scalacenter · bjaglin · Apr 16, 2025 · bjaglin · Apr 16, 2025 · bjaglin
diff --git a/.scala-steward.conf b/.scala-steward.conf
@@ -6,3 +6,10 @@ updates.pin = [
   # JGit 6.x requires Java 11, see https://www.eclipse.org/lists/cross-project-issues-dev/msg18654.html
   { groupId = "org.eclipse.jgit", artifactId = "org.eclipse.jgit", version = "5." },
 ]
+
+dependencyOverrides = [
+  {
+    dependency = { groupId = "ch.epfl.scala", artifactId = "scalafix-interfaces" },
+    pullRequests = { frequency = "@asap" },
+  },
+]
diff --git a/build.sbt b/build.sbt
@@ -101,5 +101,6 @@ scriptedParallelInstances := 2
 scriptedLaunchOpts ++= Seq(
   "-Xmx2048M",
   s"-Dplugin.version=${version.value}",
+  s"-Dscalafix-interfaces.version=${Dependencies.scalafixInterfacesVersion}",
   "-Dsbt-scalafix.uselastmodified=true" // the caching scripted relies on sbt-scalafix only checking file attributes, not content
 )
diff --git a/project/Dependencies.scala b/project/Dependencies.scala
@@ -2,11 +2,16 @@ import sbt._
 
 object Dependencies {
   val x = List(1) // scalafix:ok
-  def scalafixVersion: String = "0.14.2"
+
+  // keep this as low as possible, to allow bumping sbt-scalafix without scalafix-interfaces
+  def scalafixInterfacesVersion: String =
+    "0.14.2+48-9b6e03ac-SNAPSHOT" // scala-steward:off
 
   val all = List(
+    "ch.epfl.scala" % "scalafix-interfaces" % scalafixInterfacesVersion
+      exclude ("ch.epfl.scala", "scalafix-properties"),
+    "ch.epfl.scala" % "scalafix-interfaces" % scalafixInterfacesVersion % Test,
     "org.eclipse.jgit" % "org.eclipse.jgit" % "5.13.3.202401111512-r",
-    "ch.epfl.scala" % "scalafix-interfaces" % scalafixVersion,
     "io.get-coursier" % "interface" % "1.0.28",
     "org.scala-lang.modules" %% "scala-collection-compat" % "2.13.0"
   )

diff --git a/project/plugins.sbt b/project/plugins.sbt
@@ -10,3 +10,6 @@ Compile / unmanagedSourceDirectories ++= {
   )
 }
 libraryDependencies ++= Dependencies.all
+
+// latest version of interfaces to test compatibility & get most recent behavior for scalafix invocations
+libraryDependencies += "ch.epfl.scala" % "scalafix-interfaces" % "0.14.2"
diff --git a/readme.md b/readme.md
@@ -12,14 +12,18 @@ https://github.com/scalacenter/scalafix/issues
 
 ## Nightlies
 
-Our CI publishes a [snapshot release to Sonatype](https://oss.sonatype.org/content/repositories/snapshots/ch/epfl/scala/sbt-scalafix_2.12_1.0/)
-on every merge into main. The latest snapshot at the time of the writing can be used via:
+Our CI publishes a snapshot release to Sonatype on every merge into main. The latest snapshot(s) of
+[the plugin](https://oss.sonatype.org/content/repositories/snapshots/ch/epfl/scala/sbt-scalafix_2.12_1.0/)
+and/or [scalafix-interfaces](https://oss.sonatype.org/content/repositories/snapshots/ch/epfl/scala/scalafix-interfaces/)
+can be used via:
 
 ```diff
   // project/plugins.sbt
--addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.9.34")
-+addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.9.34+5-5dfe5fb6-SNAPSHOT")
-+resolvers += Resolver.sonatypeRepo("snapshots")
++resolvers ++= Resolver.sonatypeOssRepos("snapshots")
+-addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.14.2")
++addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.14.2+17-4ba873d2-SNAPSHOT")
+-libraryDependencies += "ch.epfl.scala" % "scalafix-interfaces" % "0.14.2"
++libraryDependencies += "ch.epfl.scala" % "scalafix-interfaces" % "0.14.2+48-9b6e03ac-SNAPSHOT"
  ```
 
