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[TrimmableTypeMap][NativeAOT] Auto-detect and scan runtime-only assemblies (fixes stripped runtime ACWs) #11982

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[TrimmableTypeMap][NativeAOT] Auto-detect and scan runtime-only assemblies (fixes stripped runtime ACWs) #11982

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30 changes: 30 additions & 0 deletions ...uild.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.AssemblyResolution.targets
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Expand Up @@ -86,6 +86,36 @@ _ResolveAssemblies MSBuild target.
</ItemGroup>
</Target>

<!--
Resolve-only variant used by the trimmable typemap generator to discover runtime-only assemblies.

The trimmable typemap generator runs in the RID-independent OUTER build over @(ReferencePath),
the compile closure, which omits runtime-only assemblies (e.g. the NativeAOT runtime host) that
have no ref-pack counterpart and are only pulled from the RID-specific runtime pack. Runtime-pack
resolution (ResolveRuntimePackAssets, reached via ResolveReferences) requires a single
RuntimeIdentifier, so the outer build invokes this target through the MSBuild task for one RID.

It stops after ResolveReferences - it does NOT run ComputeFilesToPublish/ILLink/ILC/AOT - and
returns the Android runtime-pack managed assemblies that are NOT already in @(ReferencePath)
(matched on filename). Those are exactly the runtime-only assemblies the outer generator would
otherwise miss; everything with a compile reference is already scanned via @(ReferencePath). Only
the Android runtime packs (Microsoft.Android.Runtime.*) can carry Java peers, so the .NET/BCL
runtime pack (Microsoft.NETCore.App.Runtime.*) is excluded to avoid scanning large BCL assemblies
that have none. The managed metadata is RID-independent, so resolving one RID suffices for all. -->
<Target Name="_ResolveRuntimeOnlyAssembliesForTypeMap"
DependsOnTargets="BuildOnlySettings;_FixupIntermediateAssembly;_PatchNuGetReferenceMetadata;ResolveReferences"
Returns="@(_TypeMapRuntimeOnlyAssembly)">
<ItemGroup>
<_TypeMapRuntimeOnlyAssembly Include="@(RuntimePackAsset)"
Condition=" '%(RuntimePackAsset.Extension)' == '.dll' and '%(RuntimePackAsset.AssetType)' == 'runtime' and $([System.String]::Copy('%(RuntimePackAsset.NuGetPackageId)').StartsWith('Microsoft.Android.Runtime')) " />
<!-- Drop any runtime-pack assembly that also has a compile reference (e.g. Mono.Android,
Java.Interop): the outer build already scans those via @(ReferencePath), and scanning both
the ref and runtime-pack copies would double-process the same assembly (GenerateTrimmableTypeMap
groups inputs by path). Match on filename to keep only the runtime-only assemblies. -->
<_TypeMapRuntimeOnlyAssembly Remove="@(ReferencePath)" MatchOnMetadata="Filename" />
</ItemGroup>
</Target>

<Target Name="_FixupIntermediateAssembly" Condition=" '$(_OuterIntermediateAssembly)' != '' ">
<ItemGroup>
<IntermediateAssembly Remove="@(IntermediateAssembly)" />
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73 changes: 73 additions & 0 deletions ...s/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.Trimmable.NativeAOT.targets
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Expand Up @@ -27,6 +27,15 @@
<_TrimmableTypeMapFrameworkIlcAssemblyNames Include="@(PrivateSdkAssemblies->'_%(Filename).TypeMap')" />
<_TrimmableTypeMapFrameworkIlcAssemblyNames Include="@(ReferencePath->'_%(Filename).TypeMap')"
Condition=" '%(ReferencePath.FrameworkAssembly)' == 'true' " />
<!-- Runtime-only assemblies (e.g. the NativeAOT runtime host Microsoft.Android.Runtime.NativeAOT)
come from the runtime pack and have no @(ReferencePath) counterpart, so their per-assembly
typemap DLLs are not caught by the rules above. Every runtime-pack managed assembly is a
framework/runtime assembly: classify its typemap DLL as framework so it stays an IlcReference
(ILC reads its conditional TypeMap attributes) but is removed from the unmanaged-entrypoint
roots, matching Mono.Android/Java.Interop. Their JCW native methods register via the runtime
registerNatives path. -->
<_TrimmableTypeMapFrameworkIlcAssemblyNames Include="@(RuntimePackAsset->'_%(Filename).TypeMap')"

