Mark the generated companion object with @JsExport.Ignore

[lppedd]

Let's take the following annotated Kotlin class:

@JsExport
@Serializable
public class ZCSet(
  public val desc: String?,
  public val isSel: Boolean?,
  public val subset: Int?,
)

On Kotlin/JS, when generateTypeScriptDefinitions() is enabled, and because the class is @JsExport-ed, the companion will appear in the generated TS types:

The companion should be marked with @JsExport.Ignore only when it does not exist already.
This avoids kotlinx-serialization marking non-exported something the user wants to export.

[sandwwraith]

kotlinx.serialization generates MyClass.Companion declaration to provide MyClass.Companion.serializer(): KSerializer<MyClass> user-visible function. I imagine it can be called from JS under some circumstances, so I'm not sure this class should be hidden

[sandwwraith]

@JSMonk I see some tests saying that companion can't be removed due to how plugins are designed: https://github.com/JetBrains/kotlin/blob/50a462fed144cdca8b56934d4971b567308b5e8a/plugins/kotlinx-serialization/testData/boxIr/excludedFromFileExport.kt#L34

Do you remember what the actual problem was?
Also, why not export .serializer() function as well?

[lppedd]

Hey! Completely forgot to reply to your first comment, sorry.

I imagine it can be called from JS under some circumstances

I can't think of any circumstance. Serialization is generally handled on the Kotlin side and never exposed to JS consumers of the API. And if it is, it is done through additional custom-tailored functions.

Plus, exporting kotlinx-serialization might mean bigger bundles as effectively you're disabling DCE for all the serializer() code path.

Also, why not export .serializer() function as well?

Keep in mind you'd have to make the KSerializer interface and its hierarchy exportable.