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Fix separator not backtracked when complex-typed array element fails - #1716

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olabusayoT:daf-3094-absentrep-backtrack
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Fix separator not backtracked when complex-typed array element fails#1716
olabusayoT wants to merge 1 commit into
apache:mainfrom
olabusayoT:daf-3094-absentrep-backtrack

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For a maxOccurs-bounded occursCountKind="implicit" array whose element type is complex with no possible zero-length representation (e.g. every branch of a choice requires a distinct non-empty initiator), the speculative attempt at an occurrence beyond the real data would parse its preceding separator successfully, then fail the content entirely with zero bits consumed. anyTypeElementFailedParseAttemptStatus classified this as AbsentRep, whose contract is to retain the bit position (keep the separator consumed); that is correct for a genuinely empty representation, but wrong here since there is no occurrence at all. This let the separator leak into whatever sequence child comes next, causing spurious "separator not found" / "terminator not found" errors.

Gate the AbsentRep classification on isEmptyRepZeroLength for complex types, so a structurally-impossible zero-length failure returns MissingItem instead, which forces the caller to fully backtrack the point of uncertainty including the separator.

DAFFODIL-3094

For a maxOccurs-bounded occursCountKind="implicit" array whose element type
is complex with no possible zero-length representation (e.g. every branch
of a choice requires a distinct non-empty initiator), the speculative
attempt at an occurrence beyond the real data would parse its preceding
separator successfully, then fail the content entirely with zero bits
consumed. anyTypeElementFailedParseAttemptStatus classified this as
AbsentRep, whose contract is to retain the bit position (keep the
separator consumed); that is correct for a genuinely empty representation,
but wrong here since there is no occurrence at all. This let the separator
leak into whatever sequence child comes next, causing spurious "separator
not found" / "terminator not found" errors.

Gate the AbsentRep classification on isEmptyRepZeroLength for complex
types, so a structurally-impossible zero-length failure returns
MissingItem instead, which forces the caller to fully backtrack the point
of uncertainty including the separator.

DAFFODIL-3094
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