From d91b11e32adf398a3d90b3388acffbfe1bd4788d Mon Sep 17 00:00:00 2001
From: Thorsten Sommer <SommerEngineering@users.noreply.github.com>
Date: Tue, 9 Jun 2026 10:28:04 +0200
Subject: [PATCH] Added detection for compile-time constant patterns

---
 .../UsageAnalyzers/EmptyStringAnalyzer.cs     | 84 +++++++++++--------
 1 file changed, 51 insertions(+), 33 deletions(-)

diff --git a/app/SourceCodeRules/SourceCodeRules/UsageAnalyzers/EmptyStringAnalyzer.cs b/app/SourceCodeRules/SourceCodeRules/UsageAnalyzers/EmptyStringAnalyzer.cs
index 5092d436..c4fe1392 100644
--- a/app/SourceCodeRules/SourceCodeRules/UsageAnalyzers/EmptyStringAnalyzer.cs
+++ b/app/SourceCodeRules/SourceCodeRules/UsageAnalyzers/EmptyStringAnalyzer.cs
@@ -13,76 +13,94 @@ namespace SourceCodeRules.UsageAnalyzers;
 public sealed class EmptyStringAnalyzer : DiagnosticAnalyzer
 {
     private const string DIAGNOSTIC_ID = Identifier.EMPTY_STRING_ANALYZER;
-    
+
     private static readonly string TITLE = """
                                            Use string.Empty instead of ""
                                            """;
-    
+
     private static readonly string MESSAGE_FORMAT = """
                                                     Use string.Empty instead of ""
                                                     """;
-    
-    private static readonly string DESCRIPTION = """Empty string literals ("") should be replaced with string.Empty for better code consistency and readability except in const contexts.""";
-    
+
+    private static readonly string DESCRIPTION = """Empty string literals ("") should be replaced with string.Empty for better code consistency and readability except in contexts requiring compile-time constants.""";
+
     private const string CATEGORY = "Usage";
-    
+
     private static readonly DiagnosticDescriptor RULE = new(DIAGNOSTIC_ID, TITLE, MESSAGE_FORMAT, CATEGORY, DiagnosticSeverity.Error, isEnabledByDefault: true, description: DESCRIPTION);
-    
+
     public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics => [RULE];
-    
+
     public override void Initialize(AnalysisContext context)
     {
         context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
         context.EnableConcurrentExecution();
         context.RegisterSyntaxNodeAction(AnalyzeEmptyStringLiteral, SyntaxKind.StringLiteralExpression);
     }
-    
+
     private static void AnalyzeEmptyStringLiteral(SyntaxNodeAnalysisContext context)
     {
         var stringLiteral = (LiteralExpressionSyntax)context.Node;
         if (stringLiteral.Token.ValueText != string.Empty)
             return;
-        
-        if (IsInConstContext(stringLiteral))
+
+        if (RequiresCompileTimeConstant(stringLiteral))
             return;
-        
-        if (IsInParameterDefaultValue(stringLiteral))
-            return;
-        
+
         var diagnostic = Diagnostic.Create(RULE, stringLiteral.GetLocation());
         context.ReportDiagnostic(diagnostic);
     }
-    
-    private static bool IsInConstContext(LiteralExpressionSyntax stringLiteral)
+
+    private static bool RequiresCompileTimeConstant(LiteralExpressionSyntax stringLiteral)
+    {
+        return IsInConstDeclarationInitializer(stringLiteral)
+            || IsInParameterDefaultValue(stringLiteral)
+            || IsInAttributeArgument(stringLiteral)
+            || IsInSwitchCaseLabel(stringLiteral)
+            || IsInConstantPattern(stringLiteral);
+    }
+
+    private static bool IsInConstDeclarationInitializer(LiteralExpressionSyntax stringLiteral)
     {
         var variableDeclarator = stringLiteral.FirstAncestorOrSelf<VariableDeclaratorSyntax>();
-        if (variableDeclarator is null)
+        if (variableDeclarator?.Initializer is null || !ContainsNode(variableDeclarator.Initializer.Value, stringLiteral))
             return false;
-            
+
         var declaration = variableDeclarator.Parent?.Parent;
         return declaration switch
         {
             FieldDeclarationSyntax fieldDeclaration => fieldDeclaration.Modifiers.Any(SyntaxKind.ConstKeyword),
             LocalDeclarationStatementSyntax localDeclaration => localDeclaration.Modifiers.Any(SyntaxKind.ConstKeyword),
-            
+
             _ => false
         };
     }
-    
+
     private static bool IsInParameterDefaultValue(LiteralExpressionSyntax stringLiteral)
     {
-        // Prüfen, ob das String-Literal Teil eines Parameter-Defaults ist
         var parameter = stringLiteral.FirstAncestorOrSelf<ParameterSyntax>();
-        if (parameter is null)
-            return false;
-        
-        // Überprüfen, ob das String-Literal im Default-Wert des Parameters verwendet wird
-        if (parameter.Default is not null && 
-            parameter.Default.Value == stringLiteral)
-        {
-            return true;
-        }
-    
-        return false;
+        return parameter?.Default is not null && ContainsNode(parameter.Default.Value, stringLiteral);
+    }
+
+    private static bool IsInAttributeArgument(LiteralExpressionSyntax stringLiteral)
+    {
+        var attributeArgument = stringLiteral.FirstAncestorOrSelf<AttributeArgumentSyntax>();
+        return attributeArgument is not null && ContainsNode(attributeArgument.Expression, stringLiteral);
+    }
+
+    private static bool IsInSwitchCaseLabel(LiteralExpressionSyntax stringLiteral)
+    {
+        var caseSwitchLabel = stringLiteral.FirstAncestorOrSelf<CaseSwitchLabelSyntax>();
+        return caseSwitchLabel is not null && ContainsNode(caseSwitchLabel.Value, stringLiteral);
+    }
+
+    private static bool IsInConstantPattern(LiteralExpressionSyntax stringLiteral)
+    {
+        var constantPattern = stringLiteral.FirstAncestorOrSelf<ConstantPatternSyntax>();
+        return constantPattern is not null && ContainsNode(constantPattern.Expression, stringLiteral);
+    }
+
+    private static bool ContainsNode(SyntaxNode parent, SyntaxNode child)
+    {
+        return parent.SpanStart <= child.SpanStart && child.Span.End <= parent.Span.End;
     }
 }
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