RE: [xsl] possible xalan error using function-available() and element-available()

["Michael Kay" <mike@xxxxxxxxxxxx>]

Bugs in this area are not improbable - you're probably the first person who
has used function-available with a dynamically-constructed argument except
in test cases. The processor has to do a lot of work for this, like saving
the namespace context. (Your code doesn't seem to do anything special to
ensure that the prefix of the function name is one that's actually declared
in the stylesheet)

I've always assumed that the only reason for testing function-available()
was because you wanted to call the function, and since the function call has
to use a static name, there's no conceivable reason to use
function-available with a dynamic name. Perhaps I was wrong.

Michael Kay
http://www.saxonica.com/

> -----Original Message-----
> From: James Fuller [mailto:james.fuller.2007@xxxxxxxxx] 
> Sent: 03 October 2007 14:59
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject: [xsl] possible xalan error using 
> function-available() and element-available()
> 
> simple xslt revealed a possible bug with Xalan (latest java version)
> 
> 
> a long time ago, I had a set of EXSLT (www.exslt.org) 
> coverage XSLT, which outputted a simple report ... with 
> Firefox 3.0 including a few EXSLT functions ... I dusted them off;
> 
> http://www.ruminate.co.uk/2007/09/testing-exslt-support.html
> 
> explains the process ... its, in a nutshell,  a single XSLT 
> sheet is run by an XSLT Processor and reports back what EXSLT 
> functions is supported by said XSLT Processor.
> 
> There seems to be an error thrown by Xalan when processing either
> function-available() or element-available() when the function 
> or element name is supplied as an xsl:variable
> 
> <xsl:template match="exslt:function">
>         <xsl:variable name="prefix" 
> select="../../../exslt:module/@prefix"/>
> 
> <xsl:variable name="funcname"><xsl:value-of 
> select="concat($prefix,':',@name)"/></xsl:variable>
>     <tr>
>         <td>&#160;<xsl:value-of select="$funcname"/></td>
>         <td>
>             <xsl:choose>
>                 <xsl:when 
> test="function-available(string($funcname))">
>                     <div class="good">Available</div>
>                 </xsl:when>
>                 <xsl:otherwise>
>                     <div class="bad">Not Available</div>
>                 </xsl:otherwise>
>             </xsl:choose>
>         </td>
>     </tr>
> </xsl:template>
> 
> the operative term is
> 
> function-available(string($funcname))
> 
> Works fine on some XSLT Procesors
> 
> Saxon
> http://www.webcomposite.com/result/saxon8-result.html
> 
> XSLT Proc
> http://www.webcomposite.com/result/xsltproc-result.html
> 
> and a very early version of xalan ...
> http://www.webcomposite.com/result/xalan-result.html
> 
> however, latest Xalan doesn't like $funcname, nor does it like
> string($funcname) in function-available().
> 
> throws an error related to XPath
> 
> Line #86; Column #72; XSLT Error
> (javax.xml.transform.TransformerException): Unknown error in XPath.
> 
> is this an issue with spec interpretation, a bug ... or 
> something else ?
> 
> tia, Jim Fuller