`XmlMapper`/`UntypedObjectDeserializer` mixes multiple unwrapped collections

[drewko]

Hi I found an issue with deserializing xml node containg multiple unwrapped collections.

Entity

<person>
    <name>a</name>
    <name>b</name>
    <surname>c</surname>
    <surname>d</surname>
</person>

Code

new XmlMapper().readValue(xml, Object.class);

Output

{
    name = [ c, d ], 
    surname = d
}

Problem
Could not deserialize node that contains multiple unwrapped collections. If I remove one surname, so that name is the only collection - it works properly.

Version: 2.12.1

[cowtowncoder]

Thank you for reporting this: sounds like a problem indeed. I hope to have a look soon, will add to my todo list.

[Migwel]

@cowtowncoder I'm happy to give it a try. To be sure, the expected behavior is that the XML is serialized into

{
    name = [ a, b ], 
    surname = [c, d]
}

?

After a quick look, the issue seems to be coming from the way we handle duplicates in com.fasterxml.jackson.databind.deser.std.UntypedObjectDeserializer.Vanilla#_mapObjectWithDups where the code gets confused. It could be related to #205

[cowtowncoder]

@Migwel yes definitely that would be expected. One easy thing to start with would be to write a simple test case, along with ones that exist, under "src/test/java/.../failing" in jackson-dataformat-xml -- this even if the issue itself is on databind side, I think (easier to test although technically testing would be doable with some work on databind).
Fix should be for 2.12, I think, so branch to use would be 2.12.