[TrimmableTypeMap] Implement runtime TypeManager, ValueManager, and JavaConvert by simonrozsival · Pull Request #10967 · dotnet/android

simonrozsival · 2026-03-18T17:37:58Z

Summary

Adds the runtime-side support for the trimmable typemap: type resolution, peer creation, native method registration, and AOT-safe collection marshaling. All behind RuntimeFeature.TrimmableTypeMap (defaults to false).

New runtime types

JavaPeerProxy / JavaPeerProxy<T> — AOT-safe proxy attribute base. Generated proxy types extend this and provide CreateInstance() for peer creation and GetContainerFactory() for collection marshaling.
IAndroidCallableWrapper — RegisterNatives(JniType) interface for ACW proxy types to register JNI native methods.
JavaPeerContainerFactory<T> — AOT-safe factories for arrays, lists, collections, and dictionaries without MakeGenericType().
TrimmableTypeMap — Central class owning the TypeMapping dictionary. Encapsulates all proxy attribute access: peer creation, invoker resolution, container factories, and native method registration bootstrap.
TrimmableTypeMapTypeManager — JniTypeManager subclass delegating type lookups to TrimmableTypeMap. RegisterNativeMembers throws UnreachableException (JCW static blocks handle registration).

Wiring

RuntimeFeature.TrimmableTypeMap feature switch with ILLink substitutions
JNIEnvInit (CoreCLR) and JavaInteropRuntime + JreRuntime (NativeAOT) create the new managers when the feature is on
JavaMarshalValueManager (renamed from ManagedValueManager) gets proxy-based peer creation in TryConstructPeer

RegisterNatives bootstrap

mono.android.Runtime.registerNatives(Class) Java native method added
TrimmableTypeMap.RegisterBootstrapNativeMethod() registers the JNI callback during init
When Java loads a JCW class, OnRegisterNatives resolves the proxy and calls IAndroidCallableWrapper.RegisterNatives() to bind UCO function pointers

AOT-safe JavaConvert

JavaConvert.GetJniHandleConverter() uses JavaPeerContainerFactory for IList<T>, ICollection<T>, IDictionary<K,V>
JNIEnv.ArrayCreateInstance() uses factory path

Generator update

Proxy types now extend JavaPeerProxy<T> (generic) — TargetType and GetContainerFactory() inherited from base
Generator references TrimmableTypeMap for ActivateInstance and RegisterMethod

Dependencies

Add RegisterNatives overload for raw function pointers java-interop#1391 (RegisterNatives with raw function pointers — follow-up optimization)

Test coverage

255/255 generator tests pass
Mono.Android.dll builds locally
Runtime tests require device integration (tracked by [TrimmableTypeMap] Functional validation #10793)

simonrozsival

🤖 AI Review Summary

Verdict: ⚠️ Needs Changes (CI pending)

Found 0 code issues. CI is still running (dotnet-android and Xamarin.Android-PR in progress). Review will need to be re-evaluated once CI completes.

Code review

✅ No null-forgiving operator (!) usage
✅ All new files have #nullable enable
✅ Proper Mono style (tabs, space before () and [])
✅ Namespace style consistent with existing files
✅ Feature flag with ILLink substitutions follows established pattern
✅ Interlocked.CompareExchange + Debug.Assert for single-instance safety in both TrimmableTypeMap and JavaMarshalValueManager
✅ JNI callback delegate properly rooted in static field (s_onRegisterNatives)
✅ OnRegisterNatives calls Environment.FailFast on error (unrecoverable state)
✅ All TODO comments reference tracking issues (#10794 or java-interop #1391)
✅ TypeMapException is sealed
✅ TryGetType uses [NotNullWhen(true)] annotation
✅ 255/255 generator tests pass
✅ Mono.Android.dll builds locally

Architecture notes

Clean encapsulation: all proxy attribute access goes through TrimmableTypeMap — JavaPeerProxy is not leaked to callers
JavaMarshalValueManager (renamed from ManagedValueManager) takes TrimmableTypeMap? in constructor — immutable, no settable property
TrimmableTypeMapTypeManager delegates all lookups to TrimmableTypeMap
RegisterNatives bootstrap: Java → managed callback → proxy → IAndroidCallableWrapper.RegisterNatives(JniType) → UCO function pointers
All behind RuntimeFeature.TrimmableTypeMap (default false) — zero impact when off

Review generated by android-reviewer from review guidelines.

Copilot

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- JavaPeerProxy / JavaPeerProxy<T> — AOT-safe proxy attribute base - IAndroidCallableWrapper — RegisterNatives(JniType) for ACW types - JavaPeerContainerFactory<T> — AOT-safe array/list/collection/dict - TypeMapException — error reporting Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Proxy types now extend JavaPeerProxy<T> instead of JavaPeerProxy. TargetType and GetContainerFactory() are inherited from the generic base. Generator references TrimmableTypeMap for ActivateInstance and RegisterMethod. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add TrimmableTypeMap class with core typemap functionality: TryGetType, TryCreatePeer, GetInvokerType, GetContainerFactory, ActivateInstance. Add TrimmableTypeMapTypeManager delegating to TrimmableTypeMap. Rename ManagedValueManager to JavaMarshalValueManager. Add proxy-based peer creation in TryConstructPeer via TrimmableTypeMap.TryCreatePeer. Add RuntimeFeature.TrimmableTypeMap feature switch with ILLink substitutions. Wire into JNIEnvInit (CoreCLR) and JavaInteropRuntime + JreRuntime (NativeAOT). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add registerNatives(Class) native method to mono.android.Runtime.java so JCW static initializer blocks can trigger native method registration. Add to TrimmableTypeMap: - RegisterBootstrapNativeMethod() registers the JNI callback during init - OnRegisterNatives() resolves the proxy and calls IAndroidCallableWrapper.RegisterNatives(JniType) to bind UCO ptrs - RegisterMethod() helper for per-method registration (TODO: batch) Wire RegisterBootstrapNativeMethod() call in JNIEnvInit after runtime creation. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

