Re: [xsl] XSLT3 generic grouping functions

["Martin Honnen martin.honnen@xxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

Am 08.07.2020 um 11:24 schrieb Matthieu RICAUD-DUSSARGET
m.ricaud-dussarget@xxxxxxxxxxxxxxxxxx:
> Hi all,
>
> While teaching XSLT, someone ask if it was possible to have a kind of
> generic function to group XML elements.
>
> I first answer the only way to do it was to use (eventually nested)
> <xsl:for-each-group> instruction with specific conditions according to
> the data.
>
> Later, as I was discovering XSLT3, I realize the grouping condition
> might be sent as an higher-order-function parameter, which lead me to
> write some generic grouping functions to wrap XML elements (see example
> below).
>
> The original code can be found on github at
https://github.com/ELSGestion/els-sie-xsl-lib/blob/master/src/main/xsl/els-co
mmon_xml.xsl
> Theres also some generic xsl to nest titles
(https://github.com/ELSGestion/els-sie-xsl-lib/blob/master/src/main/xsl/nest-
titles.xsl)
> and a specific implementation of it to nest HTML titles
(https://github.com/ELSGestion/els-sie-xsl-lib/blob/master/src/main/xsl/nest-
html-titles.xsl)
> Working examples can be found in the test folder
> https://github.com/ELSGestion/els-sie-xsl-lib/tree/master/src/test, as
> xspec unit test or xspec driven integration tests.
>
> I actually have a bug with Saxon 9.9
> (https://saxonica.plan.io/issues/4636) on the generic starting-with
> grouping function, but this is an occasion to share theses grouping
> libraries J
>
> Any comments, feedbacks or similar code implementation are welcome !
>
> Cheers
>
> Matthieu Ricaud-Dussarget
>
> Example of generic adjacent grouping function used to define a specific
> by-name grouping implementation (theres a similar set of functions
> for starting-with) :
>
> <xd:doc>
>
>    <xd:desc>
>
>      <xd:p>Wrap adjacent elements into a new "wrapper" element</xd:p>
>
>      <xd:p>CAUTION : any text, pi, comments within context will be
> loose</xd:p>
>
>    </xd:desc>
>
>    <xd:param name="context">Parent of the adjacent elements to
> wrap</xd:param>
>
>    <xd:param name="adjacent.function">Xpath function to set the
> adjacency condition</xd:param>
>
>    <xd:param name="wrapper">Element wrapper</xd:param>
>
>    <xd:param name="keep-context">Say if the context should be kept or
> not in the result</xd:param>
>
>    <xd:return>context (or its content) with wrapped adjacent
> element</xd:return>
>
> </xd:doc>
>
> <xsl:function name="els:wrap-elements-adjacent" as="node()*">
>
>    <xsl:param name="context" as="element()"/>
>
>    <xsl:param name="adjacent.function"/> <!--as="xs:string"-->
>
>    <xsl:param name="wrapper" as="element()"/>
>
>    <xsl:param name="keep-context" as="xs:boolean"/>
>
>    <xsl:variable name="content" as="item()*">
>
>      <xsl:for-each-group select="$context/*"
> group-adjacent="$adjacent.function(.)">


I would certainly prefer to write a "generic" function that expects a
parameter with the grouping population as a sequence of nodes and then use

      <xsl:for-each-group select="$population" ...

I don't think for-each-group adjacent is meant to be used only for child
elements of a parent, if you want to use it in a generic way then
provide a population sequence you want to group.


>        <xsl:choose>
>
>          <xsl:when test="current-grouping-key()">
>
>            <xsl:for-each select="$wrapper">
>
>              <xsl:copy>
>
>                <xsl:copy-of select="@*"/>

Doesn't
             <xsl:copy select="$wrapper">

suffice in XSLT 3?

Why the xsl:for-each?