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Debugging XSL functions (non-Java)
Posted: Mon Dec 15, 2008 7:38 pm
by DAndres109
I'm just getting my feet wet with XSL 2.0 and am currently learning about creating custom functions within an XSL stylesheet. These functions are as simple as the following:
Code: Select all
<xsl:function name="test:get-length">
<xsl:param name="input" as="xs:string" />
<xsl:sequence select="string-length($input)" />
</xsl:function>
I've tried debugging usages of this type of function using both Saxon and SaxonSA in Oxygen 10, but I am only able to see that a call has been made. I cannot step into the function call itself or inspect the parameters passed to it.
Is there a way to step into custom functions such as these?
Re: Debugging XSL functions (non-Java)
Posted: Tue Dec 16, 2008 12:11 pm
by Dan
Saxon is optimizing the XSLT execution by using code rewrite. This very clear when having a variable that gets assigned multiple times:
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<xsl:variable name="v" select="'abc'"/>
<xsl:variable name="v" select="string-join($v,'def')"/>
<xsl:variable name="v" select="string-length($v)"/>
After compilation, the processor will discard the intermediate steps and will evaluate directly:
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<xsl:variable name="v" select="string-length(string-join('abc','def'))"/>
The same is holding for the xsl:sequence constructions.
In your case, to force the XSLT processor step into the function, you should insert an evaluation that cannot be rewriten by the processor, for instance an xsl:message :
Code: Select all
<xsl:function name="test:get-length">
<xsl:param name="input" as="xs:string" />
<xsl:message select="$input"/>
<xsl:sequence select="string-length($input)" />
</xsl:function>
Re: Debugging XSL functions (non-Java)
Posted: Tue Dec 16, 2008 2:59 pm
by DAndres109
This does allow me to step into the xsl:message declaration, but the next step move will take me out of the function.
From a Saxon perspective, is there any way to disable this code optimization for debug purposes?
Re: Debugging XSL functions (non-Java)
Posted: Tue Dec 16, 2008 4:35 pm
by Dan
We had a few discussions with dr. Michael Kay regarding a debugging mode of Saxon in which the optimisations would be disabled, but unfortunately all this remained at the intention level.
I think all the people interested in this Saxon new feature should contact Michael and ask him about it:
http://www.saxonica.com/