xsl:when expands to

xsl:choose + xsl:when is the equivalent of if, else if… like so

xsl:when will thus always contain the action to perform if the test matches, so should actually expand to

instead of the self-closing variant, so you can actually write inside the element the action to perform.

As a matter of fact, then, xsl:choose should probably expand to

since it is always going to contain at least an xsl:when element.

I do not know if there are other xsl elements that always will be followed by other specific elements, and if such a thing is contemplated in Espresso for other particular xsl elements’ expansion. I do not know, then, if what I propose above is coherent with how xsl expansion is approached to, generally, in Espresso.