[WIP] Run FixLegacyResourceDesigner before trimming

src/Microsoft.Android.Sdk.ILLink/Microsoft.Android.Sdk.ILLink.csproj

@@ -16,8 +16,6 @@
     <Compile Include="..\Xamarin.Android.Build.Tasks\Linker\External\Linker\BaseMarkHandler.cs" Link="External\BaseMarkHandler.cs" />
     <Compile Include="..\Xamarin.Android.Build.Tasks\Linker\MonoDroid.Tuner\AndroidLinkConfiguration.cs" Link="MonoDroid.Tuner\AndroidLinkConfiguration.cs" />
     <Compile Include="..\Xamarin.Android.Build.Tasks\Linker\MonoDroid.Tuner\Extensions.cs" Link="MonoDroid.Tuner\Extensions.cs" />
-    <Compile Include="..\Xamarin.Android.Build.Tasks\Linker\MonoDroid.Tuner\FixLegacyResourceDesignerStep.cs" Link="MonoDroid.Tuner\FixLegacyResourceDesignerStep.cs" />
-    <Compile Include="..\Xamarin.Android.Build.Tasks\Linker\MonoDroid.Tuner\LinkDesignerBase.cs" Link="MonoDroid.Tuner\LinkDesignerBase.cs" />
 
     <!--Other .NET for Android / Java.Interop files-->
     <Compile Include="..\..\external\Java.Interop\src\Java.Interop.Tools.Cecil\Java.Interop.Tools.Cecil\CustomAttributeProviderRocks.cs" Link="Java.Interop\CustomAttributeProviderRocks.cs" />

src/Xamarin.Android.Build.Tasks/Linker/External/Linker.Steps/BaseStep.cs

@@ -89,11 +89,7 @@ public virtual void LogMessage (string message)
 
 		public virtual void LogError (int code, string message)
 		{
-#if ILLINK
-			Context.LogMessage (MessageContainer.CreateCustomErrorMessage (message, code, origin: new MessageOrigin ()));
-#else   // !ILLINK
 			Context.LogError ($"XA{code}", message);
-#endif  // !ILLINK
 		}
 	}
 }

src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/FixLegacyResourceDesignerStep.cs

@@ -14,18 +14,11 @@
 using Mono.Linker.Steps;
 
 using Mono.Tuner;
-#if ILLINK
-using Resources = Microsoft.Android.Sdk.ILLink.Properties.Resources;
-#else   // !ILLINK
 using Resources = Xamarin.Android.Tasks.Properties.Resources;
-#endif  // ILLINK
 
 namespace MonoDroid.Tuner
 {
-	public class FixLegacyResourceDesignerStep : LinkDesignerBase
-#if !ILLINK
-		, Xamarin.Android.Tasks.IAssemblyModifierPipelineStep
-#endif  // !ILLINK
+	public class FixLegacyResourceDesignerStep : LinkDesignerBase, Xamarin.Android.Tasks.IAssemblyModifierPipelineStep
 	{
 		internal const string DesignerAssemblyName = "_Microsoft.Android.Resource.Designer";
 		internal const string DesignerAssemblyNamespace = "_Microsoft.Android.Resource.Designer";
@@ -36,14 +29,6 @@ public class FixLegacyResourceDesignerStep : LinkDesignerBase
 		Dictionary<string, MethodDefinition> lookup;
 		Dictionary<string, MethodDefinition> lookupCaseInsensitive;
 
-		protected override void EndProcess ()
-		{
-			if (designerAssembly != null) {
-				LogMessage ($"  Setting Action on {designerAssembly.Name} to Link.");
-				Annotations.SetAction (designerAssembly, AssemblyAction.Link);
-			}
-		}
-
 		protected override void LoadDesigner ()
 		{
 			if (designerLoaded)
@@ -72,7 +57,6 @@ protected override void LoadDesigner ()
 			}
 		}
 
-#if !ILLINK
 		public void ProcessAssembly (AssemblyDefinition assembly, Xamarin.Android.Tasks.StepContext context)
 		{
 			// Only run this step on non-main user Android assemblies
@@ -81,7 +65,6 @@ public void ProcessAssembly (AssemblyDefinition assembly, Xamarin.Android.Tasks.
 
