Adding generation of substitution files for trimming out resources when feature switch is present

eng/ILLink.Substitutions.Resources.template

@@ -0,0 +1,10 @@
+<linker>
+  <!-- System.Resources.UseSystemResourceKeys removes resource strings and instead uses the resource key as the exception message -->
+  <assembly fullname="{AssemblyName}" feature="System.Resources.UseSystemResourceKeys" featurevalue="true">
+    <!-- System.Resources.UseSystemResourceKeys removes resource strings and instead uses the resource key as the exception message -->
+    <resource name="{StringResourcesName}.resources" action="remove" />
+    <type fullname="System.SR">
+      <method signature="System.Boolean UsingResourceKeys()" body="stub" value="true" />
+    </type>
+  </assembly>
+</linker>

eng/illink.targets

@@ -40,7 +40,6 @@
     <ILLinkTrimXmlLibraryBuild Condition="'$(ILLinkTrimXmlLibraryBuild)' == '' and Exists('$(MSBuildProjectDirectory)/ILLinkTrim_LibraryBuild.xml')">$(MSBuildProjectDirectory)/ILLinkTrim_LibraryBuild.xml</ILLinkTrimXmlLibraryBuild>
     <ILLinkDescriptorsXmlIntermediatePath>$(IntermediateOutputPath)ILLink.Descriptors.xml</ILLinkDescriptorsXmlIntermediatePath>
 
-    <ILLinkSubstitutionsXml Condition="'$(ILLinkSubstitutionsXml)' == '' and Exists('$(MSBuildProjectDirectory)/ILLink.Substitutions.xml')">$(MSBuildProjectDirectory)/ILLink.Substitutions.xml</ILLinkSubstitutionsXml>
     <ILLinkSubstitutionsXmlIntermediatePath>$(IntermediateOutputPath)ILLink.Substitutions.xml</ILLinkSubstitutionsXmlIntermediatePath>
 
     <!-- if building a PDB, tell illink to rewrite the symbols file -->
@@ -49,7 +48,6 @@
 
   <ItemGroup>
     <None Include="$(ILLinkTrimXmlLibraryBuild)" Condition="'$(ILLinkTrimXmlLibraryBuild)' != ''" />
-    <None Include="$(ILLinkSubstitutionsXml)" Condition="'$(ILLinkSubstitutionsXml)' != ''" />
     <None Include="@(ILLinkSubstitutionsXmls)" />
   </ItemGroup>
 
@@ -105,8 +103,41 @@
     </ItemGroup>
   </Target>
 
+  <PropertyGroup>
+    <ILLinkResourcesSubstitutionIntermediatePath>$(IntermediateOutputPath)ILLink.Resources.Substitutions.xml</ILLinkResourcesSubstitutionIntermediatePath>
+    <GenerateResourcesSubstitutions Condition="'$(GenerateResourcesSubstitutions)' == '' and '$(StringResourcesPath)' != ''">true</GenerateResourcesSubstitutions>
+  </PropertyGroup>
+
+  <ItemGroup Condition="'$(GenerateResourcesSubstitutions)' == 'true'">
+    <ILLinkSubstitutionsXmls Include="$(ILLinkResourcesSubstitutionIntermediatePath)" />
+  </ItemGroup>
+
+  <!-- If a library uses string resources, the following target generates a substitution xml that will be embedded on the
+  library so that if a consumer wants to run the linker they can specify a feature switch to strip out all resources
+  from the assembly. -->
+  <Target Name="GenerateResourcesSubstitutionFile"  
+          Condition="'$(GenerateResourcesSubstitutions)' == 'true'"
+          Inputs="$(MSBuildProjectFullPath)"
+          Outputs="$(ILLinkResourcesSubstitutionIntermediatePath)">
+
+    <PropertyGroup>
+      <ILLinkResourcesSubstitutionTemplate>$(MSBuildThisFileDirectory)ILLink.Substitutions.Resources.template</ILLinkResourcesSubstitutionTemplate>
+    </PropertyGroup>
+
+    <WriteLinesToFile File="$(ILLinkResourcesSubstitutionIntermediatePath)"
+                      Lines="$([System.IO.File]::ReadAllText('$(ILLinkResourcesSubstitutionTemplate)')
+                                                 .Replace('{AssemblyName}', '$(AssemblyName)')
+                                                 .Replace('{StringResourcesName}', '$(StringResourcesName)'))"
+                      Overwrite="true" />
+
+    <ItemGroup>
+      <FileWrites Include="$(ILLinkResourcesSubstitutionIntermediatePath)" />
+    </ItemGroup>
+  </Target>
+
   <Target Name="_CombineILLinkSubstitutionsXmls"
-          Condition="'$(ILLinkSubstitutionsXml)' == '' and '@(ILLinkSubstitutionsXmls)' != ''"
+          DependsOnTargets="GenerateResourcesSubstitutionFile"
+          Condition="'@(ILLinkSubstitutionsXmls)' != ''"
           Inputs="@(ILLinkSubstitutionsXmls)"
           Outputs="$(ILLinkSubstitutionsXmlIntermediatePath)">
     <PropertyGroup>

eng/testing/linker/project.csproj.template

@@ -6,6 +6,7 @@
     <RuntimeIdentifier>{RuntimeIdentifier}</RuntimeIdentifier>
     <RuntimePackDir>{RuntimePackDir}</RuntimePackDir>
     <TargetingPackDir>{TargetingPackDir}</TargetingPackDir>
+    <_ExtraTrimmerArgs>{ExtraTrimmerArgs} $(_ExtraTrimmerArgs)</_ExtraTrimmerArgs>
   </PropertyGroup>
 
