According to http://www.w3.org/TR/xpath/#section-Boolean-Functions:
The boolean function converts […] a string to true if and only if its length
is non-zero.
My XSLT 2.0 stylesheet has an xsl:if element testing a function that seems to
be returning a string of length zero, and yet the test evaluates to true. I am
processing the stylesheet with Saxon-HE 9.2.1.2J with this command line:
java -jar saxon/saxon9he.jar -it:main -xsl:./test.xsl
This is the stylesheet `test.xsl`:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
xmlns:me="null">
<xsl:variable name="PLIST" select="'./test.plist'"/>
<!-- Load external plist into variable -->
<xsl:variable name="metadata" select="document(iri-to-uri($PLIST))"/>
<!-- Function to fetch value of a key-string pair in plist -->
<xsl:function name="me:metadata">
<xsl:param name="label"/>
<xsl:value-of
select="normalize-space($metadata/plist/dict/key[text()=$label]/following::node()[1]/text())"/>
</xsl:function>
<xsl:output method="text" encoding="UTF-8"/>
<xsl:template name="main" exclude-result-prefixes="me">
<xsl:choose>
<xsl:when test="me:metadata('testkey')">
testkey = "<xsl:value-of select="me:metadata('testkey')"/>"
testkey's length = <xsl:value-of
select="string-length(me:metadata('testkey'))"/>
</xsl:when>
<xsl:otherwise>
"testkey" is empty or does not exist.
</xsl:otherwise>
</xsl:choose>
</xsl:template>
</xsl:stylesheet>
As you can see, the stylesheet imports a plist (XML) file, `test.plist`, into a
variable, and calls the function me:metadata() which returns the value of a
certain key in that plist as a string. The plist in question, which I quote
below, does contain the requested key, but its value is blank, and hence the
function should be returning a string of zero length (which is confirmed by
running the function again inside string-length()).
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"
"http://www.apple.com/DTDs/PropertyList-1.0.dtd";>
<plist version="1.0">
<dict>
<key>testkey</key>
<string></string>
</dict>
</plist>
Any idea why the test evaluates to true?
Please note that I am not wondering whether the way I wrote the stylesheet is
the most appropriate way to do what it is supposed to do, but why the test is
evaluating to true.
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