From 7d4dc172bd6049b8a9b73afff342623488327f8c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Hellander?= <bjorn.hellander@gmail.com>
Date: Sat, 25 Feb 2023 08:11:12 +0100
Subject: [PATCH] Update SA1513 codefix to use the existing newline character
 sequence #3360

---
 .../LayoutRules/SA1513CodeFixProvider.cs      |  3 +-
 .../LayoutRules/SA1513UnitTests.cs            | 24 +++++++++++++++
 .../StyleCop.Analyzers/Helpers/TokenHelper.cs | 30 +++++++++++++++++++
 3 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/StyleCop.Analyzers/StyleCop.Analyzers.CodeFixes/LayoutRules/SA1513CodeFixProvider.cs b/StyleCop.Analyzers/StyleCop.Analyzers.CodeFixes/LayoutRules/SA1513CodeFixProvider.cs
index 1b38f0f3f..bea1d10e9 100644
--- a/StyleCop.Analyzers/StyleCop.Analyzers.CodeFixes/LayoutRules/SA1513CodeFixProvider.cs
+++ b/StyleCop.Analyzers/StyleCop.Analyzers.CodeFixes/LayoutRules/SA1513CodeFixProvider.cs
@@ -65,7 +65,8 @@ private static async Task<SyntaxNode> GetTransformedDocumentAsync(Document docum
                 diagnostics.Select(diagnostic => root.FindToken(diagnostic.Location.SourceSpan.End)),
                 (originalToken, rewrittenToken) =>
                 {
-                    var newTrivia = rewrittenToken.LeadingTrivia.Insert(0, SyntaxFactory.CarriageReturnLineFeed);
+                    var endOfLineTrivia = rewrittenToken.GetPrecedingEndOfLineTrivia();
+                    var newTrivia = rewrittenToken.LeadingTrivia.Insert(0, endOfLineTrivia);
                     return rewrittenToken.WithLeadingTrivia(newTrivia);
                 });
         }
diff --git a/StyleCop.Analyzers/StyleCop.Analyzers.Test/LayoutRules/SA1513UnitTests.cs b/StyleCop.Analyzers/StyleCop.Analyzers.Test/LayoutRules/SA1513UnitTests.cs
index 2bae9eade..7bb867cc3 100644
--- a/StyleCop.Analyzers/StyleCop.Analyzers.Test/LayoutRules/SA1513UnitTests.cs
+++ b/StyleCop.Analyzers/StyleCop.Analyzers.Test/LayoutRules/SA1513UnitTests.cs
@@ -1013,5 +1013,29 @@ public void TestMethod(string extraSupport)
 
             await VerifyCSharpDiagnosticAsync(testCode, DiagnosticResult.EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
         }
+
+        [Fact]
+        [WorkItem(3360, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/3360")]
+        public async Task TestLineFeedEndOfLinesAsync()
+        {
+            var testCode =
+                "public class TestClass\n" +
+                "{\n" +
+                "}\n" +
+                "// Hello";
+
+            var fixedCode =
+                "public class TestClass\n" +
+                "{\n" +
+                "}\n" +
+                "\n" +
+                "// Hello";
+
+            DiagnosticResult[] expected =
+            {
+                Diagnostic().WithLocation(3, 2),
+            };
+            await VerifyCSharpFixAsync(testCode, expected, fixedCode, CancellationToken.None).ConfigureAwait(false);
+        }
     }
 }
diff --git a/StyleCop.Analyzers/StyleCop.Analyzers/Helpers/TokenHelper.cs b/StyleCop.Analyzers/StyleCop.Analyzers/Helpers/TokenHelper.cs
index 0f4e0bc76..9df1e5739 100644
--- a/StyleCop.Analyzers/StyleCop.Analyzers/Helpers/TokenHelper.cs
+++ b/StyleCop.Analyzers/StyleCop.Analyzers/Helpers/TokenHelper.cs
@@ -175,5 +175,35 @@ internal static bool IsFollowedByWhitespace(this SyntaxToken token)
             triviaList = token.GetNextToken().LeadingTrivia;
             return triviaList.Count > 0 && triviaList.First().IsKind(SyntaxKind.WhitespaceTrivia);
         }
+
+        /// <summary>
+        /// Returns the closest end of line trivia preceding the <paramref name="token"/>.
+        /// This currently only looks immediately before the specified token.
+        /// </summary>
+        /// <param name="token">The token to process.</param>
+        /// <returns>The closest preceding end of line trivia, or <see cref="SyntaxFactory.CarriageReturnLineFeed"/> if none is found.</returns>
+        internal static SyntaxTrivia GetPrecedingEndOfLineTrivia(this SyntaxToken token)
+        {
+            var leadingTrivia = token.LeadingTrivia;
+            for (var i = leadingTrivia.Count - 1; i >= 0; i--)
+            {
+                if (leadingTrivia[i].IsKind(SyntaxKind.EndOfLineTrivia))
+                {
+                    return leadingTrivia[i];
+                }
+            }
+
+            var prevToken = token.GetPreviousToken();
+            var prevTrailingTrivia = prevToken.TrailingTrivia;
+            for (var i = prevTrailingTrivia.Count - 1; i >= 0; i--)
+            {
+                if (prevTrailingTrivia[i].IsKind(SyntaxKind.EndOfLineTrivia))
+                {
+                    return prevTrailingTrivia[i];
+                }
+            }
+
+            return SyntaxFactory.CarriageReturnLineFeed;
+        }
     }
 }