Xpath 'instance of' not working in solr xslt - xslt

Question

I want use xslt in solr to output result in json without specific solr attributes.
{
"techproducts": [
{
"id": "GB18030TEST",
"price": "0.0"
},
{
"id": "SOLR1000",
"price": "0.0"
},
{
"id": "UTF8TEST",
"price": "0.0"
}
],
"paging": {
"count": 3
}
}
The test of type of field (numeric or boolean) test=". instance of xs:integer" in order to add or not quotes do not work and generate a 500 error.
http://localhost:8090/solr/techproducts/select?q=*&fq=price:0&fl=id,price&wt=xslt&tr=json_paginate.xsl
Caused by: javax.xml.transform.TransformerConfigurationException: solrres:/xslt/json_paginate.xsl: line 37: Attribut 'test' obligatoire manquant.
Any suggestions?
<?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" >
<xsl:strip-space elements="*"/>
<xsl:output method="text" indent="no" media-type="application/json"/>
<xsl:template match='/'>
<xsl:text>{"techproducts":[</xsl:text>
<xsl:apply-templates select="response/result/doc"/>
<xsl:text>],</xsl:text>
<xsl:text>"paging":{"count":</xsl:text><xsl:value-of select="response/result/#numFound"/><xsl:text>}}</xsl:text>
</xsl:template>
<xsl:template match="doc">
<xsl:variable name="pos" select="position()"/>
<xsl:if test="position() > 1">
<xsl:text>,</xsl:text>
</xsl:if>
<xsl:text>{</xsl:text>
<xsl:apply-templates>
<xsl:with-param name="pos"><xsl:value-of select="$pos"/></xsl:with-param>
</xsl:apply-templates>
<xsl:text>}</xsl:text>
</xsl:template>
<xsl:template match="doc/*">
<xsl:if test="position() > 1">
<xsl:text>,</xsl:text>
</xsl:if>
<xsl:text>"</xsl:text><xsl:value-of select="#name"/><xsl:text>":</xsl:text>
<xsl:choose>
<!-- if integer, do not add quotes -->
<xsl:when test=". instance of xs:integer">
<xsl:value-of select="."/>
</xsl:when>
<!-- if boolean, do not add quotes -->
<xsl:when test=". instance of xs:boolean">
<xsl:value-of select="."/>
</xsl:when>
<xsl:otherwise>
<xsl:text>"</xsl:text><xsl:value-of select="."/><xsl:text>"</xsl:text>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
</xsl:stylesheet>
To solve the problem :
I have upgraded xslt version in solr http://wiki.apache.org/solr/XsltResponseWriter and used
<xsl:choose>
<!-- if decimal, do not add quotes -->
<xsl:when test=". castable as xs:decimal">
<xsl:value-of select="."/>
</xsl:when>
<!-- if boolean, do not add quotes -->
<xsl:when test=". castable as xs:boolean">
<xsl:value-of select="."/>
</xsl:when>
<xsl:otherwise>
<xsl:text>"</xsl:text><xsl:value-of select="."/><xsl:text>"</xsl:text>
</xsl:otherwise>
</xsl:choose>

Answer 1

Here is how to achieve in XSLT 1.0 the intended behavior of the provided XSLT 2.0 code:
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:template match=
"*[not(*) and text()
and
not(contains('|true|false|', concat('|', ., '|')))]">
<xsl:value-of select='concat(&apos;"&apos;, ., &apos;"&apos;)'/>
</xsl:template>
<xsl:template match="*[not(*) and text() and number(.) = .]" priority="3">
<xsl:value-of select="number(.)"/>
</xsl:template>
</xsl:stylesheet>
When this transformation is applied on the following XML document:
<t>
<a>1</a>
<b>true</b>
<c>false</c>
<d>-3</d>
<e>x</e>
<f>.25</f>
</t>
The wanted, correct result is produced:
1
true
false
-3
"x"
0.25
Do note: In addition to the behavior that is intended in the provided XSLT 2.0 code, the above transformation also implements correct output of JSON-acceptable representation for any decimal number.
In case only processing and displaying integer values is wanted, just use:
floor(.) = .
Update:
The OP has just revealed that he could actually use an XSLT 2.0 processor.
Here is one possible XSLT 2.0 solution, which represents correctly the strings "true" and "false" as JSON Booleans, any integers and decimals to JSON numbers, and any other atomic value -- to quoted string:
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xsl:output method="text"/>
<xsl:template match=
"*[not(*) and text() and not(. = ('true', 'false'))]">
<xsl:value-of select='concat(&apos;"&apos;, ., &apos;"&apos;)'/>
</xsl:template>
<xsl:template match="*[not(*) and text() and . castable as xs:decimal]" priority="3">
<xsl:value-of select="number(.)"/>
</xsl:template>
</xsl:stylesheet>
When this transformation is applied on the same XML document (above, the same correct, wanted result is produced:
1
true
false
-3
"x"
0.25

Answer 2

Your goal is to achieve syntactically correct JSON data: no quotes for numbers and the strings "true" and "false". That's what your attempt handling these data types tells me.
In this case the following xsl:choose part should work - at least I hope so, since we don't know your input data:
XSLT-2.0: (*)
<xsl:choose>
<!-- if number, do not add quotes -->
<xsl:when test="number(.)">
<xsl:value-of select="."/>
</xsl:when>
<!-- if boolean, do not add quotes -->
<xsl:when test="matches(.,'true|false','i')">
<xsl:value-of select="lower-case(.)"/>
</xsl:when>
<xsl:otherwise>
<xsl:text>"</xsl:text><xsl:value-of select="."/><xsl:text>"</xsl:text>
</xsl:otherwise>
</xsl:choose>
It should be mentioned (see comments) that all numbers get printed without quotation marks. Not only integers. Which should be ok for a valid JSON output.
(*) the first version of my answer had a remarkable amount of errors in it which I apologize for (downvoting that answer was quite appropriate). The version shown above has been tested with Saxon and worked as expected.