 ## Team

diff --git a/src/main/scala/scalafix/sbt/BuildInfo.scala b/src/main/scala/scalafix/sbt/BuildInfo.scala
@@ -29,7 +29,9 @@ object BuildInfo {
         props.load(stream)
       case None =>
         sys.error(
-          s"failed to load the resource file '$propertiesPath'. To fix this problem, make sure to enable the sbt-scalafix in 'project/plugins.sbt' and validate that the scalafix-interfaces jar is available on the classpath of the sbt build."
+          s"failed to load the resource file '$propertiesPath'; " +
+            "to fix this problem, add \"ch.epfl.scala\" % \"scalafix-interfaces\" " +
+            "to libraryDependencies in 'project/plugins.sbt'"
         )
     }
     props
@@ -39,7 +41,8 @@ object BuildInfo {
     Option(props.getProperty(key)).getOrElse {
       sys.error(
         s"sbt-scalafix property '$key' missing in $propertiesPath; " +
-          "to fix this problem, upgrade to the latest version of Scalafix."
+          "to fix this problem, upgrade to a more recent version of " +
+          "\"ch.epfl.scala\" % \"scalafix-interfaces\""
       )
     }
 }
diff --git a/src/main/scala/scalafix/sbt/ScalafixEnable.scala b/src/main/scala/scalafix/sbt/ScalafixEnable.scala
@@ -1,188 +1,91 @@
 package scalafix.sbt
 
-import scala.jdk.CollectionConverters.*
-import scala.util.*
-
 import sbt.*
 import sbt.Keys.*
-import sbt.VersionNumber.SemVer
 
 import coursierapi.Repository
 
-import ScalafixPlugin.autoImport.scalafixResolvers
+import ScalafixPlugin.autoImport.*
 
-/** Command to automatically enable semanticdb compiler output for shell session
-  */
+/** Command to automatically prepare the build for scalafix invocations */
 object ScalafixEnable {
 
-  /** If the provided Scala binary version is supported, return the latest scala
-    * full version for which the recommended semanticdb-scalac is available
-    */
-  private lazy val recommendedSemanticdbScalacScalaVersion
-      : PartialFunction[(Long, Long), VersionNumber] = (for {
-    v <- BuildInfo.supportedScalaVersions
-    p <- CrossVersion.partialVersion(v).toList
-  } yield p -> VersionNumber(v)).toMap
-
-  /** If the provided Scala binary version is supported, return the latest scala
-    * full version for which the recommended semanticdb-scalac is available, or
-    * None if semanticdb support is built-in in the compiler
-    */
-  private lazy val maybeRecommendedSemanticdbScalacScalaVersion
-      : PartialFunction[(Long, Long), Option[VersionNumber]] =
-    recommendedSemanticdbScalacScalaVersion.andThen(Some.apply).orElse {
-      // semanticdb is built-in in the Scala 3 compiler
-      case (major, _) if major == 3 => None
-    }
+  private def latestSemanticdbScalac(
+      scalaVersion: String,
+      repositories: Seq[Repository]
+  ): Option[String] = {
+    val semanticdbScalacModule = coursierapi.Module.parse(
+      "org.scalameta:::semanticdb-scalac",
+      coursierapi.ScalaVersion.of(scalaVersion)
+    )
+    Option(
+      coursierapi.Versions.create
+        .withModule(semanticdbScalacModule)
+        .withRepositories(repositories*)
+        .versions()
+        .getMergedListings
+        .getRelease
+    ).filter(_.nonEmpty)
+  }
 
