@tostring and @logger macro annotation

00_Main.scala

package com.example

import java.time.LocalDateTime

@ToString
case class UserName(
    firs: String,
    last: String
)

@ToString
case class User(
    id: Int,
    name: UserName,
    country: String,
    createdAt: LocalDateTime
)

@Logger
object Main {

  def main(args: Array[String]): Unit = {
    val user = User(1, UserName("Toshiyuki", "Takahashi"), "Japan", LocalDateTime.now())
    logger.info(user.toString)

    // output
    // 23:44:35.499 [run-main-3a] INFO com.example.Main$ - User(id=1, name=UserName(firs=Toshiyuki, last=Takahashi), country=Japan, createdAt=2017-03-05T23:44:35.498)
  }

}

01_ToString.scala

package com.example

import scala.collection.immutable.Seq
import scala.meta._

class ToString extends scala.annotation.StaticAnnotation {

  inline def apply(defn: Any): Any = meta {

    def addStat(classDefn: Defn.Class, stat: Stat): Defn.Class = {
      val templ = classDefn.templ
      val stats = templ.stats.getOrElse(Seq.empty[Stat])
      val newStats = stats :+ stat
      val newTempl = templ.copy(stats = Some(newStats))
      classDefn.copy(templ = newTempl)
    }

    def addToStringMethod(classDefn: Defn.Class, objDefn: Defn.Object): Stat = {
      val className = classDefn.name.toString
      val paramNames = classDefn.ctor.paramss.flatten.map { param =>
        val fieldName = param.name.toString
        q"""${Lit(fieldName)} + "=" + ${Term.Name(fieldName)}"""
      }
      val body = paramNames.reduce { (a, b) => q"""$a + ", " + $b""" }
      val method = q"""override def toString(): String = ${Lit(className)} + "(" + $body + ")""""
      val classDefnWithToString = addStat(classDefn, method)
      Term.Block(scala.collection.immutable.Seq(classDefnWithToString, objDefn))
    }

    defn match {
      case Term.Block(Seq(classDefn: Defn.Class, objDefn: Defn.Object)) =>
        addToStringMethod(classDefn, objDefn)
      case classDefn: Defn.Class =>
        val objName = Term.Name(classDefn.name.toString)
        val objDefn = q"object $objName {}"
        addToStringMethod(classDefn, objDefn)
      case _ => sys.error("error")
    }

  }

}

02_Logger.scala

package com.example

import scala.annotation.StaticAnnotation
import scala.meta._
import scala.collection.immutable.Seq

class Logger extends StaticAnnotation {

  inline def apply(defn: Any): Any = meta {

    def addStatToTempl(templ: Template, stat: Stat): Template = {
      val stats = templ.stats.getOrElse(Seq.empty[Stat])
      val newStats = stat +: stats
      templ.copy(stats = Some(newStats))
    }

    def addStatToClassDefn(classDefn: Defn.Class, stat: Stat): Defn.Class = {
      val templ = classDefn.templ
      val newTempl = addStatToTempl(templ, stat)
      classDefn.copy(templ = newTempl)
    }

    def addStatToObjDefn(objDefn: Defn.Object, stat: Stat): Defn.Object = {
      val templ = objDefn.templ
      val newTempl = addStatToTempl(templ, stat)
      objDefn.copy(templ = newTempl)
    }

    def loggerMethod: Stat = {
      q"""
        private val logger = {
          import org.slf4j.LoggerFactory
          LoggerFactory.getLogger(getClass)
        }
      """
    }

    defn match {
      case objDefn: Defn.Object =>
        addStatToObjDefn(objDefn, loggerMethod)
      case classDefn: Defn.Class =>
        addStatToClassDefn(classDefn, loggerMethod)
      case Term.Block(Seq(classDefn: Defn.Class, objDefn: Defn.Object)) =>
        Term.Block(
          Seq(
            addStatToClassDefn(classDefn, loggerMethod),
            addStatToObjDefn(objDefn, loggerMethod)
          )
        )
      case _ => sys.error("error")
    }
  }

}