Kotlin SLF4J log message lazy evaluation based on log level

Slf4jLazy.kt

/*
  Lazy evaluation of the messages sent to Slf4j.
  Usage:  
    log.trace { "State dump: " + expensiveLongSerialisation(state) }
    See also https://jira.qos.ch/browse/SLF4J-371
*/

import org.slf4j.Logger
import org.slf4j.LoggerFactory
import kotlin.reflect.KClass
import kotlin.reflect.full.companionObject

inline fun Logger.error(msg: () -> String) { if (this.isErrorEnabled) this.error(msg()) }
inline fun Logger.error(ex: Exception, msg: () -> String) { if (this.isErrorEnabled) this.error(msg(), ex) }
inline fun Logger.warn(msg: () -> String) { if (this.isWarnEnabled) this.warn(msg()) }
inline fun Logger.warn(ex: Exception, msg: () -> String) { if (this.isWarnEnabled) this.warn(msg(), ex) }
inline fun Logger.info(msg: () -> String) { if (this.isInfoEnabled) this.info(msg()) }
inline fun Logger.debug(msg: () -> String) { if (this.isDebugEnabled) this.debug(msg()) }
inline fun Logger.trace(msg: () -> String) { if (this.isTraceEnabled) this.trace(msg()) }


object Logging {
    inline fun <reified R : Any> R.logger(): Lazy<Logger> = lazy { LoggerFactory.getLogger(unwrapCompanionClass(this.javaClass).name) }
}

/** Unwraps the companion class to enclosing class given a Java Class. */
fun <T : Any> unwrapCompanionClass(ofClass: Class<T>): Class<*> {
    return ofClass.enclosingClass?.takeIf {
        ofClass.enclosingClass.kotlin.companionObject?.java == ofClass
    } ?: ofClass
}

/** Unwraps the companion class to enclosing class given a Kotlin Class. */
private fun <T: Any> unwrapCompanionClass(ofClass: KClass<T>): KClass<*> {
    return unwrapCompanionClass(ofClass.java).kotlin
}