Passing node and field dynamically to xslt function - xslt

Question

I am trying to make something to act as a null check decimal fields for use in xslt transformations. I was thinking I could also make similar for other data types as I need. I made this
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:wd="urn:com.workday.report/CR_Question"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:this="urn:this-stylesheet"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<xsl:function name="this:NullCheckField" as="xsd:string">
<xsl:param name="node" as="xsd:string"/>
<xsl:param name="fieldName" as="xsd:string"/>
<xsl:variable name="variableName">
<xsl:choose>
<xsl:when test="not(exists(concat($node, '/', $fieldName)))">
<xsl:value-of select="format-number(0, '#.00')"/>
</xsl:when>
<xsl:otherwise>
<xsl:variable name="x">
<xsl:value-of select="concat($node, '/', $fieldName)"/>
</xsl:variable>
<xsl:variable name="y">
<xsl:value-of select="$x"/>
</xsl:variable>
<xsl:value-of select="format-number(number($y), '#.00')"/>
</xsl:otherwise>
</xsl:choose>
</xsl:variable>
<xsl:value-of select="$variableName"/>
</xsl:function>
<xsl:output method="text" indent="yes"/>
<xsl:template match="wd:Report_Entry">
<xsl:value-of select="this:NullCheckField('wd:Report_Data/wd:Report_Entry','wd:deduction_amount')"/>
<xsl:text>
</xsl:text>
</xsl:template>
</xsl:stylesheet>
and i tried calling it with this line
<wd:Report_Data xmlns:wd="urn:com.workday.report/CR_Question">
<wd:Report_Entry>
<wd:Employee_ID>1555111</wd:Employee_ID>
<wd:Check_Date>2022-04-28</wd:Check_Date>
<wd:NegDeductIndc>0</wd:NegDeductIndc>
<wd:Deduction_YTD>0</wd:Deduction_YTD>
</wd:Report_Entry>
<wd:Report_Entry>
<wd:Employee_ID>1555222</wd:Employee_ID>
<wd:Check_Date>2022-04-28</wd:Check_Date>
<wd:NegDeductIndc>0</wd:NegDeductIndc>
<wd:Deduction_YTD>0</wd:Deduction_YTD>
</wd:Report_Entry>
</wd:Report_Data>
When I run this, the test should fail and use the hard coded 0 since the node is not there, but instead of dropping into
<xsl:when test="not(exists(concat($node, '/', $fieldName)))">
<xsl:value-of select="format-number(0, '#.00')"/>
</xsl:when>
It keeps dropping into the and failing out. I am not sure of two things.
The first is why is my exist check not working correctly and falling into the
Other question - am I able to pass the node names and concat them like this?
Edit: Updated function as of now
<!-- param type 1 = decimal -->
<!-- param type 2 = integer -->
<!-- param type 3 = string -->
<xsl:function name="this:NullCheckField" as="xsd:string">
<xsl:param name="node"/>
<xsl:param name="type" as="xsd:integer"/>
<xsl:variable name="variableName">
<xsl:choose>
<xsl:when test="not(exists($node))">
<xsl:choose>
<xsl:when test="$type = 1">
<xsl:value-of select="format-number(0, '#.00')"/>
</xsl:when>
<xsl:when test="$type = 2">
<xsl:value-of select="0"/>
</xsl:when>
<xsl:otherwise>
<xsl:text/>
</xsl:otherwise>
</xsl:choose>
</xsl:when>
<xsl:otherwise>
<xsl:variable name="x">
<xsl:value-of select="$node[0]"/>
</xsl:variable>
<xsl:choose>
<xsl:when test="$type = 1">
<xsl:value-of select="format-number(number($x), '#.00')"/>
</xsl:when>
<xsl:when test="$type = 2">
<xsl:value-of select="number($x)"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$x"/>
</xsl:otherwise>
</xsl:choose>
</xsl:otherwise>
</xsl:choose>
</xsl:variable>
<xsl:value-of select="$variableName"/>
</xsl:function>
The problem I am trying to resolve is my integration will not always produce the empty nodes. Sometimes there is a missing node and I have been doing checks like this
<xsl:choose>
<xsl:when test="not(exists(wd:DPDEEYDEDS))">
<xsl:value-of select="' '"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="wd:DPDEEYDEDS"/>
</xsl:otherwise>
</xsl:choose>
Some of these are decimal, some are integer, some are spaces. I'm trying to do a dynamic null check. The function will be called, the field node evaluated, if it is not a missing or empty node then it formats the value, otherwise return a default 0|0.00|' '.

Answer 1

Unless you want to move to XSLT with xsl:evaluate support the whole idea of passing in strings with XPath fragments is nonsense.
If, in the context of template match="wd:Report_Entry", you want to pass that Report_Entry element to a function use . e.g. this:my-function(., 'deduction_amount'). The first function argument should be of type node() or element(), certainly you don't want to atomize the node to a string.
Then you could check e.g. test="$node/*[local-name() = $fieldName]" to check for the existence of a child element with local name $fieldName.
I don't see any need to work with element names as as strings, you can simply pass in e.g. this:my-function(wd:deduction_amount), with the type of the paramter being node()? or node()* and then do any exists check on that, if needed.
The whole construction of nested, untyped variables is unnecessarily complicated and inefficient.
I don't even see the need for the function, doing e.g. format-number((wd:deduction_amount, 0)[1], '#.00') inside the template suffices.