feat: Initial support for Scala 3 (#858)

* split source into scala 2 and 3

* First Scala 3 inspection

* Rewire plugin and feedback flow

* Bootstrap compiler differently to allow to extract the raw feedback

* Clean up OptionGet and set up for more re-use

* Set up cross ci and fix readme test

* Apply suggestions from code review

Co-authored-by: Bendix Sältz <[email protected]>

* Fix scalafix and configure Scala 3 compiler options

* sbt fix

* Build dotty feedback per compile run, not compilation unit

* Improve test coverage

* Add coverage on plugin control flows

* Add coverage on feedback reporting flow

---------

Co-authored-by: Bendix Sältz <[email protected]>

.github/workflows/pr-checks.yml

@@ -14,6 +14,8 @@ jobs:
           - 2.12.19
           - 2.13.13
           - 2.13.14
+          - 3.3.3
+          - 3.4.2
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-java@v4

.gitignore

@@ -1,4 +1,5 @@
 *.class
+*.tasty
 *.log
 
 # sbt specific
@@ -22,4 +23,4 @@ target
 .metals
 metals.sbt
 
-.bsp
+.bsp

.scalafix-2.conf

@@ -0,0 +1,23 @@
+rules = [
+DisableSyntax,
+LeakingImplicitClassVal,
+NoAutoTupling,
+NoValInForComprehension,
+ProcedureSyntax,
+RemoveUnused
+]
+
+DisableSyntax.noVars = false
+DisableSyntax.noThrows = false
+DisableSyntax.noNulls = false
+DisableSyntax.noReturns = true
+DisableSyntax.noWhileLoops = true
+DisableSyntax.noFinalize = true
+DisableSyntax.noValPatterns = true
+DisableSyntax.noUniversalEquality = false
+DisableSyntax.noUniversalEqualityMessage = "== and != are unsafe since they allow comparing two unrelated types"
+SortImports.blocks = [
+"java.",
+"scala.",
+"*"
+]

.scalafix.conf

@@ -3,7 +3,6 @@ DisableSyntax,
 LeakingImplicitClassVal,
 NoAutoTupling,
 NoValInForComprehension,
-ProcedureSyntax,
 RemoveUnused
 ]
 

.scalafmt.conf

@@ -1,5 +1,5 @@
 version = "3.8.3"
-runner.dialect = scala213source3
+runner.dialect = scala3
 maxColumn = 110
 docstrings.style = Asterisk
 assumeStandardLibraryStripMargin = true

build.sbt

@@ -1,6 +1,3 @@
-// compiler plugins
-addCompilerPlugin("org.scalameta" % "semanticdb-scalac" % "4.9.9" cross CrossVersion.full)
-
 name := "scalac-scapegoat-plugin"
 organization := "com.sksamuel.scapegoat"
 description := "Scala compiler plugin for static code analysis"
@@ -22,34 +19,50 @@ developers := List(
   )
 )
 
-scalaVersion := "2.13.14"
-crossScalaVersions := Seq("2.12.18", "2.12.19", "2.13.13", "2.13.14")
+scalaVersion := "3.4.2"
+crossScalaVersions := Seq("2.12.18", "2.12.19", "2.13.13", "2.13.14", "3.3.3", "3.4.2")
 autoScalaLibrary := false
 crossVersion := CrossVersion.full
 crossTarget := {
   // workaround for https://github.com/sbt/sbt/issues/5097
   target.value / s"scala-${scalaVersion.value}"
 }
 versionScheme := Some("early-semver")
+semanticdbEnabled := (scalaBinaryVersion.value == "3")
+scalafixConfig := Some(file(if (scalaBinaryVersion.value == "3") ".scalafix.conf" else ".scalafix-2.conf"))
 
 // https://github.com/sksamuel/scapegoat/issues/298
 ThisBuild / useCoursier := false
 
-val scalac13Options = Seq(
+val scala2Options = Seq(
+    "-Xlint",
+    "-Xlint:adapted-args",
+    "-Xlint:nullary-unit",
+)
+
+val scalac13Options = scala2Options ++ Seq(
   "-Xlint:inaccessible",
   "-Xlint:infer-any",
   "-Xlint:strict-unsealed-patmat",
   "-Yrangepos",
   "-Ywarn-unused",
   "-Xsource:3"
 )
-val scalac12Options = Seq(
+val scalac12Options = scala2Options ++ Seq(
   "-Ywarn-inaccessible",
   "-Ywarn-infer-any",
   "-Xlint:nullary-override",
   "-Xmax-classfile-name",
   "254"
 )
+val scala3Options = Seq(
+  "-Ysafe-init",
+  "-Wnonunit-statement",
+  "-Wunused:all",
+  "-Wvalue-discard",
+  // Unused locals seem to wrong on Scala XML syntax
+  "-Wconf:msg=unused value of type scala.xml.NodeBuffer:silent",
+)
 
