[TrimmableTypeMap] Refuse [JniAddNativeMethodRegistrationAttribute] with XA4251 by simonrozsival · Pull Request #11274 · dotnet/android

simonrozsival · 2026-05-03T18:50:02Z

Refuses [JniAddNativeMethodRegistrationAttribute] in the trimmable typemap.

[JniAddNativeMethodRegistrationAttribute] is a legacy Java.Interop public API. Its primary consumer — the jnimarshalmethod-gen build-time generator that used to emit [JniAddNativeMethodRegistrationAttribute] static void __RegisterNativeMembers stubs on every JCW type — was removed in dotnet/java-interop#1405. The only remaining in-tree uses are Java.Interop's own JavaProxyObject / JavaProxyThrowable infrastructure types (already bypassed in the trimmable path by #11271) and a couple of upstream Java.Interop test fixtures. Supporting it in the trimmable typemap would mean adding scanner + ModelBuilder support for an obsolete code path with no in-tree consumers and a near-zero customer base.

This PR makes the design decision explicit:

JavaPeerScanner now takes an optional ITrimmableTypeMapLogger. When it encounters [JniAddNativeMethodRegistrationAttribute] on any method, it calls ITrimmableTypeMapLogger.LogJniAddNativeMethodRegistrationAttributeError directly from the per-type scan loop. No JavaPeerInfo property is propagated; the orchestrator simply passes its logger into new JavaPeerScanner(logger).
The MSBuild logger maps the call to XA4251, so GenerateTrimmableTypeMap fails the build via TaskLoggingHelper.HasLoggedErrors.
The message instructs developers to either avoid the attribute or switch off the trimmable typemap (for example, by using the llvm-ir type map implementation), and to report the scenario at https://github.com/dotnet/android/issues so the team can evaluate whether to support it.
Java.InteropTests.InvokeVirtualFromConstructorTests (which uses the attribute) is permanently excluded under the trimmable typemap with an explanatory comment pointing at this policy.
tests/Mono.Android-Tests/Java.Interop-Tests/Java.Interop-Tests.NET.csproj excludes the upstream CallVirtualFromConstructor{Base,Derived}.cs and InvokeVirtualFromConstructorTests.cs from the test assembly compile when _AndroidTypeMapImplementation == trimmable, so the device-test build can compile through the trimmable typemap generator. (The other upstream user of the attribute, TestType.cs, is already gated by #if !NO_MARSHAL_MEMBER_BUILDER_SUPPORT, which the test csproj defines.)

Tests:

JavaPeerScannerTests.Scan_JniAddNativeMethodRegistrationAttribute_LogsError (new) gives the scanner a recording ITrimmableTypeMapLogger and asserts it logs XA4251 for HandWrittenNativeRegistrationPeer and not for unrelated fixture types.
TrimmableTypeMapGeneratorTests.Execute_WithJniAddNativeMethodRegistrationAttribute_ReportsXA4251 (new) verifies the orchestrator end-to-end emits XA4251 against the same fixture.

Device validation against an Android emulator with the CoreCLRTrimmable lane:

ANDROID_SERIAL=emulator-5554 MSBUILDDISABLENODEREUSE=1 ./dotnet-local.sh build \
    tests/Mono.Android-Tests/Mono.Android-Tests/Mono.Android.NET-Tests.csproj \
    -t:RunTestApp -c Release \
    -p:_AndroidTypeMapImplementation=trimmable -p:UseMonoRuntime=false \
    -nr:false -m:1

TestResult-Mono.Android.NET_Tests-ReleaseCoreCLRTrimmable.xml: 888 total, 0 errors, 0 failures, 21 ignored.

