Fix analyzer to skip required keyword enforcement for Attribute class properties (#2981)

* Initial plan

* Fix analyzer to skip required keyword enforcement for Attribute class properties

Co-authored-by: thomhurst <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: thomhurst <[email protected]>

Author: Copilot

TUnit.Analyzers.Tests/AttributeClassPropertyRequiredTests.cs

@@ -0,0 +1,129 @@
+using Verifier = TUnit.Analyzers.Tests.Verifiers.CSharpAnalyzerVerifier<TUnit.Analyzers.TestDataAnalyzer>;
+
+namespace TUnit.Analyzers.Tests;
+
+public class AttributeClassPropertyRequiredTests
+{
+    [Test]
+    public async Task Attribute_Class_Property_Without_Required_Should_Not_Flag_Error()
+    {
+        await Verifier
+            .VerifyAnalyzerAsync(
+                """
+                using TUnit.Core;
+                using System;
+
+                public class MyCustomAttribute : System.Attribute
+                {
+                    [ClassDataSource<string>]
+                    public string? TestProperty { get; init; } // Should NOT trigger TUnit0043
+                }
+                """
+            );
+    }
+
+    [Test]
+    public async Task Attribute_Class_Property_With_Required_Should_Not_Flag_Error()
+    {
+        await Verifier
+            .VerifyAnalyzerAsync(
+                """
+                using TUnit.Core;
+                using System;
+
+                public class MyCustomAttribute : System.Attribute
+                {
+                    [ClassDataSource<string>]
+                    public required string TestProperty { get; init; } // Should also NOT trigger error
+                }
+                """
+            );
+    }
+
+    [Test]
+    public async Task Regular_Test_Class_Property_Without_Required_Should_Flag_Error()
+    {
+        await Verifier
+            .VerifyAnalyzerAsync(
+                """
+                using TUnit.Core;
+
+                public class MyTestClass
+                {
+                    [ClassDataSource<string>]
+                    public string? {|#0:TestProperty|} { get; init; } // SHOULD trigger TUnit0043
+
+                    [Test]
+                    public void TestMethod()
+                    {
+                    }
+                }
+                """,
+
+                Verifier.Diagnostic(Rules.PropertyRequiredNotSet)
+                    .WithLocation(0)
+            );
+    }
+
+    [Test]
+    public async Task Regular_Test_Class_Property_With_Required_Should_Not_Flag_Error()
+    {
+        await Verifier
+            .VerifyAnalyzerAsync(
+                """
+                using TUnit.Core;
+
+                public class MyTestClass
+                {
+                    [ClassDataSource<string>]
+                    public required string TestProperty { get; init; } // Should NOT trigger error
+
+                    [Test]
+                    public void TestMethod()
+                    {
+                    }
+                }
+                """
+            );
+    }
+
+    [Test]
+    public async Task Indirect_Attribute_Inheritance_Should_Not_Flag_Error()
+    {
+        await Verifier
+            .VerifyAnalyzerAsync(
+                """
+                using TUnit.Core;
+                using System;
+
+                public class BaseCustomAttribute : System.Attribute
+                {
+                }
+
+                public class MyCustomAttribute : BaseCustomAttribute
+                {
+                    [ClassDataSource<string>]
+                    public string? TestProperty { get; init; } // Should NOT trigger TUnit0043
+                }
+                """
+            );
+    }
+
+    [Test]
+    public async Task Multiple_Data_Source_Attributes_On_Attribute_Class_Property()
+    {
+        await Verifier
+            .VerifyAnalyzerAsync(
+                """
+                using TUnit.Core;
+                using System;
+
+                public class MyCustomAttribute : System.Attribute
+                {
+                    [Arguments("test")]
+                    public string? TestProperty { get; init; } // Should NOT trigger TUnit0043 even with Arguments
+                }
+                """
+            );
+    }
+}

TUnit.Analyzers/TestDataAnalyzer.cs

@@ -265,7 +265,15 @@ private void CheckPropertyAccessor(SymbolAnalysisContext context, IPropertySymbo
 
         if (propertySymbol is { IsStatic: false, IsRequired: false })
         {
-            context.ReportDiagnostic(Diagnostic.Create(Rules.PropertyRequiredNotSet, propertySymbol.Locations.FirstOrDefault()));
+            // Skip required keyword enforcement if the property is in a class that inherits from System.Attribute
+            if (IsInAttributeClass(propertySymbol.ContainingType))
+            {
+                // Attribute classes don't need to enforce the required keyword for injected properties
+            }
+            else
+            {
+                context.ReportDiagnostic(Diagnostic.Create(Rules.PropertyRequiredNotSet, propertySymbol.Locations.FirstOrDefault()));
+            }
         }
 
         if (propertySymbol is { IsStatic: true, SetMethod: null })
@@ -274,6 +282,17 @@ private void CheckPropertyAccessor(SymbolAnalysisContext context, IPropertySymbo
         }
     }
 
+    private static bool IsInAttributeClass(INamedTypeSymbol? typeSymbol)
+    {
+        if (typeSymbol is null)
+        {
+            return false;
+        }
+
+        // Check if the type or any of its base types is System.Attribute
+        return typeSymbol.IsOrInherits("global::System.Attribute");
+    }
+
     private ImmutableArray<ITypeSymbol> GetTypes(ImmutableArray<IParameterSymbol> parameters, IPropertySymbol? propertySymbol)
     {
         IEnumerable<ITypeSymbol?> types = parameters.Select(x => x.Type).Concat(new[] { propertySymbol?.Type }).Where(t => t != null);