XSLT 2 - pick item from tokenize()'d list by index - xslt-2.0

Question

My environment is SAXON (last nights build) using XSLT 2.0. My real problem is that the XML document specification is sub-optimal, and in a way, my problem relates to fixing/working around that design issue.
I have a node type (<weaponmodesdata>) where all the direct children are |-separated string lists of 1-or-many elements (each child of the same <weaponmodesdata> will have the same length). I need to go over the various modes represented and "unspin" them out to separate item lists (in plain text), rather than having them all smooshed together.
Unfortunately right now I'm getting a really stubborn
XPTY0020: Required item type of the context item for the child axis is node(); supplied
value has item type xs:string
error on the lines where I pass the node that needs to be split up into my little template.
Currently I have
<xsl:template match="trait" mode="attack">
<xsl:for-each select="tokenize(weaponmodesdata/mode, '\|')">
<xsl:variable name="count" select="position()"/>
<xsl:value-of select="name"/><xsl:text> - </xsl:text>
<xsl:call-template name="split_weaponmode">
<xsl:with-param name="source" select="weaponmodesdata/damage"/>
<xsl:with-param name="item" select="$count"/>
</xsl:call-template>
<xsl:text> </xsl:text>
<xsl:call-template name="split_weaponmode">
<xsl:with-param name="source" select="weaponmodesdata/damtype"/>
<xsl:with-param name="item" select="$count"/>
</xsl:call-template>
<!-- more will go here eventually -->
<xsl:text>.
</xsl:text>
</xsl:for-each>
</xsl:template>
<xsl:template name="split_weaponmode">
<xsl:param name="source"/>
<xsl:param name="item"/>
<xsl:variable name="parts" select="tokenize($source, '\|')"/>
<xsl:for-each select="$parts">
<xsl:if test="position() = $item">
<xsl:value-of select="."/>
</xsl:if>
</xsl:for-each>
</xsl:template>
An example XML subtree relating to my issue:
<character>
<trait id="1">
<name>Spear</name>
<weaponmodesdata>
<mode>1H Thrust|2H Thrust|Thrown</mode>
<damage>thr+2|thr+3|thr+3</damage>
<damtype>imp|imp|imp</damtype>
</weaponmodesdata>
</trait>
<trait id="2">
<name>Broadsword</name>
<weaponmodesdata>
<mode>1H Thrust|1H Swing</mode>
<damage>thr+1|sw+2</damage>
<damtype>imp|cut</damtype>
</weaponmodesdata>
</trait>
</character>
Example desired output:
Spear - 1H Thrust; thr+2 imp.
Spear - 2H Thrust; thr+3 imp.
Spear - Thrown; thr+3 imp.
Broadsword - 1H Thrust; thr+1 imp.
Broadsword - 1H Swing; sw+2 cut.

Answer 1

One issue (that one causing the error message) with your code is that your for-each operates on a sequence of string value (i.e. inside the for-each body the context item is a string value), yet you have relative XPath expressions like weaponmodesdata/damage that require a context node to makes sense. So you would need to use a variable outside of the for-each to store your context node.
But I think you can simplify your code to
<xsl:stylesheet
version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
exclude-result-prefixes="xs">
<xsl:output method="text"/>
<xsl:strip-space elements="*"/>
<xsl:template match="trait">
<xsl:variable name="this" select="."/>
<xsl:variable name="count" select="count(tokenize(weaponmodesdata/*[1], '\|'))"/>
<xsl:for-each-group select="weaponmodesdata/*/tokenize(., '\|')" group-by="position() mod $count">
<xsl:value-of select="$this/name"/>
<xsl:text> - </xsl:text>
<xsl:value-of select="current-group()"/>
<xsl:text>.
</xsl:text>
</xsl:for-each-group>
</xsl:template>
</xsl:stylesheet>
If you want to stick with your approach of calling templates then make sure you store the context node of the template using e.g. <xsl:variable name="this" select="."/> so that you can access it inside of the for-each iterating over a string item.