support RemoveUnused on Scala 3.4+

Author: bjaglin

build.sbt

@@ -196,8 +196,7 @@ lazy val input = projectMatrix
     noPublishAndNoMima,
     scalacOptions ~= (_.filterNot(_ == "-Yno-adapted-args")),
     scalacOptions ++= warnAdaptedArgs.value, // For NoAutoTupling
-    scalacOptions ++= warnUnusedImports.value, // For RemoveUnused
-    scalacOptions ++= warnUnused.value, // For RemoveUnusedTerms
+    scalacOptions += warnUnused.value, // For RemoveUnusedTerms
     logLevel := Level.Error, // avoid flood of compiler warnings
     libraryDependencies ++= testsDependencies.value,
     coverageEnabled := false,
@@ -213,7 +212,6 @@ lazy val output = projectMatrix
   .in(file("scalafix-tests/output"))
   .settings(
     noPublishAndNoMima,
-    scalacOptions --= warnUnusedImports.value,
     libraryDependencies ++= testsDependencies.value,
     coverageEnabled := false,
     // mimic dependsOn(shared) but allowing binary Scala version matching

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 `-Ywarn-unused` (2.12), `-Wunused` (2.13),
+  or `-Wunused:all` (3.4+ or 3.3.4+).
 - 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 2.12.13+ or 2.13.2+, 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
 
@@ -67,7 +64,7 @@ object Main {
 }
 ```
 
-Remove unused pattern match variables:
+Remove unused pattern match variables (Scala 2 only):
 
 ```scala
 case class AB(a: Int, b: String)
@@ -87,7 +84,7 @@ object Main {
 }
 ```
 
-Remove unused function parameters:
+Remove unused function parameters (Scala 2.13 only):
 
 ```scala
 // before
@@ -129,21 +126,56 @@ import scalafix.internal.rule._
 println(scalafix.website.rule("RemoveUnused", RemoveUnusedConfig.default))
 ```
 
-## -Ywarn-unused
+## More granular scalac options
 
-Consult `scala -Y` in the command-line for more information about using
-`-Ywarn-unused`.
+You may request more granular warnings to the compiler if you opt-out
+from some rewrites in the rule configuration. 
 
