Read an object having 32+ properties with default values

[dstarcev]

When I try to read an object with more than 31 properties with default values, jackson ignores the value for the very last property. The reason may be how Kotlin compiler transforms such classes to bytecode, but I am not sure. The following test demonstrates the bug:

https://gist.github.com/dstarcev/a829685618d3c638f462028e48690ce8

[apatrida]

we can try a test case of using reflection and the constructor's callBy method to see if it works or not. likely it is an issue there and not with the Jackson module.

[apatrida]

@Udalev says

there shouldn't be, please report an issue

so we should verify by using callBy and reflection is a problem in Kotlin or not first.

[kpdonn]

I was curious about this and looking into it the bug appears to be in jackson-databind. Specifically

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 which is why it doesn't happen otherwise.

[apatrida]

yes, I just found this too. It lies and says not found for the last parameter. getParameters() returns 32, but I use getParameter one at a time and call hasParameter first which lies.

@cowtowncoder bug linked to databind.

[apatrida]

I added a test (kotlin, sorry) in git for this case, it is currently disabled. But you can load it in Intellij and debug easily into the code, or the fix is actually listed in he #1432. I'll leave this open and un-ignore the test after fixed as proof.

[swankjesse]

https://youtrack.jetbrains.com/issue/KT-18404