Hi Adrian/Stefan, Apologies for dredging up a 2-year-old thread but I've hit the same issue and found that although the posted solution works for variables declared with simple string values, it fails when considering xsl:param values or "calculated" values. Consider:
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"; xmlns:abc="bar" extension-element-prefixes="abc"> <xsl:output method="xml"/> <xsl:param name="param1">default param value</xsl:param> <xsl:template match="/"> <xsl:variable name="var1" select="concat( 'http://', $param1 )"/> <abc:foo attr1="{$var1}"/> <baz><xsl:value-of select="concat( 'XSLT ouput: ', $var1 )"/></baz> </xsl:template> </xsl:stylesheet> Now let's say I want to receive the value of "$var1" in my extension-element foo(): #!/usr/local/bin/python3 # -*- coding: utf-8 -*- import sys from lxml import etree from copy import deepcopy class FooExtensionElement( etree.XSLTExtension ): def execute( self, context, self_node, input_node, output_parent ): print( "attr1: {}".format( self_node.get( "attr1" ))) parser = etree.XMLParser( load_dtd=True ) extensions = { ( 'bar', 'foo' ) : FooExtensionElement() } transformer = etree.XSLT( etree.parse( sys.stdin, parser ), extensions = extensions ) xml_doc = etree.XML( '<dummy/>' ) result = transformer( xml_doc, param1=etree.XSLT.strparam( "passed param value" )) print( result ) When run, the output is: attr1: {$var1} <?xml version="1.0"?> <baz bif="http://passed param value">XSLT ouput: http://passed param value</baz> This shows that: * self_node.get( "attr1" ) returns the literal string "{$var1}" in execute(), i.e. the transformer has not evaluated {$var1} when passing it to abc:foo/@attr1 * baz/@bif gets the evaluated value of {$var1} as expected If I were to perform the solution suggested below and lookup //xsl:variable[ @name = 'var1']/@select from within execute(), it would return the string "concat( 'http://', $param1 )" I could attempt to evaluate this in self_node.xpath(), but I don't have access to the value of $param1, right? So this would result in: lxml.etree.XPathEvalError: Undefined variable What if I first looked up the value of $param1 in the same way as suggested below for xsl:variable? //xsl:param[ @name = 'param1']/text() would return "default param value", NOT the actual value ("passed param value") which was passed in: AFAIK, I have *no* way to access that value from execute(). This problem goes away if evaluation of {$xyz} -syntax is honored for extension-elements. As demonstrated above, this is already working perfectly for elements in the XSL which have no namespace (the "baz" element in my example). Is there a fundamental reason why extension-elements are excluded from these evaluations? If this contravenes XSLT convention, is it possible to place a map of variable/param names and their values within the 'context' parameter passed to the execute() function so that extension elements can perform their own lookup? Many thanks! Mike Adrian Bool wrote: > Hi Stefan, > Many thanks for your thoughts. I hadn't considered just executing an XPath > query directly against the XSL as simple XML – but that works! I combined > this idea with your xpath expression and now have a function that will > return the correct value: > def get_variable_from_xsl(variable_name, xsl): > xpath_results = xsl.xpath("//xsl:variable[@name=$name]", > name=variable_name, > namespaces={'xsl':'http://www.w3.org/1999/XSL/Transform' > }) > for xpath_result in xpath_results: > if xpath_result.get('name') == variable_name: > for xpath_child in xpath_result.getchildren(): > if 'select' in xpath_child.keys(): > return xpath_child.get('select') > return None > destination_url = get_variable_from_xsl('destination_url', xsl) > print(f"destination_url = {destination_url}") > Which returns: > destination_url = 'https://my.domain.example.com/' > Thanks again! > aid > On Wed, 10 Apr 2019 at 18:25, Stefan Behnel stefan...@behnel.de wrote: > > Adrian Bool schrieb am 10.04.19 um 10:49: > > I'm trying to extract from data from XSL files on an IBM DataPower > > system. > > I can't change the XSLT files - and therefore need to work around their > > current structure to get the info I need. > > Well, XSL is XML, so you can always post-process the XSL document after > > parsing it as XML, before you pass it into the XSLT() constructor. > > I'm doing this from within Python 3.7 using etree.__version__ 4.3.3. > > Here are my imports, a dummy XML object and a cutdown version of the XSL > > file from the IBM system: > > from lxml import etree > > from textwrap import dedent > > > > xml = etree.XML("""<root></root>""") > > > > xsl = etree.XML(dedent( > > """<?xml version="1.0"?> > > <xsl:stylesheet version="1.0" > > xmlns:xsl="http://www.w3.org/1999/XSL/Transform"; > > xmlns:dp="http://www.datapower.com/extensions"; > > extension-element-prefixes="dp"> > > > > <xsl:template match="node()|@*"> > > <xsl:copy> > > <xsl:apply-templates select="node()|@*"/> > > </xsl:copy> > > > > <xsl:variable name="destination_url"> > > <xsl:value-of select="'https://my.domain.example.com/'" > > > > /> > > </xsl:variable> > > > > <!--Set the destination URL in the context variable--> > > <dp:set-variable name="'var://context/mpgw/Destination'" > > > > value="$destination_url" /> > > I don't think I've ever tried this myself in lxml. I guess I would have > > expected value="{$destination_url}" rather than the plain variable > > reference here. Can't say how XSLT is meant to deal with this. > > </xsl:template> > > </xsl:stylesheet> > > """)) > > > > > > My goal is to use lxml to process this file and extract the contents of > > the > > DataPower variable 'var://context/mpgw/Destination' - i.e. the contents > > of > > the xsl:variable $destination_url - in the above case ' > > https://my.domain.example.com/'. > > I've created an XSLT extension for the "dp:set-variable" element to try > > to > > capture this information: > > class MyExtElement(etree.XSLTExtension): > > def execute(self, context, self_node, input_node, output_parent): > > if self_node.tag == '{ > > > > http://www.datapower.com/extensions%7Dset-variable': > > print(f"Setting variable of name {self_node.get('name')} > > to > > value {self_node.get('value')}") > > extensions = { ('http://www.datapower.com/extensions', > > > > 'set-variable') > > : MyExtElement() } > > result = etree.XSLT(xsl, extensions=extensions)(xml) > > print(f"Result: {result}") > > When this is being called; instead of the value of destination_url I'm > > getting the static "$destination_url" string instead - with the output of > > the above script being: > > Setting variable of name 'var://context/mpgw/Destination' to value > > > > $destination_url > > Result: <?xml version="1.0"?> > > <root/> > > I am rather suprised that the $destination_url xsl:variable was not being > > evaluated - does anyone know why this is the case? > > Given the above, I've been trying to find a way to access the > > $destination_url xsl:variable from within my XSLTExtension - but > > unfortunately with no luck. > > Did you try looking it up in the XSL document via XPath? Something like > > .xpath("//xsl:variable[@name=$name]", name="destination_url") > > (plus namespaces) > > Stefan > > _________________________________________________________________ > > Mailing list for the lxml Python XML toolkit - http://lxml.de/ > > l...@lxml.de > > https://mailman-mail5.webfaction.com/listinfo/lxml > > _______________________________________________ lxml - The Python XML Toolkit mailing list -- lxml@python.org To unsubscribe send an email to lxml-le...@python.org https://mail.python.org/mailman3/lists/lxml.python.org/ Member address: arch...@mail-archive.com
