Heading with digits only should not be considered as a numbering #189

Author: onizet

src/Html2OpenXml/Expressions/Numbering/HeadingElementExpression.cs

@@ -9,6 +9,7 @@
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
  * PARTICULAR PURPOSE.
  */
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text.RegularExpressions;
@@ -23,7 +24,8 @@ namespace HtmlToOpenXml.Expressions;
 /// </summary>
 sealed class HeadingElementExpression(IHtmlElement node) : NumberingExpressionBase(node)
 {
-    private static readonly Regex numberingRegex = new(@"^\s*(\d+\.?)*\s*");
+    private static readonly Regex numberingRegex = new(@"^\s*(?<number>[0-9\.]+\s*)[^0-9]",
+        RegexOptions.Compiled, TimeSpan.FromMilliseconds(100));
 
     /// <inheritdoc/>
     public override IEnumerable<OpenXmlElement> Interpret (ParsingContext context)
@@ -36,7 +38,7 @@ public override IEnumerable<OpenXmlElement> Interpret (ParsingContext context)
 
         var paragraph = childElements.FirstOrDefault() as Paragraph;
 
-        paragraph ??= new Paragraph(childElements);
+        paragraph ??= new(childElements);
         paragraph.ParagraphProperties ??= new();
         paragraph.ParagraphProperties.ParagraphStyleId = 
             context.DocumentStyle.GetParagraphStyle(context.DocumentStyle.DefaultStyles.HeadingStyle + level);
@@ -65,16 +67,30 @@ public override IEnumerable<OpenXmlElement> Interpret (ParsingContext context)
 
     private static bool IsNumbering(OpenXmlElement runElement)
     {
+        if (runElement.InnerText is null)
+            return false;
+
         // Check if the line starts with a number format (1., 1.1., 1.1.1.)
         // If it does, make sure we make the heading a numbered item
-        Match regexMatch = numberingRegex.Match(runElement.InnerText ?? string.Empty);
+        var headingText = runElement.InnerText;
+        Match regexMatch;
+        try
+        {
+            regexMatch = numberingRegex.Match(headingText);
+        }
+        catch (RegexMatchTimeoutException)
+        {
+            return false;
+        }
+
 
         // Make sure we only grab the heading if it starts with a number
-        if (regexMatch.Groups.Count > 1 && regexMatch.Groups[1].Captures.Count > 0)
+        if (regexMatch.Success && headingText.Length > regexMatch.Groups["number"].Length)
         {
-             // Strip numbers from text
+            // Strip numbers from text
+            headingText = headingText.Substring(regexMatch.Groups["number"].Length);
             runElement.InnerXml = runElement.InnerXml
-                .Replace(runElement.InnerText!, runElement.InnerText!.Substring(regexMatch.Length));
+                .Replace(runElement.InnerText!, headingText);
 
             return true;
         }

test/HtmlToOpenXml.Tests/HeadingTests.cs

@@ -101,5 +101,27 @@ public void MaxLevel_ShouldBeIgnored()
                     Is.Null, $"Only {maxLevel+1} levels of heading supported");
             });
         }
+
+        [Test(Description = "Heading with number but no text should be ignored (issue #189)")]
+        public void NumberingWithNoTextPattern_ReturnsSimpleHeading()
+        {
+            var elements = converter.Parse("<h1>00</h1>");
+
+            var absNum = mainPart.NumberingDefinitionsPart?.Numbering
+                .Elements<AbstractNum>()
+                .Where(abs => abs.AbstractNumDefinitionName?.Val == NumberingExpressionBase.HeadingNumberingName)
+                .SingleOrDefault();
+            Assert.That(absNum, Is.Null);
+
+            var paragraphs = elements.Cast<Paragraph>();
+            Assert.Multiple(() =>
+            {
+                Assert.That(paragraphs.Count(), Is.EqualTo(1));
+                Assert.That(paragraphs.First().InnerText, Is.EqualTo("00"));
+                Assert.That(paragraphs.First().ParagraphProperties?.NumberingProperties?.NumberingLevelReference?.Val,
+                    Is.Null,
+                    "First paragraph is not a numbering");
+            });
+        }
     }
 }