From 0b6b41c8178df226985ce6c0a7135bcc00e796cd Mon Sep 17 00:00:00 2001
From: Simon Rozsival <simon@rozsival.com>
Date: Sun, 28 Jun 2026 03:24:50 +0200
Subject: [PATCH] [TrimmableTypeMap] Don't stage shrunk assemblies into the
 shared runtime pack on NativeAOT

CheckCodeBehindIsGenerated(NativeAOT) and
CheckOldResourceDesignerWithWrongCasingIsRemoved(True,NativeAOT) failed
intermittently in CI with:

  error XACIC7028: System.IO.FileNotFoundException: Could not find file
  '.../microsoft.netcore.app.runtime.nativeaot.android-arm64/.../lib/net11.0/shrunk/System.Xml.ReaderWriter.dll'
  at _RemoveRegisterAttribute (Xamarin.Android.Common.targets).

The base _RemoveRegisterAttribute copies every @(_ResolvedAssemblies) into
its @(_ShrunkAssemblies) location. For PublishTrimmed builds the framework/
user shrunk destinations live *inside the shared NuGet runtime pack*
(.../runtimes/<rid>/lib/net11.0/shrunk/). Because multiple test projects and
the parallel per-RID inner builds all target those same shared files, they
race and fail intermittently with FileNotFoundException on a clean pack cache.
Locally the failure is masked by shrunk/ files left over from previous builds.

On NativeAOT these managed framework/user assemblies are compiled to a native
shared library by ILC and are never packaged, so the shrunk copies are only
ever used as incremental-build inputs (CollectAssemblyFilesToCompress, the one
task that reads their content, is already gated to non-NativeAOT). Override
_RemoveRegisterAttribute in the trimmable typemap path to redirect the shrunk
copies to a project-local intermediate directory instead of the shared pack.
They are still produced with CopyIfChanged so the copies keep stable
timestamps (preserving the @(_ShrunkAssemblies)/@(_ShrunkFrameworkAssemblies)
incremental up-to-date checks), but nothing is ever written into the shared
runtime pack. CoreCLR keeps the base behavior since it still packages the
managed assemblies.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 ...soft.Android.Sdk.TypeMap.Trimmable.targets | 45 +++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.Trimmable.targets b/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.Trimmable.targets
index 0a3ff223f63..47f63cc57aa 100644
--- a/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.Trimmable.targets
+++ b/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.Trimmable.targets
@@ -243,6 +243,51 @@
     </ItemGroup>
   </Target>
 
+  <!--
+    Override _RemoveRegisterAttribute for the trimmable typemap path.
+
+    The base target (Xamarin.Android.Common.targets) copies every @(_ResolvedAssemblies)
+    into its @(_ShrunkAssemblies) location. For PublishTrimmed builds the framework/user
+    @(_ShrunkAssemblies) destinations live inside the shared NuGet runtime pack
+    (e.g. .../runtimes/<rid>/lib/net11.0/shrunk/<assembly>.dll).
+
+    On NativeAOT the managed framework/user assemblies are compiled to a native shared
+    library by ILC and are never packaged, so these shrunk copies are not consumed:
+    CollectAssemblyFilesToCompress (the only task that reads their content) is gated to
+    '$(_AndroidRuntime)' != 'NativeAOT'. Staging them into the shared runtime pack is
+    therefore unsafe: concurrent builds (multiple projects and the parallel per-RID inner
+    builds) target the same shared files, so they race and fail intermittently with
+    XACIC7028 (FileNotFoundException) on a clean pack cache.
+
+    For NativeAOT, redirect the shrunk copies to a project-local intermediate directory
+    instead of the shared runtime pack. They are still produced with CopyIfChanged so the
+    copies keep stable timestamps (only rewritten when content actually changes), which
+    preserves the incremental up-to-date checks that consume @(_ShrunkAssemblies) /
+    @(_ShrunkFrameworkAssemblies) as inputs — while never writing into the shared pack.
+
+    CoreCLR (and any other trimmable runtime) keeps the base behavior because it still
+    packages the managed assemblies and therefore needs the shrunk copies in place.
+  -->
+  <Target Name="_RemoveRegisterAttribute"
+      DependsOnTargets="_PrepareAssemblies"
+      Condition="'$(AndroidLinkMode)' != 'None' AND '$(AndroidIncludeDebugSymbols)' != 'true'">
+    <ItemGroup Condition=" '$(_AndroidRuntime)' == 'NativeAOT' ">
+      <_ShrunkAssemblies Remove="@(_ShrunkAssemblies)" />
+      <_ShrunkAssemblies Include="@(_ResolvedAssemblies->'$(MonoAndroidIntermediateAssemblyDir)shrunk\%(DestinationSubPath)')" />
+      <_ShrunkFrameworkAssemblies Remove="@(_ShrunkFrameworkAssemblies)" />
+      <_ShrunkFrameworkAssemblies Include="@(_ResolvedFrameworkAssemblies->'$(MonoAndroidIntermediateAssemblyDir)shrunk\%(DestinationSubPath)')" />
+      <_ShrunkUserAssemblies Remove="@(_ShrunkUserAssemblies)" />
+      <_ShrunkUserAssemblies Include="@(_ResolvedUserAssemblies->'$(MonoAndroidIntermediateAssemblyDir)shrunk\%(DestinationSubPath)')" />
+    </ItemGroup>
+    <CopyIfChanged
+      SourceFiles="@(_ResolvedAssemblies)"
+      DestinationFiles="@(_ShrunkAssemblies)" />
+    <CopyIfChanged
+      SourceFiles="@(_ResolvedAssemblies->'%(Identity).config')"
+      DestinationFiles="@(_ShrunkAssemblies->'%(Identity).config')" />
+    <MakeDir Directories="$(MonoAndroidIntermediateAssemblyDir)shrunk" />
+  </Target>
+
   <!--
     _GenerateJavaStubs: overrides the legacy target from BuildOrder.targets.
     In the trimmable path, TypeMap generation already happened in _GenerateTrimmableTypeMap,