Can't access default serializer which is crutial for polymorphism.

[krottv]

Describe the bug

Currently if we provide @serializable(with = CustomSerializer) annotation then we no longer have access to original generated serializer. Which is fine in most cases, but it is critical when we deal with polymotphism. The main issue is that we run into dependency cycle.

To Reproduce
The following code crashes the app with NPE

@Serializable(with = MediaImageSerializer::class)
@SerialName("image")
data class MediaImage(...)

object MediaImageSerializer : JsonTransformingSerializer<MediaImage>(MediaImage.serializer()) 

The problem here is that we can't avoid @Serializable(with = MediaImageSerializer::class) here. Because the object that contains mediaImage doesn't know its type:

@Serializable
class Template(medias: List<@Serializable with [we don't know which serializer to use] Media>)

Expected behavior

We need to be able to use original generated serializer

Environment

• Kotlin version: 1.4.30-RC
• Library version: 1.0.1
• Kotlin platforms: JVM

[sandwwraith]

Duplicate of #1169, looks like

As a workaround, you can use @file:UseSerializers instead of repeating @Serializable(MediaImageSerializer::class)

[krottv]

@sandwwraith where should I put @file:UseSerializers? I tried it everywhere, doesn't make any difference, still the dafault one is always used. It doesn't work for polymorphism, seems like another issue

[sandwwraith]

Fixed by #1169