fix: Cache SemanticModel and improve null handling patterns (#1639, #1572) (#1678)

- Cache GetSemanticModelAsync result in AsyncModuleCodeFixProvider to avoid
  duplicate async calls in the loop (fixes #1572)
- Convert helper methods to static since they no longer need instance state
- Make EscapeXmlComment and EscapeIdentifier accept nullable strings for
  consistent null handling (fixes #1639)
- Return string.Empty instead of returning null from EscapeIdentifier

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: thomhurst

src/ModularPipelines.Analyzers/ModularPipelines.Analyzers.CodeFixes/AsyncModuleCodeFixProvider.cs

@@ -61,12 +61,15 @@ private async Task<Document> AddAsync(CodeFixContext context, MethodDeclarationS
 
         editor.SetModifiers(methodDeclarationSyntax, DeclarationModifiers.Override | DeclarationModifiers.Async);
 
+        // Cache the semantic model to avoid duplicate async calls
+        var semanticModel = await context.Document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
+
         foreach (var returnStatement in GetReturnStatements(methodDeclarationSyntax))
         {
             var expressionSyntax = returnStatement.ChildNodes().OfType<ExpressionSyntax>().First()!;
 
-            if (await IsTaskFromResult(expressionSyntax, context)
-                || await IsAsTaskExtension(expressionSyntax, context))
+            if (IsTaskFromResult(expressionSyntax, semanticModel)
+                || IsAsTaskExtension(expressionSyntax, semanticModel))
             {
                 var firstInnerExpression = expressionSyntax.ChildNodes().OfType<ArgumentListSyntax>().First().Arguments.First().Expression;
 
@@ -97,14 +100,17 @@ private static ReturnStatementSyntax[] GetReturnStatements(MethodDeclarationSynt
                ?? Array.Empty<ReturnStatementSyntax>();
     }
 
-    private async Task<bool> IsTaskFromResult(ExpressionSyntax expressionSyntax, CodeFixContext context)
+    private static bool IsTaskFromResult(ExpressionSyntax expressionSyntax, SemanticModel? semanticModel)
     {
         if (expressionSyntax is not InvocationExpressionSyntax invocationExpressionSyntax)
         {
             return false;
         }
 
-        var semanticModel = await context.Document.GetSemanticModelAsync();
+        if (semanticModel is null)
+        {
+            return false;
+        }
 
         var symbol = semanticModel.GetSymbolInfo(invocationExpressionSyntax).Symbol;
 
@@ -119,14 +125,17 @@ private async Task<bool> IsTaskFromResult(ExpressionSyntax expressionSyntax, Cod
             && methodSymbol.ContainingNamespace.ToDisplayString() == "System.Threading.Tasks";
     }
 
-    private async Task<bool> IsAsTaskExtension(ExpressionSyntax expressionSyntax, CodeFixContext context)
+    private static bool IsAsTaskExtension(ExpressionSyntax expressionSyntax, SemanticModel? semanticModel)
     {
         if (expressionSyntax is not InvocationExpressionSyntax invocationExpressionSyntax)
         {
             return false;
         }
 
-        var semanticModel = await context.Document.GetSemanticModelAsync();
+        if (semanticModel is null)
+        {
+            return false;
+        }
 
         var symbol = semanticModel.GetSymbolInfo(invocationExpressionSyntax).Symbol;
 

tools/ModularPipelines.OptionsGenerator/src/ModularPipelines.OptionsGenerator/Generators/GeneratorUtils.cs

@@ -14,7 +14,7 @@ public static partial class GeneratorUtils
     /// <summary>
     /// Escapes text for use in XML documentation comments.
     /// </summary>
-    public static string EscapeXmlComment(string text)
+    public static string EscapeXmlComment(string? text)
     {
         if (string.IsNullOrEmpty(text))
         {
@@ -156,11 +156,11 @@ public static string ToPascalCase(string input)
     /// <summary>
     /// Escapes a C# identifier if it's a reserved keyword by prefixing with @.
     /// </summary>
-    public static string EscapeIdentifier(string identifier)
+    public static string EscapeIdentifier(string? identifier)
     {
         if (string.IsNullOrEmpty(identifier))
         {
-            return identifier;
+            return string.Empty;
         }
 
         return CSharpKeywords.Contains(identifier) ? $"@{identifier}" : identifier;