Suppress CS8002 warning for modern .NET TFMs

src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Sdk.CSharp.targets

@@ -44,4 +44,12 @@ Copyright (c) .NET Foundation. All rights reserved.
   <PropertyGroup>
     <WarningsAsErrors Condition="'$(_BinaryFormatterObsoleteAsError)' == 'true'">$(WarningsAsErrors);SYSLIB0011</WarningsAsErrors>
   </PropertyGroup>
+
+  <!--
+    Suppress CS8002 (referenced assembly doesn't have a strong name) for modern .NET (netx.y) TFMs.
+    Strong name validation is not enforced on modern .NET runtimes, so this warning is irrelevant.
+  -->
+  <PropertyGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp'">
+    <NoWarn>$(NoWarn);CS8002</NoWarn>
+  </PropertyGroup>
 </Project>

test/Microsoft.NET.Build.Tests/GivenThatWeWantToSuppressCS8002Warning.cs

@@ -0,0 +1,133 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.NET.Build.Tests
+{
+    public class GivenThatWeWantToSuppressCS8002Warning : SdkTest
+    {
+        public GivenThatWeWantToSuppressCS8002Warning(ITestOutputHelper log) : base(log)
+        {
+        }
+
+        [Theory]
+        [InlineData("net6.0")]
+        [InlineData("net7.0")]
+        [InlineData("net8.0")]
+        public void CS8002_is_suppressed_for_modern_net_tfms(string targetFramework)
+        {
+            var testProject = new TestProject
+            {
+                Name = "TestProject",
+                TargetFrameworks = targetFramework,
+                IsExe = false,
+                SourceFiles =
+                {
+                    ["Class1.cs"] = @"
+                        public class TestClass
+                        {
+                            public void TestMethod() { }
+                        }
+                    ",
+                }
+            };
+
+            var testAsset = _testAssetsManager
+                .CreateTestProject(testProject, identifier: targetFramework);
+
+            var buildCommand = new GetValuesCommand(
+                Log,
+                Path.Combine(testAsset.TestRoot, testProject.Name),
+                targetFramework, "NoWarn")
+            {
+                DependsOnTargets = "Build"
+            };
+
+            var buildResult = buildCommand.Execute();
+            buildResult.Should().Pass();
+
+            var noWarnValues = buildCommand.GetValues();
+            noWarnValues.Should().Contain("CS8002", $"CS8002 should be suppressed for {targetFramework}");
+        }
+
+        [Theory]
+        [InlineData("net472")]
+        [InlineData("net48")]
+        [InlineData("netstandard2.0")]
+        [InlineData("netstandard2.1")]
+        public void CS8002_is_not_suppressed_for_non_modern_net_tfms(string targetFramework)
+        {
+            var testProject = new TestProject
+            {
+                Name = "TestProject",
+                TargetFrameworks = targetFramework,
+                IsExe = false,
+                SourceFiles =
+                {
+                    ["Class1.cs"] = @"
+                        public class TestClass
+                        {
+                            public void TestMethod() { }
+                        }
+                    ",
+                }
+            };
+
+            var testAsset = _testAssetsManager
+                .CreateTestProject(testProject, identifier: targetFramework);
+
+            var buildCommand = new GetValuesCommand(
+                Log,
+                Path.Combine(testAsset.TestRoot, testProject.Name),
+                targetFramework, "NoWarn")
+            {
+                DependsOnTargets = "Build"
+            };
+
+            var buildResult = buildCommand.Execute();
+            buildResult.Should().Pass();
+
+            var noWarnValues = buildCommand.GetValues();
+            noWarnValues.Should().NotContain("CS8002", $"CS8002 should NOT be suppressed for {targetFramework}");
+        }
+
+        [Fact]
+        public void CS8002_suppression_works_with_existing_nowarn()
+        {
+            var testProject = new TestProject
+            {
+                Name = "TestProject",
+                TargetFrameworks = "net8.0",
+                IsExe = false,
+                SourceFiles =
+                {
+                    ["Class1.cs"] = @"
+                        public class TestClass
+                        {
+                            public void TestMethod() { }
+                        }
+                    ",
+                }
+            };
+
+            testProject.AdditionalProperties["NoWarn"] = "CS1591";
+
+            var testAsset = _testAssetsManager
+                .CreateTestProject(testProject);
+
+            var buildCommand = new GetValuesCommand(
+                Log,
+                Path.Combine(testAsset.TestRoot, testProject.Name),
+                "net8.0", "NoWarn")
+            {
+                DependsOnTargets = "Build"
+            };
+
+            var buildResult = buildCommand.Execute();
+            buildResult.Should().Pass();
+
+            var noWarnValues = buildCommand.GetValues();
+            noWarnValues.Should().Contain("CS1591", "Existing NoWarn should be preserved");
+            noWarnValues.Should().Contain("CS8002", "CS8002 should be added to NoWarn");
+        }
+    }
+}