Fix lambda block unpacking with comments

When a single statement lambda contained comments, unpacking it to an expression body or an unparenthesized block resulted in the comments being pushed outside the lambda when it's placed inside method invocations like `Parallel.ForEach`. This checks for comments in the lambda node and forces generating a full block syntax to preserve the comments inside.

Co-authored-by: GrahamTheCoder <[email protected]>

Author: google-labs-jules[bot]

CodeConverter/CSharp/LambdaConverter.cs

@@ -75,7 +75,8 @@ public async Task<CSharpSyntaxNode> ConvertAsync(VBSyntax.LambdaExpressionSyntax
         BlockSyntax block = null;
         ExpressionSyntax expressionBody = null;
         ArrowExpressionClauseSyntax arrow = null;
-        if (!convertedStatements.TryUnpackSingleStatement(out StatementSyntax singleStatement)) {
+        bool hasComments = vbNode.DescendantTrivia().Any(t => t.IsKind(VBasic.SyntaxKind.CommentTrivia));
+        if (hasComments || !convertedStatements.TryUnpackSingleStatement(out StatementSyntax singleStatement)) {
             convertedStatements = convertedStatements.Select(l => l.WithTrailingTrivia(SyntaxFactory.ElasticCarriageReturnLineFeed)).ToList();
             block = SyntaxFactory.Block(convertedStatements);
         } else if (singleStatement.TryUnpackSingleExpressionFromStatement(out expressionBody)) {

Tests/CSharp/ExpressionTests/ExpressionTests.cs

@@ -2931,4 +2931,50 @@ public object Edit(bool flag2 = false, CrashEnum? crashEnum = default)
     }
 }");
     }
-}
+    [Fact]
+    public async Task LambdaBodyExpressionWithCommentsAsync() {
+        await TestConversionVisualBasicToCSharpAsync(@"
+Imports System.Threading.Tasks
+Imports System.Collections.Generic
+
+Public Class ConversionTest1
+    Public Sub BugRepro()
+        Dim dt As New List(Of Integer)
+
+        Parallel.ForEach(dt, Sub(row)
+                                 If Not String.IsNullOrWhiteSpace("""") Then
+                                     'comment1
+                                     Dim test1 As Boolean = True
+                                     'comment2
+                                     Dim test2 As Boolean = True
+                                     'comment3
+                                     Dim test3 As Boolean = True
+                                 End If
+                             End Sub)
+    End Sub
+End Class
+", @"using System.Collections.Generic;
+using System.Threading.Tasks;
+
+public partial class ConversionTest1
+{
+    public void BugRepro()
+    {
+        var dt = new List<int>();
+
+        Parallel.ForEach(dt, row =>
+        {
+            if (!string.IsNullOrWhiteSpace(""""))
+            {
+                // comment1
+                bool test1 = true;
+                // comment2
+                bool test2 = true;
+                // comment3
+                bool test3 = true;
+            }
+        });
+    }
+}", incompatibleWithAutomatedCommentTesting: true);
+    }
+}