Saxon » SaxonJS

This may not actually be a bug in the XX compiler at all. After some searching, I have pinned down the issue to being a stray xsl:map-entry instruction in the saxon-xforms.xsl stylesheet (at line 2803). When the instruction is removed, an XX-compiled SEF seems to work correctly without errors at runtime.

So there is a question as to why (or how) the XJ compiler and XX compiler handle compilation of this instruction differently, and what the correct behaviour really is, but actually it comes from a coding mistake. See the <xsl:map-entry key="$instance-key" select="$instance-with-explicit-namespaces"/> instruction in the code below. Generally the purpose of the template is to do some side-effect actions (js function calls), rather than write to the current result tree. For some reason it seems the XX compiled version does try to write a map to the current result tree, but the XJ compiled version doesn't.

<xsl:template name="xforms-model-construct">
        <xsl:param name="model" as="element(xforms:model)" required="yes" tunnel="yes"/>
        
        <xsl:variable name="model-key" as="xs:string" select="if (exists($model/@id)) then xs:string($model/@id) else $global-default-model-id"/>
        
        <xsl:variable name="instances" as="element(xforms:instance)*" select="$model/xforms:instance"/>       
        
        <xsl:for-each select="$instances">
            <xsl:variable name="instance-with-explicit-namespaces" as="element()">
                <xsl:apply-templates select="./*" mode="namespace-fix"/>
            </xsl:variable>
            <xsl:variable name="instance-key" as="xs:string" select="if (exists(@id)) then xs:string(@id) else $global-default-instance-id"/>
            <xsl:map-entry key="$instance-key" select="$instance-with-explicit-namespaces"/>
            <xsl:sequence select="js:setInstance($instance-key,$instance-with-explicit-namespaces)"/>
            <xsl:if test="position() = 1">
                <xsl:sequence select="js:setDefaultInstance($instance-with-explicit-namespaces)"/>
            </xsl:if>
            
        </xsl:for-each>
        
         
        <xsl:call-template name="xforms-rebuild">
            <xsl:with-param name="get-bindings" as="xs:boolean" select="true()"/>
            <xsl:with-param name="model-key" as="xs:string" select="$model-key" tunnel="yes"/>
        </xsl:call-template>
        
        <xsl:call-template name="xforms-recalculate"/>
        
    </xsl:template>

See attached reduced repro for the issue. The problem seems to be that when the output method is xml, xhtml, html, or text, the XX compiler automatically adds the build-tree="tree" property to this output definition, which the XJ compiler does not. The run-time error then occurs with the XX SEF when a map is added to the principal result tree.

Patch committed (in Saxon-JS 2 branch) in XX compiler (in static-normalize/normalize.xsl) to remove unconditional addition of build-tree attribute to output definition (when output method is xml, xhtml, html, or text). I can't see any regression caused by this change (XSLT3 and QT3 tests suites have been run).

Tests added to JS2 unit tests on dev branch: bugs/bug4607_01 should not throw error for map in unused principal result tree; bug4607_02 should throw error when principal result tree (with map) is appended to page (with "destination":"appendToPage" in SaxonJS.transform call).

Bug fix applied in the Saxon-JS 2.1 maintenance release.