Can I apply a character map to a given node? - xslt-2.0

Question

If I look at the xslt specs it seems a character map applies to the whole document, bit is it also possible to use it on a given node, or within a template ?
Example : I have a node containing look up values, but they might contain characters that don't play well with regular expressions when using it in another template. For now I use a replace functionwhich works well,, but after a few characters that becomes pretty hard to read or maintain. So if I have something like this :
<xsl:variable name="myLookup" select="
replace(
replace(
replace(
replace(
string-join(/*/lookup/*, '|'),
'\[','\\['),
'\]','\\]'),
'\(','\\('),
'\)','\\)')
"/>
is there a way to achieve something like below fictitious example ?
<xsl:character-map name="escapechar">
<xsl:output-character character="[" string="\[" />
<xsl:output-character character="]" string="\]" />
<xsl:output-character character="(" string="\(" />
<xsl:output-character character=")" string="\)" />
</xsl:character-map>
<xsl:variable name="myLookup" select="string-join(/*/lookup/*, '|')" use-character-map="escapechar"/>
I know this is not working at all, it is just to make my request a bit visual.
Any idea ?

Answer 1

I think character maps in XSLT 2.0 are a serialization feature to be applied when a result tree is serialized to a file or stream so I don't see how you could apply one to a certain string or certain node during a transformation.
As for escaping meta characters of regular expression patterns, maybe http://www.xsltfunctions.com/xsl/functx_escape-for-regex.html helps.

Answer 2

Character maps is only a serialization feature, which means that it is only executed when the final output of a transformation is produced. However, you can significantly simplify your current code.
Just use:
replace($pStr, '(\[|\]|\(|\))','\\$1')
Here is a complete example:
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:my="my:my">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:template match="/*">
<xsl:value-of select="my:escape(.)"/>
</xsl:template>
<xsl:function name="my:escape" as="xs:string">
<xsl:param name="pStr" as="xs:string"/>
<xsl:value-of select="replace($pStr, '(\[|\]|\(|\))','\\$1')"/>
</xsl:function>
</xsl:stylesheet>
When this transformation is applied on the following XML document:
<t>([a-z]*)</t>
the wanted, correct result is produced:
\(\[a-z\]*\)