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Merged
jonathanpeppers merged 14 commits into from
Apr 14, 2026
Merged

Move FixLegacyResourceDesignerStep to post-trim pipeline #11059

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70f7f30
[illink] Move FixLegacyResourceDesignerStep to post-trim pipeline
sbomer Mar 30, 2026
77de75d
[targets] Fix NativeAOT designer assembly trimming
sbomer Apr 1, 2026
e9edefd
Merge remote-tracking branch 'origin/main' into fix-resource-designer
sbomer Apr 1, 2026
f0059fd
Fix merge conflict: remove FixAbstractMethodsStep from ILLink csproj
sbomer Apr 2, 2026
64d4ed1
Root designer assembly to prevent ILLink from trimming resource prope…
sbomer Apr 2, 2026
924649e
Use TrimmerRootDescriptor instead of TrimmerRootAssembly for designer…
sbomer Apr 3, 2026
8be3817
Update SkiaSharp test to expect XA8000 instead of IL8000 for release …
sbomer Apr 3, 2026
f12d747
Merge remote-tracking branch 'origin/main' into fix-resource-designer
sbomer Apr 3, 2026
83a8f64
Fix incremental build: use WriteOnlyWhenDifferent for linker descriptor
sbomer Apr 6, 2026
6e870ef
Add TODO to simplify TrimmerRootDescriptor once dotnet/runtime#126518…
sbomer Apr 6, 2026
a92e39f
Fix SkiaSharp NativeAOT test to expect XA8000 build failure
sbomer Apr 7, 2026
4691223
Merge remote-tracking branch 'origin/main' into fix-resource-designer
sbomer Apr 7, 2026
1eec909
Update APK size reference baselines
sbomer Apr 7, 2026
196e393
Update PostTrimmingPipeline summary to mention FixLegacyResourceDesig…
sbomer Apr 13, 2026
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2 changes: 0 additions & 2 deletions src/Microsoft.Android.Sdk.ILLink/Microsoft.Android.Sdk.ILLink.csproj
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Expand Up @@ -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" />
Expand Down
4 changes: 0 additions & 4 deletions src/Xamarin.Android.Build.Tasks/Linker/External/Linker.Steps/BaseStep.cs
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Expand Up @@ -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
}
}
}
19 changes: 1 addition & 18 deletions src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/FixLegacyResourceDesignerStep.cs
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Expand Up @@ -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";
Expand All @@ -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)
Expand Down Expand Up @@ -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
Expand All @@ -81,7 +65,6 @@ public void ProcessAssembly (AssemblyDefinition assembly, Xamarin.Android.Tasks.

context.IsAssemblyModified |= ProcessAssemblyDesigner (assembly);
}
#endif // !ILLINK

internal override bool ProcessAssemblyDesigner (AssemblyDefinition assembly)
{
Expand Down
20 changes: 2 additions & 18 deletions src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/LinkDesignerBase.cs
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Expand Up @@ -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)
Expand Down
25 changes: 25 additions & 0 deletions ...rin.Android.Build.Tasks/MSBuild/Xamarin/Android/Xamarin.Android.Resource.Designer.targets
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Expand Up @@ -226,18 +226,43 @@ 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.

We use a TrimmerRootDescriptor (not TrimmerRootAssembly) to prevent ILLink from
trimming the designer's resource properties. FixLegacyResourceDesignerStep runs
after ILLink and needs all properties present when rewriting library assemblies.
A descriptor (-x) preserves types without making the assembly an entry point,
which avoids pulling netstandard.dll into the output.
See https://github.com/dotnet/runtime/issues/126518

TODO: Once dotnet/runtime#126518 is fixed and flows to dotnet/android,
simplify this to use TrimmerRootAssembly instead of the XML descriptor.
-->
<Target Name="_AddResourceDesignerToPublishFiles"
Condition=" '$(AndroidUseDesignerAssembly)' == 'True' "
AfterTargets="ComputeResolvedFilesToPublishList"
DependsOnTargets="_SetupDesignerProperties">
<PropertyGroup>
<_DesignerLinkerDescriptor>$(IntermediateOutputPath)_Microsoft.Android.Resource.Designer.xml</_DesignerLinkerDescriptor>
</PropertyGroup>
<WriteLinesToFile
File="$(_DesignerLinkerDescriptor)"
Overwrite="true"
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@jonathanpeppers jonathanpeppers Apr 13, 2026

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🤖 ⚠️ Performance — The preserve="all" descriptor prevents ILLink from trimming unused resource properties in the designer assembly. In the old ILLink custom step flow, FixLegacyResourceDesignerStep ran before MarkStep, so ILLink could track which designer properties were actually referenced and trim the rest. With the post-trim approach, all properties must survive ILLink intact.

The BuildReleaseArm64XFormsDotNet.MonoVM.apkdesc shows the designer assembly growing from ~19 KB to ~258 KB (~13× increase). For the simple app it's negligible (+400 bytes), but resource-heavy apps will see a larger impact.

