How to use saxon:node-set(document($f)) ?

Hi

I'm trying to write a stylesheet that produces some
nice error messages, instead of parser error messages,
when a configuration file cannot be loaded. Previously
I would load a configuration file (name specified on
the command line) with this:

<xsl:param name="CONFIG_FILE" select="'???'" />
<xsl:variable name="config" select="document($CONFIG_FILE)" />

This results in a fatal error if CONFIG_FILE is not
specified, with a (perhaps) unsightly error message.
Unfortunately if I put some "if"s around the document()
function, I get an RTF instead of a nodeset, but in
this case I'm prepared to use extension functions
like saxon:node-set().

So I tried this (fluff omitted) :

----- START XSL
<?xml version="1.0" encoding="UTF-8"?>

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"
                xmlns:saxon="http://icl.com/saxon"
                xmlns:file="java.io.File"
                extension-element-prefixes="saxon"
                exclude-result-prefixes="saxon">

<xsl:param name="CONFIG_FILE" select="'???'" />

<xsl:variable name="config">
  <xsl:if test="$CONFIG_FILE != '???' and
      file:exists(file:new($CONFIG_FILE))">
    <xsl:value-of select="saxon:node-set(document($CONFIG_FILE))" />
  </xsl:if>
</xsl:variable>

<xsl:template match="/">
<xsl:message terminate="yes">
  <xsl:text>$config = </xsl:text>
  <xsl:copy-of select="$config" />
</xsl:message>
</xsl:template>

</xsl:stylesheet>
----- END XSL

saxon:node-set(document($CONFIG_FILE)), and various simple
variations on that theme, appear to produce empty node-sets,
(yes it is called).

What am I doing wrong?

Thanks in advance.

-- 
Warren Hedley
Department of Engineering Science
Auckland University
New Zealand


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