Added switch expression method analyzer & code fix

app/SourceCodeRules/SourceCodeRules/AnalyzerReleases.Shipped.md

@@ -2,10 +2,11 @@
 
 ### New Rules
 
- Rule ID   | Category | Severity | Notes                       
------------|----------|----------|-----------------------------
- MWAIS0001 | Usage    | Error    | ProviderAccessAnalyzer      
- MWAIS0002 | Naming   | Error    | ConstStaticAnalyzer         
- MWAIS0003 | Naming   | Error    | UnderscorePrefixAnalyzer    
- MWAIS0004 | Usage    | Error    | RandomInstantiationAnalyzer 
- MWAIS0005 | Usage    | Error    | ThisUsageAnalyzer           
+ Rule ID   | Category | Severity | Notes                          
+-----------|----------|----------|--------------------------------
+ MWAIS0001 | Usage    | Error    | ProviderAccessAnalyzer         
+ MWAIS0002 | Naming   | Error    | ConstStaticAnalyzer            
+ MWAIS0003 | Naming   | Error    | UnderscorePrefixAnalyzer       
+ MWAIS0004 | Usage    | Error    | RandomInstantiationAnalyzer    
+ MWAIS0005 | Usage    | Error    | ThisUsageAnalyzer              
+ MWAIS0006 | Style    | Error    | SwitchExpressionMethodAnalyzer 

app/SourceCodeRules/SourceCodeRules/Identifier.cs

@@ -7,4 +7,5 @@ public static class Identifier
     public const string UNDERSCORE_PREFIX_ANALYZER = $"{Tools.ID_PREFIX}0003";
     public const string RANDOM_INSTANTIATION_ANALYZER = $"{Tools.ID_PREFIX}0004";
     public const string THIS_USAGE_ANALYZER = $"{Tools.ID_PREFIX}0005";
+    public const string SWITCH_EXPRESSION_METHOD_ANALYZER = $"{Tools.ID_PREFIX}0006";
 }

app/SourceCodeRules/SourceCodeRules/StyleAnalyzers/SwitchExpressionMethodAnalyzer.cs

@@ -0,0 +1,96 @@
+using System.Collections.Immutable;
+
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+
+namespace SourceCodeRules.StyleAnalyzers;
+
+#pragma warning disable RS1038
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+#pragma warning restore RS1038
+public class SwitchExpressionMethodAnalyzer : DiagnosticAnalyzer
+{
+    private const string DIAGNOSTIC_ID = Identifier.SWITCH_EXPRESSION_METHOD_ANALYZER;
+    
+    private static readonly string TITLE = "Method with switch expression should use inline expression body";
+    
+    private static readonly string MESSAGE_FORMAT = "Method with a switch expression should use inline expression body syntax with the switch keyword on the same line";
+    
+    private static readonly string DESCRIPTION = "Methods that only return a switch expression should use the expression body syntax (=>) with the switch keyword on the same line for better readability.";
+    
+    private const string CATEGORY = "Style";
+    
+    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(AnalyzeMethodDeclaration, SyntaxKind.MethodDeclaration);
+    }
+    
+    private static void AnalyzeMethodDeclaration(SyntaxNodeAnalysisContext context)
+    {
+        var methodDeclaration = (MethodDeclarationSyntax)context.Node;
+        
+        // Fall 1: Methode hat Block-Body mit einem Return-Statement, das eine Switch-Expression ist
+        if (methodDeclaration is { Body: not null, ExpressionBody: null })
+        {
+            var statements = methodDeclaration.Body.Statements;
+            if (statements.Count == 1 && statements[0] is ReturnStatementSyntax { Expression: SwitchExpressionSyntax })
+            {
+                var diagnostic = Diagnostic.Create(RULE, methodDeclaration.Identifier.GetLocation());
+                context.ReportDiagnostic(diagnostic);
+                return;
+            }
+        }
+        
+        // Fall 2: Methode hat Expression-Body, aber die Switch-Expression beginnt auf einer neuen Zeile
+        var expressionBody = methodDeclaration.ExpressionBody;
+        if (expressionBody?.Expression is SwitchExpressionSyntax switchExpr)
+        {
+            var arrowToken = expressionBody.ArrowToken;
+            var switchToken = switchExpr.SwitchKeyword;
+            bool hasNewLineBetweenArrowAndSwitch = false;
+                
+            foreach (var trivia in arrowToken.TrailingTrivia)
+            {
+                if (trivia.IsKind(SyntaxKind.EndOfLineTrivia))
+                {
+                    hasNewLineBetweenArrowAndSwitch = true;
+                    break;
+                }
+            }
+            
+            // Prüfe Leading Trivia des Switch-Keywords, falls notwendig
+            if (!hasNewLineBetweenArrowAndSwitch)
+            {
+                foreach (var trivia in switchToken.LeadingTrivia)
+                {
+                    if (trivia.IsKind(SyntaxKind.EndOfLineTrivia))
+                    {
+                        hasNewLineBetweenArrowAndSwitch = true;
+                        break;
+                    }
+                }
+            }
+            
+            if (hasNewLineBetweenArrowAndSwitch)
+            {
+                var diagnostic = Diagnostic.Create(RULE, methodDeclaration.Identifier.GetLocation());
+                context.ReportDiagnostic(diagnostic);
+            }
+        }
+    }
+}

