We are migrating one of our mobile codebase (alrea...

# javascript

[Martin Gagnon]

We are migrating one of our mobile codebase (already in production) to kotlin 1.4M to support Typescript and provide a JS implementation. However we have some issues regarding the new IR backend and @JSExport. Here are some questions:

Is there a way for @JsExport to export transitive dependencies ?

The following code produce an error:

@JsExport
data class A(val b: String) {
    companion object
}

e: java.lang.AssertionError: Properties without fields are not supported A.Companion_instance

Also, when using the @JsExport annotation on an object, example:

@JsExport
object A {
  var b: String = ""
}

The following TypeScript definition is generated:

/* ErrorDeclaration: Class A with kind: OBJECT */

Is there any workaround for this? Is there any plan to support those types?

[anton.bannykh]

^ cc @Svyatoslav Kuzmich [JB]

[Svyatoslav Kuzmich [JB]]

Is there a way for @JsExport to export transitive dependencies ?

No. Our current plan is to require explicit export. The reason is that only a subset of Kotlin can be sanely represented in JS and implicit export can start reporting errors in places far from the place you made an edit, or inside a code you don’t own.

Is there any workaround for this? Is there any plan to support those types?

We are working on supporting object export, including companions.

Unfortunately, I don’t think there is a workaround other than not using objects (for example using class + property instance instead).

[Martin Gagnon]

Thanks a lot for your quick answers. Will adapt things on our side!

[ankushg]

hm, we currently use quite a few Factories in our JS code like object FooFactory { fun createFoo(param1: A, param2: B): Foo }
because it lets us deal with potential dynamic inputs avoid worrying about overloaded constructors when JS is only going to use one of them

Is there a ticket I can follow for updates on object export?

[Svyatoslav Kuzmich [JB]]

@ankushg You can follow https://youtrack.jetbrains.com/issue/KT-39117

[Justin]

Adding to this thread:

It seems I can’t use @JsExport on any class that is also annotated with @Serializable because (I’m presuming) kotlinx.serialization auto-generates a companion object for classes marked as such.

That’ll be a deal-breaker for me if there’s no workaround since we need that serialization lib.

https://kotlinlang.slack.com/archives/C0B8L3U69/p1590354711300900?thread_ts=1590348596.293700&cid=C0B8L3U69

Any ideas?