[DAFFODIL-2562] Optional element at end of choice branch triggers unparse error

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.2.0
• Fix Version/s: 3.5.0
• Component/s: Back End
• Assignee: Unassigned
• Reporter: Josh Adams
• Created: 23/Sep/21 16:25
• Updated: 22/Feb/23 15:16
• Resolved: 21/Feb/23 16:45

Description

Given the following schema:

{{ <xs:group name="groupOfChoice">
<xs:sequence>
<xs:element name="key" type="xs:string" dfdl:lengthKind="explicit" dfdl:length="1" />
<xs:choice dfdl:choiceDispatchKey="

{ ./ex:key }

">
<xs:sequence dfdl:choiceBranchKey="a">
<xs:element name="elt_a" type="xs:string" dfdl:lengthKind="explicit" dfdl:length="3" />
</xs:sequence>
<xs:sequence dfdl:choiceBranchKey="b">
<xs:element name="elt_b" type="xs:string" dfdl:lengthKind="explicit" dfdl:length="3" />
<xs:element name="elt_c" type="xs:string" dfdl:lengthKind="explicit" dfdl:length="3"
minOccurs="0" maxOccurs="1" dfdl:occursCountKind="expression" dfdl:occursCount="

{ if (fn:exists(../ex:elt_b)) then 1 else 0 }

" />
</xs:sequence>
</xs:choice>
</xs:sequence>
</xs:group>}}

During unparse, the element following this group (the next element after elt_c) will have an invalid ERD and will trigger an unparse error.

I've spent a fair amount of time looking at this, but was unable to find the root cause of this issue. I'm thinking that it must be something where the various stacks tracking the current element and next element are some how getting out of sync and when we are looking for the element after elt_c, Daffodil still thinks it is withing the choice containing elt_c.

I will open a pull request with the test for this bug.