merge two xml files xslt 3 based on the value of common id element - xslt-3.0

Question

<breakfast_menu>
<food>
<name>Belgian Waffles</name>
<id>$5</id>
<description>Two of our famous Belgian Waffles with plenty of real maple syrup</description>
<calories>650</calories>
</food>
<food>
<name>Strawberry Belgian Waffles</name>
<id>7</id>
<description>Light Belgian waffles covered with strawberries and whipped cream</description>
<calories>900</calories>
</food>
<food>
<name>Berry-Berry Belgian Waffles</name>
<id>8</id>
<description>Light Belgian waffles covered with an assortment of fresh berries and whipped cream</description>
<calories>900</calories>
</food>
<food>
<name>French Toast</name>
<id>4</id>
<description>Thick slices made from our homemade sourdough bread</description>
<calories>600</calories>
</food>
<food>
<name>Homestyle Breakfast</name>
<id>6</id>
<description>Two eggs, bacon or sausage, toast, and our ever-popular hash browns</description>
<calories>950</calories>
</food>
</breakfast_menu>
i have tried to achieve the task with the help of xsl:merge. In my trials i have to specific define in xsl which elements to retrieve. How would you suggest one with the help of xslt-3, can retrieve all elements from the second xml file, minus the id element, which already exists in XML file A, and is used as the match criteria for merging the two xml files into one?
second xml file:
<CATALOG>
<PLANT>
<COMMON>Butterfly Weed</COMMON>
<BOTANICAL>Asclepias tuberosa</BOTANICAL>
<ZONE>Annual</ZONE>
<LIGHT>Sunny</LIGHT>
<id>2</id>
<AVAILABILITY>063099</AVAILABILITY>
</PLANT>
<PLANT>
<COMMON>Primrose</COMMON>
<BOTANICAL>Oenothera</BOTANICAL>
<ZONE>3 - 5</ZONE>
<LIGHT>Sunny</LIGHT>
<id>6</id>
<AVAILABILITY>013099</AVAILABILITY>
</PLANT>
<PLANT>
<COMMON>Gentian</COMMON>
<BOTANICAL>Gentiana</BOTANICAL>
<ZONE>4</ZONE>
<LIGHT>Sun or Shade</LIGHT>
<id>17</id>
<AVAILABILITY>051899</AVAILABILITY>
</PLANT>
<PLANT>
<COMMON>Blue Gentian</COMMON>
<BOTANICAL>Gentiana</BOTANICAL>
<ZONE>4</ZONE>
<LIGHT>Sun or Shade</LIGHT>
<id>18</id>
<AVAILABILITY>050299</AVAILABILITY>
</PLANT>
<PLANT>
<COMMON>Jacob's Ladder</COMMON>
<BOTANICAL>Polemonium caeruleum</BOTANICAL>
<ZONE>Annual</ZONE>
<LIGHT>Shade</LIGHT>
<id>9</id>
<AVAILABILITY>022199</AVAILABILITY>
</PLANT>
<PLANT>
<COMMON>Greek Valerian</COMMON>
<BOTANICAL>Polemonium caeruleum</BOTANICAL>
<ZONE>Annual</ZONE>
<LIGHT>Shade</LIGHT>
<id>4</id>
<AVAILABILITY>071499</AVAILABILITY>
</PLANT>
<PLANT>
<COMMON>California Poppy</COMMON>
<BOTANICAL>Eschscholzia californica</BOTANICAL>
<ZONE>Annual</ZONE>
<LIGHT>Sun</LIGHT>
<id>7</id>
<AVAILABILITY>032799</AVAILABILITY>
</PLANT>
<PLANT>
<COMMON>Shooting Star</COMMON>
<BOTANICAL>Dodecatheon</BOTANICAL>
<ZONE>Annual</ZONE>
<LIGHT>Mostly Shady</LIGHT>
<id>8</id>
<AVAILABILITY>051399</AVAILABILITY>
</PLANT>
<PLANT>
<COMMON>Snakeroot</COMMON>
<BOTANICAL>Cimicifuga</BOTANICAL>
<ZONE>Annual</ZONE>
<LIGHT>Shade</LIGHT>
<id>5</id>
<AVAILABILITY>071199</AVAILABILITY>
</PLANT>
<PLANT>
<COMMON>Cardinal Flower</COMMON>
<BOTANICAL>Lobelia cardinalis</BOTANICAL>
<ZONE>2</ZONE>
<LIGHT>Shade</LIGHT>
<id>3</id>
<AVAILABILITY>022299</AVAILABILITY>
</PLANT>
</CATALOG>
Desired output:
<breakfast_menu>
<food>
<name>Belgian Waffles</name>
<id>5</id>
<description>Two of our famous Belgian Waffles with plenty of real maple syrup</description>
<calories>650</calories>
<COMMON>Snakeroot</COMMON>
<BOTANICAL>Cimicifuga</BOTANICAL>
<ZONE>Annual</ZONE>
<LIGHT>Shade</LIGHT>
<AVAILABILITY>071199</AVAILABILITY>
</food>
<food>
<name>Strawberry Belgian Waffles</name>
<id>7</id>
<description>Light Belgian waffles covered with strawberries and whipped cream</description>
<calories>900</calories>
<COMMON>California Poppy</COMMON>
<BOTANICAL>Eschscholzia californica</BOTANICAL>
<ZONE>Annual</ZONE>
<LIGHT>Sun</LIGHT>
<AVAILABILITY>032799</AVAILABILITY>
</food>
<food>
<name>Berry-Berry Belgian Waffles</name>
<id>8</id>
<description>Light Belgian waffles covered with an assortment of fresh berries and whipped cream</description>
<calories>900</calories>
<COMMON>Shooting Star</COMMON>
<BOTANICAL>Dodecatheon</BOTANICAL>
<ZONE>Annual</ZONE>
<LIGHT>Mostly Shady</LIGHT>
<AVAILABILITY>051399</AVAILABILITY>
</food>
<food>
<name>French Toast</name>
<id>4</id>
<description>Thick slices made from our homemade sourdough bread</description>
<calories>600</calories>
<COMMON>Greek Valerian</COMMON>
<BOTANICAL>Polemonium caeruleum</BOTANICAL>
<ZONE>Annual</ZONE>
<LIGHT>Shade</LIGHT>
<AVAILABILITY>071499</AVAILABILITY>
</food>
<food>
<name>Homestyle Breakfast</name>
<id>6</id>
<description>Two eggs, bacon or sausage, toast, and our ever-popular hash browns</description>
<calories>950</calories>
<COMMON>Primrose</COMMON>
<BOTANICAL>Oenothera</BOTANICAL>
<ZONE>3 - 5</ZONE>
<LIGHT>Sunny</LIGHT>
<AVAILABILITY>013099</AVAILABILITY>
</food>
</breakfast_menu>
my approach part of it to give you an idea:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
exclude-result-prefixes="#all"
expand-text="yes"
version="3.0">
<xsl:param name="doc-A" select="doc('fileB.xml')"/>
<xsl:mode on-no-match="shallow-copy"/>
<xsl:output method="xml" indent="yes"/>
<xsl:template match="/*">
<xsl:copy>
<xsl:merge>
<xsl:merge-source sort-before-merge="yes" for-each-item="." select="food">
<xsl:merge-key select="id"/>
</xsl:merge-source>
<xsl:merge-source sort-before-merge="yes" for-each-item="$doc-A" select="//PLANT">
<xsl:merge-key select="id"/>
</xsl:merge-source>
<xsl:merge-action>
<xsl:copy>
<xsl:copy-of select="current-merge-group('A')/*, current-merge-group('B')/(* except id)"/>
</xsl:copy>
</xsl:merge-action>
</xsl:merge>
</xsl:copy>
</xsl:template>
<xsl:param name="merge-data"/>
<xsl:copy>{.}{$merge-data}</xsl:copy>
</xsl:template>
<xsl:param name="merge-data"/>
<xsl:next-match/>
</xsl:template>
</xsl:stylesheet>

