get field name of case class and get type checked new value. (scalameta 1.6.0, paradise 3.0.0-M7)

FieldNameAndValuePorter.scala

package scalaworld.macros

package com.folio.account.macros

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

/**
  * annotation for case class.
  *
  * It generates `FieldNameAndValuePorter` obect in comanion obect, that have these methods for each case class field.
  * `def fieldName(value: TypeOfField): (String, TypeOfField) = (fieldName, value)`
  *
  * @example
  *          {{{
  *          @FieldNameAndValuePorter
  *          case class Mofu(foo: Int, bar: String)
  *          obect Mofu {}
  *
  *          Mofu.FieldNameAndValuePorter.foo(1) ==> ("foo", 1)
  *          Mofu.FieldNameAndValuePorter.bar(2) ==> type error Int is not String
  *          }}}
  */
class FieldNameAndValuePorter extends scala.annotation.StaticAnnotation {
  inline def apply(defn: Any): Any = meta {
    def createPorterObject(paramss: Seq[Seq[Term.Param]]): Defn.Object = {
      val porters = paramss.flatten.map { param =>
        val fieldName = Term.Name(param.name.syntax)
        val fieldType =  param.decltpe.getOrElse(abort(s"${param.name.syntax} does not have type"))
        val argName = Term.fresh("value")
        val returnType = Type.Name(fieldType.syntax)
        q"""def $fieldName($argName: $fieldType):(_root_.scala.Predef.String, $returnType) = (${fieldName.value}, $argName)"""
      }

      q"""object FieldNameAndValuePorter { ..$porters }"""
    }

    defn match {
      // companion object exists
      case Term.Block(Seq(cls @ Defn.Class(_, name, _, ctor, _), companion: Defn.Object)) =>
        val porterObject = createPorterObject(cls.ctor.paramss)
        val newCompanion = companion.copy(
          templ = companion.templ.copy(
            stats = Some(porterObject +: companion.templ.stats.getOrElse(Nil))
          )
        )
        Term.Block(Seq(cls, newCompanion))

      // companion object does not exists
      case cls: Defn.Class =>
        val porterObject = createPorterObject(cls.ctor.paramss)
        val companion   = q"object ${Term.Name(cls.name.value)} { $porterObject }"
        Term.Block(Seq(cls, companion))

      // something wrong
      case _ =>
        println(defn.structure)
        abort("@FieldNameAndValuePorter must annotate a object.")
    }
  }
}

FieldNameAndValuePorterMain.scala

package scalaworld.macros

import org.scalatest.FunSuite

object Mofu

@FieldNameAndValuePorter
case class Mofu(wan: Int, nyan: String, gau: Double, oh: String)

class FieldNameAndValuePorterMain extends FunSuite {
  test("mofu") {
    // ("wan",2)
    println(Mofu.MacroPorter.wan(2))

    // ("nyan", "nyaa")
    println(Mofu.MacroPorter.nyan("nyaa"))

    // compile error gyan not defined
    // println(Mofu.MacroPorter.gyan(3))

    // compile error wan is not string
    // println(Mofu.MacroPorter.wan("waon"))

  }
}

UseCaseExample.scala

obect MofuSql {
  def update(columnAndValues: Map[Any, String]): Future[Unit] = {
    someLibrarySql.update(columnAndValues)
  }
}

object　MofuMain {
  val (wanValue, nyanValue) = parseSomeRequest()

  // voilerplate
  MofuSql.update(Map(
    "wan" -> wanValue,
    "nyn" -> nyanValue, // typo!
    "gau" -> "gaugau" // type unsafe (String is not Double)
  ))
  
  // macro (typo safe, value is type checked)
  MofuSql.update(Map(
    Mofu.MacroPorter.wan(wanValue),
    Mofu.MacroPorter.nyan(nyanValue),
    Mofu.MacroPorter.gau(1.3)
  )
}

普通のmacroをかく観点からすると

• scala.metaに TermName(c.freshName()) みたいなのないんですか？(ローカル変数や引数名でも念のため全部やったほうがよい？)
• String もちゃんと _root_.scala.String みたいに、全部full nameで参照するべき？

などがあるが、scala.metaだと実は違う(やらなくていい？)のか、よく知らない

ありがとうございます！

• value 直書き部分を Term.fresh("value") に変更
• Stringをfull name参照に変更

しました！

型の参照はtypeOf[String]みたいにするのがスマートな気がしますね。scala.metaで使えるのか知りませんが

なるほど・・！
http://scalameta.org/tutorial/ が更新されてるのか不明ですが _root.~ で参照しているっぽいのでダメそうですかね・・(◞‸◟)