Hi... is it impossible to serialize empty maps (`mapOf()` ) using kotlinx serialization? ```Class 'E...

# serialization

[Tianyu Zhu]

Hi... is it impossible to serialize empty maps (mapOf() ) using kotlinx serialization?

Class 'EmptyMap' is not registered for polymorphic serialization in the scope of 'Map'.
To be registered automatically, class 'EmptyMap' has to be '@Serializable', and the base class 'Map' has to be sealed and '@Serializable'.

[asdf asdf]

Can you send the code where this is happening? `Map`s already have a builtin MapSerializer, so it would be strange to serialize them polymorphically

[Tianyu Zhu]

I've looked into it a bit more...
1. It works when I just write Json.encodeToString(mapOf())
2. It doesn't work when I try to serialize it with ktor client...
3. After some debugging, it seems like ktor is not finding the LinkedHashMapSerializer. It's instead trying to find a PolymorphicSerializer...

[Tianyu Zhu]

And it's not just EmptyMap that doesn't work, I can't even serialize a LinkedHashMap using Ktor...

[glureau]

Try to specify the generic type Json.encodeToString<Map<Xxx>>(myMap)

[glureau]

If you don't specify the generic type, it's automatically inferred but it will depend on how serializers are setup by default. In you log you said it doesn't find LinkedHashMapSerializer, so I presume your parameter is a LinkedHashMap, and it's possible it's not explicitely serialized with MapSerializer.