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https://issues.apache.org/jira/browse/JEXL-384?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Henri Biestro closed JEXL-384.
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> Improve control over JexlArithmetic null argument handling
> ----------------------------------------------------------
>
> Key: JEXL-384
> URL: https://issues.apache.org/jira/browse/JEXL-384
> Project: Commons JEXL
> Issue Type: Task
> Affects Versions: 3.3
> Reporter: Hussachai Puripunpinyo
> Assignee: Henri Biestro
> Priority: Major
> Fix For: 3.3
>
>
> https://issues.apache.org/jira/browse/JEXL-359
> {quote}A typical case is '+' for string and null where one would like to
> consider null as a valid argument even if arithmetic is strict.
> {quote}
> While the above reason is valid, the code introduced in JEXL-359 causes more
> confusion, and the behavior is now inconsistent.
> Also, I'd like to give some counter arguments about not supporting null +
> string in the strict mode. If we want to make null + string works even if
> arithmetic is strict, there will be no difference between "" + "ABC" and null
> + "ABC" because both cases yield "ABC" in both strict and non-strict mode. In
> our code base, we set the engine to be strict, so users have to be careful
> about null since it can give an undesirable result. In a non-strict mode, we
> don't have a way to distinguish whether the result is the combination of null
> or empty string and a string. Users need to explicitly check for null, but
> there will be no enforcement
> which means nobody will do that check. That's why we prefer it to be strict
> and a user has to check null before using or use some namespace functions
> that we provide where null will be explicitly handled. Otherwise, the
> exception will be thrown.
> Let me elaborate why some part of JEXL-359 causes the behavior to be
> inconsistent.
> *Strict Mode*
> {code:java}
> var i = null;
> i + 'ABC'; // This will throw an exception.
> null + 'ABC'; // This yields 'ABC' - the same as non-strict mode.
> {code}
>
> *Non Strict Mode*
> {code:java}
> var i = null;
> i + 'ABC'; // This yields 'ABC';
> null + 'ABC'; // This also yields 'ABC';
> {code}
>
> You can see that the behavior of null + 'ABC' in the strict mode is not
> consistent with the null variable.
> Also, there is a way to allow string concatenation with null using a
> namespace function in a strict mode, and I think JEXL shouldn't make an
> exception for this one particular case.
> I'd like to propose the PR with some regression tests that applies to only
> null (literal) + string case.
> [https://github.com/apache/commons-jexl/pull/136]
> *Note:* I ignored one test *testNullArgs* because the feature doesn't seem to
> be defined well. It won't work with numeric types.
> I can pass around the JexlOperator to isStrict function everywhere to address
> that, but I'm trying to refrain from changing things too much since you may
> have some ideas and my code might get in the way.
> Please let me know if I can help with that, or you can merge my PR, take part
> of it or ignore it completely :)
> My idea about fixing *testNullArgs* properly is that all toString, toDouble,
> toBigDecimal functions should take an additional argument which is
> JexlOperator where a user can override for specific operator as stated in
> testNullArgs test. If that sounds right to you, I can help creating another
> Jira and PR to tackle this. Thank you.
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