Create key within xslt template

Question

I would like to transform an XML file into a CSV file. The fields I want to export are the <issues>. Each issue has a set of standard fields and some custom fields. The possible custom fields are defined in <issue-custom-fields>. Not every <issue> has all custom fields set. For the CSV export I have to add an empty field (",,") for each missing entry. How would I do this?

The following xslt file loops through all fields of issue and through all custom fields. Instead of "field value?" I would like to have look up the respective field value in the current item (if it exists, a blank if not).

XSLT version should be 1.0.

<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">

    <xsl:output method="text" />

    <xsl:template match="/">
        <xsl:apply-templates select="xml_data/issues"/>
    </xsl:template>

    <xsl:template match="issue">
        <xsl:for-each select="*">
            <xsl:choose>
                <xsl:when test="name(.) = 'custom-values'">
                    <xsl:for-each select="/xml_data/issue-custom-fields/issue-custom-field">                                
                        <xsl:variable name="f" select="id" />

                        <xsl:text>field value?</xsl:text>

                        <xsl:if test="position() != last()">
                            <xsl:text>,</xsl:text>
                        </xsl:if>
                    </xsl:for-each>
                </xsl:when>

                <xsl:otherwise>
                    <xsl:value-of select="."/>          
                    <xsl:if test="position() != last()">
                        <xsl:text>,</xsl:text>
                    </xsl:if>
                </xsl:otherwise>
            </xsl:choose>
        </xsl:for-each>         
    </xsl:template>
</xsl:transform>

acting on the following data:

<?xml version="1.0" encoding="UTF-8"?>
    <xml_data>
        <projects type="array">
            <project>
                <id type="integer">10</id>
                <name>Helpdesk</name>
                <type>open</type>
            </project>
            <project>
                <id type="integer">20</id>
                <name>Development</name>
                <type>closed</type>
            </project>
        </projects>

        <issue-custom-fields>
            <issue-custom-field>
                <id>1000</id>
                <name>Delay</name>
            </issue-custom-field>
            <issue-custom-field>
                <id>1001</id>
                <name>Means of Delivery</name>
            </issue-custom-field>
            <issue-custom-field>
                <id>1002</id>
                <name>Shipping Date</name>
            </issue-custom-field>
        </issue-custom-fields>

        <issues type="array">
            <issue>
                <id type="integer">100</id>
                <project-id type="integer">10</project-id>
                <subject>first helpdesk issue</subject>
                <description>a small problem</description>
                <custom-values>
                    <custom-value>
                        <custom-field-id>1000</custom-field-id>
                        <value>15</value>
                    </custom-value>
                    <custom-value>
                        <custom-field-id>1002</custom-field-id>
                        <value>2016-08-01</value>
                    </custom-value>
                </custom-values>
            </issue>
            <issue>
                <id type="integer">101</id>
                <project-id type="integer">10</project-id>
                <subject>second helpdesk issue</subject>
                <description>a medium problem</description>
                <custom-values>
                    <custom-value>
                        <custom-field-id>1000</custom-field-id>
                        <value>10</value>
                    </custom-value>
                    <custom-value>
                        <custom-field-id>1001</custom-field-id>
                        <value>FTP</value>
                    </custom-value>
                </custom-values>
            </issue>
            <issue>
                <id type="integer">102</id>
                <project-id type="integer">10</project-id>
                <subject>third helpdesk issue</subject>
                <description>a huge security problem</description>
                <custom-values>
                    <custom-value>
                        <custom-field-id>1001</custom-field-id>
                        <value>SSH</value>
                    </custom-value>
                </custom-values>
            </issue>
            <issue>
                <id type="integer">103</id>
                <project-id type="integer">20</project-id>
                <subject>first "development" issue</subject>
                <description>just some "strange" software</description>
                <custom-values>
                </custom-values>
            </issue>
        </issues>
    </xml_data>

Thank you very much for your help.

Answer 1

If I understand correctly, you want to do:

XSLT 1.0

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

<xsl:key name="custom-value" match="custom-value" use="concat(custom-field-id, '|', ancestor::issue/id)" />

<xsl:template match="/xml_data">
    <xsl:variable name="custom-fields" select="issue-custom-fields/issue-custom-field" />
    <!-- header -->
    <!-- standard fields -->
    <xsl:for-each select="issues/issue[1]/*[not(self::custom-values)]">
        <xsl:value-of select="name()"/>          
        <xsl:text>,</xsl:text>
    </xsl:for-each> 
    <!-- custom fields -->
    <xsl:for-each select="$custom-fields">
        <xsl:value-of select="name"/>          
        <xsl:if test="position() != last()">
            <xsl:text>,</xsl:text>
        </xsl:if>
    </xsl:for-each>
    <xsl:text>&#10;</xsl:text>
    <!-- data -->
    <xsl:for-each select="issues/issue">
        <xsl:variable name="issue-id" select="id" />
        <!-- standard fields -->
        <xsl:for-each select="*[not(self::custom-values)]">
            <xsl:value-of select="."/>          
            <xsl:text>,</xsl:text>
        </xsl:for-each>
        <!-- custom fields -->
        <xsl:for-each select="$custom-fields">
            <xsl:value-of select="key('custom-value', concat(id, '|', $issue-id))/value"/>          
            <xsl:if test="position() != last()">
                <xsl:text>,</xsl:text>
            </xsl:if>
        </xsl:for-each> 
        <xsl:text>&#10;</xsl:text>
    </xsl:for-each> 
</xsl:template>

</xsl:stylesheet>

Applied to your input example, the result will be:

id,project-id,subject,description,Delay,Means of Delivery,Shipping Date
100,10,first helpdesk issue,a small problem,15,,2016-08-01
101,10,second helpdesk issue,a medium problem,10,FTP,
102,10,third helpdesk issue,a huge security problem,,SSH,
103,20,first "development" issue,just some "strange" software,,,