Fixed invalid warning on global namespace for compiler-generated top-level Program class

Author: Bart Koelman

src/CSharpGuidelinesAnalyzer/CSharpGuidelinesAnalyzer.Test/Specs/Maintainability/NamespaceShouldMatchAssemblyNameSpecs.cs

@@ -1,5 +1,6 @@
 using CSharpGuidelinesAnalyzer.Rules.Maintainability;
 using CSharpGuidelinesAnalyzer.Test.TestDataBuilders;
+using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Diagnostics;
 using Xunit;
 
@@ -380,6 +381,44 @@ class [|C|]
                 "Type 'C' is declared in namespace 'WrongRoot.JetBrains.Annotations', which does not match with assembly name 'Company.ProductName'.");
         }
 
+        [Fact]
+        internal void When_top_level_program_it_must_be_skipped()
+        {
+            // Arrange
+            ParsedSourceCode source = new TypeSourceCodeBuilder()
+                .InAssemblyNamed("Some.Scope.Example")
+                .WithOutputKind(OutputKind.ConsoleApplication)
+                .InGlobalScope(@"
+                    System.Console.WriteLine("""");
+                ")
+                .Build();
+
+            // Act and assert
+            VerifyGuidelineDiagnostic(source);
+        }
+
+        [Fact]
+        internal void When_explicit_program_in_global_namespace_it_must_be_reported()
+        {
+            // Arrange
+            ParsedSourceCode source = new TypeSourceCodeBuilder()
+                .InAssemblyNamed("Some.Scope.Example")
+                .WithOutputKind(OutputKind.ConsoleApplication)
+                .InGlobalScope(@"
+                    static class [|Program|]
+                    {
+                        static void Main()
+                        {
+                            System.Console.WriteLine("""");
+                        }
+                    }
+                ")
+                .Build();
+
+            // Act and assert
+            VerifyGuidelineDiagnostic(source, "Type 'Program' is declared in global namespace, which does not match with assembly name 'Some.Scope.Example'.");
+        }
+
         protected override DiagnosticAnalyzer CreateAnalyzer()
         {
             return new NamespaceShouldMatchAssemblyNameAnalyzer();

src/CSharpGuidelinesAnalyzer/CSharpGuidelinesAnalyzer/Rules/Maintainability/NamespaceShouldMatchAssemblyNameAnalyzer.cs

@@ -12,6 +12,10 @@ namespace CSharpGuidelinesAnalyzer.Rules.Maintainability
     [DiagnosticAnalyzer(LanguageNames.CSharp)]
     public sealed class NamespaceShouldMatchAssemblyNameAnalyzer : DiagnosticAnalyzer
     {
+        // Copied from Microsoft.CodeAnalysis.WellKnownMemberNames, which provides these in later versions.
+        private const string TopLevelStatementsEntryPointTypeName = "Program";
+        private const string TopLevelStatementsEntryPointMethodName = "<Main>$";
+
         private const string Title = "Namespace should match with assembly name";
         private const string NamespaceMessageFormat = "Namespace '{0}' does not match with assembly name '{1}'.";
         private const string TypeInNamespaceMessageFormat = "Type '{0}' is declared in namespace '{1}', which does not match with assembly name '{2}'.";
@@ -94,12 +98,17 @@ private static void AnalyzeNamedType(SymbolAnalysisContext context)
         {
             var type = (INamedTypeSymbol)context.Symbol;
 
-            if (type.ContainingNamespace.IsGlobalNamespace && !type.IsSynthesized())
+            if (type.ContainingNamespace.IsGlobalNamespace && !type.IsSynthesized() && !IsTopLevelStatementsContainer(type))
             {
                 context.ReportDiagnostic(Diagnostic.Create(GlobalTypeRule, type.Locations[0], type.Name, type.ContainingAssembly.Name));
             }
         }
 
+        private static bool IsTopLevelStatementsContainer([NotNull] INamedTypeSymbol type)
+        {
+            return type.Name == TopLevelStatementsEntryPointTypeName && type.GetMembers(TopLevelStatementsEntryPointMethodName).Any();
+        }
+
         private sealed class TypesInNamespaceVisitor : SymbolVisitor
         {
             [ItemNotNull]