Saxon » SaxonJS

Consider this for Saxon-JS 2.0, and Saxon 9.9.

Relatedly: referring to the Saxon-CE documentation, the design for ixsl:set-attribute was inspired by xsl:attribute: "The instruction has attributes name, namespace, and select, and works in exactly the same way as xsl:attribute, except that the attribute is written directly to the current element." For some reason, we lost the namespace attribute in Saxon-JS, but it would be useful if this was reinstated.

Further fix committed on 2.0 branch for when ixsl:set-attribute/@name is supplied as a URIQualifiedName (i.e. in the form Q{uri}local). Now check in scope namespaces of the HTML element the attribute is to be added to, to find a suitable prefix to be used for the attribute name.

For example, if the XSLT stylesheet contains the namespace declaration xmlns:svg="http://www.w3.org/2000/svg", and the Xlink namespace is in scope for the relevant svg:image element in the HTML page, and bound to the xlink prefix, the following instruction:

<ixsl:set-attribute name="Q{{http://www.w3.org/1999/xlink}}href" 
            select="'../../src/logo.gif'"
            object="(ixsl:page()//svg:svg)[1]/svg:image"/>

will set the xlink:href attribute (i.e. localName "href", namespaceURI "http://www.w3.org/1999/xlink", prefix "xlink") on the svg:image element.

Without this prefix fixup, the attribute set has localName "href", namespaceURI "http://www.w3.org/1999/xlink", and prefix null. Which looks wrong in the page, and can produce unexpected results (e.g. svg:image/@href returns a value as well as svg:image/@xlink:href).

I can't wait to use this feature - it will save a lot of code (and make the code more clear). But I wonder what happens if the object attribute references more than just one element? I can imagine that all elements will be affected, but also that you want to restrict the use of the attribute to one element only. After all, it is called object and not objects.

BTW the same applies for ixsl:set-property and ixsl:set-style. Of course, behaviour of all instructions should be identical.

Yes, currently there is a cardinality check that the value supplied for the object attribute (i.e. the result of evaluating the expression) on ixsl:set-attribute and ixsl:remove-attribute is exactly one (as for the object attribute on ixsl:set-property and ixsl:set-style), because it makes sense to be consistent. So there will be an error at run time if object does not reference exactly one HTML element.

I think that if you want to be affecting multiple elements, it makes sense to stick to using xsl:for-each (as currently often used in Saxon-JS 1.x). Do you agree?

Yes, I agree. Consistency first. And furthermore, using a for-each will make it obvious to the reader of the code that more elements will be affected.

As an aside: because xsl:for-each makes you think of iteration, I always place a comment ("this iterates only once") in my code if I need to use xsl:for-each to merely change the context.