[DAFFODIL-1964] Unparsing ArrayCombinator assertion failure

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.1.0
• Fix Version/s: 2.2.0
• Component/s: Back End, Unparsing
• Assignee: Dave Thompson
• Reporter: Steve Lawrence
• Created: 11/Jul/18 16:23
• Updated: 08/Oct/18 13:38
• Resolved: 15/Aug/18 14:53

Description

A user reported an error when unparsing in the array combinator.

The schema looks something like this:

...
<xs:sequence>
  <xs:element name="foo" ... />
  <xs:element name="bar" minOccurs="1" maxOccurs="6" dfdl:occursCountKind="implicit">
    <xs:complexType>
      <xs:sequence>
        <xs:annotation>
          <xs:appinfo source="http://www.ogf.org/dfdl/">
            <dfdl:discriminator>{ expression }</dfdl:discriminator>
          </xs:appinfo>
        </xs:annotation>
        <xs:sequence dfdl:hiddenGroupRef="hiddenGrouPRef" />
        <xs:group ref="someGroupWithRequiredElement"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:sequence>
...

With XML that looks like this:

<foo>...</foo>

So the bar element is an array that requires at least one instance, but the infoset has zero instances. Trying to unparse this resultsin the following:

org.apache.daffodil.exceptions.Abort: Invariant broken: event.isStart.&&(event.node.isInstanceOf[org.apache.daffodil.infoset.DIArray])
org.apache.daffodil.exceptions.Assert$.abort(Assert.scala:129)
org.apache.daffodil.exceptions.Assert$.abort(Assert.scala:129)
org.apache.daffodil.processors.unparsers.ArrayCombinatorUnparser.unparse(ElementKindUnparsers.scala:254)
org.apache.daffodil.processors.unparsers.Unparser$class.unparse1(Unparser.scala:72)
... 

The expected result is to return an UnaparseError about expecting a start array event but not getting one. I think the assertion just needs to be changed to an UnparseError, since there is clearly a case where the assertion doesn't hold.