@github-actions github-actions Bot Jul 9, 2026

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🤖 💡 MSBuild targets — This includes every runtime-pack managed DLL, including the .NET/BCL runtime pack (Microsoft.NETCore.App.Runtime.*), whereas the sibling _ResolveRuntimeOnlyAssembliesForTypeMap deliberately filters to Microsoft.Android.Runtime and excludes the BCL. It is harmless today — these names only feed the Remove on _TrimmableTypeMapUnmanagedEntryPointAssemblyNames, and BCL assemblies have no generated _*.TypeMap DLL to remove — but the asymmetry between the two targets is a maintenance trap and inflates the item group with hundreds of no-op BCL names. Consider matching the resolve target's StartsWith('Microsoft.Android.Runtime') filter here, or add a note explaining why the broader set is intentional.

Rule: Consistency with sibling targets

Condition=" '%(RuntimePackAsset.Extension)' == '.dll' and '%(RuntimePackAsset.AssetType)' == 'runtime' " />
<!-- The root assembly (_Microsoft.Android.TypeMaps) only contains TypeMapLoader.Initialize()
and assembly-level attributes — no types that need vtable generation.
Framework per-assembly typemap DLLs must remain IlcReference inputs so ILC can read
Expand Down Expand Up @@ -66,6 +75,70 @@
BeforeTargets="_ResolveAssemblies"
DependsOnTargets="_GenerateTrimmableTypeMap" />

<!--
The trimmable typemap generator runs in the OUTER build over @(ReferencePath), which contains only
the compile closure (app + its references + the ref-pack framework assemblies). Runtime-only
assemblies - e.g. the NativeAOT runtime host Microsoft.Android.Runtime.NativeAOT - come from the
RID-specific runtime pack and have no ref-pack counterpart, so they are resolved only in the per-RID
inner build and are never in @(ReferencePath). Their Java Callable Wrapper types (e.g.
UncaughtExceptionMarshaler) would then be missing from the typemap and JCWs -> R8 has nothing to
keep -> on-device startup crash in JavaInteropRuntime.init (setDefaultUncaughtExceptionHandler).

Runtime-pack resolution (ResolveRuntimePackAssets) requires a single RuntimeIdentifier and must
happen before ILC. So, before _ResolveAssemblies spawns the per-RID ILC builds, run a lightweight
resolve-only pass for the first RID (the managed metadata is RID-independent) via
_ResolveRuntimeOnlyAssembliesForTypeMap, and cache the discovered runtime-only assemblies to a file.
This auto-detects every runtime-only Java-peer assembly - no assembly is hard-coded.

