[Mono.Android] Root Mono.Android.Export from the [Export]/[ExportField] loader, not the attributes

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

@@ -397,25 +397,6 @@ protected override IEnumerable<string> GetSimpleReferences (Type type)
 
 		delegate Delegate GetCallbackHandler ();
 
-		static MethodInfo? dynamic_callback_gen;
-
-		// See ExportAttribute.cs
-		static Delegate CreateDynamicCallback (MethodInfo method)
-		{
-			if (dynamic_callback_gen == null) {
-				var assembly = Assembly.Load ("Mono.Android.Export");
-				if (assembly == null)
-					throw new InvalidOperationException ("To use methods marked with ExportAttribute, Mono.Android.Export.dll needs to be referenced in the application");
-				var type = assembly.GetType ("Java.Interop.DynamicCallbackCodeGenerator");
-				if (type == null)
-					throw new InvalidOperationException ("The referenced Mono.Android.Export.dll does not match the expected version. The required type was not found.");
-				dynamic_callback_gen = type.GetMethod ("Create");
-				if (dynamic_callback_gen == null)
-					throw new InvalidOperationException ("The referenced Mono.Android.Export.dll does not match the expected version. The required method was not found.");
-			}
-			return (Delegate)dynamic_callback_gen.Invoke (null, new object [] { method })!;
-		}
-
 		// [Export] callback delegates are created dynamically via DynamicCallbackCodeGenerator and are not
 		// cached in static fields (unlike non-[Export] connector delegates). Without rooting them here,
 		// CoreCLR's GC can collect them between JNI registration and first invocation, causing a crash.
@@ -547,7 +528,11 @@ public override void RegisterNativeMembers (JniType nativeClass, Type type, Read
 
 							if (minfo == null)
 								throw new InvalidOperationException (FormattableString.Invariant ($"Specified managed method '{mname.ToString ()}' was not found. Signature: {signature.ToString ()}"));
-							callback = CreateDynamicCallback (minfo);
+
+							var exportAttribute = minfo.GetCustomAttribute<BaseExportAttribute> ()
+								?? throw new InvalidOperationException (FormattableString.Invariant ($"Specified managed method '{mname.ToString ()}' does not have [Export] attribute. Signature: {signature.ToString ()}"));
+
+							callback = exportAttribute.CreateDynamicCallback (minfo);
 							lock (prevent_delegate_gc_lock) {
 								prevent_delegate_gc.Add (callback);
 							}

src/Mono.Android/Android.Runtime/JNIEnvInit.cs

@@ -167,6 +167,7 @@ IntPtr GetRegisterJniNativesFnPtr () =>
 		[UnmanagedCallConv (CallConvs = new[] { typeof (CallConvCdecl) })]
 		private static unsafe partial void xamarin_app_init (IntPtr env, delegate* unmanaged <int, int, int, IntPtr*, void> get_function_pointer);
 
+		[UnconditionalSuppressMessage ("Trimming", "IL2026", Justification = "The AndroidTypeManager branch is only reached when RuntimeFeature.TrimmableTypeMap is false; the linker substitutes the feature switch and trims this branch in trimmable apps.")]
 		internal static JniRuntime.JniTypeManager CreateTypeManager (JnienvInitializeArgs args)
 		{
 			if (RuntimeFeature.TrimmableTypeMap) {

src/Mono.Android/PublicAPI/API-35/PublicAPI.Unshipped.txt

@@ -25,6 +25,7 @@ REMOVED virtual Xamarin.Android.Net.AndroidClientHandler.SetupRequest(System.Net
 REMOVED virtual Xamarin.Android.Net.AndroidClientHandler.WriteRequestContentToOutput(System.Net.Http.HttpRequestMessage! request, Java.Net.HttpURLConnection! httpConnection, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task!
 Android.App.ApplicationAttribute.EnableOnBackInvokedCallback.get -> bool
 Android.App.ApplicationAttribute.EnableOnBackInvokedCallback.set -> void
+Java.Interop.BaseExportAttribute
 Java.Interop.JavaArrayProxy
 abstract Java.Interop.JavaArrayProxy.CreateManagedArray(int length) -> System.Array!
 abstract Java.Interop.JavaArrayProxy.GetArrayTypes() -> System.Type![]!

