Allow using latest illink analyzer on netstandard projects

src/Assets/TestProjects/TrimmableNetstandardLibrary/RequiresUnreferencedCodeAttribute.cs

@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Diagnostics.CodeAnalysis
+{
+    /// <summary>
+    /// Indicates that the specified method requires dynamic access to code that is not referenced
+    /// statically, for example through <see cref="Reflection"/>.
+    /// </summary>
+    /// <remarks>
+    /// This allows tools to understand which methods are unsafe to call when removing unreferenced
+    /// code from an application.
+    /// </remarks>
+    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Class, Inherited = false)]
+    internal sealed class RequiresUnreferencedCodeAttribute : Attribute
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RequiresUnreferencedCodeAttribute"/> class
+        /// with the specified message.
+        /// </summary>
+        /// <param name="message">
+        /// A message that contains information about the usage of unreferenced code.
+        /// </param>
+        public RequiresUnreferencedCodeAttribute(string message)
+        {
+            Message = message;
+        }
+
+        /// <summary>
+        /// Gets a message that contains information about the usage of unreferenced code.
+        /// </summary>
+        public string Message { get; }
+
+        /// <summary>
+        /// Gets or sets an optional URL that contains more information about the method,
+        /// why it requires unreferenced code, and what options a consumer has to deal with it.
+        /// </summary>
+        public string? Url { get; set; }
+    }
+}

src/Assets/TestProjects/TrimmableNetstandardLibrary/TrimmableNetstandardLibrary.cs

@@ -0,0 +1,15 @@
+using System.Diagnostics.CodeAnalysis;
+
+class TrimmableNetStandardLibrary
+{
+    public static void EntryPoint()
+    {
+        RequiresUnreferencedCode();
+    }
+
+
+    [RequiresUnreferencedCode("Requires unreferenced code")]
+    static void RequiresUnreferencedCode()
+    {
+    }    
+}

src/Assets/TestProjects/TrimmableNetstandardLibrary/TrimmableNetstandardLibrary.csproj

@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), testAsset.props))\testAsset.props" />
+
+  <PropertyGroup>
+    <!-- Test infra replaces this with the value of CurrentTargetFramework so we can compare against it below. -->
+    <CurrentTargetFramework>$(CurrentTargetFramework)</CurrentTargetFramework>
+    <TargetFramework>netstandard2.0</TargetFramework>
+    <IsTrimmable>true</IsTrimmable>
+    <LangVersion>latest</LangVersion>
+    <Nullable>enable</Nullable>
+    <AnalysisLevel>latest</AnalysisLevel>
+  </PropertyGroup>
+
+  <Target Name="_AddKnownILLinkPack" BeforeTargets="ProcessFrameworkReferences">
+    <ItemGroup>
+      <KnownILLinkPack Include="@(KnownILLinkPack)"
+                       Condition="'%(TargetFramework)' == '$(CurrentTargetFramework)'"
+                       TargetFramework="$(TargetFramework)" />
+    </ItemGroup>
+  </Target>
+
+</Project>

src/Tasks/Microsoft.NET.Build.Tasks/ProcessFrameworkReferences.cs

@@ -1,4 +1,4 @@
-// Licensed to the .NET Foundation under one or more agreements.
+// Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
@@ -15,6 +15,7 @@
 using Microsoft.NET.Sdk.WorkloadManifestReader;
 using Newtonsoft.Json;
 using NuGet.Frameworks;
+using NuGet.Versioning;
 
 namespace Microsoft.NET.Build.Tasks
 {
@@ -729,8 +730,11 @@ private ToolPackSupport AddToolPack(
             }
 