The TODO references dotnet/runtime#126518 for switching to TrimmerRootAssembly. However, the _FixRootAssembly target upgrades all TrimmerRootAssembly entries to RootMode="All", so switching wouldn't reduce the preserved surface — it would just simplify the MSBuild XML. Is the size regression considered acceptable for the architectural benefits of removing the ILLink step, or is there a plan to recover trimming of unused designer properties later?

Rule: Don't remove caches without measurement (Postmortem #57)

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@sbomer sbomer Apr 13, 2026

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This is accurate, and by design per #11059 (comment).

WriteOnlyWhenDifferent="true"
Lines="&lt;linker&gt;&lt;assembly fullname=&quot;$(_DesignerAssemblyName)&quot;&gt;&lt;type fullname=&quot;*&quot; preserve=&quot;all&quot; /&gt;&lt;/assembly&gt;&lt;/linker&gt;"
/>
<ItemGroup>
<ResolvedFileToPublish Include="$(_GenerateResourceDesignerAssemblyOutput)">
<RelativePath>$(_DesignerAssemblyName).dll</RelativePath>
<CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
<PostprocessAssembly>true</PostprocessAssembly>
<IsTrimmable>true</IsTrimmable>
</ResolvedFileToPublish>
<!-- Preserve all designer types/members via descriptor so ILLink keeps resource
properties. Using a descriptor (not TrimmerRootAssembly) avoids making the
assembly an entry point, which would pull netstandard.dll into the output.
See https://github.com/dotnet/runtime/issues/126518 -->
<TrimmerRootDescriptor Include="$(_DesignerLinkerDescriptor)" />
<FileWrites Include="$(_DesignerLinkerDescriptor)" />
</ItemGroup>
</Target>

Expand Down
11 changes: 3 additions & 8 deletions ...id.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.LlvmIr.targets
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Expand Up @@ -167,7 +167,7 @@
<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 $(_ExtraTrimmerArgs)</_ExtraTrimmerArgs>
Expand Down Expand Up @@ -204,12 +204,6 @@
<_TrimmerCustomSteps Include="$(_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)"
Expand Down Expand Up @@ -254,7 +248,8 @@
Assemblies="@(_PostTrimmingAssembly)"
AddKeepAlives="$(AndroidAddKeepAlives)"
AndroidLinkResources="$(AndroidLinkResources)"
Deterministic="$(Deterministic)" />
Deterministic="$(Deterministic)"
UseDesignerAssembly="$(AndroidUseDesignerAssembly)" />
</Target>

<!-- Inject _TypeMapKind into the property cache -->
Expand Down
35 changes: 34 additions & 1 deletion src/Xamarin.Android.Build.Tasks/Tasks/PostTrimmingPipeline.cs
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Expand Up @@ -6,6 +6,7 @@
using Microsoft.Android.Build.Tasks;
using Microsoft.Build.Framework;
using Mono.Cecil;
using Mono.Linker;
Comment thread
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using MonoDroid.Tuner;

namespace Xamarin.Android.Tasks;
Expand All @@ -16,7 +17,7 @@ namespace Xamarin.Android.Tasks;
/// This opens each assembly once (via DirectoryAssemblyResolver with ReadWrite) and
/// runs all registered steps on it, then writes modified assemblies in-place. Currently
/// runs CheckForObsoletePreserveAttributeStep, StripEmbeddedLibrariesStep and
/// (optionally) AddKeepAlivesStep.
/// (optionally) AddKeepAlivesStep and FixLegacyResourceDesignerStep.
///
/// Runs in the inner build after ILLink but before ReadyToRun/crossgen2 compilation,
/// so that R2R images are generated from the already-modified assemblies.
Expand All @@ -34,6 +35,8 @@ public class PostTrimmingPipeline : AndroidTask

public bool Deterministic { get; set; }

public bool UseDesignerAssembly { get; set; }

public override bool RunTask ()
{
using var resolver = new DirectoryAssemblyResolver (
Expand Down Expand Up @@ -100,6 +103,15 @@ public override bool RunTask ()
},
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(msg) => Log.LogDebugMessage (msg)));
}
if (UseDesignerAssembly) {
// Create an MSBuildLinkContext so FixLegacyResourceDesignerStep can resolve assemblies
// and log messages. The resolver is owned by the outer 'using' block, so we intentionally
// do not dispose this context (LinkContext.Dispose would double-dispose the resolver).
var linkContext = new MSBuildLinkContext (resolver, Log);
var fixLegacyStep = new FixLegacyResourceDesignerStep ();
fixLegacyStep.Initialize (linkContext);
steps.Add (new PostTrimmingFixLegacyResourceDesignerStep (fixLegacyStep));
}
Comment thread
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foreach (var (item, assembly) in loadedAssemblies) {
var context = new StepContext (item, item);
Expand All @@ -118,3 +130,24 @@ public override bool RunTask ()
return !Log.HasLoggedErrors;
}
}