src/Mono.Android/PublicAPI/API-36.1/PublicAPI.Unshipped.txt

@@ -25,6 +25,7 @@ REMOVED virtual Xamarin.Android.Net.AndroidClientHandler.SetupRequest(System.Net
 REMOVED virtual Xamarin.Android.Net.AndroidClientHandler.WriteRequestContentToOutput(System.Net.Http.HttpRequestMessage! request, Java.Net.HttpURLConnection! httpConnection, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task!
 Android.App.ApplicationAttribute.EnableOnBackInvokedCallback.get -> bool
 Android.App.ApplicationAttribute.EnableOnBackInvokedCallback.set -> void
+Java.Interop.BaseExportAttribute
 Java.Interop.JavaArrayProxy
 abstract Java.Interop.JavaArrayProxy.CreateManagedArray(int length) -> System.Array!
 abstract Java.Interop.JavaArrayProxy.GetArrayTypes() -> System.Type![]!

src/Mono.Android/PublicAPI/API-36/PublicAPI.Unshipped.txt

@@ -4401,6 +4401,7 @@ virtual Java.Util.IdentityHashMap.Remove(Java.Lang.Object? key, Java.Lang.Object
 virtual Java.Util.IdentityHashMap.Replace(Java.Lang.Object? key, Java.Lang.Object? oldValue, Java.Lang.Object? newValue) -> bool
 Android.App.ApplicationAttribute.EnableOnBackInvokedCallback.get -> bool
 Android.App.ApplicationAttribute.EnableOnBackInvokedCallback.set -> void
+Java.Interop.BaseExportAttribute
 Java.Interop.JavaArrayProxy
 abstract Java.Interop.JavaArrayProxy.CreateManagedArray(int length) -> System.Array!
 abstract Java.Interop.JavaArrayProxy.GetArrayTypes() -> System.Type![]!

src/Mono.Android/PublicAPI/API-37/PublicAPI.Unshipped.txt

@@ -25,6 +25,7 @@ REMOVED virtual Xamarin.Android.Net.AndroidClientHandler.SetupRequest(System.Net
 REMOVED virtual Xamarin.Android.Net.AndroidClientHandler.WriteRequestContentToOutput(System.Net.Http.HttpRequestMessage! request, Java.Net.HttpURLConnection! httpConnection, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task!
 Android.App.ApplicationAttribute.EnableOnBackInvokedCallback.get -> bool
 Android.App.ApplicationAttribute.EnableOnBackInvokedCallback.set -> void
+Java.Interop.BaseExportAttribute
 Java.Interop.JavaArrayProxy
 abstract Java.Interop.JavaArrayProxy.CreateManagedArray(int length) -> System.Array!
 abstract Java.Interop.JavaArrayProxy.GetArrayTypes() -> System.Type![]!

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Resources/Base/BuildReleaseArm64SimpleDotNet.CoreCLR.apkdesc

@@ -11,13 +11,13 @@
       "Size": 2717688
     },
     "lib/arm64-v8a/libclrjit.so": {
-      "Size": 2836936
+      "Size": 2835128
     },
     "lib/arm64-v8a/libcoreclr.so": {
-      "Size": 4890752
+      "Size": 4891056
     },
     "lib/arm64-v8a/libmonodroid.so": {
-      "Size": 1264112
+      "Size": 1324320
     },
     "lib/arm64-v8a/libSystem.Globalization.Native.so": {
       "Size": 72112

src/Xamarin.Android.NamingCustomAttributes/Java.Interop/BaseExportAttribute.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Reflection;
+
+namespace Java.Interop;
+
+#if !JCW_ONLY_TYPE_NAMES
+public
+#endif  // !JCW_ONLY_TYPE_NAMES
+abstract class BaseExportAttribute : Attribute
+{
+	internal abstract Delegate CreateDynamicCallback (MethodInfo method);
+
+	static MethodInfo? dynamic_callback_gen;
+
+	private protected static Delegate CreateDynamicCallbackCore (MethodInfo method)
+	{
+		// We're loading the Mono.Android.Export assembly dynamically to avoid problems with circular dependencies.
+		// The Type.GetType (...)?.GetMethod (...) call is chained intentionally: the trimmer only recognizes the
+		// GetMethod intrinsic when the constant Type value flows directly into it, so routing it through a local breaks dataflow.
+		dynamic_callback_gen ??= Type.GetType ("Java.Interop.DynamicCallbackCodeGenerator, Mono.Android.Export")?.GetMethod ("Create")
+			?? throw new InvalidOperationException ("To use methods marked with [Export] or [ExportField], Mono.Android.Export.dll must be referenced by the application and contain a matching Java.Interop.DynamicCallbackCodeGenerator.Create method.");
+
+		return (Delegate?)dynamic_callback_gen.Invoke (null, [method])
+			?? throw new InvalidOperationException (FormattableString.Invariant ($"Unable to create dynamic callback for method '{method.Name}' on type '{method.DeclaringType?.FullName}'"));
+	}
+}

