[3.7] Don't report diagnostic for DeploymentItem on abstract class (#4539)

Author: Youssef1313

src/Analyzers/MSTest.Analyzers/UseDeploymentItemWithTestMethodOrTestClassAnalyzer.cs

@@ -52,6 +52,15 @@ public override void Initialize(AnalysisContext context)
 
     private static void AnalyzeSymbol(SymbolAnalysisContext context, INamedTypeSymbol testMethodAttributeSymbol, INamedTypeSymbol testClassAttributeSymbol, INamedTypeSymbol deploymentItemAttributeSymbol)
     {
+        if (context.Symbol is INamedTypeSymbol { IsAbstract: true })
+        {
+            // As [DeploymentItem] attribute is inherited, it's okay to be present on an abstract class that is not a test class.
+            // See https://github.com/microsoft/testfx/issues/2683 for information.
+            // For now, we do the IsAbstract check specifically for classes and not methods.
+            // If we got a convincing feedback around a false positive for the attribute on an abstract method, we can adjust the check.
+            return;
+        }
+
         bool hasDeploymentItemAttribute = false;
         bool isTestMethodOrTestClass = false;
         foreach (AttributeData attribute in context.Symbol.GetAttributes())

test/UnitTests/MSTest.Analyzers.UnitTests/UseDeploymentItemWithTestMethodOrTestClassAnalyzerTests.cs

@@ -84,6 +84,20 @@ public void MyTestMethod()
         await VerifyCS.VerifyAnalyzerAsync(code);
     }
 
+    public async Task WhenAnAbstractClassHasDeploymentItem_NoDiagnostic()
+    {
+        string code = """
+            using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+            [DeploymentItem("")]
+            public abstract class MyTestClass
+            {
+            }
+            """;
+
+        await VerifyCS.VerifyAnalyzerAsync(code);
+    }
+
     public async Task WhenAClassHasDeploymentItem_Diagnostic()
     {
         string code = """