app/SourceCodeRules/SourceCodeRules/StyleCodeFixes/SwitchExpressionMethodCodeFixProvider.cs

@@ -0,0 +1,162 @@
+using System.Collections.Immutable;
+using System.Composition;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CodeActions;
+using Microsoft.CodeAnalysis.CodeFixes;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Text;
+
+namespace SourceCodeRules.StyleCodeFixes;
+
+[ExportCodeFixProvider(LanguageNames.CSharp, Name = nameof(SwitchExpressionMethodCodeFixProvider)), Shared]
+public class SwitchExpressionMethodCodeFixProvider : CodeFixProvider
+{
+    public sealed override ImmutableArray<string> FixableDiagnosticIds => [Identifier.SWITCH_EXPRESSION_METHOD_ANALYZER];
+    
+    public sealed override FixAllProvider GetFixAllProvider() => WellKnownFixAllProviders.BatchFixer;
+    
+    public sealed override async Task RegisterCodeFixesAsync(CodeFixContext context)
+    {
+        var root = await context.Document.GetSyntaxRootAsync(context.CancellationToken).ConfigureAwait(false);
+        if (root == null)
+            return;
+        
+        var diagnostic = context.Diagnostics.First();
+        var diagnosticSpan = diagnostic.Location.SourceSpan;
+        var methodDeclaration = root.FindToken(diagnosticSpan.Start)
+            .Parent?.AncestorsAndSelf()
+            .OfType<MethodDeclarationSyntax>()
+            .First();
+        
+        if(methodDeclaration == null)
+            return;
+        
+        context.RegisterCodeFix(
+            CodeAction.Create(
+                title: "Use inline expression body for switch expression",
+                createChangedDocument: c => UseInlineExpressionBodyAsync(context.Document, methodDeclaration, c),
+                equivalenceKey: nameof(SwitchExpressionMethodCodeFixProvider)),
+            diagnostic);
+    }
+    
+    private static async Task<Document> UseInlineExpressionBodyAsync(Document document, MethodDeclarationSyntax methodDecl, CancellationToken cancellationToken)
+    {
+        var sourceText = await document.GetTextAsync(cancellationToken);
+        var parameterText = methodDecl.ParameterList.ToString();
+        var methodStartLine = sourceText.Lines.GetLineFromPosition(methodDecl.SpanStart);
+        
+        SwitchExpressionSyntax? switchExpr = null;
+        ExpressionSyntax? governingExpression = null;
+        var switchBodyText = string.Empty;
+        
+        if (methodDecl.Body != null)
+        {
+            // Case: Block-Body with a Return-Statement that contains a Switch-Expression
+            var returnStmt = (ReturnStatementSyntax)methodDecl.Body.Statements[0];
+            if (returnStmt.Expression is not SwitchExpressionSyntax matchingSwitchExpr)
+                return document;
+            
+            switchExpr = matchingSwitchExpr;
+            governingExpression = switchExpr.GoverningExpression;
+            
+            // Extract the switch body text:
+            var switchStart = switchExpr.SwitchKeyword.SpanStart;
+            var switchEnd = switchExpr.CloseBraceToken.Span.End;
+            switchBodyText = sourceText.ToString(TextSpan.FromBounds(switchStart, switchEnd));
+        }
+        else if (methodDecl.ExpressionBody != null)
+        {
+            // Case 2: Expression-Body with a poorly formatted Switch-Expression
+            switchExpr = (SwitchExpressionSyntax)methodDecl.ExpressionBody.Expression;
+            governingExpression = switchExpr.GoverningExpression;
+            
+            // Extract the switch body text:
+            var switchStart = switchExpr.SwitchKeyword.SpanStart;