Related issues

Add trimmable-specific java_runtime jars that replace Java.Interop's JavaProxyObject and JavaProxyThrowable sources only for the trimmable typemap path. Keep the existing runtime jars on Java.Interop's native-registration behavior and select the trimmable jars when _AndroidTypeMapImplementation is trimmable. Re-enable the affected Java.Interop runtime tests and add focused coverage for JavaProxyObject marshaling/object methods under the trimmable typemap path. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add comments documenting runtime jar selection and Java proxy identity semantics. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Enable the Java.Interop virtual-constructor tests in the trimmable typemap lane by swapping in Android-owned Java fixtures that use Runtime.registerNatives and generated n_* callbacks instead of ManagedPeer. Teach the trimmable typemap scanner/model to emit native registrations for hand-written Java peers that opt into JniAddNativeMethodRegistrationAttribute. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Use repository Java formatting for trimmable proxy sources and strengthen the proxy hashCode test so it compares against Java identityHashCode instead of itself. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…object # Conflicts: # tests/Mono.Android-Tests/Mono.Android-Tests/Java.Interop/TrimmableTypeMapTypeManagerTests.cs # tests/Mono.Android-Tests/Mono.Android-Tests/Xamarin.Android.RuntimeTests/NUnitInstrumentation.cs

…structor

Drop stale _net6 Java runtime artifact names and collapse the trimmable runtime jar/dex to a single shared artifact for CoreCLR and NativeAOT. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…to pick up CI fixes

…structor # Conflicts: # src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/TrimmableTypeMapBuildTests.cs # tests/Mono.Android-Tests/Mono.Android-Tests/Xamarin.Android.RuntimeTests/NUnitInstrumentation.cs

…mmableTypeMapBuildTests This cleanup is not related to fixing InvokeVirtualFromConstructorTests and belongs in a separate change. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

This PR re-enables Java.InteropTests.InvokeVirtualFromConstructorTests for the CoreCLR trimmable typemap lane by swapping desktop-JVM Java.Interop fixtures for Android/trimmable-compatible copies and extending the trimmable typemap generator to support native registrations for hand-written Java peers.

Changes:

Removes the trimmable-typemap exclusion for Java.InteropTests.InvokeVirtualFromConstructorTests and adds trimmable Java/C# fixtures for CallVirtualFromConstructor*.
Extends the trimmable typemap scanner/model to detect JniAddNativeMethodRegistrationAttribute usage and emit proxy/registration support accordingly.
Adds cleanup/validation for obsolete java_runtime_*_net6 / java_runtime_trimmable_clr artifacts (delete during build; assert not packaged in SDK tests).

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/Mono.Android-Tests/Mono.Android-Tests/Xamarin.Android.RuntimeTests/NUnitInstrumentation.cs	Re-enables `InvokeVirtualFromConstructorTests` by removing its name-based exclusion.
tests/Mono.Android-Tests/Java.Interop-Tests/Java.Interop-trimmable/CallVirtualFromConstructorDerived.cs	Adds trimmable managed peer fixture using generated `n_*` callbacks + `JniAddNativeMethodRegistrationAttribute`.
tests/Mono.Android-Tests/Java.Interop-Tests/Java.Interop-Tests.targets	Switches trimmable builds to include Android-owned Java fixtures in the test JAR and exclude the desktop versions.
tests/Mono.Android-Tests/Java.Interop-Tests/Java.Interop-Tests.NET.csproj	Conditionally swaps the managed `CallVirtualFromConstructorDerived` source between desktop and trimmable variants.
tests/Mono.Android-Tests/Java.Interop-Tests/java-trimmable/net/dot/jni/test/CallVirtualFromConstructorDerived.java	Adds Android/trimmable Java fixture using `mono.android.Runtime.registerNatives(Class)` via reflection.
tests/Mono.Android-Tests/Java.Interop-Tests/java-trimmable/net/dot/jni/test/CallVirtualFromConstructorBase.java	Adds Android/trimmable base Java fixture using `registerNatives(Class)` via reflection.
src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/TrimmableTypeMapBuildTests.cs	Verifies obsolete net6/trimmable_clr runtime artifacts are not shipped in the SDK pack.
src/Microsoft.Android.Sdk.TrimmableTypeMap/Scanner/JavaPeerScanner.cs	Detects method-level `JniAddNativeMethodRegistrationAttribute` to inform generation decisions.
src/Microsoft.Android.Sdk.TrimmableTypeMap/Scanner/JavaPeerInfo.cs	Stores whether a peer uses `JniAddNativeMethodRegistrationAttribute`.
src/Microsoft.Android.Sdk.TrimmableTypeMap/Generator/ModelBuilder.cs	Treats certain `DoNotGenerateAcw` peers with native registrations as needing proxy/registration emission.
src/java-runtime/java-runtime.targets	Deletes obsolete `java_runtime_*_net6` / `java_runtime_trimmable_clr` artifacts during build/clean.

