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[Bug 3315] [XqueryX] spurious "as" in typeswitch clause with no variable

From: <bugzilla@wiggum.w3.org>
Date: Mon, 05 Jun 2006 22:49:24 +0000
CC:
To: public-qt-comments@w3.org
Message-Id: <E1FnNsy-0003AV-EH@wiggum.w3.org>

http://www.w3.org/Bugs/Public/show_bug.cgi?id=3315

           Summary: [XqueryX] spurious "as" in typeswitch clause with no
                    variable
           Product: XPath / XQuery / XSLT
           Version: Candidate Recommendation
          Platform: PC
        OS/Version: Windows XP
            Status: NEW
          Severity: normal
          Priority: P2
         Component: XQueryX
        AssignedTo: jim.melton@acm.org
        ReportedBy: davidc@nag.co.uk
         QAContact: public-qt-comments@w3.org


The Schema for typeswitch case clause is

  <xsd:element name="typeswitchExprCaseClause">
    <xsd:complexType>
      <xsd:complexContent>
        <xsd:extension base="expr">
          <xsd:sequence>
            <xsd:element ref="variableBinding" minOccurs="0"/>
            <xsd:element ref="typeDeclaration"/>
            <xsd:element name="resultExpr" type="exprWrapper"/>

which means that there is always a "typeDeclaration" even if there is no
variable binding.

The XSLT though has

 <xsl:template match="xqx:typeswitchExprCaseClause">
    <xsl:text> case </xsl:text>
    <xsl:apply-templates select="xqx:variableBinding"/>
    <xsl:apply-templates select="xqx:typeDeclaration"/>
    <xsl:text> return </xsl:text>
    <xsl:apply-templates select="xqx:resultExpr"/>
  </xsl:template>

and

<xsl:template match="xqx:typeDeclaration">
    <xsl:text> as </xsl:text>
    <xsl:apply-templates select="*"/>
  </xsl:template>


so typeDeclaration always gets processed and the text " as " is always
generated.

so an XQuery Clause of
                        case xs:integer return -1
if converted to XQueryX and back comes out as
                        case as xs:integer return -1
which is a syntax error.

I think the correct fix is to change the schema to use sequenceType rather than
typeDeclaration as the child of typeswitchExprCaseClause as that brings XQueryX
back closer to the XQuery EBNF

[44]    CaseClause    ::=    "case" ("$" VarName "as")? SequenceType "return"
ExprSingle 

An alternative (but not so nice, I think) would be to leave the schema as-is
but add another template to the stylesheet matching
match="xqx:typeswitchExprCaseClause/xqx:typeDeclaration"
that does not put in the "as" if there is no variable binding child.
(the stylesheet will need some changes in either case to make sure tahtas is
inserted if there is a variable binding and a type.).
A third possibility that wouldn't require a change to the stylesheet would be
to make the schema allow a variable binding _or_ a sequence type but not both.
(the variable binding clause does itself allow a child sequence type).

It turns out that the XQuery Test suite (even in 0.9) had no tests for case
clauses that do not bind a variable so this has gone undetected for quite a
while.  Some additional tests by Frans Englich picked this up.

David
Received on Monday, 5 June 2006 22:49:40 UTC

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