Answer 1

I would use e.g.
<xsl:merge-action>
<xsl:copy>
<xsl:copy-of select="current-merge-group('A')/*, current-merge-group('B')/(* except id)"/>
</xsl:copy>
</xsl:merge-action>
This obviously assumes you are naming your merge sources, which you had done initially in your code, you edited that out after my answer, go figure.
Anyway, it seems you also want to ignore data from the second file so the merge action needs to check for a merge source from A:
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
exclude-result-prefixes="#all"
version="3.0">
<xsl:output indent="yes"/>
<xsl:output method="xml" indent="yes"/>
<xsl:template match="/*">
<xsl:copy>
<xsl:merge>
<xsl:merge-source name="A" sort-before-merge="yes" for-each-item="." select="food">
<xsl:merge-key select="id"/>
</xsl:merge-source>
<xsl:merge-source name="B" sort-before-merge="yes" for-each-item="$doc-A" select="//PLANT">
<xsl:merge-key select="id"/>
</xsl:merge-source>
<xsl:merge-action>
<xsl:if test="current-merge-group('A')">
<xsl:copy>
<xsl:copy-of select="current-merge-group('A')/*, current-merge-group('B')/(* except id)"/>
</xsl:copy>
</xsl:if>
</xsl:merge-action>
</xsl:merge>
</xsl:copy>
</xsl:template>
<xsl:param name="doc-A" select="doc('fileB.xml')"/>
</xsl:stylesheet>
In the end, given that xsl:merge needs to order input sources to work and given that you desired output doesn't seem to be ordered based on the id, I would think that a key based solution might work better:
<xsl:param name="ref" match="PLANT" use="id"/>
and then <xsl:mode on-no-match="shallow-copy"/> plus
<xsl:template match="food[key('ref', id, doc('fileB.xml'))]">
<xsl:copy>
<xsl:apply-templates select="*, key('ref', id, doc('fileB.xml'))/(* except id)"/>
</xsl:copy>
</xsl:template>