Test Scala 3 input/output with Scala 2.12 rule by default

Move to sbt-projectmatrix so that `sbt tests/test` checks
* Scala 2.x input/output with Scala 2.x rule and
* Scala 3 input/output with Scala 2.12 rule

src/main/g8/default.properties

@@ -1,2 +1,2 @@
-repo = My Repo
+repo = scalafix-my-rules
 scalafix_version = maven(ch.epfl.scala, scalafix-cli_2.13.5)

src/main/g8/scalafix/build.sbt

@@ -1,8 +1,10 @@
 lazy val V = _root_.scalafix.sbt.BuildInfo
+
+lazy val rulesCrossVersions = Seq(V.scala213, V.scala212, V.scala211)
+lazy val scala3Version = "3.0.0"
+
 inThisBuild(
   List(
-    scalaVersion := V.scala213,
-    crossScalaVersions := List(V.scala213, V.scala212, V.scala211),
     organization := "com.example",
     homepage := Some(url("https://github.com/com/example")),
     licenses := List(
@@ -17,44 +19,93 @@ inThisBuild(
       )
     ),
     semanticdbEnabled := true,
-    semanticdbVersion := scalafixSemanticdb.revision,
-    scalacOptions ++= List(
-      "-P:semanticdb:synthetics:on"
-    )
+    semanticdbVersion := scalafixSemanticdb.revision
   )
 )
 
-publish / skip := true
+lazy val `$repo;format="normalize"$` = (project in file("."))
+  .aggregate(
+    rules.projectRefs ++
+      input.projectRefs ++
+      output.projectRefs ++
+      tests.projectRefs: _*
+  )
+  .settings(
+    publish / skip := true
+  )
 
-lazy val rules = project.settings(
-  moduleName := "scalafix",
-  libraryDependencies += "ch.epfl.scala" %% "scalafix-core" % V.scalafixVersion
-)
+lazy val rules = projectMatrix
+  .settings(
+    moduleName := "scalafix",
+    libraryDependencies += "ch.epfl.scala" %% "scalafix-core" % V.scalafixVersion
+  )
+  .defaultAxes(VirtualAxis.jvm)
+  .jvmPlatform(rulesCrossVersions)
 
-lazy val input = project.settings(
-  publish / skip := true
-)
+lazy val input = projectMatrix
+  .settings(
+    publish / skip := true
+  )
+  .defaultAxes(VirtualAxis.jvm)
+  .jvmPlatform(
+    scalaVersions = rulesCrossVersions,
+    settings = Seq(
+      scalacOptions += "-P:semanticdb:synthetics:on"
+    )
+  )
+  .jvmPlatform(scalaVersions = Seq(scala3Version))
 
-lazy val output = project.settings(
-  publish / skip := true
-)
+lazy val output = projectMatrix
+  .settings(
+    publish / skip := true
+  )
+  .defaultAxes(VirtualAxis.jvm)
+  .jvmPlatform(scalaVersions = rulesCrossVersions :+ scala3Version)
+
+lazy val testsAggregate = Project("tests", file("target/testsAggregate"))
+  .aggregate(tests.projectRefs: _*)
 
