Question

I am looking to transform a node, based on the number of elements. i.e. 5, then close the node and re-open a new one.
see example below

<root>
  <branch>
    <foo>bar</foo>
    <foo>bar2</foo>
    <foo>bar3</foo>
    <foo>bar4</foo>
    <foo>bar5</foo>
    <foo>bar6</foo>
    <foo>bar7</foo>
  </branch>
<root>

Should become

<root>
  <branch>
    <foo>bar</foo>
    <foo>bar2</foo>
    <foo>bar3</foo>
    <foo>bar4</foo>
    <foo>bar5</foo>
   <branch>
   </branch>
    <foo>bar6</foo>
    <foo>bar7</foo>
  </branch>
<root>

Please help on how this can be done in XSLT.

Answer 1

I. This XSLT 1.0 transformation:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

 <xsl:template match="/*">
  <root>
   <xsl:apply-templates/>
  </root>
 </xsl:template>

 <xsl:template match="foo[position() mod 5 = 1]">
  <branch>
    <xsl:copy-of select=
     ". | following-sibling::*[not(position() > 4)]"/>
  </branch>
 </xsl:template>
 <xsl:template match="text()"/>
</xsl:stylesheet>

when applied on the provided XML document (corrected to well-formed):

<root>
    <branch>
        <foo>bar</foo>
        <foo>bar2</foo>
        <foo>bar3</foo>
        <foo>bar4</foo>
        <foo>bar5</foo>
        <foo>bar6</foo>
        <foo>bar7</foo>
    </branch>
</root>

produces the wanted, correct result:

<root>
   <branch>
      <foo>bar</foo>
      <foo>bar2</foo>
      <foo>bar3</foo>
      <foo>bar4</foo>
      <foo>bar5</foo>
   </branch>
   <branch>
      <foo>bar6</foo>
      <foo>bar7</foo>
   </branch>
</root>

Explanation:

This is a case of “positional grouping”, where every starting element of a group is the first of a 5-tuple (so its position satisfies: position() mod 5 = 1.

---

II. XSLT 2.0 Solution:

<xsl:stylesheet version="2.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>

 <xsl:template match="/*">
  <root>
    <xsl:for-each-group select="*/*"
         group-adjacent="(position() -1) idiv 5">
          <branch>
            <xsl:sequence select="current-group()"/>
          </branch>
    </xsl:for-each-group>
  </root>
 </xsl:template>
</xsl:stylesheet>

when this XSLT 2.0 transformation is applied on the same XML document (above), the same wanted, correct result is produced.

Explanation:

Proper use of the <xsl:for-each-group> XSLT 2.0 instruction with the group-adjacent attribute and the current-group() function.