Saxon » SaxonJS

I suspect, subject to testing, that the solution is along the following lines.

At static.xsl line 164 we do

<xsl:variable name="stylesheet-properties" as="attribute()*"
            select="
                @default-mode, @expand-text,
                if (exists($parent-version) and $version ne $parent-version) then
                    @version
                else
                    ()"/>

If there is no @expand-text attribute we should add the attribute expand-text="no" to this list. This is probably best done by turning the expression into XSLT:

<xsl:variable name="stylesheet-properties" as="attribute()*">
  <xsl:sequence select="@default-mode, @expand-text"/>
  <xsl:if test="empty(@expand-text)">
    <xsl:attribute name="expand-text" select="'no'"/>
  </xsl:if>
  <xsl:if test="exists($parent-version) and $version ne $parent-version">
    <xsl:sequence select="@version"/>
  </xsl:if>
</xsl:variable>

A use-case for the proposed new-attribute() function to construct attributes within XPath!