A synchronized setter with side-effects in Kotlin (probably a bad idea!)

sync-setter.kt

    private var writeLock = Object()

    /**
     * The canonical version of config that is on disk, barring any sneaky
     * writes; setting this property causes a disk write.
     */
    var config: Config = repo.config.readJson()
        set(newConfig) {
            synchronized(writeLock) {
                repo.config.writeJson(newConfig)
                field = newConfig
            }
        }