Saxon is getting this wrong: zero-length text nodes should never exist, unless
they are parentless.
What's happening is that the variable "x" satisfies all the conditions for a
"text-fragment" tree. Because constructs like
<xsl:variable name="z">
<xsl:value-of select="23"/>
</xsl:variable>
are encountered so frequently, Saxon uses a lightweight data structure to
represent them; this represents a tree comprising a document node with a single
text node child. The optimization logic runs "there are no child instructions
producing anything other than text nodes", therefore this data structure is
used, and it then behaves as if there is a single zero-length text node.
I suspect the same problem will arise if there's an <xsl:value-of/> child whose
select expression evaluates to a zero-length string.
Michael Kay
Saxonica
On 4 Jul 2019, at 18:01, David Carlisle
d(_dot_)p(_dot_)carlisle(_at_)gmail(_dot_)com
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:
The following stylesheet generates a variable x using a sequence
constructor that evaluates to an empty sequence...
<xsl:stylesheet version="3.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
xmlns:xs="http://www.w3.org/2001/XMLSchema";
<xsl:variable name="x">
<xsl:sequence select="()"/>
</xsl:variable>
<xsl:template match="/">
<xsl:message select="'C1:',
$x instance of xs:string,
string-length($x)
"/>
<xsl:message select="'C2:',
$x instance of document-node(),
count($x/node()),
$x/node() instance of text(),
$x/text()/string-length(.)
"/>
</xsl:template>
</xsl:stylesheet>
$x is a variable that is a document node with a text node child the
text node having zero length.
I just read https://www.w3.org/TR/xslt-30/#constructing-complex-content
10 times but still don't see where the text node came from
having the xsl:sequence there means it avoids the XSLT 1 special case
returning a string, and not having an as= attribute means there is an
implicit document node generated, but I would expected that $x was
just a document node with no children, but saxon (Saxon-HE 9.9.0.1J)
produces
$ saxon9 ev.xsl ev.xsl
C1: false 0
C2: true 1 true 0
<?xml version="1.0" encoding="UTF-8"?>
If someone could point me at the right bit of the spec I think I'm
missing a step somewhere...
David
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