Re: [xsl] Saxon error: "If none of the conditions is satisfied, an empty sequence..."

Subject: Re: [xsl] Saxon error: "If none of the conditions is satisfied, an empty sequence..."
From: Michael Kay <mike@xxxxxxxxxxxx>
Date: Tue, 24 May 2011 00:12:54 +0100
On 23/05/2011 23:47, tom a wrote:
Hello,

When attempting to compile a stylesheet containing the following variable
definition:

<xsl:variablename="seq_position"as="xs:integer*">
<xsl:choose>
<xsl:whentest="name() eq 'step1'">
<xsl:sequenceselect="count(preceding-sibling::step1) + 1"/>
</xsl:when>
<xsl:whentest="name() eq 'step2'">
<xsl:sequenceselect="count(preceding-sibling::step2) + 1"/>
</xsl:when>
<xsl:whentest="name() eq 'step3'">
<xsl:sequenceselect="count(preceding-sibling::step3) + 1"/>
</xsl:when>
<xsl:otherwise>
<xsl:sequenceselect="99+1"/><!--trying to placate saxon->
</xsl:otherwise>
</xsl:choose>
</xsl:variable>
I get the error:
"XTTE0570: Conditional expession: If none of the conditions is satisfied, an
empty sequence
will be returned, but this is not allowed as the value of variable
$seq_position"
I haven't the foggiest idea why this would be. Any help would be most greatly
appreciated.

I assume you only get the error when the xsl:otherwise branch is absent, and when the declared type really doesn't allow an empty sequence (for example, as="xs:integer+" rather than as="xs:integer*"). The reason for the error is that omitting the otherwise branch is equivalent to writing


<xsl:otherwise><xsl:sequence select="()"/></xsl:otherwise>

and this would give a type error on the grounds that () is not a legal value for the variable.

However, there have been a number of complaints about this interpretation of the spec, and I'm going to change it in the next release so you get a compile time warning, followed by a run-time error if the otherwise branch is actually selected.

Michael Kay
Saxonica

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