Preserve null policy in wrapped Java Maps
#10129
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SethTisue
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library:collections
| override def getOrElseUpdate(key: K, op: => V): V = underlying.computeIfAbsent(key, _ => op) | ||
| override def getOrElseUpdate(key: K, op: => V): V = | ||
| underlying.computeIfAbsent(key, _ => op) match { | ||
| case null => super.getOrElseUpdate(key, op) |
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would be good to clarify super[Which] here (and below)
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I see, super[concurrent.Map].getOrElseUpdate is not allowed, interesting language limitation.
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It seems null handling of JConcurrentMapWrapper.putIfAbsent is not aligned with Scala's semantics, if the underlying map contained a binding with value null, it will return None. Would it make sense to fix this?
I guess it's not too important as both concurrent map implementations in the JDK don't support null. Is there a known / commonly used one that does?
LGTM
| override def getOrElseUpdate(key: K, op: => V): V = underlying.computeIfAbsent(key, _ => op) | ||
| override def getOrElseUpdate(key: K, op: => V): V = | ||
| underlying.computeIfAbsent(key, _ => op) match { | ||
| case null => super.getOrElseUpdate(key, op) |
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I see, super[concurrent.Map].getOrElseUpdate is not allowed, interesting language limitation.
| } | ||
| try Option(underlying.compute(key, remap)) | ||
| catch { | ||
| case PutNull => super.updateWith(key)(remappingFunction) |
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So the dance is between
- supporting Scala semantics for
updateWith(can putSome(null)) - supporting the underlying map's contract (the
ConcurrentHashMap.computemethod evaluates the argument function only once)
and we can't have both, so for Some(null) the function will re-evaluate. That looks fine to me.
lrytz
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lrytz
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@som-snytt I pushed a commit to remove the |
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I think the non-concurrent case was for efficiency. |
When using `compute`, which has "remove" semantics for `null` value, try alternative means when user wants to put a `null`. In particular, if the underlying map wants to throw NPE, the fallback should do so.
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Ah, that's a good reason 👍 thanks. |
SethTisue
changed the title
Maps
When using
compute, which has "remove" semantics fornullvalue,try alternative means when user wants to put a
null. In particular,if the underlying map wants to throw NPE, the fallback should do so.
Follow-up to #10027