> UcoMethods { get; } = new ();
 
+	/// <summary>UCO constructor wrappers.</summary>
+	public List<UcoConstructorData> UcoConstructors { get; } = new ();
+
+	/// <summary>RegisterNatives registrations (method name, JNI signature, wrapper name).</summary>
+	public List<NativeRegistrationData> NativeRegistrations { get; } = new ();
+}
 
 /// <summary>
 /// A cross-assembly type reference (assembly name + full managed type name).
@@ -101,6 +111,58 @@ sealed record TypeRefData
 	public required string AssemblyName { get; init; }
 }
 
+/// <summary>
+/// An [UnmanagedCallersOnly] static wrapper for a marshal method.
+/// Body: load all args → call n_* callback → ret.
+/// </summary>
+sealed record UcoMethodData
+{
+	/// <summary>Name of the generated wrapper method, e.g., "n_onCreate_uco_0".</summary>
+	public required string WrapperName { get; init; }
+
+	/// <summary>Name of the n_* callback to call, e.g., "n_OnCreate".</summary>
+	public required string CallbackMethodName { get; init; }
+
+	/// <summary>Type containing the callback method.</summary>
+	public required TypeRefData CallbackType { get; init; }
+
+	/// <summary>JNI method signature, e.g., "(Landroid/os/Bundle;)V". Used to determine CLR parameter types.</summary>
+	public required string JniSignature { get; init; }
+}
+
+/// <summary>
+/// An [UnmanagedCallersOnly] static wrapper for a constructor callback.
+/// Signature must match the full JNI native method signature (jnienv + self + ctor params)
+/// so the ABI is correct when JNI dispatches the call.
+/// Body: TrimmableNativeRegistration.ActivateInstance(self, typeof(TargetType)).
+/// </summary>
+sealed record UcoConstructorData
+{
+	/// <summary>Name of the generated wrapper, e.g., "nctor_0_uco".</summary>
+	public required string WrapperName { get; init; }
+
+	/// <summary>Target type to pass to ActivateInstance.</summary>
+	public required TypeRefData TargetType { get; init; }
+
+	/// <summary>JNI constructor signature, e.g., "(Landroid/content/Context;)V". Used for RegisterNatives registration.</summary>
+	public required string JniSignature { get; init; }
+}
+
+/// <summary>
+/// One JNI native method registration in RegisterNatives.
+/// </summary>
+sealed record NativeRegistrationData
+{
+	/// <summary>JNI method name to register, e.g., "n_onCreate" or "nctor_0".</summary>
+	public required string JniMethodName { get; init; }
+
+	/// <summary>JNI method signature, e.g., "(Landroid/os/Bundle;)V".</summary>
+	public required string JniSignature { get; init; }
+
+	/// <summary>Name of the UCO wrapper method whose function pointer to register.</summary>
+	public required string WrapperMethodName { get; init; }
+}
+
 /// <summary>
 /// Describes how the proxy's CreateInstance should construct the managed peer.
 /// </summary>

src/Microsoft.Android.Sdk.TrimmableTypeMap/Generator/ModelBuilder.cs

@@ -83,6 +83,9 @@ public static TypeMapAssemblyData Build (IReadOnlyList<JavaPeerInfo> peers, stri
 		var referencedAssemblies = new SortedSet<string> (StringComparer.Ordinal);
 		foreach (var proxy in model.ProxyTypes) {
 			AddIfCrossAssembly (referencedAssemblies, proxy.TargetType?.AssemblyName, assemblyName);
+			foreach (var uco in proxy.UcoMethods) {
+				AddIfCrossAssembly (referencedAssemblies, uco.CallbackType.AssemblyName, assemblyName);
+			}
 			if (proxy.ActivationCtor != null && !proxy.ActivationCtor.IsOnLeafType) {
 				AddIfCrossAssembly (referencedAssemblies, proxy.ActivationCtor.DeclaringType.AssemblyName, assemblyName);
 			}
@@ -103,10 +106,11 @@ static void EmitPeers (TypeMapAssemblyData model, string jniName,
 			string entryJniName = i == 0 ? jniName : $"{jniName}[{i}]";
 
 			bool hasProxy = peer.ActivationCtor != null || peer.InvokerTypeName != null;
+			bool isAcw = !peer.DoNotGenerateAcw && !peer.IsInterface && peer.MarshalMethods.Count > 0;
 
