XSLT 1.0 - Create node set and pass as a parameter

Question

Using XSLT 1.0, I'm trying to essentially create a small node set and then pass it as a parameter to a template, something like the following:

<xsl:call-template name="widget">
  <xsl:with-param name="flags">
    <items>
      <item>widget.recent-posts.trim-length=100</item>
      <item>widget.recent-posts.how-many=3</item>
      <item>widget.recent-posts.show-excerpt</item>
    </items>
  </xsl:with-param>
</xsl:call-template>

The idea is that then from within the widget template I could write something like:

<xsl:value-of select="$flags/item[1]" />

Obviously I get compile errors.. how can I achieve this sort of thing?

Answer 1

Well, I managed to get around this in the following way:

First add a custom namespace to your stylesheet, e.g. xmlns:myns="http://my.ns.com"

Then define the nodeset at the top of the stylesheet:

<myns:recent-posts-flags>
    <item>widget.recent-posts.trim-length=100</item>
    <item>widget.recent-posts.how-many=3</item>
    <item>widget.recent-posts.show-excerpt</item>
</myns:recent-posts-flags>

Then reference in the following way:

<xsl:call-template name="widget">
    <xsl:with-param name="flags" select="document('')/*/myns:recent-posts-flags" />
</xsl:call-template>

This works, but it would still be ideal for me to define the node-set within the <xsl:with-param> tag itself, as in the first example I gave.. anyone think that would be possible?

Answer 2

There is a way (non-standard) in XSLT 1.0 to create temporary trees dynamically and evaluate XPath expressions on them, however this requires using the xxx:node-set() function.

Whenever nodes are dynamically created inside the body of an xsl:variable or an xsl:param, the type of that xsl:variable / xsl:param is RTF (Result Tree Fragment) and the W3 XSLT 1.0 Spec. limits severyly the kind of XPath expressions that can be evaluated against an RTF.

As a workaround, almost every XSLT 1.0 vendor has their own xxx:node-set() extension function that takes an RTF and produces a normal node-set from it.

The namespace to which the xxx prefix (or any other prefix you choose) is bound is different for different vendors. For MSXML and the two .NET XSLT processor it is: "urn:schemas-microsoft-com:xslt". The EXSLT library uses the namespace: "http://exslt.org/common". This namespace EXSLT is implemented on many XSLT 1.0 processors and it is recommended to use its xxx:node-set() extension, if possible.

Here is a quick example:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
 xmlns:msxsl="urn:schemas-microsoft-com:xslt"
 xmlns:ext="http://exslt.org/common"
  exclude-result-prefixes="ext msxsl"
 >
 <xsl:template match="/">
  <xsl:variable name="vTempRTF">
   <a>
    <b/>
   </a>
  </xsl:variable>

  <xsl:copy-of select="ext:node-set($vTempRTF)/a/*"/>
 </xsl:template>
</xsl:stylesheet>