 			context.IsAssemblyModified |= ProcessAssemblyDesigner (assembly);
 		}
-#endif  // !ILLINK
 
 		internal override bool ProcessAssemblyDesigner (AssemblyDefinition assembly)
 		{

src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/LinkDesignerBase.cs

@@ -4,43 +4,27 @@
 using Mono.Linker;
 using Mono.Linker.Steps;
 using System;
-using System.Linq;
 using Xamarin.Android.Tasks;
 using System.Collections.Generic;
 using System.Globalization;
 using Mono.Cecil.Cil;
 using System.Text.RegularExpressions;
 using Mono.Collections.Generic;
-#if ILLINK
-using Microsoft.Android.Sdk.ILLink;
-#endif
 
 
 namespace MonoDroid.Tuner  {
 	public abstract class LinkDesignerBase : BaseStep
 	{
 		protected IMetadataResolver Cache => Context;
 
-		public
-#if !ILLINK
-		override
-#endif
-		void LogMessage (string message)
+		public override void LogMessage (string message)
 		{
 			Context.LogMessage (message);
 		}
 
-		public
-#if !ILLINK
-		override
-#endif
-		void LogError (int code, string error)
+		public override void LogError (int code, string error)
 		{
-#if ILLINK
-			Context.LogMessage (MessageContainer.CreateCustomErrorMessage (error, code, origin: new MessageOrigin ()));
-#else   // !ILLINK
 			Context.LogError ($"XA{code}", error);
-#endif  // !ILLINK
 		}
 
 		public virtual AssemblyDefinition Resolve (AssemblyNameReference name)

src/Xamarin.Android.Build.Tasks/MSBuild/Xamarin/Android/Xamarin.Android.Resource.Designer.targets

@@ -226,6 +226,11 @@ Copyright (C) 2016 Xamarin. All rights reserved.
     In additon we MUST set the `PostprocessAssembly` metadata to `true` so that the file
     is processed by the ILLink step. If we do not do this then the reference to
     `netstandard.dll` is not replaced with `System.Private.CoreLib` and the app crashes.
+
+    No TrimmerRootDescriptor is needed: PreTrimmingFixLegacyDesigner rewrites library
+    assemblies *before* ILLink, replacing designer field loads with calls to the designer
+    assembly's property getters. ILLink then naturally preserves only the referenced
+    properties through its mark step, allowing everything else to be trimmed.
 -->
 <Target Name="_AddResourceDesignerToPublishFiles"
     Condition=" '$(AndroidUseDesignerAssembly)' == 'True' "

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.LlvmIr.targets

@@ -8,6 +8,7 @@
   <UsingTask TaskName="Xamarin.Android.Tasks.RemoveRegisterAttribute" AssemblyFile="$(_XamarinAndroidBuildTasksAssembly)" />
   <UsingTask TaskName="Xamarin.Android.Tasks.GenerateProguardConfiguration" AssemblyFile="$(_XamarinAndroidBuildTasksAssembly)" />
   <UsingTask TaskName="Xamarin.Android.Tasks.PostTrimmingPipeline" AssemblyFile="$(_XamarinAndroidBuildTasksAssembly)" />
+  <UsingTask TaskName="Xamarin.Android.Tasks.PreTrimmingFixLegacyDesigner" AssemblyFile="$(_XamarinAndroidBuildTasksAssembly)" />
 
