UnsupportedOnJs
@RequiresOptIn(message = "Not provided by the Firebase JS SDK: on JS this member does nothing, or fails where it must return a value (see its documentation). Opt in with @OptIn(UnsupportedOnJs::class) if that is acceptable.", level = RequiresOptIn.Level.WARNING)
@Target(allowedTargets = [AnnotationTarget.CLASS, AnnotationTarget.FUNCTION, AnnotationTarget.PROPERTY, AnnotationTarget.CONSTRUCTOR] )
Marks a member of the com.google.firebase layer that the Firebase JS SDK does not provide: on JS it does nothing (or fails, where it must return a value), as its documentation says. The marker is on the JS actual only, so the warning appears when code is compiled for a JS target, in common code included; opt in with @OptIn(UnsupportedOnJs::class) where the JS behaviour is acceptable.