Test for xsi:nil="true" - xslt-2.0

Question

I wish to test for xsi:nil="true".
I'm using the replies from kjhughes & Michael Kay in these posts, respectively.
How to implement if-else statement in XSLT?
How do I check if XML value is nil in XSLT
XML:
<OSM>
<EstablishmentDetail>
<RatingValue>5</RatingValue>
<RatingDate>2008-05-15</RatingDate>
</EstablishmentDetail>
<EstablishmentDetail>
<RatingValue>AwaitingInspection</RatingValue>
<RatingDate xsi:nil="true"/>
</EstablishmentDetail>
</OSM>
A snip of the XSL:
<xsl:template>
"Value": "<xsl:value-of select="if (nilled(RatingDate)) then RatingValue else 'XX' "/>",
</xsl:template>
It's producing output but both are 'XX'. Is it just a syntax error?

Answer 1

The function https://www.w3.org/TR/xpath-functions/#func-nilled is meant to work with schema-aware XSLT and validated input i.e. if you use Saxon EE you can expect it to do its job:
In practice, the function returns true only for an element node that
has the attribute xsi:nil="true" and that is successfully validated
against a schema that defines the element to be nillable;

Answer 2

Need to add the namespace in the input document:
<OSM xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<EstablishmentDetail>
<RatingValue>5</RatingValue>
<RatingDate>2008-05-15</RatingDate>
</EstablishmentDetail>
<EstablishmentDetail>
<RatingValue>AwaitingInspection</RatingValue>
<RatingDate xsi:nil="true"/>
</EstablishmentDetail>
</OSM>
I'm not getting the right value out of the standard fn:nilled() function hence substituted a user function:
<?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:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:l="local:functions">
<xsl:output method="xml" indent="yes" />
<xsl:template match="/">
<RatingValues>
<xsl:for-each select="//EstablishmentDetail">
<EstablishmentDetail index="{position()}" >
<RatingValue>
<xsl:value-of select="('XX'[l:nilled(current()/RatingDate) ],
current()/RatingValue)[1]" />
</RatingValue>
<Nilled>
<xsl:value-of select="nilled(RatingDate)" />
</Nilled>
</EstablishmentDetail>
</xsl:for-each>
</RatingValues>
</xsl:template>
<xsl:function name="l:nilled" as="xs:boolean" >
<xsl:param name="e" as="element()" />
<xsl:sequence select="exists($e/#xsi:nil) and $e/#xsi:nil eq 'true'" />
</xsl:function>
</xsl:stylesheet>
which produces:
<?xml version="1.0" encoding="UTF-8"?>
<RatingValues xmlns:l="local:functions" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<EstablishmentDetail index="1">
<RatingValue>5</RatingValue>
<Nilled>false</Nilled>
</EstablishmentDetail>
<EstablishmentDetail index="2">
<RatingValue>XX</RatingValue>
<Nilled>false</Nilled>
</EstablishmentDetail>
</RatingValues>
The Nilled elements in the output just to show that I'm getting false for both cases.