Automatic Validations

By bringing in zio-config-refined module, you get validations for your config parameters almost for free. zio-config elegantly integrates with Refined library for you to achieve this with same ergnomics.

Those who are not familiar with refined library (https://github.com/fthomas/refined) , check it out and the below examples would make sense.

 import zio.config.ConfigDescriptor
 import zio.config.refined.refine

 import eu.timepit.refined._, api._, string._

 // A string config, such that it should be a Url
 val urlConfig: ConfigDescriptor[Refined[String, Url]] =
   refine[String, Url]("URL")

A much more interesting is being able to get a refined type out of an already derived ConfigDescriptor. Take a look at the below example

 import zio.config._, ConfigDescriptor._
 import zio.config.refined.refine
 import zio.config.magnolia.DeriveConfigDescriptor.descriptor

 import eu.timepit.refined._, api._, numeric._, collection._

 case class MyConfig(url: String, port: Int)

 val configs: ConfigDescriptor[List[MyConfig]] =
   list("databases")(descriptor[MyConfig])

 // A list of database configs, such that size should be greater than 2.
 val databaseList: ConfigDescriptor[Refined[List[MyConfig], Size[Greater[W.`2`.T]]]] =
   refine[Size[Greater[W.`2`.T]]](configs)

You can also use auto derivations with refined.

import eu.timepit.refined.W
import eu.timepit.refined.api.Refined
import eu.timepit.refined.collection.{ NonEmpty, Size }
import zio.config.refined._
import zio.config._
import ConfigDescriptor._
import zio.config.magnolia.DeriveConfigDescriptor.descriptor

object RefinedReadConfig extends App {
  case class RefinedProd(
    ldap: Refined[String, NonEmpty],
    port: Refined[Int, GreaterEqual[W.`1024`.T]],
    dbUrl: Option[Refined[String, NonEmpty]],
    longs: Refined[List[Long], Size[Greater[W.`2`.T]]]
  )

  val configMultiMap =
    Map(
      "LDAP"     -> ::("ldap", Nil),
      "PORT"     -> ::("1999", Nil),
      "DBURL"   -> ::("ddd", Nil),
      "LONGS" -> ::("1234", List("2345", "3456"))
    )

  val result =
    read(descriptor[RefinedProd].mapKey(_.toUpperCase) from ConfigSource.fromMultiMap(configMultiMap))

  // Right(RefinedProd(ldap,1999,Some(ddd),List(1234, 2345, 3456)))
}