Steve Lawrence created DAFFODIL-2755:
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Summary: infoset nodes removed by InfosetWalker tha are still
needed, null pointer exception
Key: DAFFODIL-2755
URL: https://issues.apache.org/jira/browse/DAFFODIL-2755
Project: Daffodil
Issue Type: Bug
Components: Back End
Affects Versions: 3.4.0
Reporter: Steve Lawrence
Functions in SequenceChildParseResultHelper.scala and
SeparatedSequenceChildParseResultHelper.scala call the
maybeMostRecentlyAddedChild() function, which has a purpose of getting the
child that was most recently added to the infoset and inspecting it element to
determine things nil/normal/missing representation and determine the parse
status. This seems to usually be used when dealing with postfix separators, but
there may be other cases and more specific circumstances needed.
However, in some cases it is possible that the InfosetWalker has already walked
and remove elements from the Infoset because it thinks they aren't needed
anymore. But this function does actually still need them, which can lead to
null exceptions.
Fortunately, the InfosetWalker only removes infoset elements periodically
depending on a number of factors, so it's fairly rare that this case actually
happens. But when it does it appears very random. To reliably cause the issue,
we can force the infoset walker to remove elements as soon as it thinks it's
possible by setting the InfosetWalker minSkip value to zero. After doing that,
the below schema and data reliably reproduce the issue.
Data:
{code}
|classificiation;body1;body1;body3;|
{code}
{code:xml}
<?xml version="1.0" encoding="UTF-8"?>
<schema
xmlns="http://www.w3.org/2001/XMLSchema";
xmlns:xs="http://www.w3.org/2001/XMLSchema";
xmlns:dfdl="http://www.ogf.org/dfdl/dfdl-1.0/";>
<include schemaLocation="org/apache/daffodil/xsd/DFDLGeneralFormat.dfdl.xsd"
/>
<annotation>
<appinfo source="http://www.ogf.org/dfdl/";>
<dfdl:format xmlns="" ref="GeneralFormat" lengthKind="delimited" />
</appinfo>
</annotation>
<element name="file">
<complexType>
<sequence dfdl:initiator="|" dfdl:terminator="|" dfdl:separator=";">
<element name="first" type="xs:string" />
<sequence dfdl:separator=";" dfdl:separatorPosition="postfix">
<element name="field" type="xs:string" minOccurs="0"
maxOccurs="unbounded" />
</sequence>
</sequence>
</complexType>
</element>
</schema>
{code}
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