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https://issues.apache.org/jira/browse/DAFFODIL-2879?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17825731#comment-17825731
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Steve Lawrence commented on DAFFODIL-2879:
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> Though, I thought we had an issue where optionals required a predicate? So
> maybe scalars and optionals can't be allowed either? So maybe a path step can
> never be ambiguous? It must reference either an array, optional or scala?
I've confirmed that optionals do not require a predicate, in fact optionals are
not even allowed to have predicates. DAFFODIL-2013 was the issue for this, but
that bug is just wrong--I've added a test to confirm that is the case.
So, I think it is fine for expressions to ambiguously reference a scalar or
optional because they are the same from the infosets perspecive--optionals
might just be missing. But an an expression cannot ambiguously reference an
array or a scala/optional, because the two implementations are completely
different.
One potential issue is what if we have an expression like this:
{code}
fn:count(/ambigous/path/to/scalarOrOptional)
{code}
The fn:count function is supposed to be an SDE if it references a scalar
(DAFFODIL-2711), but maybe if it's ambiguous and it *could* reference an
optional also then we allow it? So fn:count must unambigously reference either
an array or non-array, and if it's a non-array then it must be able to
reference an optional.
> Group evaluation throwing ClassCastException for optional element
> -----------------------------------------------------------------
>
> Key: DAFFODIL-2879
> URL: https://issues.apache.org/jira/browse/DAFFODIL-2879
> Project: Daffodil
> Issue Type: Bug
> Components: Back End
> Affects Versions: 3.6.0
> Reporter: Peter Katlic
> Priority: Major
>
> A group is defined with an element using fn:count and referenced inside a
> sequence of array and optional elements. See the test count_21b in
> daffodil-test/src/test/resources/org/apache/daffodil/section23/dfdl_functions/Functions.tdml
> for an example.
> Group schema:
> {code:java}
> <xs:group name="countGroup">
> <xs:sequence>
> <xs:element name="count" type="xs:int" dfdl:representation="binary"
> dfdl:inputValueCalc="{ fn:count(../ex:foo) }"/>
> </xs:sequence>
> </xs:group>{code}
> Sequence schema:
> {code:java}
> <xs:element name="arrayOptional">
> <xs:complexType>
> <xs:sequence>
> <xs:element name="array">
> <xs:complexType>
> <xs:sequence>
> <xs:element name="foo" type="xs:int" minOccurs="2" maxOccurs="2"
> dfdl:representation="binary"/>
> <xs:group ref="countGroup"/>
> </xs:sequence>
> </xs:complexType>
> </xs:element>
> <xs:element name="optional">
> <xs:complexType>
> <xs:sequence>
> <xs:element name="foo" type="xs:int" minOccurs="0" maxOccurs="1"
> dfdl:representation="binary"/>
> <!-- throws ClassCastException, possible bug in Daffodil group
> evaluation -->
> <!-- <xs:group ref="countGroup"/> -->
> <xs:element name="count" type="xs:int"
> dfdl:representation="binary" dfdl:inputValueCalc="{ fn:count(../ex:foo) }"/>
> </xs:sequence>
> </xs:complexType>
> </xs:element>
> </xs:sequence>
> </xs:complexType>
> </xs:element>{code}
> Uncommenting
> {code:java}
> <xs:group ref="countGroup"/>{code}
> and commenting out
> {code:java}
> <xs:element name="count" type="xs:int" dfdl:representation="binary"
> dfdl:inputValueCalc="{ fn:count(../ex:foo) }"/>{code}
> will produce the following error:
> {code:java}
> java.lang.ClassCastException: class
> org.apache.daffodil.runtime1.infoset.DISimple cannot be cast to class
> org.apache.daffodil.runtime1.infoset.DIArray{code}
> It seems as if the optional is evaluated as a DownArray instead of a
> DownElement.
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