Use xmlstarlet to add missing elements? - bash

Question

I have a number of vendor records which contain multiple addresses e.g.
<vendor>
<addresses>
<address primary="yes">
<line1 />
<city />
<state />
....
</address>
<address primary="no">
<line1 />
<city />
<state />
....
</address>
</addresses>
</vendor>
Some required elements are missing -- preventing updating of the records. Can xmlstarlet can be used to add an element with a default value if it is missing?

Answer 1

Here's a simple example. I'll use xmllint --auto for the xml source. Then we'll add an <add-me> element as a child of <info> if it doesn't exist using the identity transform pattern.
Source xml:
xmllint --auto
<?xml version="1.0"?>
<info>abc</info>
Add the missing element:
xmllint --auto | xsltproc add-missing.xsl -
<?xml version="1.0"?>
<info><add-me>some stuff</add-me>abc</info>
add-missing.xsl:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="info">
<xsl:copy>
<xsl:if test="not(add-me)">
<add-me>some stuff</add-me>
</xsl:if>
<xsl:apply-templates select="#*|node()"/>
</xsl:copy>
</xsl:template>
<xsl:template match="#*|node()">
<xsl:copy>
<xsl:apply-templates select="#*|node()"/>
</xsl:copy>
</xsl:template>
</xsl:stylesheet>

Answer 2

Another XSLT w/xmlstarlet option is to use a variable that contains the required elements (with or without default values) and treat is as a node set (using the supported exsl:node-set() function).
You can then iterate over the node set to see if an element with the same name already exists. If it does, use it. Otherwise use the default.
Example...
XML Input (input.xml)
<vendor>
<addresses>
<address primary="yes">
<line1>address 1 line1</line1>
<state>address 1 state1</state>
</address>
<address primary="no">
<line1>address 2 line1</line1>
<city>address 2 city</city>
<state>address 2 state</state>
</address>
</addresses>
</vendor>
XSLT 1.0 (so.xsl)
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:exsl="http://exslt.org/common" exclude-result-prefixes="exsl">
<xsl:output indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:variable name="req_elems">
<req>
<line1/>
<city/>
<state/>
<country/>
</req>
</xsl:variable>
<xsl:template match="#*|node()">
<xsl:copy>
<xsl:apply-templates select="#*|node()"/>
</xsl:copy>
</xsl:template>
<xsl:template match="address">
<xsl:variable name="ctx" select="."/>
<xsl:copy>
<xsl:apply-templates select="#*"/>
<xsl:for-each select="exsl:node-set($req_elems)/req/*">
<xsl:choose>
<xsl:when test="$ctx/*[local-name()=local-name(current())]">
<xsl:apply-templates select="$ctx/*[local-name()=local-name(current())]"/>
</xsl:when>
<xsl:otherwise>
<xsl:apply-templates select="."/>
</xsl:otherwise>
</xsl:choose>
</xsl:for-each>
</xsl:copy>
</xsl:template>
</xsl:stylesheet>
XML Output
<vendor>
<addresses>
<address primary="yes">
<line1>address 1 line1</line1>
<city/>
<state>address 1 state1</state>
<country/>
</address>
<address primary="no">
<line1>address 2 line1</line1>
<city>address 2 city</city>
<state>address 2 state</state>
<country/>
</address>
</addresses>
</vendor>
Note: This only works if the only allowed elements in address are the same as $req_elements. For example, if you have an element named "foo" in address, it will be dropped from the output.