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Re: [xsl] xsl:if test = empty string, returns true


Subject: Re: [xsl] xsl:if test = empty string, returns true
From: Jorge <chocolate.camera@xxxxxxxxx>
Date: Sun, 13 May 2012 23:17:06 +0200

> Change it to the following to work:

>

> 	<xsl:function name="me:metadata" as="xsd:string?">

Indeed does!

> And, you are looking for the adjacent node (which in your example is a text
node), rather than the adjacent element (unless you are invoking saxon with
the option to strip white-space text nodes from your input, in which case that
is not true).

No I wasn't invoking saxon with such option, but did try nevertheless to use:

	<xsl:strip-space elements="plist dict"/>

and

	<xsl:strip-space elements="*"/>

Still, even with or without those, if I assigned a value to the string, the
function did capture it and showed it in the output of my original stylesheet
in either case. Why does following::node()[1] return the string's value in
both cases then?

> BTW, I very rarely ever have to address text() nodes

Well, I did that to try to force the function to return a string instead of a
tree :-/ As you can see there are still concepts of XSL that I am not quite
grasping yet.

>        <xsl:template name="main" exclude-result-prefixes="me">
>
> Why not put the exclude-result-prefixes on the document element?

That was just a mistake of copy-pasting when creating the test XSLT for the
ML. Thanks for pointing it out.

> I hope the additional comments are considered helpful and not critical.  I
wouldn't want readers of the archive to use text() as you are.

More than appreciated. I simply wanted to discourage answers that focused on
issues that did not address my main question. Please excuse me for the
prejudice.


El 13/05/2012, a las 22:24, G. Ken Holman escribis:

> At 2012-05-13 22:03 +0200, Jorge wrote:
>> 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($PLIST))"/>
>> >
>> >       <!-- Function to fetch value of a key-string pair in plist -->
>> >       <xsl:function name="me:metadata">
>
> Not having added an as= constraint, you are creating a temporary tree with a
text node child.
>
> Change it to the following to work:
>
>       <xsl:function name="me:metadata" as="xsd:string?">
>
>
>> >               <xsl:param name="label"/>
>> >               <xsl:value-of
select="normalize-space($metadata/plist/dict/key[text()=$label]/following::no
de()[1]/text())"/>
>
> Note that the following:: axis looks all the way to the end of the document.
And, you are looking for the adjacent node (which in your example is a text
node), rather than the adjacent element (unless you are invoking saxon with
the option to strip white-space text nodes from your input, in which case that
is not true).  So I suggest using following-sibling::* in case you do end up
with white-space text nodes.
>
> BTW, I very rarely ever have to address text() nodes and the above would be
better written as:
>
> <xsl:value-of
select="normalize-space($metadata/plist/dict/key[.=$label]/following-sibling:
:*[1])"/>
>
> This is not just a matter of style ... consider how your code would not work
when there is more than one text node:
>
>  <key>test<!--used to end here-->key</key>
>
>
>> >       </xsl:function>
>> >
>> >       <xsl:output method="text" encoding="UTF-8"/>
>> >
>> >       <xsl:template name="main" exclude-result-prefixes="me">
>
>
> Why not put the exclude-result-prefixes on the document element?
>
>
>> >               <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>
>> ...
>> Any idea why the test evaluates to true?
>
> Because the returned data type of the function value is a temporary tree and
while it may or may not have a text node child, the document node in the tree
makes the test 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.
>
> Nevertheless I hope the additional comments are considered helpful and not
critical.  I wouldn't want readers of the archive to use text() as you are.
>
> . . . . . . . . Ken
>
> --
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