src/Xamarin.Android.NamingCustomAttributes/Java.Interop/ExportAttribute.cs

@@ -1,26 +1,21 @@
 using System;
-using System.Diagnostics.CodeAnalysis;
+using System.Reflection;
 
 namespace Java.Interop {
 
 	[Serializable]
 	[AttributeUsage (AttributeTargets.Method | AttributeTargets.Constructor, 
 			AllowMultiple=false, 
 			Inherited=false)]
-#if !NETSTANDARD2_0
-	[RequiresUnreferencedCode ("[ExportAttribute] uses dynamic features.")]
-#endif
 #if !JCW_ONLY_TYPE_NAMES
 	public
 #endif  // !JCW_ONLY_TYPE_NAMES
-	partial class ExportAttribute : Attribute {
+	partial class ExportAttribute : BaseExportAttribute {
 
-		[DynamicDependency (DynamicallyAccessedMemberTypes.All, "Java.Interop.DynamicCallbackCodeGenerator", "Mono.Android.Export")]
 		public ExportAttribute ()
 		{
 		}
 
-		[DynamicDependency (DynamicallyAccessedMemberTypes.All, "Java.Interop.DynamicCallbackCodeGenerator", "Mono.Android.Export")]
 		public ExportAttribute (string name)
 		{
 			Name = name;
@@ -30,6 +25,11 @@ public ExportAttribute (string name)
 		public string?                SuperArgumentsString    {get; set;}
 		public Type []?               Throws                  {get; set;}
 		internal string []?           ThrownNames             {get; set;} // msbuild internal use
+
+		internal override Delegate CreateDynamicCallback (MethodInfo method)
+		{
+			return CreateDynamicCallbackCore (method);
+		}
 	}
 }
 

src/Xamarin.Android.NamingCustomAttributes/Java.Interop/ExportFieldAttribute.cs

@@ -1,5 +1,5 @@
 using System;
-using System.Diagnostics.CodeAnalysis;
+using System.Reflection;
 
 namespace Java.Interop {
 
@@ -10,16 +10,18 @@ namespace Java.Interop {
 #if !JCW_ONLY_TYPE_NAMES
 	public
 #endif  // !JCW_ONLY_TYPE_NAMES
-	partial class ExportFieldAttribute : Attribute {
+	partial class ExportFieldAttribute : BaseExportAttribute {
 
-		[DynamicDependency (DynamicallyAccessedMemberTypes.All, "Java.Interop.DynamicCallbackCodeGenerator", "Mono.Android.Export")]
 		public ExportFieldAttribute (string name)
 		{
 			Name = name;
 		}
 
 		public string                 Name                    {get; set;}
+
+		internal override Delegate CreateDynamicCallback (MethodInfo method)
+		{
+			return CreateDynamicCallbackCore (method);
+		}
 	}
 }
-
-

src/Xamarin.Android.NamingCustomAttributes/Xamarin.Android.NamingCustomAttributes.projitems

@@ -14,6 +14,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Android.Content\ContentProviderAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Android.Content\ContentProviderAttribute.Partial.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Android.Runtime\RegisterAttribute.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Java.Interop\BaseExportAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Java.Interop\ExportAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Java.Interop\ExportFieldAttribute.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Java.Interop\ExportParameterAttribute.cs" />

tests/api-compatibility/acceptable-breakages-vReference-net11.0.txt

@@ -47,4 +47,5 @@ MembersMustExist : Member 'public void Android.Telecom.CallControl.RequestVideoS
 TypesMustExist : Type 'Android.Text.IInputType' does not exist in the implementation but it does exist in the contract.
 TypesMustExist : Type 'Xamarin.Android.Net.AndroidClientHandler' does not exist in the implementation but it does exist in the contract.
 CannotRemoveBaseTypeOrInterface : Type 'Android.Views.InputMethods.EditorInfo' does not implement interface 'Android.Text.IInputType' in the implementation but it does in the contract.
+CannotRemoveAttribute : Attribute 'System.Diagnostics.CodeAnalysis.RequiresUnreferencedCodeAttribute' exists on 'Java.Interop.ExportAttribute' in the contract but not the implementation.
 CannotRemoveAttribute : Attribute 'System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute' exists on parameter 'targetType' on member 'Android.Graphics.ColorValueMarshaler.CreateGenericValue(Java.Interop.JniObjectReference, Java.Interop.JniObjectReferenceOptions, System.Type)' in the contract but not the implementation.