How to comment in XSLT and not HTML

Just make sure that you put your <!-- comments --> AFTER the opening XML declaration (if you use one, which you really don't need):

BREAKS:

<!-- a comment -->
<?xml version="1.0"?>

WORKS:

<?xml version="1.0"?>
<!-- a comment -->

I scratched my head on this same issue for a bit while debugging someone else's XSLT... seems obvious, but easily overlooked.

Note that white space on either side of the comments can end up in the output stream, depending on your XSLT processor and its settings for handling white-space. If this is an issue for your output, make sure the comment is bracketed by xslt tags.

EG

<xsl:for-each select="someTag">
  <xsl:text>"</xsl:text>
    <!-- output the id -->
<xsl:value-of select="@id"/>
<xsl:text>"</xsl:text>
</xsl:for-each>

Will output " someTagID" (the indent tab/spaces in front of the comment tag are output). To remove, either unindent it flush with left margin, or bracket it like

<xsl:text>"</xsl:text><!-- output the id --><xsl:value-of select="@id"/>

This is the way to do it in order to create a comment node that won't be displayed in html

<xsl:comment>

  <!-- Content:template -->

</xsl:comment>

You use standard XML comments:

<!-- Comment -->

These are not processed by the XSLT transformer.