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

I have decided to re-write all the orchestrator, without Spring, without 
Zookeeper, without Redis, and with only 4 server instances instead of 12.
See you in Prague,
Christophe

Le 24/01/2019 à 00:47, Michael Kay mike(_at_)saxonica(_dot_)com a écrit :
> > On 23 Jan 2019, at 23:05, 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:
> > It has been very difficult to understand, and your help, especially 
> > on the code that may raise this error, help us a lot.
> Debugging XSLT can be very challenging. I'm working on a complex 
> stylesheet myself at the moment (more details, come to XML Prague) and 
> I've been trying to improve the diagnostics and debugging aids in the 
> product as I go.
> > As a conclusion, this orchestrator is going to be re-written totally. 
> > Never trust a program made by a developer you can't trust !
> Never hesitate to refactor code that's poorly structured, regardless 
> of who wrote it. Base your decisions on the code, not the author. The 
> best developers write bad code if their understanding of the 
> requirements was still evolving while they wrote it.
> Michael Kay
> Saxonica
>
> > Thanks a lot,
> > 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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