   <!-- Logic to override the default IlLink tasks that come from the SDK and use the one

eng/testing/linker/trimmingTests.targets

@@ -68,7 +68,8 @@
                                                  .Replace('{RuntimePackDir}', '%(TestConsoleApps.RuntimePackDirectory)')
                                                  .Replace('{TargetingPackDir}','$(MicrosoftNetCoreAppRefPackDir)')
                                                  .Replace('{RuntimeIdentifier}','%(TestConsoleApps.TestRuntimeIdentifier)')
-                                                 .Replace('{MicrosoftNETILLinkTasksVersion}', '$(MicrosoftNETILLinkTasksVersion)'))"
+                                                 .Replace('{MicrosoftNETILLinkTasksVersion}', '$(MicrosoftNETILLinkTasksVersion)')
+                                                 .Replace('{ExtraTrimmerArgs}', '%(TestConsoleApps.ExtraTrimmerArgs)'))"
                       Overwrite="true" />
     <Copy SourceFiles="$(_projectSourceFile)"
           DestinationFolder="$(_projectDir)" />

src/libraries/Common/src/System/SR.cs

@@ -10,14 +10,20 @@ namespace System
 {
     internal partial class SR
     {
+#if (!NETSTANDARD1_0 && !NETSTANDARD1_1 && !NET45) // AppContext is not supported on < NetStandard1.3 or < .NET Framework 4.5
+        private static readonly bool s_usingResourceKeys = AppContext.TryGetSwitch("System.Resources.UseSystemResourceKeys", out bool usingResourceKeys) ? usingResourceKeys : false;
+#endif
+
         // This method is used to decide if we need to append the exception message parameters to the message when calling SR.Format.
-        // by default it returns false.
+        // by default it returns the value of System.Resources.UseSystemResourceKeys AppContext switch or false if not specified.
         // Native code generators can replace the value this returns based on user input at the time of native code generation.
-        // Marked as NoInlining because if this is used in an AoT compiled app that is not compiled into a single file, the user
-        // could compile each module with a different setting for this. We want to make sure there's a consistent behavior
-        // that doesn't depend on which native module this method got inlined into.
-        [MethodImpl(MethodImplOptions.NoInlining)]
-        private static bool UsingResourceKeys() => false;
+        // The Linker is also capable of replacing the value of this method when the application is being trimmed.
+        private static bool UsingResourceKeys() =>
+#if (!NETSTANDARD1_0 && !NETSTANDARD1_1 && !NET45) // AppContext is not supported on < NetStandard1.3 or < .NET Framework 4.5
+            s_usingResourceKeys;
+#else
+            false;
+#endif
 
         internal static string GetResourceString(string resourceKey, string? defaultString = null)
         {

src/libraries/System.Collections.Immutable/src/System.Collections.Immutable.csproj

@@ -105,6 +105,9 @@
     <Reference Include="System.Runtime.Extensions" />
     <Reference Include="System.Threading" />
   </ItemGroup>
+  <ItemGroup Condition="'$(TargetFramework)' == 'netstandard1.3'">
+    <Reference Include="System.AppContext" />
+  </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard1.3' or '$(TargetFramework)' == '$(NetCoreAppCurrent)'">
     <Reference Include="System.Runtime.InteropServices" />
   </ItemGroup>

src/libraries/System.Diagnostics.DiagnosticSource/src/System.Diagnostics.DiagnosticSource.csproj

@@ -90,6 +90,9 @@
     <Reference Include="System.Threading" />
     <Reference Include="System.Resources.ResourceManager" />
   </ItemGroup>
+  <ItemGroup Condition="'$(TargetFramework)' == 'netstandard1.3'">
+    <Reference Include="System.AppContext" />
+  </ItemGroup>
   <ItemGroup Condition="$(TargetFramework.StartsWith('net4'))">
     <Compile Include="AssemblyInfo.netfx.cs" />
     <Compile Include="System\Diagnostics\Activity.DateTime.netfx.cs" />

src/libraries/System.IO.Packaging/src/System.IO.Packaging.csproj

@@ -11,6 +11,7 @@
     <IsPartialFacadeAssembly Condition="$(TargetFramework.StartsWith('net4'))">true</IsPartialFacadeAssembly>
   </PropertyGroup>
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard1.3'">
+    <Reference Include="System.AppContext" />
     <Reference Include="System.Collections" />
     <Reference Include="System.Diagnostics.Debug" />
     <Reference Include="System.Globalization" />

