Fix: keep trailing content out of an unmatched emphasis closer (#743)

src/Markdig.Tests/TestEmphasisRoundtrip.cs

@@ -0,0 +1,68 @@
+// 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.Renderers.Roundtrip;
+using Markdig.Syntax;
+
+namespace Markdig.Tests;
+
+[TestFixture]
+public class TestEmphasisRoundtrip
+{
+    private static string RoundTrip(string markdown, MarkdownPipeline pipeline)
+    {
+        MarkdownDocument document = Markdown.Parse(markdown, pipeline);
+        var writer = new StringWriter();
+        var renderer = new RoundtripRenderer(writer);
+        pipeline.Setup(renderer);
+        renderer.Write(document);
+        return writer.ToString();
+    }
+
+    // Leftover delimiter characters below the minimum count used to stay nested
+    // inside the emphasis they closed, moving the following text to the end of
+    // the block. https://github.com/xoofx/markdig/issues/743
+    [Test]
+    public void GridTableSeparatorRoundtripsWithTrackTrivia()
+    {
+        string markdown =
+            "+---------------+---------------+--------------------+\n" +
+            "| Fruit         | Price         | Advantages         |\n" +
+            "+===============+===============+====================+\n" +
+            "| Bananas       | first line    | first line         |\n" +
+            "|               | next line     | next line          |\n" +
+            "+---------------+---------------+--------------------+\n";
+
+        var pipeline = new MarkdownPipelineBuilder()
+            .UseAutoLinks()
+            .UseEmphasisExtras()
+            .UseListExtras()
+            .EnableTrackTrivia()
+            .Build();
+
+        Assert.That(RoundTrip(markdown, pipeline), Is.EqualTo(markdown));
+    }
+
+    // Same defect, minimal: leftovers (15 = 7 * 2 + 1) below the "==" minimum.
+    [Test]
+    public void UnbalancedMarkedRunsRoundtrip()
+    {
+        string markdown = "+===============+===============+\n";
+
+        var pipeline = new MarkdownPipelineBuilder()
+            .UseEmphasisExtras()
+            .EnableTrackTrivia()
+            .Build();
+
+        Assert.That(RoundTrip(markdown, pipeline), Is.EqualTo(markdown));
+    }
+
+    // The fix must not prevent balanced "marked" emphasis from being detected.
+    [Test]
+    public void BalancedMarkedEmphasisStillParses()
+    {
+        var pipeline = new MarkdownPipelineBuilder().UseEmphasisExtras().Build();
+        Assert.That(Markdown.ToHtml("==bold==", pipeline).Trim(), Is.EqualTo("<p><mark>bold</mark></p>"));
+    }
+}

src/Markdig/Parsers/Inlines/EmphasisInlineParser.cs

@@ -419,6 +419,19 @@ private void ProcessEmphasis(InlineProcessor processor, List<EmphasisDelimiterIn
                         break;
                     }
                 }
+
+                // Leftover delimiter characters keep the following inlines nested inside
+                // the emphasis; move them out so they keep their original position.
+                if (closeDelimiter.DelimiterCount > 0 && closeDelimiter.Parent is EmphasisInline closerParentEmphasis)
+                {
+                    var outermostEmphasis = closerParentEmphasis;
+                    while (outermostEmphasis.Parent is EmphasisInline ancestorEmphasis)
+                    {
+                        outermostEmphasis = ancestorEmphasis;
+                    }
+
+                    closeDelimiter.MoveChildrenAfter(outermostEmphasis);
+                }
             }
         }