Add mandatory nodes with XSLT - xslt

Question

I am facing an xslt/xpath problem and hope someone could help, in a few words here is what I try to achieve.
I have to transform an XML document where some nodes may be missing, these missing nodes are mandatory in the final result. I have the set of mandatory node names available in an xsl:param.
The base document is:
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="TRANSFORM.xslt"?>
<BEGIN>
<CLIENT>
<NUMBER>0021732561</NUMBER>
<NAME1>John</NAME1>
<NAME2>Connor</NAME2>
</CLIENT>
<PRODUCTS>
<PRODUCT_ID>12</PRODUCT_ID>
<DESCRIPTION>blah blah</DESCRIPTION>
</PRODUCTS>
<PRODUCTS>
<PRODUCT_ID>13</PRODUCT_ID>
<DESCRIPTION>description ...</DESCRIPTION>
</PRODUCTS>
<OPTIONS>
<OPTION_ID>1</OPTION_ID>
<DESCRIPTION>blah blah blah ...</DESCRIPTION>
</OPTIONS>
<PROMOTIONS>
<PROMOTION_ID>1</PROMOTION_ID>
<DESCRIPTION>blah blah blah ...</DESCRIPTION>
</PROMOTIONS>
</BEGIN>
Here is the stylesheet so far:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:fn="http://www.w3.org/2005/xpath-functions">
<xsl:output method="xml" encoding="UTF-8" indent="yes"/>
<xsl:param name="mandatoryNodes" as="xs:string*" select=" 'PRODUCTS', 'OPTIONS', 'PROMOTIONS' "/>
<xsl:template match="/">
<xsl:apply-templates select="child::node()"/>
</xsl:template>
<xsl:template match="node()">
<xsl:copy>
<xsl:apply-templates/>
</xsl:copy>
</xsl:template>
<xsl:template match="BEGIN">
<xsl:element name="BEGIN">
<xsl:for-each select="$mandatoryNodes">
<!-- If there is no node with this name -->
<xsl:if test="count(*[name() = 'current()']) = 0">
<xsl:element name="{current()}" />
</xsl:if>
</xsl:for-each>
<xsl:apply-templates select="child::node()"/>
</xsl:element>
</xsl:template>
</xsl:stylesheet>
I tried the transformation in XML Spy, the xsl:iftest failed saying that 'current item is PRODUCTS of type xs:string.
I've tried the same xsl:if outside of a for-each and it seems to work ... what am I missing ?

Answer 1

Inside of <xsl:for-each select="$mandatoryNodes"> the context item is a string but you want to access the primary input document and its nodes so you need to store that document or the template's context node in a variable and use that e.g.
<xsl:template match="BEGIN">
<xsl:variable name="this" select="."/>
<xsl:element name="BEGIN">
<xsl:for-each select="$mandatoryNodes">
<!-- If there is no child node of `BEGIN` with this name -->
<xsl:if test="count($this/*[name() = current()]) = 0">
<xsl:element name="{current()}" />
</xsl:if>
</xsl:for-each>
<xsl:apply-templates select="child::node()"/>
</xsl:element>
</xsl:template>