Add AutoLinkOptions.AllowDomainWithoutPeriod

src/Markdig.Tests/TestAutoLinks.cs

@@ -0,0 +1,22 @@
+using Markdig.Extensions.AutoLinks;
+
+namespace Markdig.Tests;
+
+[TestFixture]
+public class TestAutoLinks
+{
+    [Test]
+    [TestCase("https://localhost", "<p><a href=\"https://localhost\">https://localhost</a></p>")]
+    [TestCase("http://localhost", "<p><a href=\"http://localhost\">http://localhost</a></p>")]
+    [TestCase("https://l", "<p><a href=\"https://l\">https://l</a></p>")]
+    [TestCase("www.l", "<p><a href=\"http://www.l\">www.l</a></p>")]
+    public void TestLinksWithAllowDomainWithoutPeriod(string markdown, string expected)
+    {
+        var pipeline = new MarkdownPipelineBuilder()
+            .UseAutoLinks(new AutoLinkOptions { AllowDomainWithoutPeriod = true })
+            .Build();
+        var html = Markdown.ToHtml(markdown, pipeline);
+
+        Assert.That(html, Is.EqualTo(expected).IgnoreWhiteSpace);
+    }
+}

src/Markdig/Extensions/AutoLinks/AutoLinkOptions.cs

@@ -22,4 +22,9 @@ public class AutoLinkOptions
     /// Should a www link be prefixed with https:// instead of http:// (false by default)
     /// </summary>
     public bool UseHttpsForWWWLinks { get; set; }
+
+    /// <summary>
+    /// Should a link host name with no period, e.g. https://localhost, be allowed (false by default)
+    /// </summary>
+    public bool AllowDomainWithoutPeriod { get; set; }
 }

src/Markdig/Extensions/AutoLinks/AutoLinkParser.cs

@@ -164,7 +164,7 @@ public class AutoLinkParser : InlineParser
             }
 
             // Do not need to check if a telephone number is a valid domain
-            if (c != 't' && !LinkHelper.IsValidDomain(link, domainOffset))
+            if (c != 't' && !LinkHelper.IsValidDomain(link, domainOffset, Options.AllowDomainWithoutPeriod))
             {
                 return false;
             }

src/Markdig/Helpers/LinkHelper.cs

@@ -1006,7 +1006,7 @@ public static class LinkHelper
         return c == '\0' || c.IsSpaceOrTab() || c.IsControl() || (isAutoLink && c == '<'); // TODO: specs unclear. space is strict or relaxed? (includes tabs?)
     }
 
-    public static bool IsValidDomain(string link, int prefixLength)
+    public static bool IsValidDomain(string link, int prefixLength, bool allowDomainWithoutPeriod)
     {
         // https://github.github.com/gfm/#extended-www-autolink
         // A valid domain consists of alphanumeric characters, underscores (_), hyphens (-) and periods (.).
@@ -1052,7 +1052,7 @@ public static class LinkHelper
             segmentHasCharacters = true;
         }
 
-        return segmentCount != 1 && // At least one dot was present
+        return (segmentCount != 1 || allowDomainWithoutPeriod) && // At least one dot was present
             segmentHasCharacters && // Last segment has valid characters
             segmentCount - lastUnderscoreSegment >= 2; // No underscores are present in the last two segments of the domain
     }