How to preserve attributes in xsl:variable body? [duplicate] - xslt-1.0

Question

This question already has an answer here:
Setting a variable conditionally with no cut of ancestor axis
(1 answer)
Closed 5 months ago.
data
<mydoc>
<setting>foo</setting>
<foo sound="aaaa"/>
<bar sound="brrr"/>
<cat sound="meow"/>
</mydoc>
if no conditional logic is needed,
<xsl:variable name="result1" select="/mydoc/foo"/>
works fine.
but if I need conditional logic,
<xsl:variable name="result2">
<xsl:choose>
<xsl:when test="/setting='foo'">
<!-- what to put here -->
</xsl:when>
<xsl:when test="/setting='cat'">
<!-- what to put here -->
</xsl:when>
<xsl:otherwise>
<!-- what to put here -->
</xsl:otherwise>
</xsl:choose>
</xsl:variable>
desired output:
when setting = 'foo', result = <foo sound="aaa"/> (the whole element complete with attribute)
when setting = 'cat', result = <cat sound="meow"/> (the whole element complete with attribute)
otherwise, result = <bar sound="brrr"/> (the whole element complete with attribute)
How do I get the result2 variable to be an element with attributes, as it does in result1? I want to use $result2/sound, and some other elements / attributes of $result2 and / or it's children.

Answer 1

<xsl:variable name="result2" select="/mydoc[setting='foo']/foo |
/mydoc[setting='cat']/cat |
/mydoc[not(setting='foo' or setting='cat')]/bar"/>
Because of the conditions in square brackets exactly one member of the union will effectively be selected.
If you put something inside the <xsl:variable> element rather than use select, your variable will contain a result tree fragment, not a nodeset.

Answer 2

If you insist on using xsl:choose (why?) then the only option open to you is to use xsl:copy. However, this has some side effects:
This will create a copy of the selected node/s and make it a child of the variable; in effect, it will create a separate document and the copied nodes will no longer be descendants of the XML input's root;
The variable will be a result-tree-fragment and you won't be able to process it in any way unless you convert it to a node-set first. Here, "process" includes accessing individual nodes inside the variable.
The following example demonstrates this:
XML
<mydoc>
<setting>foo</setting>
<foo bar="a"/>
<bar foo="b"/>
</mydoc>
XSLT 1.0
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:exsl="http://exslt.org/common"
exclude-result-prefixes="exsl">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
<xsl:template match="/mydoc">
<xsl:variable name="temp">
<xsl:choose>
<xsl:when test="setting='foo'">
<xsl:copy-of select="foo"/>
</xsl:when>
<xsl:otherwise>
<xsl:copy-of select="bar"/>
</xsl:otherwise>
</xsl:choose>
</xsl:variable>
<output>
<xsl:value-of select="exsl:node-set($temp)/foo/#bar" />
</output>
</xsl:template>
</xsl:stylesheet>
Result
<?xml version="1.0" encoding="UTF-8"?>
<output>a</output>
Do note that if you change:
<xsl:value-of select="exsl:node-set($temp)/foo/#bar" />
to:
<xsl:value-of select="$temp/foo/#bar" />
you will get an error.