Re: [xsl] Signature of a function that may throw an error

SaxonEE 9.8.0-14.

Christophe

Le 22/01/2019 à 17:28, Michael Kay mike(_at_)saxonica(_dot_)com a écrit :
> The XPath spec defines the return type of the error() function as 
> "none", and the role of "none" in the type system is pretty much 
> unspecified. As a result, there was always a steady stream of problems 
> with edge cases in the W3C test suites in this area.
> Saxon actually implements the static return type of error() as item(), 
> which is intended to ensure that you won't get a static type error 
> from this sort of construct.
> This particular example doesn't seem to give a static error with Saxon 
> 9.9, though the error message looks like it comes from Saxon. The code 
> that produces this error is intended for the case where one of the 
> branches of the conditional always returns an empty sequence 
> (typically, an implicit xsl:otherwise).
> What software version are you running?
>
> Michael Kay
> Saxonica
>
>
>
> > On 22 Jan 2019, at 14:36, Christophe Marchand cmarchand(_at_)oxiane(_dot_)com 
> > <mailto:cmarchand(_at_)oxiane(_dot_)com> 
> > <xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com 
> > <mailto:xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com>> wrote:
> > Hello,
> >
> > I have a function that must return a xs:string, or raise an error, if 
> > result value can not be computed, or is empty-sequence.
> > Here is function :
> >
> >   <xsl:function name="conf:getConfVar" as="xs:string">
> >     <xsl:param name="conf" as="element(els-conf:conf)"/>
> >     <xsl:param name="varName" as="xs:string"/>
> >     <xsl:sequence select="
> >       if (exists($conf/els-conf:variable[@name=$varName]))
> >       then $conf/els-conf:variable[@name=$varName]/@value
> >       else (
> >         error(
> >           $conf:ERROR_MISSING_ENTRY,
> >           concat('Entry ',$varName,' is missing in environment 
> > configuration')
> >         )
> >       )
> >       "/>
> >   </xsl:function>
> >
> > When a variable does not exist in $conf, I expect an error being 
> > raised, and expect to catch it in a xsl:try / xsl:catch.
> > But, in this case, I get this :
> >
> > XTTE0780: Conditional expression: The condition is not satisfied, so 
> > an empty sequence is returned, but this is not allowed as the result 
> > of call to conf:getConfVar
> > in xsl:sequence/@select ....
> >
> >   * I understand that error() function never return a value, so
> >     return value does not satisfies xsl:function/@as constrint. Is it
> >     correct ?
> >   * How could I write this, as I want the return type being
> >     xs:string, and not xs:string?, and I want my error to be raised
> >     when entry is missing ?
> >
> > Best regards,
> > Christophe
> >
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