How can I pass HTML-element as parameter to XSLT function? - xslt

Question

I have the following XSLT-function that I use in a XSLT file to generate XHTML output:
<xsl:function name="local:if-not-empty">
<xsl:param name="prefix"/>
<xsl:param name="str"/>
<xsl:param name="suffix"/>
<xsl:if test="$str != ''"><xsl:value-of select="concat($prefix, $str, $suffix)"/></xsl:if>
</xsl:function>
it simply checks whether a string str is not empty and, if so, returns the string, concatenated with a prefix and a suffix.
The function works fine as long as I only pass simple strings. But when I try to pass HTML elements as prefix or suffix, e.g.:
<xsl:value-of select="local:if-not-empty('', /some/xpath/expression, '<br/>')"/>
I get the following error message:
SXXP0003: Error reported by XML parser: The value of attribute "select"
associated with an element type "null" must not contain the '<' character.
The next thing I tried was to define a variable:
<xsl:variable name="br"><br/></xsl:variable>
and pass it to the function:
<xsl:value-of select="local:if-not-empty('', /some/xpath/expression, $br)"/>
but here, of course, I get an empty string, as the value of the element is extracted, and not the element itself copied.
My final hopeless attempt was to define a text element in the variable:
<xsl:variable name="br">
<xsl:text disable-output-escaping="yes"><br/></xsl:text>
</xsl:variable>
and pass this to the function, but this wasn't permitted, either.
XTSE0010: xsl:text must not contain child elements
I probably don't understand the intricate inner workings of XSLT, but in my opinion adding a <br/> element within a XSLT-transformation through a generic function seems legitimate...
Anyways... I'd appreciate if anyone could give me an alternative solution. I'd also like to understand why this doesn't work...
PS: I'm using Saxon-HE 9.4.0.1J, Java version 1.6.0_24

Answer 1

Try this:
<xsl:value-of select="local:if-not-empty('', /some/xpath/expression, '<br/>')" disable-output-escaping="yes"/>

Answer 2

Instead of concat, use: <xsl:copy-of> and pass as parameters items not strings:
<xsl:copy-of select="$pPrefix"/>
<xsl:copy-of select="$pStr"/>
<xsl:copy-of select="$pSuffix"/>
Here is a complete example:
<xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:local="my:local" exclude-result-prefixes="local">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:variable name="vBr"><br/></xsl:variable>
<xsl:template match="/">
<xsl:sequence select="local:if-not-empty('a', 'b', $vBr/*)"/>
</xsl:template>
<xsl:function name="local:if-not-empty">
<xsl:param name="pPrefix"/>
<xsl:param name="pStr"/>
<xsl:param name="pSuffix"/>
<xsl:if test="$pStr != ''">
<xsl:copy-of select="$pPrefix"/>
<xsl:copy-of select="$pStr"/>
<xsl:copy-of select="$pSuffix"/>
</xsl:if>
</xsl:function>
</xsl:stylesheet>
When this transformation is applied on any XML document (not used), the wanted, correct result is produced:
a b<br/>

Answer 3

The problem is that <br/> is not a string - it is an XML element, so it cannot be manipulated using string functions. You need a separate function like this:
<xsl:function name="local:br-if-not-empty">
<xsl:param name="prefix"/>
<xsl:param name="str"/>
<xsl:if test="$str != ''">
<xsl:value-of select="concat($prefix, $str)"/>
<br/>
</xsl:if>
</xsl:function>
or a 'trick' like this where you handle <br/> as a separate case:
<xsl:function name="local:if-not-empty">
<xsl:param name="prefix"/>
<xsl:param name="str"/>
<xsl:param name="suffix"/>
<xsl:if test="$str != ''">
<xsl:value-of select="concat($prefix, $str)"/>
<xsl:choose>
<xsl:when test="$suffix = '<br/>'>
<br/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$suffix"/>
</xsl:otherwise>
</xsl:choose>
</xsl:if>
</xsl:function>