Off by 1 bug in PropertyValueBuffer

[kpdonn]

Came across this looking at FasterXML/jackson-module-kotlin#46

There is a bug here: https://github.com/FasterXML/jackson-databind/blob/master/src/main/java/com/fasterxml/jackson/databind/deser/impl/PropertyValueBuffer.java#L276-L281

_paramsSeenBig.set(ix); needs to be before if (--_paramsNeeded <= 0) { return true; } otherwise it is skipped for the last element. That code block only gets executed if there are 32+ parameters.

[cowtowncoder]

Thank you for reporting this. I had the feeling something like this would be wrong based on that comment for a problem you reported for kotlin module.

Would it be easy to get a simple repro to guard against regression? If not, I can try to cook one up.

Either way I can then fix this for 2.8(.5)

[kpdonn]

There is a test in Kotlin in FasterXML/jackson-module-kotlin#46. It doesn't look like the bug has any outward effects normally in Java since the only thing it seems to break is PropertyValueBuffer.hasParameter() which isn't normally called.

Here is something I managed to come up with to reproduce it in plain Java: https://gist.github.com/kpdonn/368a760ab52a9bbb0b334c2a37fae0d2

[cowtowncoder]

@kpdonn Appreciate your help, thank you!

[apatrida]

I uncommented out the test in the kotlin module for the 2.9.x branch, it now passes.