Question

Is there a way to avoid processing of already processed nodes?

Input XML

<?xml version="1.0" encoding="UTF-8"?>
<root>
    <node1>node1.1</node1>
    <node2>node2.1</node2>
    <node2>node2.2</node2>
    <node1>node1.2</node1>
</root>

XSL

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">

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

    <xsl:template match="node1">
        [Node1]:<xsl:value-of select="."></xsl:value-of>
        <xsl:apply-templates select="following-sibling::node2"/>
        [End node1]
    </xsl:template>

    <xsl:template match="node2">
            [Node2]:<xsl:value-of select="."></xsl:value-of>
    </xsl:template>

</xsl:stylesheet>

Output

<?xml version="1.0" encoding="UTF-8"?>

        [Node1]:node1.1
            [Node2]:node2.1
            [Node2]:node2.2
        [End node1]

            [Node2]:node2.1

            [Node2]:node2.2

        [Node1]:node1.2
        [End node1]

As you can see template <xsl:template match="node2"> is applied twice for every node2 element – one time from node1 template and second time when XSLT processor is transforming node2 element.

Is there any solution to avoid applying of xsl:template match="node2" second time?
I need to stop processing of node2 when I just processed it in template for node1.

Important
This example is just an emulation of more complex use case.
This means that we have additonal limitation – we can’t modify template for root element processing.

I want to know if there is any way to stop processing of elements or move processing to some other elements.

Answer 1

You can use mode to name the template to use.

You can create an empty catch-all node that will output nothing, taking care of apply-templates calls that have no select.

The following stylesheet outputs what you need:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">

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

    <xsl:template match="node1">
        [Node1]:<xsl:value-of select="."></xsl:value-of>
        <xsl:apply-templates select="following-sibling::node2" mode="fromNode1"/>
        [End node1]
    </xsl:template>

    <xsl:template match="node2" mode="fromNode1">
            [Node2]:<xsl:value-of select="."></xsl:value-of>
    </xsl:template>

    <xsl:template match="node2"></xsl:template>
</xsl:stylesheet>

Note the empty modeless template at the end, and the added mode attribute on the template and the calling apply-templates.