 ```
-$ scala -Ywarn-unused:help
-Enable or disable specific `unused' warnings
-  imports    Warn if an import selector is not referenced.
-  patvars    Warn if a variable bound in a pattern is unused.
-  privates   Warn if a private member is unused.
-  locals     Warn if a local definition is unused.
-  explicits  Warn if an explicit parameter is unused.
-  implicits  Warn if an implicit parameter is unused.
-  params     Enable -Ywarn-unused:explicits,implicits.
-  linted     -Xlint:unused.
+$ scala212 -Wunused:help
+Enable or disable specific `unused` warnings
+  imports     Warn if an import selector is not referenced.
+  patvars     Warn if a variable bound in a pattern is unused.
+  privates    Warn if a private member is unused.
+  locals      Warn if a local definition is unused.
+  explicits   Warn if an explicit parameter is unused.
+  implicits   Warn if an implicit parameter is unused.
+  synthetics  Warn if a synthetic implicit parameter (context bound) is unused.
+  nowarn      Warn if a @nowarn annotation does not suppress any warnings.
+  params      Enable -Wunused:explicits,implicits,synthetics.
+  linted      -Xlint:unused.
 Default: All choices are enabled by default.
 ```
+
+```
+$ scala3 -W
+...
+       -Wunused  Enable or disable specific `unused` warnings
+                 Choices : 
+                 - nowarn, 
+                 - all, 
+                 - imports :
+                 	Warn if an import selector is not referenced.
+                 	NOTE : overrided by -Wunused:strict-no-implicit-warn, 
+                 - privates :
+                 	Warn if a private member is unused, 
+                 - locals :
+                 	Warn if a local definition is unused, 
+                 - explicits :
+                 	Warn if an explicit parameter is unused, 
+                 - implicits :
+                 	Warn if an implicit parameter is unused, 
+                 - params :
+                 	Enable -Wunused:explicits,implicits, 
+                 - linted :
+                 	Enable -Wunused:imports,privates,locals,implicits, 
+                 - strict-no-implicit-warn :
+                 	Same as -Wunused:import, only for imports of explicit named
+                 members.
+                 	NOTE : This overrides -Wunused:imports and NOT set by
+                 -Wunused:all,
+                 - unsafe-warn-patvars :
+                 	(UNSAFE) Warn if a variable bound in a pattern is unused.
+                 	This warning can generate false positive, as warning cannot be
+                 	suppressed yet.
+```

docs/users/installation.md

@@ -9,7 +9,7 @@ title: Installation
 
 **Java LTS (8, 11, 17 or 21)**
 
-**Scala 2.12, 2.13 or 3.x** (all rules are not available for Scala 3.x)
+**Scala 2.12, 2.13 or 3.x**
 
 ## sbt
 
@@ -259,7 +259,7 @@ Central. To install a custom rule, add it to `scalafixDependencies`
 ```scala
 // at the top of build.sbt
 ThisBuild / scalafixDependencies +=
-  "ch.epfl.scala" %% "example-scalafix-rule" % "3.0.0"
+  "com.geirsson" %% "example-scalafix-rule" % "1.3.0"
 ```
 
 Start sbt and type `scalafix <TAB>`, once the `example-scalafix-rule` dependency

project/ScalafixBuild.scala

@@ -75,14 +75,10 @@ object ScalafixBuild extends AutoPlugin with GhpagesKeys {
     lazy val isScala212 = Def.setting {
       scalaVersion.value.startsWith("2.12")
     }
-    lazy val warnUnusedImports = Def.setting {
-      if (isScala3.value) Nil
-      else if (isScala213.value) Seq("-Wunused:imports")
-      else Seq("-Ywarn-unused-import")
-    }
     lazy val warnUnused = Def.setting {
-      if (isScala2.value) Seq("-Ywarn-unused")
-      else Nil
+      if (isScala3.value) "-Wunused:all"
+      else if (isScala213.value) "-Wunused"
+      else "-Ywarn-unused"
     }
     lazy val targetJvm = Def.setting {
       if (isScala3.value) Seq("-release:8")
@@ -109,13 +105,13 @@ object ScalafixBuild extends AutoPlugin with GhpagesKeys {
       scalaXml +: otherLibs
     }
     lazy val compilerOptions = Def.setting(
-      warnUnusedImports.value ++
-        targetJvm.value ++
+      targetJvm.value ++
         Seq(
           "-encoding",
           "UTF-8",
           "-feature",
-          "-unchecked"
+          "-unchecked",
+          warnUnused.value
         )
     )
 

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

@@ -26,26 +26,33 @@ 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 -Wunused"
   override def isRewrite: Boolean = true
 
   private def warnUnusedPrefix = List("-Wunused", "-Ywarn-unused")
   private def warnUnusedString = List("-Xlint", "-Xlint:unused")
   override def withConfiguration(config: Configuration): Configured[Rule] = {
+    def diagnosticsUnavailableInSemanticdb(version: String) =
+      version.startsWith("3.0") ||
+        version.startsWith("3.1") ||
+        version.startsWith("3.2") ||
+        version.startsWith("3.3.1") ||
+        version.startsWith("3.3.2") ||
+        version.startsWith("3.3.3")
+
     val hasWarnUnused = config.scalacOptions.exists(option =>
       warnUnusedPrefix.exists(prefix => option.startsWith(prefix)) ||
         warnUnusedString.contains(option)
     )
-    if (config.scalaVersion.startsWith("3"))
+    if (!hasWarnUnused) {
       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"
+        """|A Scala compiler option is required to use RemoveUnused. To fix this problem,
+          |update your build to add -Ywarn-unused (with 2.12), -Wunused (with 2.13), or 
+          |-Wunused:all (with 3.4+ or 3.3.4+)""".stripMargin
       )
-    else if (!hasWarnUnused) {
+    } else if (diagnosticsUnavailableInSemanticdb(config.scalaVersion)) {
       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
+        "You must use a more recent version of the Scala 3 compiler (3.4+ or 3.3.4+)"
       )
     } else {
       config.conf
@@ -64,18 +71,23 @@ class RemoveUnused(config: RemoveUnusedConfig)
       raw"^pattern var .* in (value|method) .* is never used".r
 
     doc.diagnostics.foreach { diagnostic =>
