[GitHub] nifi issue #1409: NIFI-1962 - Fixed NPE in toDate() EL function

[ijokarumawak <gi...@git.apache.org>]

Github user ijokarumawak commented on the issue:

    https://github.com/apache/nifi/pull/1409
  
    Thanks @pvillard31 for tackling this. I reviewed the code and tested. While this PR fixes toDate to work even when an attribute value is null, there's another method that throws NPE, that is StandardAttributeExpression.evaluate. It has similar code.
    
    Also, I felt that changing Query class is too much for fixing a particular toDate EL function. Besides that, when I tested toNumber passing a non-existing attribute, it works fine, before applying this fix.
    
    So I looked at the code closer and found NumberToDateEvaluator may be the one should be fixed, because functions below react against null input value as followings:
    
    - NumberToDateEvaluator returns `null` <-- We probably need to fix this to return new DateQueryResult(null)
    - StringToDateEvaluator returns new DateQueryResult(null)
    - WholeNumberCastEvaluator returns new WholeNumberQueryResult(null) : this is an implementation for toNumber() function
    
    It seems returning XXXQueryResult(null) is a convention in EL functions when input is null.
    
    How do you think?


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