Verify compiler target framework

Author: jjonescz

test/Microsoft.NET.Build.Tests/RoslynBuildTaskTests.cs

@@ -3,6 +3,7 @@
 
 using System.Reflection;
 using System.Runtime.CompilerServices;
+using System.Runtime.Versioning;
 using Basic.CompilerLog.Util;
 using Microsoft.Build.Logging.StructuredLogger;
 using Microsoft.CodeAnalysis;
@@ -12,6 +13,9 @@ namespace Microsoft.NET.Build.Tests;
 
 public sealed class RoslynBuildTaskTests(ITestOutputHelper log) : SdkTest(log)
 {
+    private const string CoreTargetFrameworkName = ".NETCoreApp";
+    private const string FxTargetFrameworkName = ".NETFramework";
+
     private static string CompilerFileNameWithoutExtension(Language language) => language switch
     {
         Language.CSharp => "csc",
@@ -28,7 +32,7 @@ public void FullMSBuild_SdkStyle(bool useSharedCompilation, Language language)
     {
         var testAsset = CreateProject(useSharedCompilation, language);
         var buildCommand = BuildAndRunUsingMSBuild(testAsset);
-        VerifyCompiler(buildCommand, AppHostCompilerFileName(language), useSharedCompilation);
+        VerifyCompiler(buildCommand, AppHostCompilerFileName(language), CoreTargetFrameworkName, useSharedCompilation);
     }
 
     [FullMSBuildOnlyTheory, CombinatorialData]
@@ -39,7 +43,7 @@ public void FullMSBuild_SdkStyle_OptOut(bool useSharedCompilation, Language lang
             doc.Root!.Element("PropertyGroup")!.Add(new XElement("RoslynCompilerType", "Framework"));
         });
         var buildCommand = BuildAndRunUsingMSBuild(testAsset);
-        VerifyCompiler(buildCommand, AppHostCompilerFileName(language), useSharedCompilation);
+        VerifyCompiler(buildCommand, AppHostCompilerFileName(language), FxTargetFrameworkName, useSharedCompilation);
     }
 
     [FullMSBuildOnlyTheory, CombinatorialData]
@@ -51,7 +55,7 @@ public void FullMSBuild_NonSdkStyle(bool useSharedCompilation, Language language
             project.TargetFrameworkVersion = "v4.7.2";
         });
         var buildCommand = BuildAndRunUsingMSBuild(testAsset);
-        VerifyCompiler(buildCommand, AppHostCompilerFileName(language), useSharedCompilation);
+        VerifyCompiler(buildCommand, AppHostCompilerFileName(language), FxTargetFrameworkName, useSharedCompilation);
     }
 
     [FullMSBuildOnlyTheory, CombinatorialData]
@@ -60,15 +64,18 @@ public void FullMSBuild_SdkStyle_ToolsetPackage(bool useSharedCompilation, Langu
         var testAsset = CreateProject(useSharedCompilation, language, AddCompilersToolsetPackage);
         ReadOnlySpan<string> args = useFrameworkCompiler ? ["-p:RoslynCompilerType=Framework"] : [];
         var buildCommand = BuildAndRunUsingMSBuild(testAsset, args);
-        VerifyCompiler(buildCommand, DotNetExecCompilerFileName(language), useSharedCompilation, toolsetPackage: true);
+        VerifyCompiler(buildCommand,
+            DotNetExecCompilerFileName(language),
+            useFrameworkCompiler ? FxTargetFrameworkName : CoreTargetFrameworkName,
+            useSharedCompilation, toolsetPackage: true);
     }
 
     [Theory, CombinatorialData]
     public void DotNet(bool useSharedCompilation, Language language)
     {
         var testAsset = CreateProject(useSharedCompilation, language);
         var buildCommand = BuildAndRunUsingDotNet(testAsset);
-        VerifyCompiler(buildCommand, AppHostCompilerFileName(language), useSharedCompilation);
+        VerifyCompiler(buildCommand, AppHostCompilerFileName(language), CoreTargetFrameworkName, useSharedCompilation);
     }
 
     //  https://github.com/dotnet/sdk/issues/49665
@@ -77,7 +84,7 @@ public void DotNet_ToolsetPackage(bool useSharedCompilation, Language language)
     {
         var testAsset = CreateProject(useSharedCompilation, language, AddCompilersToolsetPackage);
         var buildCommand = BuildAndRunUsingDotNet(testAsset);
-        VerifyCompiler(buildCommand, DotNetExecCompilerFileName(language), useSharedCompilation, toolsetPackage: true);
+        VerifyCompiler(buildCommand, DotNetExecCompilerFileName(language), CoreTargetFrameworkName, useSharedCompilation, toolsetPackage: true);
     }
 
     private TestAsset CreateProject(bool useSharedCompilation, Language language, Action<TestProject>? configure = null, [CallerMemberName] string callingMethod = "")
@@ -159,7 +166,7 @@ private void Run(FileInfo outputFile)
             .And.HaveStdOut("42");
     }
 
-    private static void VerifyCompiler(TestCommand buildCommand, string compilerFileName, bool usedCompilerServer, bool toolsetPackage = false)
+    private static void VerifyCompiler(TestCommand buildCommand, string compilerFileName, string targetFrameworkName, bool usedCompilerServer, bool toolsetPackage = false)
     {
         var binaryLogPath = Path.Join(buildCommand.WorkingDirectory, "msbuild.binlog");
         using (var reader = BinaryLogReader.Create(binaryLogPath))
@@ -176,6 +183,8 @@ private static void VerifyCompiler(TestCommand buildCommand, string compilerFile
             {
                 call.CompilerFilePath.Should().NotContain(toolsetPackageName);
             }
+
+            GetTargetFramework(call.CompilerFilePath).Should().StartWith($"{targetFrameworkName},");
         }
 
         // Verify compiler server message.
@@ -186,6 +195,19 @@ private static void VerifyCompiler(TestCommand buildCommand, string compilerFile
             : "CompilerServer: tool - using command line tool by design");
     }
 
+    private static string? GetTargetFramework(string dllPath)
+    {
+        var tpa = ((string?)AppContext.GetData("TRUSTED_PLATFORM_ASSEMBLIES"))?.Split(Path.PathSeparator) ?? [];
+        var resolver = new PathAssemblyResolver([.. tpa, dllPath]);
+        using var mlc = new MetadataLoadContext(resolver);
+        var asm = mlc.LoadFromAssemblyPath(dllPath);
+        var attrFullName = typeof(TargetFrameworkAttribute).FullName;
+        return asm.GetCustomAttributesData()
+            .Where(a => a.AttributeType.FullName == attrFullName)
+            .Select(a => a.ConstructorArguments[0].Value)
+            .FirstOrDefault() as string;
+    }
+
     public enum Language
     {
         CSharp,