title: How to track the source line (location) of an XML element?
body: <p>I assume that there is probably no satisfactory answer to this question, but I ask it anyway in case I missed something.</p>
  
  <p>Basically, I want to find out the line in the source document from which a certain XML element originated, given the element instance. I want this only for better diagnostic error messages - the XML is part of a configuration file, and if there is something wrong with it, I want to be able to point the reader of the error message to exactly the right place in the XML document so he can correct the error.</p>
  
  <p>I understand that the standard Scala XML support probably has no built-in feature like this. After all, it would be wasteful to annotate every single <code>NodeSeq</code> instance with such information, and not every XML element even has a source document from which it has been parsed. It seems to me that the standard Scala XML parser throws the line information away, and later on there is no way to retrieve it.</p>
  
  <p>But switching to another XML framework is not an option. Adding another library dependency "only" for the sake of better diagnostic error messages seems inappropriate to me. Also, despite some shortcomings, I really like the built-in pattern matching support for XML.</p>
  
  <p>My only hope is that you can show me a way to alter or subclass the standard Scala XML parser such that the nodes it produces will be annotated with the number of the source line. Maybe a special subclass of <code>NodeSeq</code> can be created for this. Or maybe only <code>Atom</code> can be subclassed because <code>NodeSeq</code> is too dynamic? I don't know.</p>
  
  <p>Anyway, my hopes are close to zero. I don't think there is a place in the parser where we can hook in to change the way nodes are created, and that at that place the line information is available. Still, I wonder why I have not found this question before. Please point me to the original if this is a duplicate.</p>