Fix markdown heading parsing at end of input

DiscordChatExporter.Cli.Tests/Specs/HtmlMarkdownHeadingSpecs.cs

@@ -0,0 +1,137 @@
+using System;
+using System.IO;
+using System.Threading.Tasks;
+using DiscordChatExporter.Core.Discord;
+using DiscordChatExporter.Core.Discord.Data;
+using DiscordChatExporter.Core.Exporting;
+using DiscordChatExporter.Core.Exporting.Filtering;
+using DiscordChatExporter.Core.Exporting.Partitioning;
+using FluentAssertions;
+using Xunit;
+
+namespace DiscordChatExporter.Cli.Tests.Specs;
+
+public class HtmlMarkdownHeadingSpecs
+{
+    private static async ValueTask<string> FormatMarkdownAsync(string markdown) =>
+        await HtmlMarkdownVisitor.FormatAsync(null!, markdown);
+
+    private static ExportContext CreateExportContext(bool shouldFormatMarkdown)
+    {
+        var guild = Guild.DirectMessages;
+        var channel = new Channel(
+            new Snowflake(1),
+            ChannelKind.DirectTextChat,
+            guild.Id,
+            null,
+            "test",
+            null,
+            null,
+            null,
+            false,
+            null
+        );
+
+        var request = new ExportRequest(
+            guild,
+            channel,
+            Path.Combine(Path.GetTempPath(), "DiscordChatExporter.Tests", "test.html"),
+            null,
+            ExportFormat.HtmlDark,
+            null,
+            null,
+            PartitionLimit.Null,
+            MessageFilter.Null,
+            false,
+            shouldFormatMarkdown,
+            false,
+            true,
+            "en-US",
+            true
+        );
+
+        return new ExportContext(new DiscordClient(""), request);
+    }
+
+    private static Message CreateMessage(string content) =>
+        new(
+            new Snowflake(2),
+            MessageKind.Default,
+            MessageFlags.None,
+            new User(new Snowflake(3), false, 1234, "test-user", "Test User", ""),
+            DateTimeOffset.Parse("2024-01-01T00:00:00+00:00"),
+            null,
+            null,
+            false,
+            content,
+            [],
+            [],
+            [],
+            [],
+            [],
+            null,
+            null,
+            null,
+            null
+        );
+
+    [Theory]
+    [InlineData("# Heading", "<h1>Heading</h1>")]
+    [InlineData("# Heading\nbody", "<h1>Heading</h1>body")]
+    [InlineData("# Heading\r\nbody", "<h1>Heading</h1>body")]
+    [InlineData("## Heading", "<h2>Heading</h2>")]
+    [InlineData("### Heading", "<h3>Heading</h3>")]
+    public async Task I_can_render_markdown_headings_as_html(string markdown, string expectedHtml)
+    {
+        // Act
+        var html = await FormatMarkdownAsync(markdown);
+
+        // Assert
+        html.Should().Be(expectedHtml);
+    }
+
+    [Theory]
+    [InlineData("#hashtag")]
+    [InlineData("#")]
+    [InlineData("#\nHeading")]
+    [InlineData("#\r\nHeading")]
+    public async Task I_do_not_render_non_heading_hash_text_as_html_heading(string markdown)
+    {
+        // Act
+        var html = await FormatMarkdownAsync(markdown);
+
+        // Assert
+        html.Should().Be(markdown);
+        html.Should().NotContain("<h");
+    }
+
+    [Fact]
+    public async Task I_can_escape_html_sensitive_text_inside_markdown_headings()
+    {
+        // Act
+        var html = await FormatMarkdownAsync("# <Heading> & \"quote\"");
+
+        // Assert
+        html.Should().Be("<h1>&lt;Heading&gt; &amp; &quot;quote&quot;</h1>");
+    }
+
+    [Fact]
+    public async Task I_keep_markdown_headings_literal_when_formatting_is_disabled()
+    {
+        // Arrange
+        var context = CreateExportContext(false);
+        var message = CreateMessage("# <Heading> & \"quote\"");
+
+        // Act
+        var html = await new MessageGroupTemplate
+        {
+            Context = context,
+            Messages = [message],
+        }.RenderAsync();
+
+        // Assert
+        html.Should().Contain("# &lt;Heading&gt; &amp;");
+        html.Should().NotContain("# <Heading>");
+        html.Should().NotContain("<h1>");
+    }
+}

DiscordChatExporter.Core/Markdown/Parsing/MarkdownParser.cs

@@ -131,8 +131,8 @@ internal static partial class MarkdownParser
 
     private static readonly IMatcher<MarkdownContext, MarkdownNode> HeadingNodeMatcher =
         new RegexMatcher<MarkdownContext, MarkdownNode>(
-            // Consume the linebreak so that it's not attached to following nodes.
+            // Consume the linebreak, if present, so that it's not attached to following nodes.
-            new Regex(@"^(\#{1,3})\s(.+)\n", DefaultRegexOptions),
+            new Regex(@"^(\#{1,3})[^\S\r\n]+([^\r\n]+)(?:\r?\n|$)", DefaultRegexOptions),
             (c, s, m) => new HeadingNode(m.Groups[1].Length, Parse(c, s.Relocate(m.Groups[2])))
         );
 

DiscordChatExporter.Core/Properties/AssemblyInfo.cs

@@ -0,0 +1,3 @@
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("DiscordChatExporter.Cli.Tests")]