[jira] [Created] (DAFFODIL-2691) parse errors on debug traces when there is nothing wrong

["Mike Beckerle (Jira)" <ji...@apache.org>]

Mike Beckerle created DAFFODIL-2691:
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             Summary: parse errors on debug traces when there is nothing wrong
                 Key: DAFFODIL-2691
                 URL: https://issues.apache.org/jira/browse/DAFFODIL-2691
             Project: Daffodil
          Issue Type: Improvement
          Components: Diagnostics
    Affects Versions: 3.3.0
            Reporter: Mike Beckerle


User reports looking at a debug trace and seeing a parse error associated with internal behavior of Daffodil. 

The specific situation is for a nillable element. The parser is trying the nil representation, then it issues a parse error and backtracks to try the normal representation. This shows up on the diagnostic output as a parse error associated with the nilled element, which parsed fine, just wasn't nil. 

Really we shouldn't use regular failure backtracking internally like this, as it misleads users. Really we need a nilledElement combinator that orchestrates trying the nil representation and then tries the other representations if that doesn't work. The point being to eliminate user-visible backtracking and diagnostics activity. 



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