eZ Publish 5 Add "onclick" attribute to "link" element

content.ini.append.php

[link]
CustomAttributes[]
CustomAttributes[]=onclick

ezpublish.yml

ezpublish:
    system:
        my_siteaccess:
            fieldtypes:
                ezxml:
                    custom_tags:
                        - { path: %kernel.root_dir%/../src/Djoo/BaseBundle/Resources/xsl/link.xsl, priority: 10 }

link.xsl

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet
        version="1.0"
        xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
        xmlns:xhtml="http://ez.no/namespaces/ezpublish3/xhtml/"
        xmlns:custom="http://ez.no/namespaces/ezpublish3/custom/"
        xmlns:image="http://ez.no/namespaces/ezpublish3/image/"
        exclude-result-prefixes="xhtml custom image">
 
    <!-- Original template transforms into <b> -->
    <xsl:template match="link">
        <a>
            <xsl:attribute name="href">
                <xsl:value-of select="@url"/>
            </xsl:attribute>
            <xsl:attribute name="target">
                <xsl:choose>
                    <xsl:when test="@target">
                        <xsl:value-of select="@target"/>
                    </xsl:when>
                    <xsl:otherwise>_self</xsl:otherwise>
                </xsl:choose>
            </xsl:attribute>
            <xsl:if test="@xhtml:title">
                <xsl:attribute name="title">
                    <xsl:value-of select="@xhtml:title"/>
                </xsl:attribute>
            </xsl:if>
            <xsl:if test="@custom:onclick">
                <xsl:attribute name="onclick">
                    <xsl:value-of select="@custom:onclick"/>
                </xsl:attribute>
            </xsl:if>
            <xsl:copy-of select="@class"/>
            <xsl:apply-templates/>
        </a>
    </xsl:template>
 
</xsl:stylesheet>