-lazy val tests = project
+lazy val tests = projectMatrix
   .settings(
     publish / skip := true,
     libraryDependencies += "ch.epfl.scala" % "scalafix-testkit" % V.scalafixVersion % Test cross CrossVersion.full,
-    Compile / compile :=
-      (Compile / compile).dependsOn(input / Compile / compile).value,
     scalafixTestkitOutputSourceDirectories :=
-      (output / Compile / unmanagedSourceDirectories).value,
+      TargetAxis
+        .resolve(output, Compile / unmanagedSourceDirectories)
+        .value,
     scalafixTestkitInputSourceDirectories :=
-      (input / Compile / unmanagedSourceDirectories).value,
+      TargetAxis
+        .resolve(input, Compile / unmanagedSourceDirectories)
+        .value,
     scalafixTestkitInputClasspath :=
-      (input / Compile / fullClasspath).value,
+      TargetAxis.resolve(input, Compile / fullClasspath).value,
     scalafixTestkitInputScalacOptions :=
-      (input / Compile / scalacOptions).value,
+      TargetAxis.resolve(input, Compile / scalacOptions).value,
     scalafixTestkitInputScalaVersion :=
-      (input / Compile / scalaVersion).value
+      TargetAxis.resolve(input, Compile / scalaVersion).value
+  )
+  .defaultAxes(
+    rulesCrossVersions.map(VirtualAxis.scalaABIVersion) :+ VirtualAxis.jvm: _*
+  )
+  .customRow(
+    scalaVersions = Seq(V.scala212),
+    axisValues = Seq(TargetAxis(scala3Version), VirtualAxis.jvm),
+    settings = Seq()
+  )
+  .customRow(
+    scalaVersions = Seq(V.scala213),
+    axisValues = Seq(TargetAxis(V.scala213), VirtualAxis.jvm),
+    settings = Seq()
+  )
+  .customRow(
+    scalaVersions = Seq(V.scala212),
+    axisValues = Seq(TargetAxis(V.scala212), VirtualAxis.jvm),
+    settings = Seq()
+  )
+  .customRow(
+    scalaVersions = Seq(V.scala211),
+    axisValues = Seq(TargetAxis(V.scala211), VirtualAxis.jvm),
+    settings = Seq()
   )
   .dependsOn(rules)
   .enablePlugins(ScalafixTestkitPlugin)

src/main/g8/scalafix/input/src/main/scala-3/fix/$repo__Camel$SignificantIndentation.scala

@@ -0,0 +1,8 @@
+/*
+rule = $repo;format="Camel"$
+*/
+package fix
+
+object $repo;format="Camel"$SignificantIndentation:
+  val a = 1
+  // Add code that needs fixing here.

src/main/g8/scalafix/output/src/main/scala-3/fix/$repo__Camel$SignificantIndentation.scala

@@ -0,0 +1,5 @@
+package fix
+
+object $repo;format="Camel"$SignificantIndentation:
+  val a = 1
+  // Add code that needs fixing here.

src/main/g8/scalafix/project/TargetAxis.scala

@@ -0,0 +1,47 @@
+import sbt._
+import sbt.internal.ProjectMatrix
+import sbtprojectmatrix.ProjectMatrixPlugin.autoImport._
+
+/** Use on ProjectMatrix rows to tag an affinity to a custom scalaVersion */
+case class TargetAxis(scalaVersion: String) extends VirtualAxis.WeakAxis {
+
+  private val scalaBinaryVersion = CrossVersion.binaryScalaVersion(scalaVersion)
+
+  override val idSuffix = s"Target\${scalaBinaryVersion.replace('.', '_')}"
+  override val directorySuffix = s"target\$scalaBinaryVersion"
+}
+
+object TargetAxis {
+
+  private def targetScalaVersion(virtualAxes: Seq[VirtualAxis]): String =
+    virtualAxes.collectFirst { case a: TargetAxis => a.scalaVersion }.get
+
+  /** When invoked on a ProjectMatrix with a TargetAxis, lookup the project
+    * generated by `matrix` with a scalaVersion matching the one defined in
+    * that and resolve `key`.
+    */
+  def resolve[T](
+      matrix: ProjectMatrix,
+      key: TaskKey[T]
+  ): Def.Initialize[Task[T]] =
+    Def.taskDyn {
+      val sv = targetScalaVersion(virtualAxes.value)
+      val project = matrix.finder().apply(sv)
+      Def.task((project / key).value)
+    }
+
+  /** When invoked on a ProjectMatrix with a TargetAxis, lookup the project
+    * generated by `matrix` with a scalaVersion matching the one defined in
+    * that and resolve `key`.
+    */
+  def resolve[T](
+      matrix: ProjectMatrix,
+      key: SettingKey[T]
+  ): Def.Initialize[T] =
+    Def.settingDyn {
+      val sv = targetScalaVersion(virtualAxes.value)
+      val project = matrix.finder().apply(sv)
+      Def.setting((project / key).value)
+    }
+
+}

src/main/g8/scalafix/project/plugins.sbt

@@ -1,2 +1,3 @@
 resolvers += Resolver.sonatypeRepo("snapshots")
 addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.9.27+39-c332bbde-SNAPSHOT")
+addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.10.0")