 			JavaPeerProxyData? proxy = null;
 			if (hasProxy) {
-				proxy = BuildProxyType (peer);
+				proxy = BuildProxyType (peer, isAcw);
 				model.ProxyTypes.Add (proxy);
 			}
 
@@ -178,7 +182,7 @@ static void AddIfCrossAssembly (SortedSet<string> set, string? asmName, string o
 		}
 	}
 
-	static JavaPeerProxyData BuildProxyType (JavaPeerInfo peer)
+	static JavaPeerProxyData BuildProxyType (JavaPeerInfo peer, bool isAcw)
 	{
 		// Use managed type name for proxy naming to guarantee uniqueness across aliases
 		// (two types with the same JNI name will have different managed names).
@@ -190,6 +194,7 @@ static JavaPeerProxyData BuildProxyType (JavaPeerInfo peer)
 				ManagedTypeName = peer.ManagedTypeName,
 				AssemblyName = peer.AssemblyName,
 			},
+			IsAcw = isAcw,
 			IsGenericDefinition = peer.IsGenericDefinition,
 		};
 
@@ -212,9 +217,80 @@ static JavaPeerProxyData BuildProxyType (JavaPeerInfo peer)
 			};
 		}
 
+		if (isAcw) {
+			BuildUcoMethods (peer, proxy);
+			BuildUcoConstructors (peer, proxy);
+			BuildNativeRegistrations (proxy);
+		}
+
 		return proxy;
 	}
 
+	static void BuildUcoMethods (JavaPeerInfo peer, JavaPeerProxyData proxy)
+	{
+		int ucoIndex = 0;
+		for (int i = 0; i < peer.MarshalMethods.Count; i++) {
+			var mm = peer.MarshalMethods [i];
+			if (mm.IsConstructor) {
+				continue;
+			}
+
+			proxy.UcoMethods.Add (new UcoMethodData {
+				WrapperName = $"n_{mm.JniName}_uco_{ucoIndex}",
+				CallbackMethodName = mm.NativeCallbackName,
+				CallbackType = new TypeRefData {
+					ManagedTypeName = !string.IsNullOrEmpty (mm.DeclaringTypeName) ? mm.DeclaringTypeName : peer.ManagedTypeName,
+					AssemblyName = !string.IsNullOrEmpty (mm.DeclaringAssemblyName) ? mm.DeclaringAssemblyName : peer.AssemblyName,
+				},
+				JniSignature = mm.JniSignature,
+			});
+			ucoIndex++;
+		}
+	}
+
+	static void BuildUcoConstructors (JavaPeerInfo peer, JavaPeerProxyData proxy)
+	{
+		if (peer.ActivationCtor == null || peer.JavaConstructors.Count == 0) {
+			return;
+		}
+
+		foreach (var ctor in peer.JavaConstructors) {
+			proxy.UcoConstructors.Add (new UcoConstructorData {
+				WrapperName = $"nctor_{ctor.ConstructorIndex}_uco",
+				JniSignature = ctor.JniSignature,
+				TargetType = new TypeRefData {
+					ManagedTypeName = peer.ManagedTypeName,
+					AssemblyName = peer.AssemblyName,
+				},
+			});
+		}
+	}
+
+	static void BuildNativeRegistrations (JavaPeerProxyData proxy)
+	{
+		foreach (var uco in proxy.UcoMethods) {
+			proxy.NativeRegistrations.Add (new NativeRegistrationData {
+				JniMethodName = uco.CallbackMethodName,
+				JniSignature = uco.JniSignature,
+				WrapperMethodName = uco.WrapperName,
+			});
+		}
+
+		foreach (var uco in proxy.UcoConstructors) {
+			string jniName = uco.WrapperName;
+			int ucoSuffix = jniName.LastIndexOf ("_uco", StringComparison.Ordinal);
+			if (ucoSuffix >= 0) {
+				jniName = jniName.Substring (0, ucoSuffix);
+			}
+
+			proxy.NativeRegistrations.Add (new NativeRegistrationData {
+				JniMethodName = jniName,
+				JniSignature = uco.JniSignature,
+				WrapperMethodName = uco.WrapperName,
+			});
+		}
+	}
+
 	static TypeMapAttributeData BuildEntry (JavaPeerInfo peer, JavaPeerProxyData? proxy,
 		string outputAssemblyName, string jniName)
 	{