   <PropertyGroup>
     <_RemoveRegisterFlag>$(MonoAndroidIntermediateAssemblyDir)shrunk\shrunk.flag</_RemoveRegisterFlag>
@@ -167,7 +168,7 @@
   <Target Name="_PrepareLinking"
       Condition=" '$(PublishTrimmed)' == 'true' "
       AfterTargets="ComputeResolvedFilesToPublishList"
-      DependsOnTargets="GetReferenceAssemblyPaths;_CreatePropertiesCache">
+      DependsOnTargets="GetReferenceAssemblyPaths;_CreatePropertiesCache;_AddResourceDesignerToPublishFiles">
     <PropertyGroup>
       <TrimmerRemoveSymbols Condition=" '$(AndroidIncludeDebugSymbols)' != 'true' ">true</TrimmerRemoveSymbols>
       <_ExtraTrimmerArgs Condition=" '$(_EnableSerializationDiscovery)' != 'false' ">--enable-serialization-discovery $(_ExtraTrimmerArgs)</_ExtraTrimmerArgs>
@@ -204,12 +205,6 @@
       <_TrimmerCustomSteps Include="$(_AndroidLinkerCustomStepAssembly)" Type="Microsoft.Android.Sdk.ILLink.PreserveJavaInterfaces" />
       <!-- Custom steps that run after MarkStep -->
       <!-- Custom steps that run after CleanStep -->
-      <_TrimmerCustomSteps
-          Condition=" '$(AndroidUseDesignerAssembly)' == 'true' "
-          Include="$(_AndroidLinkerCustomStepAssembly)"
-          BeforeStep="MarkStep"
-          Type="MonoDroid.Tuner.FixLegacyResourceDesignerStep"
-      />
       <_TrimmerCustomSteps
           Condition=" '$(_AndroidTypeMapImplementation)' == 'managed' "
           Include="$(_AndroidLinkerCustomStepAssembly)"
@@ -229,6 +224,25 @@
     </ItemGroup>
   </Target>
 
+  <!--
+    Fix legacy resource designer references *before* ILLink runs. This rewrites
+    library assemblies so their resource field accesses (ldsfld) become calls to the
+    designer assembly's property getters, and clears the per-library designer classes.
+    Because the rewritten IL no longer references the old designer fields, ILLink can
+    freely trim unused designer types without needing a root descriptor.
+  -->
+  <Target Name="_PreTrimmingFixLegacyDesigner"
+      BeforeTargets="ILLink"
+      Condition=" '$(PublishTrimmed)' == 'true' and '$(AndroidUseDesignerAssembly)' == 'True' ">
+    <ItemGroup>
+      <_PreTrimmingAssembly Include="@(ResolvedFileToPublish)" Condition=" '%(Extension)' == '.dll' and '%(ResolvedFileToPublish.PostprocessAssembly)' == 'true' " />
+    </ItemGroup>
+    <PreTrimmingFixLegacyDesigner
+        Assemblies="@(_PreTrimmingAssembly)"
+        TargetName="$(TargetName)"
+        Deterministic="$(Deterministic)" />
+  </Target>
+
   <Target Name="_TouchAndroidLinkFlag"
       AfterTargets="ILLink"
       Condition=" '$(PublishTrimmed)' == 'true' and '$(RunILLink)' != 'false' and Exists('$(_LinkSemaphore)') "

