chore: fix code block layout corrupted issue.

Author: filzrev

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

@@ -102,9 +102,15 @@ public static bool NeedEmptyLineBefore(this XElement node)
 
         switch (prevNode.NodeType)
         {
-            // If prev node is HTML element. No need to insert empty line.
             case XmlNodeType.Element:
-                return false;
+
+                // No need to insert empty line, if prev node is HTML element and it's not <pre> tag. T
+                if (node.Name != "pre")
+                    return false;
+
+                // <pre> tag needs empty line before. Without this setting, markdown parser treat code as markdown block.
+                var prevElementNode = (XElement)prevNode;
+                return prevElementNode.Name.LocalName != "pre";
 
             // Ensure empty lines exists before text node.
             case XmlNodeType.Text:
@@ -126,6 +132,12 @@ public static void InsertEmptyLineBefore(this XElement elem)
         if (!elem.TryGetNonWhitespacePrevNode(out var prevNode))
             return;
 
+        if (prevNode.NodeType == XmlNodeType.Element)
+        {
+            elem.AddBeforeSelf(new XText("\n"));
+            return;
+        }
+
         Debug.Assert(prevNode.NodeType == XmlNodeType.Text);
 
         var prevTextNode = (XText)prevNode;

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

@@ -69,4 +69,51 @@ public void Code_Inline()
             Paragraph2
             """);
     }
+
+
+    [Fact]
+    public void Code_HtmlTagExistBefore()
+    {
+        ValidateSummary(
+            // Input XML
+            """
+            <summary>
+            paragraph1
+            <para>paragraph2</para>
+            <code><![CDATA[
+            public class Sample
+            {
+                line1
+            
+                line2
+            }]]></code>
+            <code><![CDATA[
+            public class Sample2
+            {
+                line1
+            
+                line2
+            }]]></code>
+            </summary>
+            """,
+            // Expected Markdown
+            """
+            paragraph1
+
+            <p>paragraph2</p>
+
+            <pre><code class="lang-csharp">public class Sample
+            {
+                line1
+           
+                line2
+            }</code></pre>
+            <pre><code class="lang-csharp">public class Sample2
+            {
+                line1
+            
+                line2
+            }</code></pre>
+            """);
+    }
 }

test/Docfx.Dotnet.Tests/XmlCommentUnitTest.cs

@@ -581,6 +581,7 @@ public sealed class Issue10385
             <p>
             Paragraph.
             </p>
+
             <pre><code class="lang-csharp">public sealed class Issue10385
             {
                 public int AAA {get;set;}