Flattening with XSLT: I want to move one kind element one level - xslt

Question

I have a XML file where elements B are inside elements A and I want to move them up. From:
<?xml version="1.0" encoding="utf-8"?>
<root>
<A>
<C>Text</C>
Text again
More text
<D>Other text</D>
<B>Text again</B>
<C>No</C>
<D>May be</D>
<B>What?</B>
</A>
<A>
Something
<B>Nothing</B>
<D>Again</D>
<B>Content</B>
End
</A>
</root>
I would like to have:
<?xml version="1.0" encoding="utf-8"?>
<root>
<A>
<C>Text</C>
Text again
More text
<D>Other text</D>
</A>
<B>Text again</B>
<A>
<C>No</C>
<D>May be</D>
</A>
<B>What?</B>
<A>
Something
</A>
<B>Nothing</B>
<A>
<D>Again</D>
</A>
<B>Content</B>
<A>
End
</A>
</root>
The closest XSLT program I have is this:
<xsl:stylesheet
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
exclude-result-prefixes="xs" version="1.0">
<xsl:output method="xml" indent="yes"/>
<xsl:template match="#* | node()">
<xsl:copy>
<xsl:apply-templates select="#* | node()"/>
</xsl:copy>
</xsl:template>
<xsl:template match="A">
<xsl:for-each select="*">
<xsl:choose>
<xsl:when test="name()='B'">
<xsl:apply-templates select="."/>
</xsl:when>
<xsl:otherwise>
<xsl:element name="A">
<xsl:apply-templates select="."/>
</xsl:element>
</xsl:otherwise>
</xsl:choose>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
It has two problems: it ignores text nodes (this is probably just a matter of adding |text() to the select="*") but, more important, it creates a element for each node while I would like them to stay together under one . For instance, the above stylesheet makes:
<A><C>No</C></A>
<A><D>May be</D></A>
where I want:
<A><C>No</C>
<D>May be</D></A>
In my XML files, are always direct children of , and there is no or nesting.
The main use case is producing HTML where UL and OL cannot be inside a P.
This question is related but not identical to xslt flattening out child elements in a DocBook para element (and may be also to Flatten xml hierarchy using XSLT
)

Answer 1

As I said in the comment to your question, this is not about moving elements up in hierarchy. It is about grouping nodes, and creating a new parent A element for each group determined by the dividing B element.
In XSLT 1.0 this can be achieved using a so-called sibling recursion:
XSLT 1.0
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
<xsl:template match="/root">
<xsl:copy>
<xsl:apply-templates select="A"/>
</xsl:copy>
</xsl:template>
<xsl:template match="A">
<xsl:copy>
<xsl:apply-templates select="node()[1][not(self::B)]" mode="sibling"/>
</xsl:copy>
<xsl:apply-templates select="B[1]" mode="sibling"/>
</xsl:template>
<xsl:template match="node()" mode="sibling">
<xsl:copy-of select="." />
<xsl:apply-templates select="following-sibling::node()[1][not(self::B)]" mode="sibling"/>
</xsl:template>
<xsl:template match="B" mode="sibling">
<xsl:copy-of select="." />
<xsl:if test="following-sibling::node()[normalize-space()]">
<A>
<xsl:apply-templates select="following-sibling::node()[1][not(self::B)]" mode="sibling"/>
</A>
<xsl:apply-templates select="following-sibling::B[1]" mode="sibling"/>
</xsl:if>
</xsl:template>
</xsl:stylesheet>

Answer 2

An XSLT-1.0 solution - which is quite ugly - is the following. The output is as desired, but only for this simple MCVE. A general solution would be far more complicated as #michael.hor257k mentioned in the comments. Without more data it is unlikely to create a better solution in XSLT-1.0. Solutions for XSLT-2.0 and above may simplify this.
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="/root">
<xsl:copy>
<xsl:for-each select="A">
<xsl:if test="normalize-space(text()[1])">
<A>
<xsl:copy-of select="text()[1]" />
</A>
</xsl:if>
<xsl:if test="preceding::*">
<xsl:copy-of select="B[1]" />
</xsl:if>
<A>
<xsl:copy-of select="C[1] | C[1]/following-sibling::text()[1] | D[1]" />
</A>
<xsl:if test="not(preceding::*)">
<xsl:copy-of select="B[1]" />
</xsl:if>
<A>
<xsl:copy-of select="C[2] | C[2]/following-sibling::text()[1]" />
<xsl:if test="D[2]">
<xsl:copy-of select="D[2]" />
</xsl:if>
</A>
<xsl:copy-of select="B[2]" />
<xsl:if test="normalize-space(text()[last()])">
<A>
<xsl:copy-of select="text()[last()]" />
</A>
</xsl:if>
</xsl:for-each>
</xsl:copy>
</xsl:template>
</xsl:stylesheet>
Concerning the situation of
<A><C>No</C></A>
<A><D>May be</D></A>
It is handled appropriately in the above code. So its output is
<A>
<C>No</C>
<D>May be</D>
</A>

Answer 3

Easy in XSLT 2 or 3 with group-adjacent=". instance of element(B)" or group-adjacent="boolean(self::B)", here is an XSLT 3 example (XSLT 3 is supported by Saxon 9.8 or 9.9 on Java and .NET (https://sourceforge.net/projects/saxon/files/Saxon-HE/) and by Altova since 2017 releases):
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
exclude-result-prefixes="#all"
version="3.0">
<xsl:mode on-no-match="shallow-copy"/>
<xsl:output indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:template match="A">
<xsl:for-each-group select="node()" group-adjacent=". instance of element(B)">
<xsl:choose>
<xsl:when test="current-grouping-key()">
<xsl:apply-templates select="current-group()"/>
</xsl:when>
<xsl:otherwise>
<xsl:copy select="..">
<xsl:apply-templates select="current-group()"/>
</xsl:copy>
</xsl:otherwise>
</xsl:choose>
</xsl:for-each-group>
</xsl:template>
</xsl:stylesheet>
https://xsltfiddle.liberty-development.net/gWmuiKv
In XSLT 2 you need to spell out the <xsl:mode on-no-match="shallow-copy"/> as the identity transformation template and use xsl:element instead xsl:copy:
<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0">
<xsl:template match="#*|node()">
<xsl:copy>
<xsl:apply-templates select="#*|node()"/>
</xsl:copy>
</xsl:template>
<xsl:output indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:template match="A">
<xsl:for-each-group select="node()" group-adjacent=". instance of element(B)">
<xsl:choose>
<xsl:when test="current-grouping-key()">
<xsl:apply-templates select="current-group()"/>
</xsl:when>
<xsl:otherwise>
<xsl:element name="{name(..)}" namespace="{namespace-uri(..)}">
<xsl:apply-templates select="current-group()"/>
</xsl:element>
</xsl:otherwise>
</xsl:choose>
</xsl:for-each-group>
</xsl:template>
</xsl:transform>
http://xsltransform.hikmatu.com/pPqsHT2