-  /** Collect compatible projects across the entire build */
-  private def collectProjects(extracted: Extracted): Seq[CompatibleProject] =
+  private def collectProjects(extracted: Extracted): Seq[CompatibleProject] = {
+    val repositories = (ThisBuild / scalafixResolvers)
+      .get(extracted.structure.data)
+      .getOrElse(Seq.empty)
     for {
-      p <- extracted.structure.allProjectRefs
-      scalaV <- (p / scalaVersion).get(extracted.structure.data).toList
-      partialVersion <- CrossVersion.partialVersion(scalaV).toList
-      maybeRecommendedSemanticdbScalacV <-
-        maybeRecommendedSemanticdbScalacScalaVersion.lift(partialVersion).toList
-      scalafixResolvers0 <- (p / scalafixResolvers)
-        .get(extracted.structure.data)
-        .toList
-      semanticdbCompilerPlugin0 <- (p / semanticdbCompilerPlugin)
-        .get(extracted.structure.data)
-        .toList
-    } yield CompatibleProject(
-      p,
-      VersionNumber(scalaV),
-      semanticdbCompilerPlugin0,
-      scalafixResolvers0,
-      maybeRecommendedSemanticdbScalacV
-    )
+      (scalaVersion, projectRefs) <-
+        extracted.structure.allProjectRefs
+          .flatMap { projectRef =>
+            (projectRef / scalaVersion)
+              .get(extracted.structure.data)
+              .map(sv => (sv, projectRef))
+          }
+          .foldLeft(Map.empty[String, Seq[ProjectRef]]) {
+            case (acc, (sv, projectRef)) =>
+              acc.updated(sv, acc.getOrElse(sv, Seq.empty) :+ projectRef)
+          }
+          .toSeq
+      maybeSemanticdbVersion <-
+        if (scalaVersion.startsWith("2."))
+          latestSemanticdbScalac(scalaVersion, repositories) match {
+            case None =>
+              Seq.empty // don't activate semanticdb
+            case Some(version) =>
+              Seq(Some(version)) // activate semanticdb with plugin
+          }
+        else Seq(None) // activate semanticdb without plugin
+      projectRef <- projectRefs
+    } yield CompatibleProject(projectRef, maybeSemanticdbVersion)
+  }
 
   private case class CompatibleProject(
       ref: ProjectRef,
-      scalaVersion0: VersionNumber,
-      semanticdbCompilerPlugin0: ModuleID,
-      scalafixResolvers0: Seq[Repository],
-      maybeRecommendedSemanticdbScalacScalaV: Option[VersionNumber]
+      semanticdbVersion: Option[String]
   )
 
