Question

I have an XML document that I want to generate unique IDs for. Some nodes may already have the attribute in which case this is to be replaced. I want all nodes in the document to have the attribute.

An example document would be

<root>
<anode uid='123'/>
<anode/>
</root>

I am using the following stylesheet

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

    <xsl:template match="*">
        <xsl:copy>
            <xsl:attribute name="uid">
                <xsl:value-of select="generate-id(.)"/>
            </xsl:attribute>
            <xsl:apply-templates select="@*|node()"/>
        </xsl:copy>
    </xsl:template>
</xsl:stylesheet>

And am getting the following output. This is close to what I want, but how do I prevent the existing ID from being created as a text node?

<root uid="id515559">
<anode uid="id515560">123</anode>
<anode uid="id515562"/>
</root>

I have looked at XSLT: How to change an attribute value during <xsl:copy>? but I couldn’t get this to create new attributes.

If it makes a difference I’m using lxml to process the stylesheet.

Answer 1

The Built-in template rule is being applied to the input @uid by the line:

<xsl:apply-templates select="@*|node()"/>

The Default template for an attribute copies the text, behaving as though you had defined a template thus:

<xsl:template match="text()|@*">
  <xsl:value-of select="."/>
</xsl:template>

In order to prevent this being applied, either change your apply-templates select attribute so that it does not apply to attributes, or define a new blank template for any attribute, thus:

<xsl:template match="@*" />

You could even be more specific, using a similar template to ignore uid attributes only, thus:

<xsl:template match="@uid" />