I want to port the custom serializer at <https://github.com/Vampire/setup-wsl/blob/master/buildSrc/s...

# serialization

[Vampire]

I want to port the custom serializer at https://github.com/Vampire/setup-wsl/blob/master/buildSrc/src/main/kotlin/net/kautler/dao/GitHubAction.kt#L73 that still runs on 0.20.0 to 1.3.x.
I there have used override val descriptor = SerialDescriptor("...", CONTEXTUAL) for the KSerializer.
How would I port that to 1.3.x as the function does not expect a kind anymore?

[Sebastian Schuberth]

Would using the (experimental) `@Serializer`annotation maybe work?

[Sebastian Schuberth]

Ah, sorry, just saw you're actually already using it at https://github.com/Vampire/setup-wsl/blob/bcd134a8857d9afc02db9cc3fa981a30e231ab61/buildSrc/src/main/kotlin/net/kautler/dao/GitHubAction.kt#L67. I thought specifying the descriptor is then not required anymore.

[Vampire]

Hm, not at my box right now, but I think if I remove the descriptor it complains that it is missing and if I make the class abstract it cannot instantiate it.

[Sebastian Schuberth]

At least for primitive types this works for me, see e.g. https://github.com/oss-review-toolkit/ort/blob/470e2f323b516389bd96a63a81c67b74891[…]36f8/clients/scanoss/src/main/kotlin/model/BooleanSerializer.kt

[Sebastian Schuberth]

Also see https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/serializers.md#deriving-external-serializer-for-another-kotlin-class-experimental

[Vampire]

Your example does not match, because it is not about a generic type. For a generic type like in my case you do not need an object, but a class with constructor and also a provided descriptor. And additionally the serializer is contextual. I needed quite some time and comments to get it working properly back then with 0.20.0.

[Vampire]

Hm, I found that it works if I use

@InternalSerializationApi
override val descriptor = buildSerialDescriptor("...", CONTEXTUAL)

but I don't like the internal serialization api being used.
It's documentation says that it should not be used, and if necessary issues filed.
So is there another way to get a serial descriptor with CONTEXTUAL kind?

[Emil Kantis]

Wouldn't a Map serial descriptor be appropriate in this case?

mapSerialDescriptor<String, Output>()

[Vampire]

No, it must be a contextual descriptor or the processes is not done contextually