Fix AK1001 code fix for one liner lambda expression (#56)

src/Akka.Analyzers.Fixes/AK1000/MustCloseOverSenderWhenUsingPipeToFixer.cs

@@ -60,16 +60,6 @@ private static async Task<Document> UseLocalVariableForSenderAsync(Document docu
                 SyntaxFactory.IdentifierName("Sender")))
             .WithAdditionalAnnotations(Formatter.Annotation); // need this line to get indentation right
 
-        // Find an appropriate insertion point for the local variable
-        var insertionPoint = invocationExpr.FirstAncestorOrSelf<StatementSyntax>();
-
-        if (insertionPoint == null)
-            // Unable to find a valid insertion point
-            return document;
-
-        // Insert the local variable declaration at the found insertion point
-        editor.InsertBefore(insertionPoint, senderVariable);
-
         // Identify the 'recipient' argument - assuming it's the first argument
         var arguments = invocationExpr.ArgumentList.Arguments;
 
@@ -93,8 +83,40 @@ private static async Task<Document> UseLocalVariableForSenderAsync(Document docu
         var newArgumentList = SyntaxFactory.ArgumentList(newArguments);
         var newInvocationExpr = invocationExpr.WithArgumentList(newArgumentList);
 
-        // Make sure to replace the old invocation with the new one
-        editor.ReplaceNode(invocationExpr, newInvocationExpr);
+        // Check to see if we're inside a lambda expression and it does not have a body block
+        var lambdaExpr = invocationExpr.FirstAncestorOrSelf<LambdaExpressionSyntax>();
+        if (lambdaExpr?.Body is ExpressionSyntax exprSyntax)
+        {
+            // Make sure to replace the old invocation with the new one
+            var newExprSyntax = exprSyntax.ReplaceNode(invocationExpr, newInvocationExpr);
+
+            // Create a new block with the original lambda body as a statement
+            var originalBody = SyntaxFactory.ExpressionStatement(newExprSyntax);
+
+            // Insert the local variable declaration at the start of the lambda block
+            var bodyBlock = SyntaxFactory.Block(
+                senderVariable.WithTrailingTrivia(SyntaxFactory.ElasticCarriageReturnLineFeed), 
+                originalBody.WithTrailingTrivia(SyntaxFactory.ElasticCarriageReturnLineFeed));
+
+            // Replace the original with the new one
+            var newLambdaExpr = lambdaExpr.WithBody(null).WithBlock(bodyBlock);
+            editor.ReplaceNode(lambdaExpr, newLambdaExpr);
+        }
+        else
+        {
+            // Find an appropriate insertion point for the local variable
+            var insertionPoint = invocationExpr.FirstAncestorOrSelf<StatementSyntax>();
+
+            if (insertionPoint == null)
+                // Unable to find a valid insertion point
+                return document;
+
+            // Insert the local variable declaration at the found insertion point
+            editor.InsertBefore(insertionPoint, senderVariable);
+
+            // Make sure to replace the old invocation with the new one
+            editor.ReplaceNode(invocationExpr, newInvocationExpr);
+        }
 
         var newDocument = editor.GetChangedDocument(); // error happens here
 

src/Akka.Analyzers.Tests/Fixes/AK1000/MustCloseOverSenderWhenUsingPipeToFixerSpecs.cs

@@ -62,6 +62,59 @@ async Task<int> LocalFunction(){
             expectedDiagnostic);
     }
 
+    [Fact]
+    public Task AddClosureInsideOneLinerReceiveMethod()
+    {
+        var before =
+"""
+using Akka.Actor;
+using System.Threading.Tasks;
+
+public sealed class MyActor : ReceiveActor
+{
+    public MyActor()
+    {
+        Receive<string>(str => MessageHandler(str).PipeTo(Sender));
+    }
+
+    private Task<int> MessageHandler(string str)
+    {
+        return Task.FromResult(str.Length);
+    }
+}
+""";
+
+        var after =
+"""
+using Akka.Actor;
+using System.Threading.Tasks;
+
+public sealed class MyActor : ReceiveActor
+{
+    public MyActor()
+    {
+        Receive<string>(str =>
+        {
+            var sender = this.Sender;
+            MessageHandler(str).PipeTo(sender);
+        });
+    }
+
+    private Task<int> MessageHandler(string str)
+    {
+        return Task.FromResult(str.Length);
+    }
+}
+""";
+
+        var expectedDiagnostic = Verify.Diagnostic()
+            .WithSpan(8, 52, 8, 58)
+            .WithArguments("Sender");
+
+        return Verify.VerifyCodeFix(before, after, MustCloseOverSenderWhenUsingPipeToFixer.Key_FixPipeToSender,
+            expectedDiagnostic);
+    }
+
     [Fact]
     public Task AddClosureInsideUntypedActor()
     {