support RemoveUnused on Scala 3.3.0

Author: bjaglin

build.sbt

@@ -178,8 +178,7 @@ lazy val testsInput = projectMatrix
     noPublishAndNoMima,
     scalacOptions ~= (_.filterNot(_ == "-Yno-adapted-args")),
     scalacOptions ++= warnAdaptedArgs.value, // For NoAutoTupling
-    scalacOptions ++= warnUnusedImports.value, // For RemoveUnused
-    scalacOptions ++= warnUnused.value, // For RemoveUnusedTerms
+    scalacOptions += "Wunused", // For RemoveUnusedTerms
     logLevel := Level.Error, // avoid flood of compiler warnings
     libraryDependencies ++= testsDependencies.value,
     coverageEnabled := false

docs/rules/RemoveUnused.md

@@ -14,15 +14,12 @@ example diff from running `sbt "scalafix RemoveUnused"`.
 
 To use this rule:
 
-- Enable the Scala compiler option `-Ywarn-unused` (or `-Wunused` in 2.13). In
-  sbt, this is done with `scalacOptions += "-Ywarn-unused"`.
+- Enable the Scala compiler option `-Wunused`. In sbt, this is done with
+  `scalacOptions += "-Wunused"`.
 - Disable `-Xfatal-warnings` if you have it enabled. This is required so the
   compiler warnings do not fail the build before running Scalafix. If you are
   running 2.13.2 or later, you may keep `-Xfatal-warnings` by modifying how
   specific warnings are handled via `scalacOptions += "-Wconf:cat=unused:info"`.
-- This rule **can't work** yet on Scala 3 projects since the compiler option `warn-unused`
-  is not yet available in Scala 3. You need to remove `RemoveUnused` 
-  from `.scalafix.conf` for Scala 3 projects.
 
 ## Examples
 
@@ -146,4 +143,4 @@ Enable or disable specific `unused' warnings
   params     Enable -Ywarn-unused:explicits,implicits.
   linted     -Xlint:unused.
 Default: All choices are enabled by default.
-```
+```

project/Dependencies.scala

@@ -9,7 +9,7 @@ import scala.util.Try
 object Dependencies {
   val scala212 = "2.12.17"
   val scala213 = "2.13.10"
-  val scala3 = "3.2.2"
+  val scala3 = "3.3.0-RC5"
 
   val buildScalaVersions = Seq(scala212, scala213, scala3)
   val testTargetScalaVersions = Seq(scala212, scala213, scala3)

project/ScalafixBuild.scala

@@ -46,14 +46,9 @@ object ScalafixBuild extends AutoPlugin with GhpagesKeys {
       scalaVersion.value.startsWith("2.12")
     }
     lazy val warnUnusedImports = Def.setting {
-      if (isScala3.value) Nil
-      else if (isScala213.value) Seq("-Wunused:imports")
+      if (isScala213.value || isScala3.value) Seq("-Wunused:imports")
       else Seq("-Ywarn-unused-import")
     }
-    lazy val warnUnused = Def.setting {
-      if (isScala2.value) Seq("-Ywarn-unused")
-      else Nil
-    }
     lazy val targetJvm = Def.setting {
       if (isScala3.value) Seq("-Xtarget:8")
       else if (isScala213.value) Seq("-release", "8")

scalafix-rules/src/main/scala/scalafix/internal/rule/RemoveUnused.scala

@@ -26,7 +26,7 @@ class RemoveUnused(config: RemoveUnusedConfig)
   def this() = this(RemoveUnusedConfig.default)
 
   override def description: String =
-    "Removes unused imports and terms that reported by the compiler under -Ywarn-unused"
+    "Removes unused imports and terms that reported by the compiler under -Yunused"
   override def isRewrite: Boolean = true
 
   private def warnUnusedPrefix = List("-Wunused", "-Ywarn-unused")
@@ -36,17 +36,18 @@ class RemoveUnused(config: RemoveUnusedConfig)
       warnUnusedPrefix.exists(prefix => option.startsWith(prefix)) ||
         warnUnusedString.contains(option)
     )
-    if (config.scalaVersion.startsWith("3"))
-      Configured.error(
-        "This rule is specific to Scala 2, because the compiler option `-Ywarn-unused` is not available yet in scala 3 " +
-          "To fix this error, remove RemoveUnused from .scalafix.conf"
-      )
-    else if (!hasWarnUnused) {
-      Configured.error(
-        s"""|The Scala compiler option "-Ywarn-unused" is required to use RemoveUnused.
-          |To fix this problem, update your build to use at least one Scala compiler
-          |option like -Ywarn-unused, -Xlint:unused (2.12.2 or above), or -Wunused (2.13 only)""".stripMargin
-      )
+    if (!hasWarnUnused) {
+      if (config.scalaVersion.startsWith("3"))
+        Configured.error(
+        """|The Scala compiler option "-Ywarn-unused" (available from Scala 3.3.0-RC2) is
+           |required to use RemoveUnused. To fix this problem, update your build to add it.""".stripMargin
+        )
+      else
+        Configured.error(
+        """|A Scala compiler option is required to use RemoveUnused. To fix this problem,
+           |update your build to add either -Ywarn-unused, -Xlint:unused (2.12.2 or above),
+           |or -Wunused (2.13).""".stripMargin
+        )
     } else {
       config.conf
         .getOrElse("RemoveUnused")(this.config)