Make Blob have "$type" field when serialized

[Emplexx]

When you serialize a blob

val blob = Blob.StandardBlob(BlobRef(""), "", 0)
val serialized = json.encodeToJsonElement(blob)
println(serialized)

it prints {"ref":{"$link":""},"mimeType":"","size":0}. As you can see, there is no "$type":"blob" field, which makes it impossible to make a post with an image for example (it fails with the following error: {"error":"InvalidRequest","message":"Invalid app.bsky.feed.post record: Record/embed/images/0/image should be a blob ref"})

@SerialName("blob") annotation on the sealed interface seems to have no effect because of the custom BlobSerializer serializer being used, so the workaround I found is to add a property inside the class annotated with @EncodeDefault which forces it to serialize the property

Then the code above prints: {"ref":{"$link":""},"mimeType":"","size":0,"$type":"blob"}

[christiandeange]

the workaround I found is to add a property inside the class

Sounds reasonable. Just to make sure, does this still work with deserializing a Blob coming from the API? My worry is that removing the @SerialName("blob") annotation from the class itself might prevent that from being the case.

[Emplexx]

I just tried it with a blob from a real API response, and it works

From my understanding, @SerialName("blob") is not applied appropriately, because with polymorphism @SerialName describes names of sub-classes rather than the parent class. I could be wrong about this but that is what the documentation suggests, in all examples the annotation is applied to sub-classes

However, leaving the class annotated doesn't affect serialization so it could just be left as before, the annotation doesn't have to be removed

[christiandeange]

@Emplexx I think you're just missing an import in here, otherwise everything LGTM

[Emplexx]

My apologies, I didn't realise

[christiandeange]

@Emplexx I think there's an (intentional) API difference that was introduced and is now failing in the PR build, if you run ./gradlew apiDump that should update the expected API dump