Merge pull request stevencohn#1151 from stevencohn/1150-remove-empty-…

…with-formula

consider mathML comments as text content

OneMore/Commands/Clean/RemoveEmptyCommand.cs

@@ -9,6 +9,7 @@ namespace River.OneMoreAddIn.Commands
  using System.Collections.Generic;
  using System.Globalization;
  using System.Linq;
+ using System.Text.RegularExpressions;
  using System.Threading.Tasks;
  using System.Windows.Forms;
  using System.Xml.Linq;
@@ -122,7 +123,7 @@ public bool CollapseEmptyLines()
  var elements = range
  .Select(e => e.Parent)
  .Distinct()
- .Where(e => e.TextValue().Trim().Length == 0)
+ .Where(e => e.TextValue().Trim().Length == 0 && !e.IsMathML())
  .ToList();
 
  if (elements?.Any() != true)

OneMore/Helpers/Extensions/XElementExtensions.cs

@@ -427,6 +427,20 @@ public static XElement FirstAncestor(this XElement element, XName name, XName br
  }
 
 
+ /// <summary>
+ /// Determines if the content of the element consists only of a mathML statement
+ /// which is identified when its CDATA specifies an XML comment.
+ /// </summary>
+ /// <param name="element"></param>
+ /// <returns></returns>
+ public static bool IsMathML(this XElement element)
+ {
+ var cdata = element.GetCData();
+ return cdata != null &&
+ Regex.IsMatch(cdata.Value, @"<!--.+?-->", RegexOptions.Singleline);
+ }
+
+
  /// <summary>
  /// OneMore Extension >> Extract the sanitized text value of the given element
  /// </summary>