At 2012-05-09 17:02 +0200, Christian Roth wrote:
this is a heads-up for a pitfall (that at least I have fallen into
several times now...) with respect to XSLT 2, 9.4 "Creating implicit
document nodes":
<http://www.w3.org/TR/xslt20/#temporary-trees>
With the source document:
--src.xml--
<a>
<b/>
</a>
-----------
and this transformation
...
<xsl:variable name="v1"><xsl:sequence select="a"/></xsl:variable>
<xsl:variable name="v2" select="a"/>
...
However, I've spent considerable time debugging stylesheets where
accessing a tunnel variable with $var/elem sometimes yielded nothing
(see v2 in my example above) until I found that in some places, the
variable was defined using <xsl:sequence> (because some complex
content construction takes place which is either not doable or
hardly readable using a single XPath expression), and using a select
attribute at other places.
Fine. But the declaration you use is so very important. You've
declared $v1 to be a tree and $v2 to be an element. So you've
declared two very different animals and you cannot use the same
syntax to address them.
$v1/a and $v2/a are both addressing the <a> child of the
variable. Only $v1 has an <a> child variable. And worrisomely if
the <a> in $v2 had an <a> child you would be addressing the child
rather than what you want.
Is there a technique or pattern I could employ (maybe utilizing the
@as attribute somehow?) to unify the access to variable contents
where I know that the sequences are node sequences, regardless of
their content construction using @select or <xsl:sequence>?
If you had:
<xsl:variable name="v1" as="element()">
<xsl:sequence select="a"/>
</xsl:variable>
<xsl:variable name="v2" select="a"/>
... then in both $v1 and $v2 *are* <a> (i.e. you wouldn't need to say
$v/a to get at <a>). See the working example below.
Does that help? It isn't a document tree, but of course <a> can have
descendants. If you want multiple elements in a sequence then use element()+.
. . . . . . . . . . . Ken
T:\ftemp>type christian.xml
<?xml version="1.0" encoding="UTF-8"?>
<a>
<b/>
</a>
T:\ftemp>xslt2 christian.xml christian.xsl
<?xml version="1.0" encoding="UTF-8"?>v1: ab
v2: ab
T:\ftemp>type christian.xsl
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
xmlns:xs="http://www.w3.org/2001/XMLSchema";
exclude-result-prefixes="xs"
version="2.0">
<xsl:template match="/">
<xsl:variable name="v1" as="element()">
<xsl:sequence select="a"/>
</xsl:variable>
<xsl:variable name="v2" select="a"/>
<xsl:text>v1: </xsl:text>
<xsl:apply-templates select="$v1" mode="out"/>
<xsl:text>
</xsl:text>
<xsl:text>v2: </xsl:text>
<xsl:apply-templates select="$v2" mode="out"/>
</xsl:template>
<xsl:template match="*" mode="out">
<xsl:value-of select="name()"/>
<xsl:apply-templates mode="#current"/>
</xsl:template>
<xsl:template match="text()" mode="#all"/>
</xsl:stylesheet>
T:\ftemp>
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