The nested resolve is gated on Inputs/Outputs so it only re-runs when the reference graph could have
changed (restore output or the cached build properties), not on every incremental build. The
always-run loader below reads the cached list into the item the generator consumes, keeping the
generator's Inputs stable across builds.
-->
<Target Name="_ResolveRuntimeOnlyAssembliesForTrimmableTypeMap"
Condition=" '$(_AndroidTypeMapImplementation)' == 'trimmable' and '$(_OuterIntermediateOutputPath)' == '' and '$(DesignTimeBuild)' != 'true' "
Inputs="$(ProjectAssetsFile);$(_AndroidBuildPropertiesCache)"
Outputs="$(_TypeMapOutputDirectory)runtime-only-assemblies.txt">
<PropertyGroup>
<_TrimmableTypeMapResolveRid Condition=" '$(RuntimeIdentifiers)' != '' ">$([System.String]::Copy('$(RuntimeIdentifiers)').Split(';')[0])</_TrimmableTypeMapResolveRid>
<_TrimmableTypeMapResolveRid Condition=" '$(_TrimmableTypeMapResolveRid)' == '' ">$(RuntimeIdentifier)</_TrimmableTypeMapResolveRid>
<!-- Item lists (e.g. @(IntermediateAssembly)) cannot be embedded directly in the MSBuild task's
Properties string, so flatten them into this property and pass it via AdditionalProperties
item metadata, mirroring _ResolveAssemblies. -->
<_TrimmableTypeMapResolveProperties>_ComputeFilesToPublishForRuntimeIdentifiers=true;SelfContained=true;DesignTimeBuild=$(DesignTimeBuild);AppendRuntimeIdentifierToOutputPath=true;ResolveAssemblyReferencesFindRelatedSatellites=false;SkipCompilerExecution=true;_OuterIntermediateAssembly=@(IntermediateAssembly);_OuterOutputPath=$(OutputPath);_OuterIntermediateOutputPath=$(IntermediateOutputPath);_AndroidNdkDirectory=$(_AndroidNdkDirectory)</_TrimmableTypeMapResolveProperties>
</PropertyGroup>
<ItemGroup Condition=" '$(_TrimmableTypeMapResolveRid)' != '' ">
<_TrimmableTypeMapResolveProject Include="$(MSBuildProjectFile)"
AdditionalProperties="RuntimeIdentifier=$(_TrimmableTypeMapResolveRid);$(_TrimmableTypeMapResolveProperties)" />
</ItemGroup>
<MSBuild
Condition=" '$(_TrimmableTypeMapResolveRid)' != '' "
Projects="@(_TrimmableTypeMapResolveProject)"
Targets="_ResolveRuntimeOnlyAssembliesForTypeMap">
<Output TaskParameter="TargetOutputs" ItemName="_ResolvedRuntimeOnlyAssemblyForTypeMap" />
</MSBuild>
<MakeDir Directories="$(_TypeMapOutputDirectory)" />
<WriteLinesToFile
File="$(_TypeMapOutputDirectory)runtime-only-assemblies.txt"
Lines="@(_ResolvedRuntimeOnlyAssemblyForTypeMap)"
Overwrite="true"
WriteOnlyWhenDifferent="true" />
<ItemGroup>
<FileWrites Include="$(_TypeMapOutputDirectory)runtime-only-assemblies.txt" />
</ItemGroup>
</Target>

<Target Name="_AddRuntimeOnlyAssembliesToTrimmableTypeMap"
Condition=" '$(_AndroidTypeMapImplementation)' == 'trimmable' and '$(_OuterIntermediateOutputPath)' == '' and '$(DesignTimeBuild)' != 'true' "
DependsOnTargets="_ResolveRuntimeOnlyAssembliesForTrimmableTypeMap"
BeforeTargets="_GenerateTrimmableTypeMap">
<ReadLinesFromFile
File="$(_TypeMapOutputDirectory)runtime-only-assemblies.txt"
Condition=" Exists('$(_TypeMapOutputDirectory)runtime-only-assemblies.txt') ">
<Output TaskParameter="Lines" ItemName="_AndroidTrimmableTypeMapExtraFrameworkAssembly" />
</ReadLinesFromFile>
</Target>

<Target Name="_CollectTrimmableNativeAotDgmlFiles"
Condition=" '$(PublishTrimmed)' == 'true' and '$(_ProguardProjectConfiguration)' != '' ">
<ItemGroup>
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7 changes: 6 additions & 1 deletion ...Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.Trimmable.targets
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Expand Up @@ -99,7 +99,7 @@
Condition=" '$(_AndroidTypeMapImplementation)' == 'trimmable' and '$(DesignTimeBuild)' != 'true' and '@(ReferencePath->Count())' != '0' and '$(_OuterIntermediateOutputPath)' == '' "
AfterTargets="CoreCompile"
DependsOnTargets="_GetLibraryImports"
Inputs="@(ReferencePath);@(PrivateSdkAssemblies);@(FrameworkAssemblies);@(ExtractedManifestDocuments);$(IntermediateOutputPath)$(TargetFileName);$(_AndroidManifestAbs);$(_AndroidBuildPropertiesCache)"
Inputs="@(ReferencePath);@(PrivateSdkAssemblies);@(FrameworkAssemblies);@(ExtractedManifestDocuments);@(_AndroidTrimmableTypeMapExtraFrameworkAssembly);$(IntermediateOutputPath)$(TargetFileName);$(_AndroidManifestAbs);$(_AndroidBuildPropertiesCache)"
Outputs="$(_TrimmableTypeMapOutputStamp)">