simonrozsival · 2026-05-11T10:56:16Z

+#nullable enable
+
+using System;
+using System.Runtime.CompilerServices;


The file this comment was on (tests/Mono.Android-Tests/Java.Interop-Tests/Java.Interop-trimmable/CallVirtualFromConstructorDerived.cs) has since been removed — this PR no longer adds Java.Interop-trimmable fixtures for the attribute; we refuse the attribute outright with XA4251 instead.

simonrozsival · 2026-05-11T10:56:18Z

 			var isInterface = (typeDef.Attributes & TypeAttributes.Interface) != 0;
 			var isAbstract = (typeDef.Attributes & TypeAttributes.Abstract) != 0;
 			var isGenericDefinition = typeDef.GetGenericParameters ().Count > 0;
+			var hasJniAddNativeMethodRegistrationAttribute = HasJniAddNativeMethodRegistrationAttribute (typeDef, index);


Addressed in 1a71bb3. The doNotGenerateAcw short-circuit no longer applies after the rework — XA4251 should fire even for non-peer types — but the per-type method-attribute walk is now gated on a cheap assembly-level fast-check (AssemblyIndex.MayUseJniAddNativeMethodRegistrationAttribute), so the inner loop runs only when the assembly's TypeRefs / TypeDefs actually mention the attribute name.

…emap [JniAddNativeMethodRegistrationAttribute] is a legacy Java.Interop API whose primary consumer — the jnimarshalmethod-gen build-time generator — was removed in dotnet/java-interop#1405. The trimmable typemap deliberately does not support this attribute. When the scanner detects the attribute on any method, the generator emits XA4251 telling the developer to either avoid it or switch off the trimmable typemap (for example, by using the 'llvm-ir' type map implementation) and report the scenario at https://github.com/dotnet/android/issues. The build fails via TaskLoggingHelper.HasLoggedErrors. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Address review feedback: - Drop JavaPeerInfo.HasJniAddNativeMethodRegistrationAttribute. The scanner now takes an optional ITrimmableTypeMapLogger and reports XA4251 directly when it encounters the attribute, instead of propagating a bool the rest of the pipeline doesn't otherwise need. - Drop the orchestrator's post-scan loop; TrimmableTypeMapGenerator just passes its logger into JavaPeerScanner. - Reset external/Java.Interop and external/xamarin-android-tools to the SHAs on main; this PR doesn't need either submodule moved. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…t/dot/jni/test/GetThis.java This file is unrelated to the XA4251 work; it was accidentally removed during an earlier 'git rm -r java-trimmable' cleanup. It's still needed by JavaObjectTest.DisposeAccessesThis under the trimmable typemap. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The upstream Java.Interop test fixture CallVirtualFromConstructorDerived uses [JniAddNativeMethodRegistrationAttribute]. Now that the trimmable typemap refuses that attribute with XA4251, the offending sources need to be excluded from the test assembly when building for the trimmable type map; otherwise the build cannot reach the device tests at all. Validated locally: ANDROID_SERIAL=emulator-5554 MSBUILDDISABLENODEREUSE=1 \ ./dotnet-local.sh build \ tests/Mono.Android-Tests/Mono.Android-Tests/Mono.Android.NET-Tests.csproj \ -t:RunTestApp -c Release \ -p:_AndroidTypeMapImplementation=trimmable \ -p:UseMonoRuntime=false -nr:false -m:1 TestResult-Mono.Android.NET_Tests-ReleaseCoreCLRTrimmable.xml: 888 total, 0 errors, 0 failures, 21 ignored. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Code-review caught that the prior placement of the XA4251 check sat *after* the scanner's per-type filtering, so a type carrying the attribute but no [Register] (and not extending a Java peer) would slip past the diagnostic and the build would silently succeed. Hoist the check to immediately after the <Module> skip so it fires uniformly for every non-<Module> type, regardless of whether the type would otherwise have been added to the typemap. Add a NonPeerNativeRegistration fixture to the scanner test to guard the regression. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…bute Address Copilot reviewer feedback on the per-type method-attribute walk. AssemblyIndex.Build now does a cheap pass over the TypeReferences and TypeDefinitions tables to set MayUseJniAddNativeMethodRegistrationAttribute, and the scanner short-circuits the per-method walk in the overwhelmingly common case where the assembly neither imports nor declares the attribute. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Squashed prerequisites from PR #11274 (trimmable-virtual-constructor): reject [JniAddNativeMethodRegistrationAttribute] with XA4251 in the trimmable typemap path and exclude the upstream InvokeVirtualFromConstructor fixtures so the trimmable test assembly builds. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival changed the title ~~Use trimmable virtual-constructor fixtures~~ [TrimmableTypeMap] Use trimmable virtual-constructor fixtures May 3, 2026