When TrimmableTypeMap is available, use JavaPeerContainerFactory from the proxy for IList<T>, ICollection<T>, IDictionary<K,V> marshaling and array creation instead of MakeGenericType/Array.CreateInstance. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Ranks 1-3: direct new T[], T[][], T[][][] — fully AOT-safe. Rank 4+: when dynamic code is supported (CoreCLR), falls back to MakeArrayType + CreateInstanceFromArrayType. Throws on NativeAOT. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Add missing using Android.Runtime for JniHandleOwnership - Add DynamicallyAccessedMembers annotations required by JavaList<T>, JavaCollection<T>, JavaDictionary<K,V> on factory type parameters - Fix IJniNameProviderAttribute lookup (not an Attribute, use GetCustomAttributes instead of GetCustomAttribute<T>) - Fix JniType constructor (takes string, not JniObjectReference) - Restore #pragma warning disable IL3050 for Array.CreateInstance fallback path - Suppress IL2073 on GetInvokerType (invoker types preserved by MarkJavaObjects trimmer step) Build succeeds locally. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Pass TrimmableTypeMap via constructor instead of settable property. Use Interlocked.CompareExchange for single-instance safety. Keep RegisterBootstrapNativeMethod as separate call (JNI runtime must be initialized first). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Updated from macOS-7 CI build 13601673. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

jonathanpeppers

This file grew:

"lib/arm64-v8a/lib_System.Private.CoreLib.dll.so": {
--      "Size": 633928
++      "Size": 691720
    },

It's probably OK, but I wonder what did it.

jonathanpeppers · 2026-03-19T14:29:05Z

src/Mono.Android/Java.Interop/TypeMapException.cs

+#nullable enable
+
+using System;
+
+namespace Java.Interop
+{
+	/// <summary>
+	/// Exception thrown when a type mapping operation fails at runtime.
+	/// </summary>
+	public sealed class TypeMapException : Exception
+	{
+		public TypeMapException (string message) : base (message) { }
+		public TypeMapException (string message, Exception innerException) : base (message, innerException) { }
+	}


If this doesn't add extra info to the exception, can we just use InvalidOperationException or similar?

And the message would talk about a typemap.

jonathanpeppers · 2026-03-19T19:33:34Z

src/Mono.Android/Java.Interop/IAndroidCallableWrapper.cs

+	/// ACW types are .NET types that have a corresponding generated Java class
+	/// which calls back into .NET via JNI native methods.
+	/// </summary>
+	public interface IAndroidCallableWrapper


Can some of the new types in here be internal?

simonrozsival requested review from grendello and jonathanpeppers as code owners March 18, 2026 17:37

simonrozsival added the trimmable-type-map label Mar 18, 2026

Copilot AI review requested due to automatic review settings March 18, 2026 17:38

Copilot started reviewing on behalf of simonrozsival March 18, 2026 17:38 View session

simonrozsival commented Mar 18, 2026

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simonrozsival mentioned this pull request Mar 18, 2026

[TrimmableTypeMap] Unify InTune/method replacement support between AndroidTypeManager and TrimmableTypeMapTypeManager #10968

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Copilot AI reviewed Mar 18, 2026

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simonrozsival force-pushed the dev/simonrozsival/trimmable-typemap-runtime-pr branch from e27ad18 to d1e28a1 Compare March 19, 2026 08:10

simonrozsival added the copilot `copilot-cli` or other AIs were used to author this label Mar 19, 2026

simonrozsival and others added 8 commits March 19, 2026 17:46

simonrozsival force-pushed the dev/simonrozsival/trimmable-typemap-runtime-pr branch from d1e28a1 to b07f9b9 Compare March 19, 2026 16:46

[tests] Update BuildReleaseArm64SimpleDotNet.MonoVM.apkdesc

9b414a8

Updated from macOS-7 CI build 13601673. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

jonathanpeppers reviewed Mar 19, 2026

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[TrimmableTypeMap] Implement runtime TypeManager, ValueManager, and JavaConvert#10967

[TrimmableTypeMap] Implement runtime TypeManager, ValueManager, and JavaConvert#10967
simonrozsival wants to merge 9 commits intomainfrom
dev/simonrozsival/trimmable-typemap-runtime-pr

simonrozsival commented Mar 18, 2026 •

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Summary

New runtime types

Wiring

RegisterNatives bootstrap

AOT-safe JavaConvert

Generator update

Dependencies

Test coverage

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simonrozsival commented Mar 18, 2026 •

edited

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