Don't fall back to .NET Standard package pruning for .NET Framework (#51288)

dsplaisted · web-flow · commit b0f6af0ddba1 · 2025-10-16T13:42:23.000-04:00
diff --git a/src/Tasks/Microsoft.NET.Build.Tasks/GetPackagesToPrune.cs b/src/Tasks/Microsoft.NET.Build.Tasks/GetPackagesToPrune.cs
@@ -235,12 +235,6 @@ static Dictionary<string, NuGetVersion> LoadPackagesToPruneFromFrameworkPackages
         {
             var nugetFramework = new NuGetFramework(targetFrameworkIdentifier, Version.Parse(targetFrameworkVersion));
 
-            //  FrameworkPackages just has data for .NET Framework 4.6.1, so turn on fallback for anything greater than that so it will resolve to the .NET Framework 4.6.1 data
-            if (!acceptNearestMatch && nugetFramework.IsDesktop() && nugetFramework.Version > new Version(4,6,1))
-            {
-                acceptNearestMatch = true;
-            }
-
             var frameworkPackages = FrameworkPackages.GetFrameworkPackages(nugetFramework, [frameworkReference], acceptNearestMatch)
                 .SelectMany(packages => packages)
                 .ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
diff --git a/test/Microsoft.NET.Build.Tests/GivenThatWeWantToBuildAnAppWithoutTransitiveProjectRefs.cs b/test/Microsoft.NET.Build.Tests/GivenThatWeWantToBuildAnAppWithoutTransitiveProjectRefs.cs
@@ -82,6 +82,7 @@ public void It_cleans_the_project_successfully_with_static_graph_and_isolation()
                 "1.exe",
                 "1.pdb",
                 "1.exe.config",
+                "System.Diagnostics.DiagnosticSource.dll",
             };
 
             foreach (var targetFramework in targetFrameworks)
diff --git a/test/Microsoft.NET.Build.Tests/GivenThatWeWantToResolveConflicts.cs b/test/Microsoft.NET.Build.Tests/GivenThatWeWantToResolveConflicts.cs
@@ -329,8 +329,8 @@ public void PlatformPackagesCanBePruned(bool prunePackages)
         [InlineData("netstandard1.1", false)]
         [InlineData("netstandard1.0", false)]
         [InlineData("net451", false)]
-        [InlineData("net462")]
-        [InlineData("net481")]
+        [InlineData("net462", false)]
+        [InlineData("net481", false)]
         //  These target frameworks shouldn't prune packages unless explicitly enabled
         [InlineData("net9.0", false, "")]
         [InlineData("netstandard2.1", false, "")]
@@ -492,6 +492,45 @@ public void WithMultitargetedProjects_PruningsDefaultsAreApplies(string framewor
             }
         }
 
+        [Fact]
+        public void WithMultitargetedProject_NETFrameworkIsNotPruned()
+        {
+            var project = new TestProject("MultitargetedPruning")
+            {
+                TargetFrameworks = ToolsetInfo.CurrentTargetFramework + ";net462",
+            };
+            project.PackageReferences.Add(new TestPackageReference("System.ValueTuple", "4.6.1"));
+            project.SourceFiles.Add("Test.cs", @"
+public class Class1
+{
+    public (int, int) GetTuple() => (1, 2);
+}
+");
+            var testAsset = _testAssetsManager.CreateTestProject(project, identifier: "NETFrameworkIsNotPruned");
+            var buildCommand = new BuildCommand(testAsset);
+            buildCommand.Execute().Should().Pass();
+            var assetsFilePath = Path.Combine(buildCommand.GetBaseIntermediateDirectory().FullName, "project.assets.json");
+            var lockFile = LockFileUtilities.GetLockFile(assetsFilePath, new NullLogger());
+
+            foreach (var lockFileTarget in lockFile.Targets)
+            {
+                var valueTupleLibrary = lockFileTarget.Libraries.Where(library => library.Name.Equals("System.ValueTuple", StringComparison.OrdinalIgnoreCase)).Single();
+                var runtimeAssemblies = valueTupleLibrary.RuntimeAssemblies.Where(a => !Path.GetFileName(a.Path).Equals("_._"));
+                var compileTimeAssemblies = valueTupleLibrary.CompileTimeAssemblies.Where(a => !Path.GetFileName(a.Path).Equals("_._"));
+
+                if (lockFileTarget.TargetFramework.Framework.Equals(".NETFramework", StringComparison.OrdinalIgnoreCase))
+                {
+                    runtimeAssemblies.Should().NotBeEmpty();
+                    compileTimeAssemblies.Should().NotBeEmpty();
+                }
+                else
+                {
+                    runtimeAssemblies.Should().BeEmpty();
+                    compileTimeAssemblies.Should().BeEmpty();
+                }
+            }
+        }
+
         static List<KeyValuePair<string, string>> ParsePrunePackageReferenceJson(string json)
         {
             List<KeyValuePair<string, string>> ret = new();
