scalasbtcompiler-flagscircescalac

sbt compile fails with bad option: '-Ywarn-macros:after'

With a build.sbt file like:

ThisBuild / organization := "com.company"
ThisBuild / version := "1.0.0-SNAPSHOT"
ThisBuild / scalaVersion := "2.11.12"

Global / concurrentRestrictions += Tags.limit(Tags.Test, 1)

Global / scalacOptions ++= Seq("-Ypartial-unification",
                               "-unchecked",
                               "-Xfatal-warnings",
                               "-Ywarn-dead-code",
                               "-Ywarn-inaccessible",
                               "-Ywarn-unused",
                               "-Ywarn-unused-import",
                               "-Ywarn-macros:after")

I get [error] bad option: '-Ywarn-macros:none' after running sbt clean compile

Without -Ywarn-macros:after, the unused import warning raises spurious warnings in files using Circe macros, for example: import io.circe.{ Decoder, Encoder }.

Solution

  • -Ywarn-macros wasn't added until Scala 2.12, so the error is expected.

    Can you upgrade to Scala 2.12? If you are stuck on 2.11, perhaps you will need to live without -Ywarn-unused-import. (Unused warnings in general have greatly improved as the 2.12.x series has progressed, thanks to tireless work on it by Som Snytt.)

    You might be able to confine the Circe-using code to a subproject, and then disable unused warnings in that subproject only, in order to leave them enabled in the rest of your codebase.

    Another possibility is to try https://github.com/ghik/silencer.