fix: issue 10965

Author: filzrev

src/Docfx.Dotnet/Parsers/XmlComment.Extensions.cs

@@ -43,7 +43,7 @@ private static string GetMarkdownText(XElement elem)
                 node.InsertEmptyLineBefore();
 
             if (node.NeedEmptyLineAfter())
-                node.AddAfterSelf(new XText("\n"));
+                node.InsertEmptyLineAfter();
         }
 
         return elem.GetInnerXml();
@@ -143,7 +143,23 @@ public static void InsertEmptyLineBefore(this XElement elem)
         }
         else
         {
-            elem.AddBeforeSelf(new XText("\n"));
+            if (prevTextNode.Value.EndsWith('\n'))
+            {
+                elem.AddBeforeSelf(new XText("\n"));
+            }
+            else
+            {
+                // HTML block tag is adjacent to markdown without new line.
+                // In this case, it need to append `\n\n` and copy last line indent chars.
+                int startIndex = lastLine.IndexOfAnyExcept(' ', '\t');
+                ReadOnlySpan<char> indent = startIndex switch
+                {
+                    < 0 => lastLine,
+                    0 => [],
+                    _ => lastLine.Slice(0, startIndex),
+                };
+                elem.AddBeforeSelf(new XText($"\n\n{indent}"));
+            }
         }
     }
 
@@ -203,6 +219,21 @@ public static bool NeedEmptyLineAfter(this XElement node)
                 return false;
         }
     }
+
+    public static void InsertEmptyLineAfter(this XElement elem)
+    {
+        if (!elem.TryGetNonWhitespaceNextNode(out var nextNode))
+            return;
+
+        Debug.Assert(nextNode.NodeType == XmlNodeType.Text);
+
+        var nextTextNode = (XText)nextNode;
+        if (nextTextNode.Value.StartsWith('\n'))
+            elem.AddAfterSelf(new XText("\n"));
+        else
+            elem.AddAfterSelf(new XText("\n\n"));
+    }
+
     private static bool StartsWithEmptyLine(this ReadOnlySpan<char> span)
     {
         var index = span.IndexOfAnyExcept([' ', '\t']);

test/Docfx.Dotnet.Tests/XmlCommentTests/XmlCommentSummaryTest.Code.cs

@@ -28,6 +28,28 @@ public void Code_Block()
             """);
     }
 
+    [Fact]
+    public void Code_Block_WithoutNewLine()
+    {
+        ValidateSummary(
+           // Input XML
+           """
+           <summary>
+           Paragraph1<code><![CDATA[
+           DELETE /articles/1 HTTP/1.1
+           ]]></code>Paragraph2
+           </summary>
+           """,
+           // Expected Markdown
+           """
+           Paragraph1
+
+           <pre><code class="lang-csharp">DELETE /articles/1 HTTP/1.1</code></pre>
+
+           Paragraph2
+           """);
+    }
+
     [Fact]
     public void Code_Inline()
     {