simonrozsival added copilot `copilot-cli` or other AIs were used to author this trimmable-type-map labels May 3, 2026

simonrozsival force-pushed the trimmable-java-proxy-object branch from 1467afa to e66930e Compare May 4, 2026 18:21

simonrozsival force-pushed the trimmable-virtual-constructor branch from 711aeae to 7e2737b Compare May 4, 2026 18:23

simonrozsival and others added 3 commits May 4, 2026 20:31

Address trimmable runtime review comments

0644b70

Add comments documenting runtime jar selection and Java proxy identity semantics. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival force-pushed the trimmable-java-proxy-object branch from e66930e to 0644b70 Compare May 4, 2026 18:31

simonrozsival force-pushed the trimmable-virtual-constructor branch from 7e2737b to dc13b42 Compare May 4, 2026 18:31

simonrozsival and others added 7 commits May 5, 2026 11:31

Merge branch 'main' into trimmable-java-proxy-object

b1d1947

Address Java proxy review comments

80d4af4

Use repository Java formatting for trimmable proxy sources and strengthen the proxy hashCode test so it compares against Java identityHashCode instead of itself. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Merge branch 'trimmable-java-proxy-object' into trimmable-virtual-con…

2cb67ee

…structor

Simplify trimmable runtime artifacts

43bc2ed

Drop stale _net6 Java runtime artifact names and collapse the trimmable runtime jar/dex to a single shared artifact for CoreCLR and NativeAOT. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Merge main into trimmable-java-proxy-object to pick up CI fixes

92a4836

Merge trimmable-java-proxy-object into trimmable-virtual-constructor …

5a7e957

…to pick up CI fixes

Base automatically changed from trimmable-java-proxy-object to main May 11, 2026 07:16

simonrozsival marked this pull request as ready for review May 11, 2026 09:11

simonrozsival requested a review from jonathanpeppers as a code owner May 11, 2026 09:11

Copilot AI review requested due to automatic review settings May 11, 2026 09:11

Copilot started reviewing on behalf of simonrozsival May 11, 2026 09:12 View session

Drop unrelated obsolete-jar cleanup from java-runtime.targets and Tri…

f863ba1

…mmableTypeMapBuildTests This cleanup is not related to fixing InvokeVirtualFromConstructorTests and belongs in a separate change. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot AI reviewed May 11, 2026

View reviewed changes

simonrozsival changed the title ~~[TrimmableTypeMap] Use trimmable virtual-constructor fixtures~~ [TrimmableTypeMap] Refuse [JniAddNativeMethodRegistrationAttribute] with XA4251 May 11, 2026

simonrozsival and others added 3 commits May 11, 2026 12:05

simonrozsival force-pushed the trimmable-virtual-constructor branch from 7ad46cf to 7d607c5 Compare May 11, 2026 10:53

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[TrimmableTypeMap] Refuse [JniAddNativeMethodRegistrationAttribute] with XA4251#11274

[TrimmableTypeMap] Refuse [JniAddNativeMethodRegistrationAttribute] with XA4251#11274
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