From 5e91b9b763c628f9ac00bb14abbce9a77c1d98fe Mon Sep 17 00:00:00 2001
From: Michael Naumov <mnaoumov@gmail.com>
Date: Tue, 17 May 2022 16:46:24 -0600
Subject: [PATCH] Add YamlFrontMatterRoundtripRenderer

---
 .../TestYamlFrontMatterBlock.cs               | 25 +++++++++++++++++
 src/Markdig.Tests/TestRoundtrip.cs            |  2 ++
 .../Yaml/YamlFrontMatterExtension.cs          |  8 +++---
 ...erer.cs => YamlFrontMatterHtmlRenderer.cs} |  2 +-
 .../Yaml/YamlFrontMatterRoundtripRenderer.cs  | 27 +++++++++++++++++++
 5 files changed, 59 insertions(+), 5 deletions(-)
 create mode 100644 src/Markdig.Tests/RoundtripSpecs/TestYamlFrontMatterBlock.cs
 rename src/Markdig/Extensions/Yaml/{YamlFrontMatterRenderer.cs => YamlFrontMatterHtmlRenderer.cs} (86%)
 create mode 100644 src/Markdig/Extensions/Yaml/YamlFrontMatterRoundtripRenderer.cs

diff --git a/src/Markdig.Tests/RoundtripSpecs/TestYamlFrontMatterBlock.cs b/src/Markdig.Tests/RoundtripSpecs/TestYamlFrontMatterBlock.cs
new file mode 100644
index 000000000..de769c4d8
--- /dev/null
+++ b/src/Markdig.Tests/RoundtripSpecs/TestYamlFrontMatterBlock.cs
@@ -0,0 +1,25 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Markdig.Renderers.Roundtrip;
+using Markdig.Syntax;
+using NUnit.Framework;
+using static Markdig.Tests.TestRoundtrip;
+
+namespace Markdig.Tests.RoundtripSpecs
+{
+    [TestFixture]
+    public class TestYamlFrontMatterBlock
+    {
+        [TestCase("---\nkey1: value1\nkey2: value2\n---\n\nContent\n")]
+        [TestCase("No front matter")]
+        [TestCase("Looks like front matter but actually is not\n---\nkey1: value1\nkey2: value2\n---")]
+        public void FrontMatterBlockIsPreserved(string value)
+        {
+            RoundTrip(value);
+        }
+    }
+}
diff --git a/src/Markdig.Tests/TestRoundtrip.cs b/src/Markdig.Tests/TestRoundtrip.cs
index 5851e139b..8347eae1c 100644
--- a/src/Markdig.Tests/TestRoundtrip.cs
+++ b/src/Markdig.Tests/TestRoundtrip.cs
@@ -16,10 +16,12 @@ internal static void RoundTrip(string markdown, string context = null)
         {
             var pipelineBuilder = new MarkdownPipelineBuilder();
             pipelineBuilder.EnableTrackTrivia();
+            pipelineBuilder.UseYamlFrontMatter();
             MarkdownPipeline pipeline = pipelineBuilder.Build();
             MarkdownDocument markdownDocument = Markdown.Parse(markdown, pipeline);
             var sw = new StringWriter();
             var nr = new RoundtripRenderer(sw);
+            pipeline.Setup(nr);
 
             nr.Write(markdownDocument);
 
diff --git a/src/Markdig/Extensions/Yaml/YamlFrontMatterExtension.cs b/src/Markdig/Extensions/Yaml/YamlFrontMatterExtension.cs
index 9cb50a21e..f8144f5e8 100644
--- a/src/Markdig/Extensions/Yaml/YamlFrontMatterExtension.cs
+++ b/src/Markdig/Extensions/Yaml/YamlFrontMatterExtension.cs
@@ -1,10 +1,9 @@
-// Copyright (c) Alexandre Mutel. All rights reserved.
+// Copyright (c) Alexandre Mutel. All rights reserved.
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 
 using Markdig.Parsers;
 using Markdig.Renderers;
-using Markdig.Renderers.Html;
 
 namespace Markdig.Extensions.Yaml
 {
@@ -24,9 +23,10 @@ public void Setup(MarkdownPipelineBuilder pipeline)
 
         public void Setup(MarkdownPipeline pipeline, IMarkdownRenderer renderer)
         {
-            if (!renderer.ObjectRenderers.Contains<YamlFrontMatterRenderer>())
+            if (!renderer.ObjectRenderers.Contains<YamlFrontMatterHtmlRenderer>())
             {
-                renderer.ObjectRenderers.InsertBefore<CodeBlockRenderer>(new YamlFrontMatterRenderer());
+                renderer.ObjectRenderers.InsertBefore<Renderers.Html.CodeBlockRenderer> (new YamlFrontMatterHtmlRenderer());
+                renderer.ObjectRenderers.InsertBefore<Renderers.Roundtrip.CodeBlockRenderer>(new YamlFrontMatterRoundtripRenderer());
             }
         }
     }
diff --git a/src/Markdig/Extensions/Yaml/YamlFrontMatterRenderer.cs b/src/Markdig/Extensions/Yaml/YamlFrontMatterHtmlRenderer.cs
similarity index 86%
rename from src/Markdig/Extensions/Yaml/YamlFrontMatterRenderer.cs
rename to src/Markdig/Extensions/Yaml/YamlFrontMatterHtmlRenderer.cs
index 1b56042b6..c06493163 100644
--- a/src/Markdig/Extensions/Yaml/YamlFrontMatterRenderer.cs
+++ b/src/Markdig/Extensions/Yaml/YamlFrontMatterHtmlRenderer.cs
@@ -11,7 +11,7 @@ namespace Markdig.Extensions.Yaml
     /// Empty renderer for a <see cref="YamlFrontMatterBlock"/>
     /// </summary>
     /// <seealso cref="HtmlObjectRenderer{YamlFrontMatterBlock}" />
-    public class YamlFrontMatterRenderer : HtmlObjectRenderer<YamlFrontMatterBlock>
+    public class YamlFrontMatterHtmlRenderer : HtmlObjectRenderer<YamlFrontMatterBlock>
     {
         protected override void Write(HtmlRenderer renderer, YamlFrontMatterBlock obj)
         {
diff --git a/src/Markdig/Extensions/Yaml/YamlFrontMatterRoundtripRenderer.cs b/src/Markdig/Extensions/Yaml/YamlFrontMatterRoundtripRenderer.cs
new file mode 100644
index 000000000..ed542fc62
--- /dev/null
+++ b/src/Markdig/Extensions/Yaml/YamlFrontMatterRoundtripRenderer.cs
@@ -0,0 +1,27 @@
+// Copyright (c) Alexandre Mutel. All rights reserved.
+// This file is licensed under the BSD-Clause 2 license.
+// See the license.txt file in the project root for more information.
+
+using System;
+using Markdig.Renderers;
+using Markdig.Renderers.Roundtrip;
+
+namespace Markdig.Extensions.Yaml
+{
+    public class YamlFrontMatterRoundtripRenderer : MarkdownObjectRenderer<RoundtripRenderer, YamlFrontMatterBlock>
+    {
+        private readonly CodeBlockRenderer _codeBlockRenderer;
+
+        public YamlFrontMatterRoundtripRenderer()
+        {
+            _codeBlockRenderer = new CodeBlockRenderer();
+        }
+
+        protected override void Write(RoundtripRenderer renderer, YamlFrontMatterBlock obj)
+        {
+            renderer.Writer.WriteLine("---");
+            _codeBlockRenderer.Write(renderer, obj);
+            renderer.Writer.WriteLine("---");
+        }
+    }
+}
\ No newline at end of file