Thanks for opening the issue. Could you also post here what happens when adding @JSExport directly on object innerObj, because that would be the root cause. @JSExportAll is merely a shortcut for many @JSExports.

The compiler complains @JSExport is forbidden on objects and classes.

As a workaround, it's possible to export a getter for the object instead:

class ClassWithInnerObj {
  val x = 1

  @JSExport
  def innerObj: innerObjInternal.type = innerObjInternal

  object innerObjInternal extends js.Object {
    val y = 2
  }
}

Thanks for the workaround. I use it in the adapter code generation of the ScalaTsPlugin. After this is fixed I would like to get rid of the workaround because it causes two members to be created in the TypeScript declaration file. There is the danger to access the 'object field' directly instead of the assigned value.