field_rename_old.kt

// Latest security rules look for a `familyName` field instead of `surname`. This
// function will not therefore work.
fun addPerson(firstName: String, surname: String): Task<Void> {
    val data = hashMapOf(
        "firstName" to firstName,
        "surname" to surname
    )
    return db.collection("people").document()
        .set(data)
}


// New documents doesn't have a `surname` field. The assertion will fail for
// those documents.
fun getPerson(personId: String) {
    db.collection("people").document(personId)
        .get()
        .addOnSuccessListener { snapshot ->
            val data = snapshot.data ?: hashMapOf()
            val surname = data["surname"]
            assert(surname is String)                   
            updateView(surname)
        }
}