Fix issue with disappearing newlines after multiline documentation comment (#77521)

* Fix issue with disappearing newlines after multiline documentation comments

* Fix formatting issues

* Convert LineBreaksAfterLeading to local function

* Update function syntax to match conventions

Co-authored-by: Jan Jones <jan.jones.cz@gmail.com>

* Fix compilation errors

---------

Co-authored-by: Jan Jones <jan.jones.cz@gmail.com>

Author: dgounaris

src/Compilers/CSharp/Portable/Syntax/SyntaxNormalizer.cs

@@ -100,7 +100,7 @@ public override SyntaxToken VisitToken(SyntaxToken token)
                     isTrailing: false,
                     indentAfterLineBreak: NeedsIndentAfterLineBreak(token),
                     mustHaveSeparator: false,
-                    lineBreaksAfter: 0));
+                    lineBreaksAfter: lineBreaksAfterLeading(token)));
 
                 var nextToken = this.GetNextRelevantToken(token);
 
@@ -118,6 +118,22 @@ public override SyntaxToken VisitToken(SyntaxToken token)
                     lineBreaksAfter: lineBreaksAfter));
 
                 return tk;
+
+                static int lineBreaksAfterLeading(SyntaxToken syntaxToken)
+                {
+                    if (syntaxToken.LeadingTrivia.Count < 2)
+                    {
+                        return 0;
+                    }
+
+                    if (syntaxToken.LeadingTrivia[^2].IsKind(SyntaxKind.MultiLineDocumentationCommentTrivia) &&
+                        syntaxToken.LeadingTrivia[^1].IsKind(SyntaxKind.EndOfLineTrivia))
+                    {
+                        return 1;
+                    }
+
+                    return 0;
+                }
             }
             finally
             {
@@ -1247,7 +1263,7 @@ private static bool EndsInLineBreak(SyntaxTrivia trivia)
                 }
                 else
                 {
-                    return IsLineBreak(node.GetLastToken());
+                    return !node.IsKind(SyntaxKind.MultiLineDocumentationCommentTrivia) && IsLineBreak(node.GetLastToken());
                 }
             }
 

src/Compilers/CSharp/Test/Syntax/Syntax/SyntaxNormalizerTests.cs

@@ -3790,6 +3790,26 @@ void goo()
 "}");
         }
 
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/76856")]
+        public void TestNormalizeDocumentationMultiLineCommentsWithTrailingNewline()
+        {
+            TestNormalizeStatement("""
+               /**
+                * 
+                * Escape XML special characters
+                */
+               private String EscapeXML(String str)
+               {
+               """, """
+                    ///
+                    /// 
+                    /// Escape XML special characters
+                    //////
+                    private String EscapeXML(String str)
+                    {
+                    """);
+        }
+
         [Fact]
         public void TestNormalizeEOL()
         {