Saxon error "XPTY0019: Required item type of first operand of '/' is node(); supplied value has item type xs:string"

Question

I have an XSL program which in turn generates an XSL program, which depending on the input might look like this:

<xsl:variable name="patterns"/> <!--empty in this particular case-->

<xsl:template name="token">
    <xsl:for-each select="$patterns/pattern">
...

When I then run the generated stylesheet, Saxon, bless its heart, is apparently doing some kind of static analysis and complains:

XPTY0019: Required item type of first operand of '/' is node(); supplied value has item type xs:string

and won't even compile the stylesheet.

My workaround was to generate a dummy element in the $patterns nodeset, but is there any cleaner approach here, or way to suppress the compile error?

Solution

According to http://www.w3.org/TR/xslt20/#variable-values, "If the variable-binding element has empty content and has neither a select attribute nor an as attribute, then the supplied value of the variable is a zero-length string.".

So you need to change that, for instance by doing <xsl:variable name="patterns" select="()"/> to bind an empty sequence as the variable value.

Comments

[Admin]

Thanks for the info, problem solved with an as=node()* attribute.

[Admin]

Thanks. The problem is that the XSLT is being generated on the fly, by something that looks like <tns:variable name="patterns"> <xsl:apply-templates select="terminal/any"/> </tns:variable> (where tns is a namespace prefix mapped to xsl on output), so I don't know in advance whether the variable will be empty or not, which is why the as attribute was the perfect solution for me, seeing as how I'm using XSLT 2.0.