preceding-sibling::comment()

bonekrusher · October 1st, 2008, 05:35 AM

Hi, I am trying to get the value of a preceding comment. In the below example, If my context node is "foo", how do I get the comment immediately before the "foo" element.

Code:

<root>

    <data>Some Data</data>

    <foo>Some Foo</foo>
</root>

The below xslt returns all the preceding comments. I just want "This is the comment I want" .

Code:

<xsl:for-each select="foo">
 <xsl:value-of select="preceding-sibling::comment()"/>
</xsl:for-each/>

Thanks for the help.

Bones

mhkay · October 1st, 2008, 05:49 AM

preceding-sibling::comment()[1]

will return the most recent preceding sibling comment

preceding-sibling::node()[1][self::comment()]

will return the immediately preceding node if and only if it is a comment

preceding-sibling::node()[not(self::text()[.=''])][1][self::comment()]

will return the immediately preceding node, ignoring whitespace-only text nodes, if and only if it is a comment

Take your pick.

Michael Kay
http://www.saxonica.com/
Author, XSLT 2.0 and XPath 2.0 Programmer's Reference

bonekrusher · October 1st, 2008, 06:33 AM

Hi Michael,

Thank you for the help. Using

Code:

preceding-sibling::node()[1][self::comment()]

Returns nothing. I am probably missing something.

Here is my actual input:

Code:

<xsl:template match="ACM:PARA">
    <fo:inline font-family="{$default-font}" font-size="{$default-font-size}">
        <xsl:apply-templates/>
    </fo:inline>
</xsl:template>

Here is my xsl:

Code:

<xsl:for-each select="//xsl:template[@match]">
            <template type="match" base="{subsequence(reverse(tokenize(document-uri(/), '/')), 1, 1)}">
                <xsl:copy-of select="@*"/>
                <xsl:attribute name="line"><xsl:value-of select="saxon:line-number()"/></xsl:attribute>
                    <xsl:attribute name="comments"><xsl:value-of select="preceding-sibling::node()[1][self::comment()]"/></xsl:attribute>
                <xsl:value-of select="@match"/>
            </template>
</xsl:for-each>

Some background - I am writing a stylesheet to describe stylesheets - Something similar to java Docs.

Thanks for the help.

Martin Honnen · October 1st, 2008, 06:46 AM

There is a text node with white space between the comment and the xsl:template element. Therefore preceding-sibling::node()[1][self:comment()] is empty. I think you want preceding-sibling::comment()[1] instead.

--
Martin Honnen
Microsoft MVP - XML

bonekrusher · October 1st, 2008, 07:00 AM

Thanks Martin,

preceding-sibling::comment()[1] selects the last preceding comment() even if its not the immediately preceding node.

Any other thoughts?

Martin Honnen · October 1st, 2008, 07:08 AM

It is not clear which comment nodes exactly you are looking for.
As I said, in your sample input the comment is not the immediately preceding node as there is a text node with white space between the comment and the xsl:template element.
Nevertheless I thought you want to select that comment.
Perhaps
preceding-sibling::node()[not(self::text()[normalize-space(.)=''])][1][self::comment()]
is more what you want.

--
Martin Honnen
Microsoft MVP - XML

bonekrusher · October 1st, 2008, 07:13 AM

Thanks Martin,

Code:

preceding-sibling::node()[not(self::text()[normalize-space(.)=''])][1][self::comment()]

Works :)

What is unclear to me is the mention of whitespace. Where is the whitespace?

Martin Honnen · October 1st, 2008, 07:19 AM

If you have

Code:

<foo/>

then the foo element node is preceded and succeeded directly by a comment node.
However with

Code:

<foo/>

there is a text node with white space between each comment node and the element node.

--
Martin Honnen
Microsoft MVP - XML

bonekrusher · October 1st, 2008, 07:27 AM

Thank you for the clarification.

Given the following example:

Code:

<foo/>

I assumed the line break was not considered whitespace.

Thanks again,

Bones

samjudson · October 1st, 2008, 08:03 AM

Nope, the line breaks are exactly what IS considered whitespace (along with spaces and tabs).

/- Sam Judson : Wrox Technical Editor -/