 scalacOptions := {
   val common = Seq(
@@ -58,13 +71,11 @@ scalacOptions := {
     "-feature",
     "-encoding",
     "utf8",
-    "-Xlint",
-    "-Xlint:adapted-args",
-    "-Xlint:nullary-unit"
   )
   common ++ (scalaBinaryVersion.value match {
     case "2.12" => scalac12Options
     case "2.13" => scalac13Options
+    case "3"    => scala3Options
   })
 }
 javacOptions ++= Seq("-source", "1.8", "-target", "1.8")
@@ -85,20 +96,33 @@ def check(code: String) = {
 """
 
 libraryDependencies ++= Seq(
-  "org.scala-lang" % "scala-reflect"  % scalaVersion.value % "provided",
-  "org.scala-lang" % "scala-compiler" % scalaVersion.value % "provided",
   "org.scala-lang.modules" %% "scala-xml" % "2.3.0" excludeAll ExclusionRule(organization = "org.scala-lang"),
   "org.scala-lang.modules" %% "scala-collection-compat" % "2.12.0" excludeAll ExclusionRule(organization =
     "org.scala-lang"
   ),
-  "org.scala-lang" % "scala-compiler" % scalaVersion.value % "test",
-  "org.scalatest" %% "scalatest"      % "3.2.19"           % "test",
-  "org.mockito"    % "mockito-all"    % "1.10.19"          % "test",
-  "joda-time"      % "joda-time"      % "2.12.7"           % "test",
-  "org.joda"       % "joda-convert"   % "2.2.3"            % "test",
-  "org.slf4j"      % "slf4j-api"      % "2.0.13"           % "test"
+  "org.scalatest" %% "scalatest"    % "3.2.19"  % "test",
+  "org.mockito"    % "mockito-all"  % "1.10.19" % "test",
+  "joda-time"      % "joda-time"    % "2.12.7"  % "test",
+  "org.joda"       % "joda-convert" % "2.2.3"   % "test",
+  "org.slf4j"      % "slf4j-api"    % "2.0.13"  % "test"
 )
 
+libraryDependencies ++= (if (scalaBinaryVersion.value == "3") {
+                           Seq(
+                             "org.scala-lang" %% "scala3-compiler" % scalaVersion.value % "provided",
+                             "org.scala-lang" %% "scala3-compiler" % scalaVersion.value % "test"
+                           )
+                         } else {
+                           Seq(
+                             "org.scala-lang" % "scala-reflect"  % scalaVersion.value % "provided",
+                             "org.scala-lang" % "scala-compiler" % scalaVersion.value % "provided",
+                             "org.scala-lang" % "scala-compiler" % scalaVersion.value % "test",
+                             compilerPlugin(
+                               "org.scalameta" % "semanticdb-scalac" % "4.9.9" cross CrossVersion.full
+                             )
+                           )
+                         })
+
 // Test
 Test / run / fork := true
 Test / logBuffered := false

src/main/resources/plugin.properties

@@ -0,0 +1 @@
+pluginClass=com.sksamuel.scapegoat.ScapegoatPlugin

src/main/scala-2/com/sksamuel/scapegoat/FeedbackScala2.scala

@@ -0,0 +1,22 @@
+package com.sksamuel.scapegoat
+
+import scala.tools.nsc.reporters.Reporter
+import scala.reflect.internal.util.Position
+
+class FeedbackScala2(
+  reporter: Reporter,
+  configuration: Configuration
+) extends Feedback[Position](configuration) {
+
+  protected def toSourcePath(pos: Position): String = pos.source.file.path
+  protected def toSourceLine(pos: Position): Int = pos.line
+
+  override protected def report(pos: Position, level: Level, message: String): Unit = {
+    level match {
+      case Levels.Error   => reporter.error(pos, message)
+      case Levels.Warning => reporter.warning(pos, message)
+      case Levels.Info    => reporter.echo(pos, message)
+      case Levels.Ignore  => ()
+    }
+  }
+}

src/main/scala-2/com/sksamuel/scapegoat/Inspection.scala

@@ -0,0 +1,18 @@
+package com.sksamuel.scapegoat
+
+/**
+ * @author
+ *   Stephen Samuel
+ */
+abstract class Inspection(
+  override val text: String,
+  override val defaultLevel: Level,
+  override val description: String,
+  override val explanation: String
+) extends InspectionBase {
+
+  val self: Inspection = this
+
+  def inspector(ctx: InspectionContext): Inspector
+
+}

src/main/scala/com/sksamuel/scapegoat/Inspection.scala → src/main/scala-2/com/sksamuel/scapegoat/Inspector.scala

@@ -3,26 +3,6 @@ package com.sksamuel.scapegoat
 import scala.reflect.internal.util.Position
 import scala.tools.nsc.Global
 
-/**
- * @author
- *   Stephen Samuel
- */
-abstract class Inspection(
-  val text: String,
-  val defaultLevel: Level,
-  val description: String,
-  val explanation: String
-) {
-
-  val self: Inspection = this
-
-  def inspector(ctx: InspectionContext): Inspector
-
-  def isEnabled: Boolean = true
-
-  def name: String = getClass.getSimpleName
-}
-
 abstract class Inspector(val context: InspectionContext) {
 
   /**
@@ -37,7 +17,7 @@ abstract class Inspector(val context: InspectionContext) {
   def postInspection(): Unit = ()
 }
 