+            var switchEnd = switchExpr.CloseBraceToken.Span.End;
+            switchBodyText = sourceText.ToString(TextSpan.FromBounds(switchStart, switchEnd));
+        }
+        
+        if (switchExpr is null || governingExpression is null)
+            return document;
+        
+        // Extract the governing expression and the switch body:
+        var govExprText = sourceText.ToString(governingExpression.Span);
+        
+        // Create the new method with inline expression body and correct formatting:
+        var returnTypeText = methodDecl.ReturnType.ToString();
+        var modifiersText = string.Join(" ", methodDecl.Modifiers);
+        var methodNameText = methodDecl.Identifier.Text;
+        
+        // Determine the indentation of the method:
+        var methodIndentation = "";
+        for (var i = methodStartLine.Start; i < methodDecl.SpanStart; i++)
+        {
+            if (char.IsWhiteSpace(sourceText[i]))
+                methodIndentation += sourceText[i];
+            else
+                break;
+        }
+        
+        // Erstelle die neue Methode mit Expression-Body und korrekter Formatierung
+        var newMethodText = new StringBuilder();
+        newMethodText.Append($"{modifiersText} {returnTypeText} {methodNameText}{parameterText} => {govExprText} switch");
+        
+        // Formatiere die geschweiften Klammern und den Switch-Body
+        var switchBody = switchBodyText.Substring("switch".Length).Trim();
+        
+        // Bestimme die Einrückung für die Switch-Cases (4 Spaces oder 1 Tab mehr als die Methode)
+        var caseIndentation = methodIndentation + "    "; // 4 Spaces Einrückung
+        
+        // Verarbeite die Klammern und formatiere den Body
+        var formattedSwitchBody = FormatSwitchBody(switchBody, methodIndentation, caseIndentation);
+        newMethodText.Append(formattedSwitchBody);
+        
+        // Ersetze die alte Methoden-Deklaration mit dem neuen Text
+        var newText = sourceText.Replace(methodDecl.Span, newMethodText.ToString());
+        return document.WithText(newText);
+    }
+    
+    private static string FormatSwitchBody(string switchBody, string methodIndentation, string caseIndentation)
+    {
+        var result = new StringBuilder();
+        
+        // Remove braces from the switch body:
+        var bodyWithoutBraces = switchBody.Trim();
+        if (bodyWithoutBraces.StartsWith("{"))
+            bodyWithoutBraces = bodyWithoutBraces.Substring(1);
+        if (bodyWithoutBraces.EndsWith("}"))
+            bodyWithoutBraces = bodyWithoutBraces.Substring(0, bodyWithoutBraces.Length - 1);
+        
+        bodyWithoutBraces = bodyWithoutBraces.Trim();
+        
+        // Add braces with correct indentation:
+        result.AppendLine();
+        result.Append($"{methodIndentation}{{");
+        
+        // Process each line of the switch body:
+        var lines = bodyWithoutBraces.Split(["\r\n", "\n"], System.StringSplitOptions.None);
+        foreach (var line in lines)
+        {
+            result.AppendLine();
+            
+            var trimmedLine = line.Trim();
+            if (string.IsNullOrWhiteSpace(trimmedLine))
+                continue;
+            
+            // Add correct indentation for each case:
+            result.Append(caseIndentation);
+            result.Append(trimmedLine);
+        }
+        
+        // Add the closing brace with correct indentation:
+        result.AppendLine();
+        result.Append($"{methodIndentation}}};");
+        
+        return result.ToString();
+    }
+}