How to compile and execute scala code at run-time in Scala3?

I would like to compile and execute Scala code given as a String at run-time using Scala3. Like for example in Scala 2 I would have used Reflection

import scala.reflect.runtime.universe as ru
import scala.tools.reflect.ToolBox
val scalaCode = q"""println("Hello world!")"""
val evalMirror = ru.runtimeMirror(this.getClass.getClassLoader)
val toolBox = evalMirror.mkToolBox()
toolBox.eval(scalaCode) //Hello world!

If I try to run this code in Scala3 I get

Scala 2 macro cannot be used in Dotty. See https://dotty.epfl.ch/docs/reference/dropped-features/macros.html
To turn this error into a warning, pass -Xignore-scala2-macros to the compiler

How can I translate this code in Scala3 ?

Solution

This program compiles Scala 3 code dynamically:

import dotty.tools.dotc.Driver
import java.net.{URL, URLClassLoader}
import java.nio.file.{Files, Path}
import java.io.File

object DynamicCompiler:

  private val driver = Driver()

  def compile(code: String, className: String, outputDir: Path): Boolean =
    val sourceFile = Files.createTempFile(className, ".scala").toFile
    sourceFile.deleteOnExit()
    Files.writeString(sourceFile.toPath, code)

    val args = Array(
       sourceFile.getAbsolutePath,
       "-d",
       outputDir.toAbsolutePath.toString,
       "-classpath",
       System.getProperty("java.class.path")
    )

    val result = driver.process(args)
    !result.hasErrors

  def loadClass(className: String, classDir: Path): Option[Class[?]] =
    val loader = URLClassLoader(Array(classDir.toUri.toURL), getClass.getClassLoader)
    try Some(loader.loadClass(className))
    catch case _: ClassNotFoundException => None

  def main(args: Array[String]): Unit =
    val outDir = Files.createTempDirectory("scala3-compiled")
    val objectName = "DynamicRoot"
    val className = "Root"

    val code =
      s"""
         |case class Address(city: Option[String], country: Option[String], street: Option[String])
         |case class Person(address: Option[Address], age: Option[Long], name: Option[String])
         |case class $className(people: Option[Seq[Person]])
         |object $objectName
         |""".stripMargin

    if compile(code, objectName, outDir) then
      println(s"Compilation succeeded. Output in: $outDir")
      loadClass(objectName, outDir) match
        case Some(objCls) => println(s"Loaded object class: $objCls")
        case None         => println(s"Failed to load object class: $objectName")

      loadClass(className, outDir) match
        case Some(rootCls) => println(s"Loaded case class: $rootCls")
        case None          => println(s"Failed to load case class: $className")
    else
      println("Compilation failed.")