   lazy val command: Command = Command.command(
     "scalafixEnable",
     briefHelp =
       "Configure SemanticdbPlugin for scalafix on supported projects.",
-    detail = """1. set semanticdbEnabled := true
-      |2. for scala 2.x,
-      |  - set semanticdbCompilerPlugin to the scalameta version tracked by scalafix if available for scalaVersion, 
-      |  - otherwise set semanticdbCompilerPlugin to a compatible version available for scalaVersion,
-      |  - otherwise force scalaVersion to the latest version supported by the scalameta version tracked by scalafix.""".stripMargin
+    detail = """1. set scalafixAllowDynamicFallback := true
+      |2. set semanticdbEnabled := true
+      |3. for scala 2.x, set semanticdbVersion to the latest scalameta version""".stripMargin
   ) { s =>
     val extracted = Project.extract(s)
     val scalacOptionsSettings = Seq(Compile, Test).flatMap(
       inConfig(_)(ScalafixPlugin.relaxScalacOptionsConfigSettings)
     )
+    val dynamicFallbackSetting =
+      scalafixAllowDynamicFallback := true
     val settings = for {
       project <- collectProjects(extracted)
-      enableSemanticdbPlugin <-
-        project.maybeRecommendedSemanticdbScalacScalaV.toList
-          .flatMap { recommendedSemanticdbScalacScalaV =>
-
-            import scalafix.internal.sbt.Implicits._
-            val semanticdbScalacModule =
-              coursierapi.Dependency
-                .parse(
-                  project.semanticdbCompilerPlugin0.asCoursierCoordinates,
-                  coursierapi.ScalaVersion.of(project.scalaVersion0.toString)
-                )
-                .getModule
-            val recommendedSemanticdbV =
-              VersionNumber(BuildInfo.scalametaVersion)
-            val compatibleSemanticdbVs = Try(
-              coursierapi.Versions.create
-                .withRepositories(project.scalafixResolvers0*)
-                .withModule(semanticdbScalacModule)
-                .versions()
-                .getMergedListings
-                .getAvailable
-                .asScala
-                .map(VersionNumber.apply)
-                // don't use snapshots
-                .filter(_.extras == Nil)
-                // https://github.com/scalameta/scalameta/blob/main/COMPATIBILITY.md
-                .filter(SemVer.isCompatible(_, recommendedSemanticdbV))
-                .toList
-            )
-
-            compatibleSemanticdbVs match {
-              case Success(Nil) | Failure(_) =>
-                Seq(
-                  scalaVersion := {
-                    val v = recommendedSemanticdbScalacScalaV.toString
-                    sLog.value.warn(
-                      s"Forcing scalaVersion to $v in project " +
-                        s"${project.ref.project} since no semanticdb-scalac " +
-                        s"version binary-compatible with $recommendedSemanticdbV " +
-                        s"and cross-published for scala " +
-                        s"${project.scalaVersion0.toString} was found - " +
-                        s"consider bumping scala"
-                    )
-                    v
-                  },
-                  semanticdbVersion := recommendedSemanticdbV.toString
-                )
-              case Success(available)
-                  if available.contains(recommendedSemanticdbV) =>
-                Seq(
-                  semanticdbVersion := recommendedSemanticdbV.toString
-                )
-              case Success(earliestAvailable :: tail) =>
-                val safeRecommendedSemanticdbV =
-                  if (recommendedSemanticdbV.toString == "4.13.1.1")
-                    VersionNumber("4.13.1")
-                  else recommendedSemanticdbV
-
-                val futureVersion =
-                  SemanticSelector.apply(s">${safeRecommendedSemanticdbV}")
-
-                if (earliestAvailable.matchesSemVer(futureVersion)) {
-                  Seq(
-                    semanticdbVersion := {
-                      val v = earliestAvailable.toString
-                      sLog.value.info(
-                        s"Setting semanticdbVersion to $v in project " +
-                          s"${project.ref.project} since the version " +
-                          s"${recommendedSemanticdbV} tracked by scalafix " +
-                          s"${BuildInfo.scalafixVersion} will not be " +
-                          s"published for scala " +
-                          s"${project.scalaVersion0.toString} - " +
-                          s"consider upgrading sbt-scalafix"
-                      )
-                      v
-                    }
-                  )
-                } else {
-                  val latestAvailable =
-                    tail.lastOption.getOrElse(earliestAvailable)
-                  Seq(
-                    semanticdbVersion := {
-                      val v = latestAvailable.toString
-                      sLog.value.info(
-                        s"Setting semanticdbVersion to $v in project " +
-                          s"${project.ref.project} since the version " +
-                          s"${recommendedSemanticdbV} tracked by scalafix " +
-                          s"${BuildInfo.scalafixVersion} is no longer " +
-                          s"published for scala " +
-                          s"${project.scalaVersion0.toString} - " +
-                          s"consider bumping scala"
-                      )
-                      v
-                    }
-                  )
-                }
-            }
-          } :+ (semanticdbEnabled := true)
-      settings <-
-        inScope(ThisScope.copy(project = Select(project.ref)))(
-          scalacOptionsSettings ++ enableSemanticdbPlugin
-        )
+      semanticdbPluginSettings <- (semanticdbEnabled := true) +:
+        project.semanticdbVersion.map { version =>
+          semanticdbVersion := version
+        }.toSeq
+      settings <- inScope(ThisScope.copy(project = Select(project.ref)))(
+        scalacOptionsSettings ++ semanticdbPluginSettings :+ dynamicFallbackSetting
+      )
     } yield settings
     extracted.appendWithSession(settings, s)
   }