-final case class InspectionContext(global: Global, feedback: Feedback) {
+final case class InspectionContext(global: Global, feedback: Feedback[Position]) {
 
   def warn(pos: Position, inspection: Inspection): Unit =
     feedback.warn(pos, inspection, None, None)

src/main/scala/com/sksamuel/scapegoat/plugin.scala → src/main/scala-2/com/sksamuel/scapegoat/plugin.scala

@@ -27,16 +27,17 @@ class ScapegoatPlugin(val global: Global) extends Plugin {
   override val optionsHelp: Option[String] = Some(Configuration.optionsHelp)
 }
 
-class ScapegoatComponent(val global: Global, inspections: Seq[Inspection])
+class ScapegoatComponent(val global: Global, override val inspections: Seq[Inspection])
     extends PluginComponent
+    with ScapegoatBasePlugin
     with TypingTransformers
     with Transform {
 
   require(inspections != null)
 
   import global._
 
-  var configuration: Configuration = null
+  override var configuration: Configuration = null
 
   val debug: Boolean = false
   var summary: Boolean = true
@@ -47,19 +48,9 @@ class ScapegoatComponent(val global: Global, inspections: Seq[Inspection])
   override val runsAfter: List[String] = List("typer")
   override val runsBefore = List[String]("patmat")
 
-  def disableAll: Boolean = configuration.disabledInspections.exists(_.compareToIgnoreCase("all") == 0)
+  lazy val feedback = new FeedbackScala2(global.reporter, configuration)
 
-  def activeInspections: Seq[Inspection] = {
-    if (configuration.enabledInspections.isEmpty)
-      (inspections ++ configuration.customInspectors)
-        .filterNot(inspection => configuration.disabledInspections.contains(inspection.name))
-    else
-      (inspections ++ configuration.customInspectors)
-        .filter(inspection => configuration.enabledInspections.contains(inspection.name))
-  }
-  lazy val feedback = new Feedback(global.reporter, configuration)
-
-  def writeReport(isDisabled: Boolean, reportName: String, writer: (File, Feedback) => File): Unit = {
+  def writeReport(isDisabled: Boolean, reportName: String, writer: (File, Feedback[_]) => File): Unit = {
     if (!isDisabled) {
       configuration.dataDir.foreach { outputDir =>
         val output = writer(outputDir, feedback)

src/main/scala-3/com/sksamuel/scapegoat/FeedbackDotty.scala

@@ -0,0 +1,22 @@
+package com.sksamuel.scapegoat
+
+import dotty.tools.dotc.core.Contexts.Context
+import dotty.tools.dotc.core.Decorators.toMessage
+import dotty.tools.dotc.reporting.Diagnostic
+import dotty.tools.dotc.util.SourcePosition
+
+class FeedbackDotty(configuration: Configuration)(using ctx: Context)
+    extends Feedback[SourcePosition](configuration) {
+
+  protected def toSourcePath(pos: SourcePosition): String = pos.source().path()
+  protected def toSourceLine(pos: SourcePosition): Int = pos.line
+  protected def report(pos: SourcePosition, level: Level, message: String): Unit = {
+    level match {
+      case Levels.Error   => ctx.reporter.report(Diagnostic.Error(message, pos))
+      case Levels.Warning => ctx.reporter.report(Diagnostic.Warning(message.toMessage, pos))
+      case Levels.Info    => ctx.reporter.report(Diagnostic.Info(message, pos))
+      case Levels.Ignore  => ()
+    }
+  }
+
+}

src/main/scala-3/com/sksamuel/scapegoat/Inspection.scala

@@ -0,0 +1,18 @@
+package com.sksamuel.scapegoat
+
+import dotty.tools.dotc.ast.tpd
+import dotty.tools.dotc.core.Contexts.Context
+import dotty.tools.dotc.util.SourcePosition
+
+abstract class Inspection(
+  val text: String,
+  val defaultLevel: Level,
+  val description: String,
+  val explanation: String
+) extends InspectionBase {
+
+  val self: Inspection = this
+
+  def inspect(feedback: Feedback[SourcePosition], tree: tpd.Tree)(using Context): Unit
+
+}

src/main/scala-3/com/sksamuel/scapegoat/InspectionTraverser.scala

@@ -0,0 +1,14 @@
+package com.sksamuel.scapegoat
+
+import dotty.tools.dotc.ast.tpd.*
+import dotty.tools.dotc.core.Contexts.Context
+import dotty.tools.dotc.util.NoSource
+
+abstract class InspectionTraverser extends TreeTraverser {
+
+  extension (tree: Tree)(using Context)
+    def asSnippet: Option[String] = tree.source match
+      case NoSource => None
+      case _        => Some(tree.source.content().slice(tree.sourcePos.start, tree.sourcePos.end).mkString)
+
+}

src/main/scala-3/com/sksamuel/scapegoat/Inspections.scala

@@ -0,0 +1,11 @@
+package com.sksamuel.scapegoat
+
+import com.sksamuel.scapegoat.inspections.option._
+
+object Inspections {
+
+  final val inspections: List[Inspection] = List(
+    new OptionGet
+  )
+
+}