XSLT: Test Parameter to know if it has been set

Question

I have a situation where the param won't be set, but my attempts to capture & handle the sitation aren't working.

I'm using the following:

<xsl:template match="xs:complexType">
  <xsl:param name="prefix" />

  <xsl:variable name="prefix-no-core">
    <xsl:choose>
      <!-- if no value, default to 'AcRec' -->
      <xsl:when test="not($prefix)"> 
        <xsl:value-of select="'AcRec'" />
      </xsl:when>
      <!-- if 'core', leave as empty string -->
      <xsl:when test="$prefix = 'core'">
      </xsl:when>
      <!-- if 'AcRec', set the value -->
      <xsl:when test="$prefix = 'AcRec'">
        <xsl:value-of select="$prefix" />
      </xsl:when>      
    </xsl:choose>
  </xsl:variable>

  <xs:complexType name="{concat($prefix-no-core, @name)}">
  ...
</xsl:template>

I've also tried $prefix='' in the first test - neither work. but if I use:

<xsl:value-of select="not($prefix)" />

... the value prints out as true. But using that in my xsl:choose doesn't produce any output.

Answer 1

Note: replaced old answer, check history if you want it.

The following input:

<test xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt;
    <xs:complexType name="something"/>
    <xs:complexType name="somethingElse"/>
</test>

Fed to the following XSLT:

<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" version="2.0">
    <xsl:template match="/">
     <xsl:for-each select="node()">
      <xsl:apply-templates/>
     </xsl:for-each>
    </xsl:template>

    <xsl:template match="xs:complexType">
     <xsl:param name="prefix" />
     <xsl:variable name="prefix-no-core">
      <xsl:choose>
       <xsl:when test="not($prefix)">AcRec</xsl:when>
       <xsl:when test="$prefix = 'core'"/>
       <xsl:when test="$prefix = 'AcRec'">AcRec</xsl:when>                       
      </xsl:choose>
     </xsl:variable>

     <xs:complexType name="{concat($prefix-no-core, @name)}"/>
    </xsl:template>
</xsl:transform>

Gives the following result:

<xs:complexType name="AcRecsomething" xmlns:xs="http://www.w3.org/2001/XMLSchema"/&gt;
<xs:complexType name="AcRecsomethingElse" xmlns:xs="http://www.w3.org/2001/XMLSchema"/&gt;

I'm not sure what more you're looking for...

Answer 2

It's a hack, but I have had success by first wrapping the parameter with the normalize-space() function before testing for an empty param.

<xsl:value-of select="not(normalize-space($prefix))" />

Answer 3

Of the suggestions made to date, the only solution that worked was to always set the parameter value when a call to the template is made. For example, previously I had:

<xsl:apply-templates select="//xs:complexType[@name='AddressType']" />

This had to be changed to:

<xsl:apply-templates select="//xs:complexType[@name='AddressType']">
  <xsl:with-param name="prefix" select="'AcRec'" />
</xsl:apply-templates>

I'd really like to know why not($param) and $param='' don't work in a WHEN test, yet I can get the value of not($param) in a xsl:value-of statement.