<ItemGroup>
Expand All @@ -108,9 +108,14 @@
<_TypeMapInputAssemblies Include="@(ResolvedFrameworkAssemblies)" />
<_TypeMapInputAssemblies Include="@(PrivateSdkAssemblies)" />
<_TypeMapInputAssemblies Include="@(FrameworkAssemblies)" />
<!-- Runtime-only framework assemblies that have no counterpart in @(ReferencePath) (e.g. the
NativeAOT runtime host Microsoft.Android.Runtime.NativeAOT.dll, injected by the trimmable
NativeAOT targets). They carry Java Callable Wrapper types that must be in the typemap. -->
<_TypeMapInputAssemblies Include="@(_AndroidTrimmableTypeMapExtraFrameworkAssembly)" />
<_TypeMapFrameworkAssemblies Include="@(ResolvedFrameworkAssemblies)" />
<_TypeMapFrameworkAssemblies Include="@(PrivateSdkAssemblies)" />
<_TypeMapFrameworkAssemblies Include="@(FrameworkAssemblies)" />
<_TypeMapFrameworkAssemblies Include="@(_AndroidTrimmableTypeMapExtraFrameworkAssembly)" />
<_TypeMapInputAssemblies Include="$(IntermediateOutputPath)$(TargetFileName)"
Condition="Exists('$(IntermediateOutputPath)$(TargetFileName)')" />
<!-- Library (.aar) manifests to merge into the app manifest. Only on the legacy manifest
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32 changes: 32 additions & 0 deletions ...marin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/TrimmableTypeMapBuildTests.cs
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Expand Up @@ -67,6 +67,38 @@ public void Build_WithTrimmableTypeMap_IncrementalBuild ([Values] bool isRelease
}
}

[Test]
public void Build_WithTrimmableTypeMap_KeepsNativeAotRuntimeHostAcws ()
{
const bool isRelease = true;
if (IgnoreUnsupportedConfiguration (AndroidRuntime.NativeAOT, release: isRelease)) {
return;
}

var proj = new XamarinAndroidApplicationProject {
IsRelease = isRelease,
LinkTool = "r8",
};
proj.SetRuntime (AndroidRuntime.NativeAOT);
proj.SetProperty ("_AndroidTypeMapImplementation", "trimmable");

using var builder = CreateApkBuilder ();
Assert.IsTrue (builder.Build (proj), "Build should have succeeded.");

var dexFile = builder.Output.GetIntermediaryPath (Path.Combine ("android", "bin", "classes.dex"));
FileAssert.Exists (dexFile);

// Regression test: the NativeAOT runtime host assembly (Microsoft.Android.Runtime.NativeAOT) is
// resolved only in the per-RID inner build, so the RID-independent outer-build trimmable typemap
// generator never scanned it. Its only Java Callable Wrapper type, UncaughtExceptionMarshaler,
// therefore had no JCW and no typemap entry -> the runtime ACW is absent from classes.dex and the
// app crashes at startup in JavaInteropRuntime.init (setDefaultUncaughtExceptionHandler). A
// reference assembly for the host is now shipped in the SDK pack and fed to the generator. The JCW

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🤖 ⚠️ Documentation — This comment claims a "reference assembly for the host is now shipped in the SDK pack and fed to the generator," but that is not what the PR does. The final implementation auto-detects runtime-only assemblies at build time via the nested _ResolveRuntimeOnlyAssembliesForTypeMap resolve pass — the PR description itself states "No hard-coded assembly names, no per-assembly reference-assembly plumbing." This stale wording describes the abandoned ref-assembly approach (cf. the ...-refasm branch name) and will mislead anyone debugging this area later. Please reword it to describe the resolve-and-cache mechanism that the test actually exercises.

Rule: Remove stale comments (Postmortem #59)

// name is CRC-hashed (e.g. `scrc64...UncaughtExceptionMarshaler`), so match on the type name suffix.
Assert.IsTrue (DexUtils.ContainsClass ("UncaughtExceptionMarshaler;", dexFile, AndroidSdkPath),
$"`{dexFile}` should include the UncaughtExceptionMarshaler runtime ACW.");
}

[Test]
public void Build_WithTrimmableTypeMap_DeletesStaleGeneratedJavaSourcesAndCopies ()
{
Expand Down
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