[xsl] How to use document() of doc() function with copy idiom, or how to access nodes of doc() tree

[Abel Braaksma Online <abel.online@xxxxxxxxx>]

Dear list,

I have been trying some variants, but I think I've been stuck in the 
namespaces and context location labyrinth. What I want seems easy: I 
have a set of documents, all valid XML and want to output the contents 
of these documents, either as one big XML document, or as a set of 
documents.

In essence: using the copy idiom on each document and, optionally, doing 
something with the tree that is input from the document() function.

Problem: all my nodes are gone and the external documents are output as 
one big piece of text (except for the tags "doc" and "input-file") and I 
don't seem to be able to find specific values, like the "tableData" tag 
below. I know this is usually a namespace problem, but I don't know how 
to solve it. Because it does not even work for one input file, I provide 
a stripped down version of my XSLT below, that parses one external xml 
document.

Namespace of input xml document: this is equal to the current xslt 
document (just because saxon needs an input document. I don't actually 
use it)
Namespace of document() xml doc: "http://www.nuntia.com/tablewiz1.0";
Namespace of output document: "http://www.nuntia.com/tablewiz1.0";

XSLT file:
<xsl:stylesheet version="2.0" 
   xmlns = "http://www.nuntia.com/tablewiz1.0";
   exclude-result-prefixes = "nuntia xsl xs fn xdt"
   xpath-default-namespace = "http://www.nuntia.com/tablewiz1.0";>
  
   <xsl:output indent="yes" />
  
   <!-- name of the input file or files -->
   <xsl:param name="input-file" select="'test.xml'" />

   <!-- load the documents -->
   <xsl:variable name="documents">
           <doc>
               <input-filename><xsl:value-of select="." /></input-filename>
               <xsl:value-of select="document($input-file)" />
           </doc>
   </xsl:variable>
  
   <xsl:template match="/">
       <output>
           <xsl:for-each select="$documents/doc">
               <xsl:apply-templates select="." mode="copy" />
           </xsl:for-each>
       </output>
   </xsl:template>
  
   <xsl:template match="node() | @*" mode="copy">
       <xsl:copy>
           <xsl:apply-templates select="@* | node()" mode="copy"/>
       </xsl:copy>
   </xsl:template>
  
</xsl:stylesheet>

XML file that is input using document() function, namely test.xml:
<?xml version="1.0" encoding="UTF-8"?>
<tableData name="bla">
  <description>Table description</description>
  <rows total="3">
      <row id="35" row-index="not-applicable">
          <cell>Row1Cell1</cell>
          <cell>Row1Cell2</cell>
      </row>
  </rows>
</tableData>