Trim whitespace from parent element only - xslt

Question

I'd like to trim the leading whitespace inside p tags in XML, so this:
<p> Hey, <em>italics</em> and <em>italics</em>!</p>
Becomes this:
<p>Hey, <em>italics</em> and <em>italics</em>!</p>
(Trimming trailing whitespace won't hurt, but it's not mandatory.)
Now, I know normalize-whitespace() is supposed to do this, but if I try to apply it to the text nodes..
<xsl:template match="text()">
<xsl:text>[</xsl:text>
<xsl:value-of select="normalize-space(.)"/>
<xsl:text>]</xsl:text>
</xsl:template>
...it's applied to each text node (in brackets) individually and sucks them dry:
[Hey,]<em>[italics]</em>[and]<em>[italics]</em>[!]
My XSLT looks basically like this:
<xsl:template match="p">
<xsl:apply-templates/>
</xsl:template>
So is there any way I can let apply-templates complete and then run normalize-space on the output, which should do the right thing?

Answer 1

This stylesheet:
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*"/>
</xsl:copy>
</xsl:template>
<xsl:template match="p//text()[1][generate-id()=
generate-id(ancestor::p[1]
/descendant::text()[1])]">
<xsl:variable name="vFirstNotSpace"
select="substring(normalize-space(),1,1)"/>
<xsl:value-of select="concat($vFirstNotSpace,
substring-after(.,$vFirstNotSpace))"/>
</xsl:template>
</xsl:stylesheet>
Output:
<p>Hey, <em>italics</em> and <em>italics</em>!</p>
Edit 2: Better expression (now only three function calls).
Edit 3: Matching the first descendant text node (not just the first node if it's a text node). Thanks to #Dimitre's comment.
Now, with this input:
<p><b> Hey, </b><em>italics</em> and <em>italics</em>!</p>
Output:
<p><b>Hey, </b><em>italics</em> and <em>italics</em>!</p>

Answer 2

I would do something like this:
<xsl:template match="p">
<xsl:apply-templates/>
</xsl:template>
<!-- strip leading whitespace -->
<xsl:template match="p/node()[1][self::text()]">
<xsl:call-template name="left-trim">
<xsl:with-param name="s" value="."/>
</xsl:call-template>
</xsl:template>
This will strip left space from the initial node child of a <p> element, if it is a text node. It will not strip space from the first text node child, if it is not the first node child. E.g. in
<p><em>Hey</em> there</p>
I intentionally avoid stripping the space from the front of 'there', because that would make the words run together when rendered in a browser. If you did want to strip that space, change the match pattern to
match="p/text()[1]"
If you also want to strip trailing whitespace, as your title possibly implies, add these two templates:
<!-- strip trailing whitespace -->
<xsl:template match="p/node()[last()][self::text()]">
<xsl:call-template name="right-trim">
<xsl:with-param name="s" value="."/>
</xsl:call-template>
</xsl:template>
<!-- strip leading/trailing whitespace on sole text node -->
<xsl:template match="p/node()[position() = 1 and
position() = last()][self::text()]"
priority="2">
<xsl:value-of select="normalize-space(.)"/>
</xsl:template>
The definitions of the left-trim and right-trim templates are at Trim Template for XSLT (untested). They might be slow for documents with lots of <p>s. If you can use XSLT 2.0, you can replace the call-templates with
<xsl:value-of select="replace(.,'^\s+','')" />
and
<xsl:value-of select="replace(.,'\s+$','')" />
(Thanks to Priscilla Walmsley.)

Answer 3

You want:
<xsl:template match="text()">
<xsl:value-of select=
"substring(
substring(normalize-space(concat('[',.,']')),2),
1,
string-length(.)
)"/>
</xsl:template>
This wraps the string in "[]", then performs normalize-string(), then finally removes the wrapping characters.