将参数传递给scalameta paradise宏

我正在尝试创建宏注释，但需要传递参数

class ToPojo(param1: String, param2: String) extends StaticAnnotation {
  inline def apply(defn: Any): Any = meta {
        ...
  }
}

它被用作

@ToPojo("p1", "p2")
case class Entity(a: Int, m: Map[Long, Boolean])

上面代码的问题是，实体已经以defn的形式获取apply，并且注释已被剥离，因此我无法从那里获取参数。此外，由于apply方法是内联的，因此无法从apply方法访问param1和param2字段

您能告诉我使用scala meta克服此问题的最简单方法吗？我考虑使用两个注释

@ToPojo
@ToPojoParams("p1", "p2")
case class Entity(a: Int, m: Map[Long, Boolean])

但那是又黑又丑的

---

非常感谢

如第节“ScalaMeta天堂描述”中所述

您可以将其作为Scalameta树进行匹配

请注意，这段代码有点幼稚，不处理命名参数。如果您有许多参数，那么编写所有可能的常用参数和命名参数的组合是很无聊的。因此，您可以尝试以下方法：

package examples

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

class MyMacro(p1: String, p2: Int) extends scala.annotation.StaticAnnotation {


  inline def apply(defn: Any): Any = meta {
    val params = Params.extractParams(this)
    //some implementation
    ... 
  }

}


case class Params(p1: String, p2: Int) {
  def update(name: String, value: Any): Params = name match {
    case "p1" => copy(p1 = value.asInstanceOf[String])
    case "p2" => copy(p2 = value.asInstanceOf[Int])
    case _ => ???
  }
}

object Params {
  private val paramsNames = List("p1", "p2")

  def extractParams(tree: Stat): Params = {
    val args: immutable.Seq[Term.Arg] = tree.asInstanceOf[Term.New].templ.parents.head.asInstanceOf[Term.Apply].args

    args.zipWithIndex.foldLeft(Params(null, 0))((acc, argAndIndex) => argAndIndex._1 match {
      case q"${Lit(value)}" => acc.update(paramsNames(argAndIndex._2), value)
      case q"${Term.Arg.Named(name, Lit(value))}" => acc.update(name.value, value)
    })
  }
}

package examples

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

class MyMacro(p1: String, p2: Int) extends scala.annotation.StaticAnnotation {


  inline def apply(defn: Any): Any = meta {
    val params = Params.extractParams(this)
    //some implementation
    ... 
  }

}


case class Params(p1: String, p2: Int) {
  def update(name: String, value: Any): Params = name match {
    case "p1" => copy(p1 = value.asInstanceOf[String])
    case "p2" => copy(p2 = value.asInstanceOf[Int])
    case _ => ???
  }
}

object Params {
  private val paramsNames = List("p1", "p2")

  def extractParams(tree: Stat): Params = {
    val args: immutable.Seq[Term.Arg] = tree.asInstanceOf[Term.New].templ.parents.head.asInstanceOf[Term.Apply].args

    args.zipWithIndex.foldLeft(Params(null, 0))((acc, argAndIndex) => argAndIndex._1 match {
      case q"${Lit(value)}" => acc.update(paramsNames(argAndIndex._2), value)
      case q"${Term.Arg.Named(name, Lit(value))}" => acc.update(name.value, value)
    })
  }
}