src/Xamarin.Android.Build.Tasks/Tasks/PreTrimmingFixLegacyDesigner.cs

@@ -0,0 +1,71 @@
+#nullable enable
+
+using System.IO;
+using Java.Interop.Tools.Cecil;
+using Microsoft.Android.Build.Tasks;
+using Microsoft.Build.Framework;
+using Mono.Cecil;
+using MonoDroid.Tuner;
+
+namespace Xamarin.Android.Tasks;
+
+/// <summary>
+/// Runs <see cref="FixLegacyResourceDesignerStep"/> on assemblies that are about to be
+/// trimmed by ILLink. This rewrites library assemblies so their resource field accesses
+/// (ldsfld) become calls to the designer assembly's property getters.
+///
+/// Running this *before* ILLink means the trimmer sees the rewritten IL and can freely
+/// trim unused designer types/fields. This avoids the need to root the entire designer
+/// assembly during trimming (which causes an APK size regression).
+/// </summary>
+public class PreTrimmingFixLegacyDesigner : AndroidTask
+{
+	public override string TaskPrefix => "PTD";
+
+	[Required]
+	public ITaskItem [] Assemblies { get; set; } = [];
+
+	[Required]
+	public string TargetName { get; set; } = "";
+
+	public bool Deterministic { get; set; }
+
+	public override bool RunTask ()
+	{
+		using var resolver = new DirectoryAssemblyResolver (
+			this.CreateTaskLogger (), loadDebugSymbols: true);
+
+		foreach (var assembly in Assemblies) {
+			var dir = Path.GetFullPath (Path.GetDirectoryName (assembly.ItemSpec) ?? "");
+			if (!resolver.SearchDirectories.Contains (dir)) {
+				resolver.SearchDirectories.Add (dir);
+			}
+		}
+
+		var linkContext = new MSBuildLinkContext (resolver, Log);
+		var fixLegacyStep = new FixLegacyResourceDesignerStep ();
+		fixLegacyStep.Initialize (linkContext);
+
+		foreach (var item in Assemblies) {
+			// Match the filtering in FixLegacyResourceDesignerStep.ProcessAssembly:
+			// skip the main assembly and framework/BCL assemblies.
+			if (Path.GetFileNameWithoutExtension (item.ItemSpec) == TargetName) {
+				continue;
+			}
+			if (MonoAndroidHelper.IsFrameworkAssembly (item)) {
+				continue;
+			}
+
+			var assembly = resolver.GetAssembly (item.ItemSpec);
+			if (fixLegacyStep.ProcessAssemblyDesigner (assembly)) {
+				Log.LogDebugMessage ($"  Writing modified assembly: {item.ItemSpec}");
+				assembly.Write (item.ItemSpec, new WriterParameters {
+					WriteSymbols = assembly.MainModule.HasSymbols,
+					DeterministicMvid = Deterministic,
+				});
+			}
+		}
+
+		return !Log.HasLoggedErrors;
+	}
+}

src/Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.csproj

@@ -45,7 +45,7 @@
     <Compile Include="..\..\bin\Build$(Configuration)\XABuildConfig.cs" />
 
     <!-- Include only the linker sources required for the build tasks (LinkAssembliesNoShrink and PostTrimmingPipeline) -->
-    <!-- These include: AddKeepAlivesStep, AddKeepAlivesHelper, CheckForObsoletePreserveAttributeStep, StripEmbeddedLibrariesStep, PostTrimmingAddKeepAlivesStep, FixAbstractMethodsStep, FixLegacyResourceDesignerStep -->
+    <!-- These include: AddKeepAlivesStep, AddKeepAlivesHelper, CheckForObsoletePreserveAttributeStep, StripEmbeddedLibrariesStep, PostTrimmingAddKeepAlivesStep, FixAbstractMethodsStep, FixLegacyResourceDesignerStep, LinkDesignerBase -->
     <Compile Remove="Linker\**" />
     <Compile Include="Linker\MonoDroid.Tuner\FindTypeMapObjectsStep.cs" />
     <Compile Include="Linker\MonoDroid.Tuner\FindJavaObjectsStep.cs" />

tests/MSBuildDeviceIntegration/Tests/InstallAndRunTests.cs

@@ -1420,10 +1420,9 @@ private void OnPaintSurface(object sender, SKPaintSurfaceEventArgs e)
 			using (var b = CreateApkBuilder (Path.Combine ("temp", TestName, app.ProjectName))) {
 				b.BuildLogFile = "build1.log";
 				b.ThrowOnBuildFailure = false;
-				// TODO: fix for NativeAOT
-				if (!addResource && runtime != AndroidRuntime.NativeAOT) {
+				if (!addResource) {
 					Assert.IsFalse (b.Build (app, doNotCleanupOnUpdate: true), $"Build of {app.ProjectName} should have failed.");
-					Assert.IsTrue (b.LastBuildOutput.ContainsText (isRelease ? "IL8000" : "XA8000"));
+					Assert.IsTrue (b.LastBuildOutput.ContainsText ("XA8000"));
 					Assert.IsTrue (b.LastBuildOutput.ContainsText ("@styleable/SKCanvasView"), "Expected '@styleable/SKCanvasView' in build output.");
 					Assert.IsTrue (b.LastBuildOutput.ContainsText ("@styleable/SKCanvasView_ignorePixelScaling"), "Expected '@styleable/SKCanvasView_ignorePixelScaling' in build output.");
 					return;