Question

What is an XSLT 2.0 stylesheet that will transform

<paramList>
    <param name="y" out="true"/>
    <param name="y" in="true"/>
    <param name="z" out="true"/>
    <param name="x" in="true"/>
</paramList>

into

<paramList>
    <param name="x" in="true" />
    <param name="y" in="true" out="true"/>
    <param name="z" out="true"/>
</paramList>

In the result, “in, only” parameters precede “in & out” parameters, which, in turn, precede “out, only” parameters. Also, the two “y” elements have been combined into one.

Answer 1

<?xml version="1.0" ?>
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:template match="/paramList">
  <xsl:copy>
    <xsl:for-each-group select="param" group-by="@name">
      <xsl:sort select="current-group()/@in" order="descending"/>
      <xsl:sort select="current-group()/@out"/>
      <param name="{current-grouping-key()}">
        <xsl:for-each select="current-group()/@*">
          <xsl:copy/>
        </xsl:for-each>
      </param>
    </xsl:for-each-group>
  </xsl:copy>
</xsl:template>

</xsl:stylesheet>