run more tests against scala 3 targets

build.sbt

@@ -284,7 +284,22 @@ lazy val unit = projectMatrix
     ),
     Test / test := (Test / test)
       .dependsOn(cli.projectRefs.map(_ / publishLocalTransitive): _*)
-      .value
+      .value,
+    Test / unmanagedSourceDirectories ++= {
+      val sourceDir = (Test / sourceDirectory).value
+      val maybeTargetScalaVersion =
+        TargetAxis
+          .targetScalaVersion(virtualAxes.value)
+          .flatMap(CrossVersion.partialVersion(_))
+      maybeTargetScalaVersion match {
+        case Some((n, m)) =>
+          Seq(
+            sourceDir / s"scala-target$n",
+            sourceDir / s"scala-target$n.$m"
+          )
+        case _ => Seq()
+      }
+    }
   )
   .defaultAxes(VirtualAxis.jvm)
   .jvmPlatform(

project/ScalafixBuild.scala

@@ -129,7 +129,7 @@ object ScalafixBuild extends AutoPlugin with GhpagesKeys {
         s
     },
     commands += Command.command("ci-3") { s =>
-      "unit2_12Target3/testOnly scalafix.tests.rule.RuleSuite" ::
+      "unit2_12Target3/test" ::
         s
     },
     commands += Command.command("ci-213") { s =>

project/TargetAxis.scala

@@ -14,8 +14,8 @@ case class TargetAxis(scalaVersion: String) extends VirtualAxis.WeakAxis {
 
 object TargetAxis {
 
-  private def targetScalaVersion(virtualAxes: Seq[VirtualAxis]): String =
-    virtualAxes.collectFirst { case a: TargetAxis => a.scalaVersion }.get
+  def targetScalaVersion(virtualAxes: Seq[VirtualAxis]): Option[String] =
+    virtualAxes.collectFirst { case a: TargetAxis => a.scalaVersion }
 
   /**
    * When invoked on a ProjectMatrix with a TargetAxis, lookup the project
@@ -27,7 +27,7 @@ object TargetAxis {
       key: TaskKey[T]
   ): Def.Initialize[Task[T]] =
     Def.taskDyn {
-      val sv = targetScalaVersion(virtualAxes.value)
+      val sv = targetScalaVersion(virtualAxes.value).get
       val project = matrix.finder().apply(sv)
       Def.task((project / key).value)
     }
@@ -42,7 +42,7 @@ object TargetAxis {
       key: SettingKey[T]
   ): Def.Initialize[T] =
     Def.settingDyn {
-      val sv = targetScalaVersion(virtualAxes.value)
+      val sv = targetScalaVersion(virtualAxes.value).get
       val project = matrix.finder().apply(sv)
       Def.setting((project / key).value)
     }

scalafix-tests/unit/src/test/scala-2.12/scalafix/tests/v0/LegacySyntheticsSuite.scala → scalafix-tests/unit/src/test/scala-target2.12/scalafix/tests/v0/LegacySyntheticsSuite.scala

@@ -3,6 +3,7 @@ package scalafix.tests.v0
 import scala.meta._
 import scalafix.tests.core.BaseSemanticSuite
 
+// LegacySyntheticsTest cannot be compiled with Scala 2.13 or Scala 3
 class LegacySyntheticsSuite extends BaseSemanticSuite("LegacySyntheticsTest") {
 
   test("text") {

scalafix-tests/unit/src/test/scala/scalafix/tests/cli/BaseCliSuite.scala → scalafix-tests/unit/src/test/scala-target2/scalafix/tests/cli/BaseCliSuite.scala

@@ -159,10 +159,16 @@ trait BaseCliSuite extends AnyFunSuite with DiffAssertions {
     )
   }
 
+  // The defaults of this helper expect to find test input which is currently
+  // built only on scala 2.x since building them for Scala 3 would trigger
+  // test failures as the rules they exercise are not supported on Scala 3.
+  // TODO: switch defaults to rely on much more simple test input/rules so
+  // that we don't need to hardcode a scala version here.
+  val sourceDir = "scalafix-tests/input/src/main/scala-2"
+
   def sourceDirectory: AbsolutePath =
     props.inputSourceDirectories
-      // TODO: This test won't work for scala 3. The path is hardcoded
-      .find(dir => dir.toNIO.endsWith("scala-2")) // Skip scala-2.12
+      .find(dir => dir.toNIO.endsWith(sourceDir))
       .getOrElse {
         throw new IllegalArgumentException(
           props.inputSourceDirectories.toString()
@@ -195,8 +201,7 @@ trait BaseCliSuite extends AnyFunSuite with DiffAssertions {
     test(name, SkipWindows) {
       val fileIsFixed = expectedExit.isOk
       val cwd = Files.createTempDirectory("scalafix")
-      val inputSourceDirectory =
-        cwd.resolve("scalafix-tests/input/src/main/scala-2/")
+      val inputSourceDirectory = cwd.resolve(sourceDir)
       Files.createDirectories(inputSourceDirectory)
       val root = AbsolutePath(inputSourceDirectory)
       val out = new ByteArrayOutputStream()

scalafix-tests/unit/src/test/scala/scalafix/tests/core/PrettyTypeSuite.scala → scalafix-tests/unit/src/test/scala-target2/scalafix/tests/util/PrettyTypeSuite.scala

@@ -29,6 +29,9 @@ class BasePrettyTypeSuite extends BaseSemanticSuite("TypeToTreeInput") {
 
   val classpath: Classpath =
     Classpaths.withDirectories(semanticdbTargetRoots :+ classDir)
+
+  // As of scalameta 4.5.3, this relies on scalap (and not on TASTy), so it
+  // cannot work against classes compiled with Scala 3
   val table: GlobalSymbolTable = GlobalSymbolTable(classpath, includeJdk = true)
 }
 

scalafix-tests/unit/src/test/scala/scalafix/tests/v1/SymbolSuite.scala → scalafix-tests/unit/src/test/scala-target2/scalafix/tests/v1/SymbolSuite.scala

@@ -22,6 +22,9 @@ class SymbolSuite extends munit.FunSuite {
       case Term.ApplyInfix(_, Term.Name("shouldBe"), _, arg :: Nil) => arg
     }
 
+    // The symbol lookup fails against Scala 3.1.1 SemanticDB as the position
+    // there excludes surrounding parentheses while 2.x (scalac-semanticdb) and
+    // the parser include them
     assertNotEquals(arg.symbol, Symbol.None)
   }