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https://issues.apache.org/jira/browse/GROOVY-7914?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15436534#comment-15436534
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Dario Bertini commented on GROOVY-7914:
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You're obviously free to decide not to fix this, but there are several reasons
to fix/reconsider this behavior:
- Groovy's semantics are different from Java's (obviously), Java defines
.equals as implementing an "equivalence relation on non-null object
references". Which is a cop-out to justify a NPE when `a.equals(b)` because `a`
is `null`. Groovy does not have a special behavior for null: its own null has a
type with a name (unlike Java) and `null.equals(null)` works just fine in
Groovy.
- In no place is Groovy's `==` operator documented to have a different behavior
than `.equals`. See http://groovy-lang.org/operators.html#_identity_operator
- Worrying about performance without any benchmark to demonstrate the problem
in the real world is premature optimization
- Not fixing this, would prioritize performance over correctness
- Every other dynamically typed language worth its salt avoids special casing
this (I confirmed with Python, Ruby, Clojure...)
- If people want to check referece identity rather than equality (for
performance reasons or whatever other reason), they can (and should be taught
to) be explicit, by doing `instance.is null`
- Principle of least surprise
> Comparison operator does not delegate to .equals() for null
> -----------------------------------------------------------
>
> Key: GROOVY-7914
> URL: https://issues.apache.org/jira/browse/GROOVY-7914
> Project: Groovy
> Issue Type: Bug
> Reporter: Dario Bertini
>
> This might be related to https://issues.apache.org/jira/browse/GROOVY-4526
> supposedly a PR over there has been merged, but the bug is still flagged as
> open (and indeed, I can locally reproduce it).
> This one instead caused problems when handling org.json.JSONObject
> That type uses its own internal JSONObject.Null class to represent null
> inside json (which is useful to distinguish between keys being missing, and
> values explicitly being set to null)
> it overrides .equals(other) to check if the other object is null, but that
> method is never invoked
> basically:
> JSONObject.NULL == null
> false
> JSONObject.NULL.equals(null)
> true
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