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -2,6 +2,8 @@
   <PropertyGroup>
     <HasSharedItems>true</HasSharedItems>
     <SharedGUID>c5ed3c1d-b572-46f1-8f96-522a85ce1179</SharedGUID>
+    <StringResourcesName Condition="'$(StringResourcesName)' == ''">System.Private.CoreLib.Strings</StringResourcesName>
+    <GenerateResourcesSubstitutions>true</GenerateResourcesSubstitutions>
   </PropertyGroup>
   <PropertyGroup Label="Configuration">
     <Import_RootNamespace />

src/libraries/System.Private.CoreLib/src/System/SR.cs

@@ -21,7 +21,7 @@ internal static partial class SR
         // Needed for debugger integration
         internal static string GetResourceString(string resourceKey)
         {
-            return GetResourceString(resourceKey, string.Empty);
+            return GetResourceString(resourceKey, null);
         }
 
         private static string InternalGetResourceString(string key)

src/libraries/System.Runtime/tests/System.Runtime.Tests.csproj

@@ -135,6 +135,7 @@
     <Compile Include="System\TypeLoadExceptionTests.cs" />
     <Compile Include="System\TypeUnloadedExceptionTests.cs" />
     <Compile Include="System\TupleTests.cs" />
+    <Compile Include="System\UseResourceKeysTest.cs" />
     <Compile Include="System\UInt16Tests.cs" />
     <Compile Include="System\UInt32Tests.cs" />
     <Compile Include="System\UInt64Tests.cs" />

src/libraries/System.Runtime/tests/System/UseResourceKeysTest.cs

@@ -0,0 +1,50 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.DotNet.RemoteExecutor;
+using Xunit;
+
+namespace System.Runtime.Tests
+{
+    public class UseResourceKeysTest
+    {
+        [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        public void ReturnsResourceKeyWhenFeatureSwitchIsEnabled()
+        {
+            RemoteInvokeOptions options = new RemoteInvokeOptions();
+            options.RuntimeConfigurationOptions.Add("System.Resources.UseSystemResourceKeys", true);
+
+            RemoteExecutor.Invoke(() =>
+            {
+                try
+                {
+                    throw new AggregateException();
+                }
+                catch (Exception e)
+                {
+                    Assert.Equal("AggregateException_ctor_DefaultMessage", e.Message);
+                }
+            }, options).Dispose();
+        }
+
+        [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        public void ReturnsResourceWhenFeatureSwitchIsDisabled()
+        {
+            RemoteInvokeOptions options = new RemoteInvokeOptions();
+            options.RuntimeConfigurationOptions.Add("System.Resources.UseSystemResourceKeys", false);
+
+            RemoteExecutor.Invoke(() =>
+            {
+                try
+                {
+                    throw new ArgumentException();
+                }
+                catch (Exception e)
+                {
+                    Assert.NotEqual("AggregateException_ctor_DefaultMessage", e.Message);
+                }
+            }, options).Dispose();
+        }
+    }
+}

src/libraries/System.Runtime/tests/TrimmingTests/System.Runtime.TrimmingTests.proj

@@ -15,6 +15,11 @@
       linker repo here: https://github.com/mono/linker/issues/1285 -->
       <AdditionalArgs>/p:DebugType=Embedded</AdditionalArgs>
     </TestConsoleAppSourceFiles>
+    <TestConsoleAppSourceFiles Include="VerifyResourcesGetTrimmedTest.cs">
+      <!-- Setting the Trimming feature switch to make sure that the Resources get trimmed by the linker
+      as this test will ensure exceptions are using Resource keys -->
+      <ExtraTrimmerArgs>--feature System.Resources.UseSystemResourceKeys true</ExtraTrimmerArgs>
+    </TestConsoleAppSourceFiles>
   </ItemGroup>
 
   <Import Project="$([MSBuild]::GetPathOfFileAbove(Directory.Build.targets))" />

src/libraries/System.Runtime/tests/TrimmingTests/VerifyResourcesGetTrimmedTest.cs

@@ -0,0 +1,27 @@
+using System;
+
+class Program
+{
+    static int Main(string[] args)
+    {
+        try
+        {
+            throw new AggregateException();
+        }
+        catch (Exception e)
+        {
+            // When the Trimmer recieves the feature switch to use resource keys then exception
+            // messages shouldn't return the exception message resource, but instead the resource
+            // key. This test is passing in the feature switch so we make sure that the resources
+            // got trimmed correctly.
+            if (e.Message == "AggregateException_ctor_DefaultMessage")
+            {
+                return 100;
+            }
+            else
+            {
+                return -1;
+            }
+        }
+    }
+}

src/libraries/System.Threading.Channels/src/System.Threading.Channels.csproj

@@ -31,6 +31,7 @@
              Link="Common\System\Collections\Concurrent\SingleProducerConsumerQueue.cs" />
   </ItemGroup>
   <ItemGroup>
+    <Reference Include="System.AppContext" Condition="'$(TargetFramework)' == 'netstandard1.3'" />
     <Reference Include="System.Collections" />
     <Reference Include="System.Collections.Concurrent" />
     <Reference Include="System.Diagnostics.Debug" />