-      if (config.imports && diagnostic.message == "Unused import") {
+      val msg = diagnostic.message
+      if (config.imports && diagnostic.message.toLowerCase == "unused import") {
         isUnusedImport += diagnostic.position
       } else if (
         config.privates &&
-        diagnostic.message.startsWith("private") &&
-        diagnostic.message.endsWith("is never used")
+        (
+          (msg.startsWith("private") && msg.endsWith("is never used")) ||
+            msg == "unused private member"
+        )
       ) {
         isUnusedTerm += diagnostic.position
       } else if (
         config.locals &&
-        diagnostic.message.startsWith("local") &&
-        diagnostic.message.endsWith("is never used")
+        (
+          (msg.startsWith("local") && msg.endsWith("is never used")) ||
+            msg == "unused local definition"
+        )
       ) {
         isUnusedTerm += diagnostic.position
       } else if (
@@ -85,8 +97,7 @@ class RemoveUnused(config: RemoveUnusedConfig)
         isUnusedPattern += diagnostic.position
       } else if (
         config.params &&
-        diagnostic.message.startsWith("parameter") &&
-        diagnostic.message.endsWith("is never used")
+        (msg.startsWith("parameter") && msg.endsWith("is never used"))
       ) {
         isUnusedParam += diagnostic.position
       }
@@ -116,29 +127,33 @@ class RemoveUnused(config: RemoveUnusedConfig)
           .atomic
       }
 
+      def isUnusedImportee(importee: Importee): Boolean = {
+        val pos = importee match {
+          case Importee.Rename(from, _) => from.pos
+          case _ => importee.pos
+        }
+        isUnusedImport.exists { unused =>
+          unused.start <= pos.start && pos.end <= unused.end
+        }
+      }
+
       doc.tree.collect {
         case Importer(_, importees)
             if importees.forall(_.is[Importee.Unimport]) =>
           importees.map(Patch.removeImportee).asPatch
         case Importer(_, importees) =>
           val hasUsedWildcard = importees.exists {
-            case i: Importee.Wildcard => !isUnusedImport(importPosition(i))
+            case i: Importee.Wildcard => !isUnusedImportee(i)
             case _ => false
           }
           importees.collect {
             case i @ Importee.Rename(_, to)
-                if isUnusedImport(importPosition(i)) && hasUsedWildcard =>
+                if isUnusedImportee(i) && hasUsedWildcard =>
               // Unimport the identifier instead of removing the importee since
               // unused renamed may still impact compilation by shadowing an identifier.
               // See https://github.com/scalacenter/scalafix/issues/614
               Patch.replaceTree(to, "_").atomic
-            case i
-                if isUnusedImport
-                  .exists(unused =>
-                    unused.start <= importPosition(i).start && importPosition(
-                      i
-                    ).end <= unused.end
-                  ) =>
+            case i if isUnusedImportee(i) =>
               Patch.removeImportee(i).atomic
           }.asPatch
         case i: Defn if isUnusedTerm(i.pos) =>
@@ -182,11 +197,6 @@ class RemoveUnused(config: RemoveUnusedConfig)
     }
   }
 
-  private def importPosition(importee: Importee): Position = importee match {
-    case Importee.Rename(from, _) => from.pos
-    case _ => importee.pos
-  }
-
   // Given ("val x = 2", "2"), returns "val x = ".
   private def leftTokens(t: Tree, right: Tree): Tokens = {
     val startT = t.tokens.start

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

@@ -12,13 +12,9 @@ case class RemoveUnusedConfig(
     privates: Boolean = true,
     @Description("Remove unused local definitions")
     locals: Boolean = true,
-    @Description(
-      "Remove unused pattern match variables (compatible with Scala 2.12 and 2.13)"
-    )
+    @Description("Remove unused pattern match variables")
     patternvars: Boolean = true,
-    @Description(
-      "Remove unused function parameters (compatible with Scala 2.12 and 2.13)"
-    )
+    @Description("Remove unused function parameters")
     params: Boolean = true
 )
 

scalafix-tests/input/src/main/scala-3/test/removeUnused/RemoveUnusedParams.scala

@@ -0,0 +1,12 @@
+/*
+rule = RemoveUnused
+ */
+package test.removeUnused
+
+object UnusedParams {
+  val f: String => Unit = unused => println("f")
+  val ff = (unused: String) => println("f")
+  val fs = (used: String, unused: Long) => println(used)
+  def g(x: String => Unit): Unit = ???
+  g{implicit string => println("g")}
+}

scalafix-tests/input/src/main/scala-2/test/removeUnused/RemoveUnusedImports.scala renamed to scalafix-tests/input/src/main/scala/test/removeUnused/RemoveUnusedImports.scala

@@ -5,7 +5,7 @@ package test.removeUnused
 
 object RemoveUnusedTerms {
 
-  def foo {
+  def foo = {
     val a = "unused"
     val aa = println(5)
     var b = 0

scalafix-tests/input/src/main/scala-2/test/removeUnused/RemoveUnusedImports2.scala renamed to scalafix-tests/input/src/main/scala/test/removeUnused/RemoveUnusedImports2.scala

@@ -43,7 +43,7 @@ trait BaseCliSuite extends AnyFunSuite with DiffAssertions {
   val ps = new PrintStream(new ByteArrayOutputStream())
 
   val removeImportsPath: RelativePath =
-    RelativePath("scala-2/test/removeUnused/RemoveUnusedImports.scala")
+    RelativePath("scala/test/removeUnused/RemoveUnusedImports.scala")
   val explicitResultTypesPath: RelativePath =
     RelativePath(
       "scala-2/test/explicitResultTypes/ExplicitResultTypesBase.scala"

scalafix-tests/input/src/main/scala-2/test/removeUnused/RemoveUnusedImportsCommas.scala renamed to scalafix-tests/input/src/main/scala/test/removeUnused/RemoveUnusedImportsCommas.scala

@@ -245,15 +245,4 @@ class CliSemanticSuite extends BaseCliSuite {
     assert(exit.is(ExitStatus.MissingSemanticdbError))
   }
 
-  checkSemantic(
-    name = "ScalaVersion Scala3",
-    args = Array(
-      "--classpath",
-      defaultClasspath,
-      "--scalaVersion",
-      "3.0.0-RC3"
-    ),
-    expectedExit = ExitStatus.CommandLineError
-  )
-
 }