Summary

I want to deserialize a Kotlin class with type parameters, using the `org.mongodb:bson-kotlin` (reflection-based) driver.

My understanding is that I should call the `CodecProvider.get(Class<T>, List<Type>)` overload to specify the type parameters; since they are removed at compile-time, the reflection-based implementation cannot figure them out by itself.

I therefore have the following type:

data class BsonDocumentUser(
    val a: String = "Bob",
    val b: Int,
)

data class BsonDocumentTypeParameter<T>(
    val value: T,
)

codecRegistry.get(BsonDocumentTypeParameter::class, listOf(BsonDocumentUser::class))

However, this does not return the codec.

Looking at the implementation:

• In `org.bson.internal.ProvidersCodecRegistry#get(java.lang.Class<T>, java.util.List<java.lang.reflect.Type>)`, a new ChildCodecRegistry is created, but does nothing
• In `org.bson.internal.ProvidersCodecRegistry#get(org.bson.internal.ChildCodecRegistry<T>)`, a new CodecCacheKey is created.
• Immediately, `org.bson.internal.CodecCache#get` is called on the new cache key.

At this point, `org.bson.internal.CodecCache#putIfAbsent` has not been called, so of course the codec cache returns null.

Am I supposed to register the type somewhere so the codec cache is populated in advance? Is there something else I'm doing wrong?

Versions

• Java driver 5.6.2
• The MongoDB server version & topology should not impact this; I'm using 7.0.31 standalone