Client library can use `tethys-derivation_2.x` with scope `provided`

[JeJutic]

Can a library which uses tethys-derivation_2.x set provided scope on it? That is, does expanded macro code use any internal tethys-derivation API? It seems like not, but I might be wrong.

If it is actually supported, it would be nice to write it explicitly in README.

[JeJutic]

I tested it for a simple case with library project:

ThisBuild / version := "0.1.0-SNAPSHOT"

ThisBuild / scalaVersion := "2.13.18"

val tethysVersion = "0.29.7"

lazy val root = (project in file("."))
  .settings(
    organization := "org.abc",
    name := "lib-w-autoderivation",
    libraryDependencies ++= Seq(
      "com.tethys-json" %% "tethys-core" % tethysVersion,
      "com.tethys-json" %% "tethys-jackson213" % tethysVersion,
      "com.tethys-json" %% "tethys-derivation" % tethysVersion % "provided"
    )
  )

package org

import tethys.JsonReader
import tethys.derivation.semiauto.jsonReader

package object abc {
  case class Person(
    id: Int,
    name: String,
    phone: Option[String],
    default: String = ""
  )

  object Person {
    implicit val jsonReaderPerson: JsonReader[Person] = jsonReader[Person]
  }

  case class Wrapper(person: Person)

  object Wrapper {
    implicit val jsonReaderWrapper: JsonReader[Wrapper] = jsonReader[Wrapper]
  }
}

and a project which uses this library:

ThisBuild / version := "0.1.0-SNAPSHOT"

ThisBuild / scalaVersion := "2.13.18"

val tethysVersion = "0.29.7"

lazy val root = (project in file("."))
  .settings(
    name := "app-without-autoderivation-dep",
    libraryDependencies ++= Seq(
      "com.tethys-json" %% "tethys-core" % tethysVersion,
      "com.tethys-json" %% "tethys-jackson213" % tethysVersion,
      "org.abc" %% "lib-w-autoderivation" % "0.1.0-SNAPSHOT"
    )
  )

import tethys._
import tethys.jackson._

object Main {
  def main(args: Array[String]): Unit = {
    println("""{"person": {"id": 42, "name": "Name"}}""".jsonAs[org.abc.Wrapper])
  }
}

As expected:

[] run Main
Right(Wrapper(Person(42,Name,None,)))
[]dependencyTree
[info] app-without-autoderivation-dep:app-without-autoderivation-dep_2.13:0.1.0-SNAPS..
[info]   +-com.tethys-json:tethys-core_2.13:0.29.7 [S]
[info]   | +-org.scala-lang:scala-reflect:2.13.17 (evicted by: 2.13.18)
[info]   | +-org.scala-lang:scala-reflect:2.13.18 [S]
[info]   | 
[info]   +-com.tethys-json:tethys-jackson213_2.13:0.29.7 [S]
[info]   | +-com.fasterxml.jackson.core:jackson-core:2.13.5
[info]   | +-com.tethys-json:tethys-core_2.13:0.29.7 [S]
[info]   |   +-org.scala-lang:scala-reflect:2.13.17 (evicted by: 2.13.18)
[info]   |   +-org.scala-lang:scala-reflect:2.13.18 [S]
[info]   |   
[info]   +-org.abc:lib-w-autoderivation_2.13:0.1.0-SNAPSHOT [S]
[info]     +-com.tethys-json:tethys-core_2.13:0.29.7 [S]
[info]     | +-org.scala-lang:scala-reflect:2.13.17 (evicted by: 2.13.18)
[info]     | +-org.scala-lang:scala-reflect:2.13.18 [S]
[info]     | 
[info]     +-com.tethys-json:tethys-jackson213_2.13:0.29.7 [S]
[info]       +-com.fasterxml.jackson.core:jackson-core:2.13.5
[info]       +-com.tethys-json:tethys-core_2.13:0.29.7 [S]
[info]         +-org.scala-lang:scala-reflect:2.13.17 (evicted by: 2.13.18)
[info]         +-org.scala-lang:scala-reflect:2.13.18 [S]

[dos65]

That's an interesting observation.

However, even if it works now, there are no guarantees that it works in all cases. How we can prove that there are zero leaks of classes defined in derivation module in generated macro code?

Also, I don't know who would need such usage? provided scope usually is used in case if jar will be provided at runtime. Not in case when you don't need it at all.

[JeJutic]

provided scope usually is used in case if jar will be provided at runtime. Not in case when you don't need it at all.

Afaik sometimes it's used to provide the dependency at compile time but not share it transitively with library users. It might be useful if library user doesn't want to depend on tethys-derivation.

How we can prove that there are zero leaks

Testing is non-trivial indeed. To do it, we should automatize publishing a library with ADTs and their autoderivations and create a side project / subproject which would fetch it and ran tests.