diff --git a/src/main/scala/scalafix/sbt/ScalafixPlugin.scala b/src/main/scala/scalafix/sbt/ScalafixPlugin.scala
@@ -89,7 +89,13 @@ object ScalafixPlugin extends AutoPlugin {
           "Defaults to a wrapper around `sbt.Logger`."
       )
 
-    val scalafixSemanticdb: ModuleID =
+    val scalafixAllowDynamicFallback: SettingKey[Boolean] =
+      settingKey[Boolean](
+        "Control whether the latest version of scalafix may be downloaded instead of failing when " +
+          "scalafix-interfaces is not explicitly provided. Off by default because non-deterministic."
+      )
+
+    lazy val scalafixSemanticdb: ModuleID =
       scalafixSemanticdb(BuildInfo.scalametaVersion)
     def scalafixSemanticdb(scalametaVersion: String): ModuleID =
       ("org.scalameta" % "semanticdb-scalac" % scalametaVersion)
@@ -263,7 +269,8 @@ object ScalafixPlugin extends AutoPlugin {
                       "via `semanticdbVersion` does follow the version recommended " +
                       "for Scalafix, but is not supported for the given Scala " +
                       s"version ${scalaV}. Please consider upgrading to a more recent version " +
-                      "of sbt-scalafix and/or Scala, or uninstalling sbt-scalafix plugin."
+                      "of \"ch.epfl.scala\" % \"scalafix-interfaces\" and/or Scala, or " +
+                      "uninstalling sbt-scalafix."
                   throw inc.copy(message = Some(msg))
                 case _ =>
               }
@@ -287,6 +294,7 @@ object ScalafixPlugin extends AutoPlugin {
     scalafixCaching := true,
     scalafixResolvers := defaultScalafixResolvers,
     scalafixDependencies := Nil,
+    scalafixAllowDynamicFallback := false,
     commands += ScalafixEnable.command,
     scalafixInterfaceCache := new BlockingCache,
     concurrentRestrictions += Tags.exclusiveGroup(Scalafix),
@@ -443,6 +451,12 @@ object ScalafixPlugin extends AutoPlugin {
       config: ConfigKey
   ): Def.Initialize[Task[Unit]] = {
     val task = Def.taskDyn {
+      if (!scalafixAllowDynamicFallback.value) {
+        // force scalafix properties to be loaded, to trigger an actionnable error instead
+        // of letting the built-in scalafix-interfaces fallback to the latest scalafix version
+        BuildInfo.scalafixVersion
+      }
+
       implicit val conv: FileConverter = fileConverter.value
 
       val errorLogger =

diff --git a/src/sbt-test/sbt-scalafix/basic/project/plugins.sbt b/src/sbt-test/sbt-scalafix/basic/project/plugins.sbt
@@ -1,3 +1,5 @@
 resolvers += Resolver.sonatypeRepo("public")
 libraryDependencies += "com.googlecode.java-diff-utils" % "diffutils" % "1.3.0"
 addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % sys.props("plugin.version"))
+libraryDependencies += "ch.epfl.scala" % "scalafix-interfaces" %
+  sys.props("scalafix-interfaces.version")
diff --git a/src/sbt-test/sbt-scalafix/build-lint/project/plugins.sbt b/src/sbt-test/sbt-scalafix/build-lint/project/plugins.sbt
@@ -1,2 +1,4 @@
 resolvers += Resolver.sonatypeRepo("public")
 addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % sys.props("plugin.version"))
+libraryDependencies += "ch.epfl.scala" % "scalafix-interfaces" %
+  sys.props("scalafix-interfaces.version")