             // Before net8.0, ILLink analyzers shipped in a separate package.
-            // Add the analyzer package with version taken from KnownILLinkPack.
-            if (normalizedTargetFrameworkVersion < new Version(8, 0) && toolPackType is ToolPackType.ILLink)
+            // Add the analyzer package with version taken from KnownILLinkPack if the version is less than 8.0.0.
+            // The version comparison doesn't consider prerelease labels, so 8.0.0-foo will be considered equal to 8.0.0 and
+            // will not get the extra analyzer package reference.
+            if (toolPackType is ToolPackType.ILLink &&
+                new VersionComparer(VersionComparison.Version).Compare(NuGetVersion.Parse(packVersion), new NuGetVersion(8, 0, 0)) < 0)
             {
                 var analyzerPackage = new TaskItem("Microsoft.NET.ILLink.Analyzers");
                 analyzerPackage.SetMetadata(MetadataKeys.Version, packVersion);

src/Tests/Microsoft.NET.Publish.Tests/GivenThatWeWantToRunILLink.cs

@@ -161,6 +161,26 @@ public void ILLink_fails_when_no_matching_pack_is_found(string targetFramework)
                 .And.HaveStdOutContaining("error NETSDK1195");
         }
 
+        [RequiresMSBuildVersionTheory("17.0.0.32901")]
+        // TODO: enable netstandard2.0 once ProcessFrameworkReferences is fixed to run
+        // when tool packs are referenced. See https://github.com/dotnet/sdk/pull/33062.
+        // Currently netstandard2.0 skips ProcessFrameworkReference because FrameworkReference
+        // is empty.
+        // [InlineData("netstandard2.0")]
+        [InlineData("netstandard2.1")]
+        public void ILLink_can_use_latest_with_unsupported_target_framework(string targetFramework)
+        {
+            var projectName = "TrimmableNetstandardLibrary";
+            var testAsset = _testAssetsManager.CopyTestAsset(projectName)
+                .WithSource()
+                .WithTargetFramework(targetFramework);
+
+            var buildCommand = new BuildCommand(testAsset);
+            buildCommand.Execute("/p:IsTrimmable=true")
+                .Should().Pass()
+                .And.HaveStdOutContaining("warning IL2026");
+        }
+
         [RequiresMSBuildVersionTheory("17.0.0.32901")]
         [MemberData(nameof(SupportedTfms), MemberType = typeof(PublishTestUtils))]
         public void PrepareForILLink_can_set_IsTrimmable(string targetFramework)

src/Tests/Microsoft.NET.TestFramework/TestAsset.cs

@@ -100,7 +100,13 @@ public TestAsset WithSource()
                 File.Copy(srcFile, destFile, true);
             }
 
-            string[][] Properties = { new string[] { "TargetFramework", "$(CurrentTargetFramework)", ToolsetInfo.CurrentTargetFramework }, new string[] { "RuntimeIdentifier", "$(LatestWinRuntimeIdentifier)", ToolsetInfo.LatestWinRuntimeIdentifier }, new string[] { "RuntimeIdentifier", "$(LatestLinuxRuntimeIdentifier)", ToolsetInfo.LatestLinuxRuntimeIdentifier }, new string[] { "RuntimeIdentifier", "$(LatestMacRuntimeIdentifier)", ToolsetInfo.LatestMacRuntimeIdentifier }, new string[] { "RuntimeIdentifier", "$(LatestRuntimeIdentifiers)", ToolsetInfo.LatestRuntimeIdentifiers } };
+            string[][] Properties = {
+                new string[] { "TargetFramework", "$(CurrentTargetFramework)", ToolsetInfo.CurrentTargetFramework },
+                new string[] { "CurrentTargetFramework", "$(CurrentTargetFramework)", ToolsetInfo.CurrentTargetFramework },
+                new string[] { "RuntimeIdentifier", "$(LatestWinRuntimeIdentifier)", ToolsetInfo.LatestWinRuntimeIdentifier },
+                new string[] { "RuntimeIdentifier", "$(LatestLinuxRuntimeIdentifier)", ToolsetInfo.LatestLinuxRuntimeIdentifier },
+                new string[] { "RuntimeIdentifier", "$(LatestMacRuntimeIdentifier)", ToolsetInfo.LatestMacRuntimeIdentifier },
+                new string[] { "RuntimeIdentifier", "$(LatestRuntimeIdentifiers)", ToolsetInfo.LatestRuntimeIdentifiers } };
 
             foreach (string[] property in Properties)
             {