/// <summary>
/// Thin wrapper around <see cref="FixLegacyResourceDesignerStep"/> for the post-trimming pipeline.
/// Calls <see cref="FixLegacyResourceDesignerStep.ProcessAssemblyDesigner"/> directly, matching the
/// behavior of the former ILLink path which processed all assemblies without StepContext flag filtering.
/// Assemblies without a resource designer are skipped internally by ProcessAssemblyDesigner.
/// </summary>
class PostTrimmingFixLegacyResourceDesignerStep : IAssemblyModifierPipelineStep
{
readonly FixLegacyResourceDesignerStep _inner;

public PostTrimmingFixLegacyResourceDesignerStep (FixLegacyResourceDesignerStep inner)
{
_inner = inner;
}

public void ProcessAssembly (AssemblyDefinition assembly, StepContext context)
{
context.IsAssemblyModified |= _inner.ProcessAssemblyDesigner (assembly);
}
}
20 changes: 10 additions & 10 deletions ...s/Tests/Xamarin.ProjectTools/Resources/Base/BuildReleaseArm64SimpleDotNet.CoreCLR.apkdesc
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Expand Up @@ -5,25 +5,25 @@
"Size": 3036
},
"classes.dex": {
"Size": 397520
"Size": 400044
},
"lib/arm64-v8a/libassembly-store.so": {
"Size": 3091928
"Size": 3115312
},
"lib/arm64-v8a/libclrjit.so": {
"Size": 3141224
"Size": 3202072
},
"lib/arm64-v8a/libcoreclr.so": {
"Size": 5736320
"Size": 5766640
},
"lib/arm64-v8a/libmonodroid.so": {
"Size": 1375784
"Size": 1365104
},
"lib/arm64-v8a/libmscordaccore.so": {
"Size": 2442416
"Size": 2493552
},
"lib/arm64-v8a/libmscordbi.so": {
"Size": 1894280
"Size": 1902744
},
"lib/arm64-v8a/libSystem.Globalization.Native.so": {
"Size": 71936
Expand All @@ -32,13 +32,13 @@
"Size": 1281696
},
"lib/arm64-v8a/libSystem.Native.so": {
"Size": 105664
"Size": 107904
},
"lib/arm64-v8a/libSystem.Security.Cryptography.Native.Android.so": {
"Size": 165536
},
"lib/arm64-v8a/libxamarin-app.so": {
"Size": 20128
"Size": 20520
},
"META-INF/BNDLTOOL.RSA": {
"Size": 1221
Expand Down Expand Up @@ -74,5 +74,5 @@
"Size": 1904
}
},
"PackageSize": 9176858
"PackageSize": 9258778
}
14 changes: 7 additions & 7 deletions ...ks/Tests/Xamarin.ProjectTools/Resources/Base/BuildReleaseArm64SimpleDotNet.MonoVM.apkdesc
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Expand Up @@ -8,16 +8,16 @@
"Size": 22388
},
"lib/arm64-v8a/lib__Microsoft.Android.Resource.Designer.dll.so": {
"Size": 18288
"Size": 18696
},
"lib/arm64-v8a/lib_Java.Interop.dll.so": {
"Size": 88040
"Size": 88048
},
"lib/arm64-v8a/lib_Mono.Android.dll.so": {
"Size": 118024
"Size": 117928
},
"lib/arm64-v8a/lib_Mono.Android.Runtime.dll.so": {
"Size": 26544
"Size": 26464
},
"lib/arm64-v8a/lib_System.Console.dll.so": {
"Size": 24432
Expand All @@ -35,7 +35,7 @@
"Size": 21632
},
"lib/arm64-v8a/lib_UnnamedProject.dll.so": {
"Size": 20032
"Size": 20144
},
"lib/arm64-v8a/libarc.bin.so": {
"Size": 19176
Expand All @@ -44,7 +44,7 @@
"Size": 36616
},
"lib/arm64-v8a/libmonodroid.so": {
"Size": 1386512
"Size": 1386072
},
"lib/arm64-v8a/libmonosgen-2.0.so": {
"Size": 3124368
Expand All @@ -62,7 +62,7 @@
"Size": 165536
},
"lib/arm64-v8a/libxamarin-app.so": {
"Size": 19840
"Size": 19792
},
"META-INF/BNDLTOOL.RSA": {
"Size": 1221
Expand Down
8 changes: 4 additions & 4 deletions ...Tests/Xamarin.ProjectTools/Resources/Base/BuildReleaseArm64SimpleDotNet.NativeAOT.apkdesc
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Expand Up @@ -5,13 +5,13 @@
"Size": 3124
},
"classes.dex": {
"Size": 24224
"Size": 25400
},
"lib/arm64-v8a/libUnnamedProject.so": {
"Size": 4968680
"Size": 5056848
},
"META-INF/BNDLTOOL.RSA": {
"Size": 1211
"Size": 1221
},
"META-INF/BNDLTOOL.SF": {
"Size": 1211
Expand Down Expand Up @@ -44,5 +44,5 @@
"Size": 1904
}
},
"PackageSize": 2094050
"PackageSize": 2122722
}
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