Re: XSLT lingual extensions?

This seems to have a high level of overlap with the proposed XSLT 4.0 extension allowing extension instructions to invoke named templates:

https://qt4cg.org/specifications/xslt-40/Overview.html#invoking-templates-with-extension-instructions


Michael Kay
Saxonica



On 2 Jan 2023, at 20:23, Sasha Firsov <suns@firsov.net<mailto:suns@firsov.net>> wrote:

Thinking of macro in XSLT...

In many programming languages the capability of extending lingual constructs been found not just a useful but even not-separable part of the language itself.  For example, the macros in C are an essential part of the standard and almost any shared code.

XSLT itself has some capability to extend its own functionality inside of XPath. Which is powerful for data and string utilities but does not give much on the integration of markup itself.

During  Declarative Custom Element proposal preparation I faced the challenge of TEMPLATE tag syntax into XSLT translation. The SLOT tag can be easily expressed via <value-of  select=...

function slot2xsl( s )
{
    const v = document.createElementNS( XSL_NS_URL, 'value-of' );
    v.setAttribute( 'select', `//*[@slot="${ s.name }"]` );
    s.parentNode.replaceChild( v, s );
}

While for POC(link<https://unpkg.com/@epa-wg/custom-element@0.0/index.html>) it is OK kind of XSLT pre-processing on JS level, the XSLT by itself is the best for such kind of XSLT-to-XSLT transformation. As optimization, the XSLT pipeline could be set but it means extra step and disconnection between the HTML template source and final transformation. The less steps in the pipeline, the better DX/DE( Developer Experience/Developer Efficiency).

Hence proposing the macro definition for XSLT:
defined construct would be transformed into XSLT one and treated as inline XSLT.

<slot name="slot1"> 😃</slot>

translated into

<xsl:value-of select='//*[@slot="slot1"]'/>

I guess there is no need for new XSLT syntax to support macro definition, the usual

<xsl:template match="slot">
   <template:value-of><xsl:attribute name="select"
      >//*[@slot="<xsl:value-of select="@name">"]</xsl:attribute></template:value-of>

would be sufficient with one extra exception on the pipe priority so it  would run during the XSLT load ( and take XSLT itself as data) instead of the transformation phase.

🤔 How to
* present the XSLT load vs transformation phase
* present the output XSLT ( via template: namespace?)

-s