add scalafixCallback setting key to customize diagnostics reporting

src/main/scala/scalafix/internal/sbt/ScalafixInterface.scala

@@ -121,11 +121,14 @@ object ScalafixInterface {
     ScalafixInterface
   ] = new BlockingCache
 
+  private[scalafix] val defaultLogger: Logger = ConsoleLogger(System.out)
+
   def fromToolClasspath(
       scalafixBinaryScalaVersion: String,
       scalafixDependencies: Seq[ModuleID],
       scalafixCustomResolvers: Seq[Repository],
-      logger: Logger = ConsoleLogger(System.out)
+      logger: Logger,
+      callback: ScalafixMainCallback
   ): () => ScalafixInterface =
     new LazyValue({ () =>
       fromToolClasspathMemo.getOrElseUpdate(
@@ -145,7 +148,6 @@ object ScalafixInterface {
               "Scala 2.11 is no longer supported. Please downgrade to the final version supporting " +
                 "it: sbt-scalafix 0.10.4."
             )
-          val callback = new ScalafixLogger(logger)
           val scalafixArguments = ScalafixAPI
             .fetchAndClassloadInstance(
               scalafixBinaryScalaVersion,

src/main/scala/scalafix/sbt/ScalafixPlugin.scala

@@ -9,7 +9,7 @@ import sbt.Keys._
 import sbt._
 import sbt.internal.sbtscalafix.JLineAccess
 import sbt.plugins.JvmPlugin
-import scalafix.interfaces.ScalafixError
+import scalafix.interfaces.{ScalafixError, ScalafixMainCallback}
 import scalafix.internal.sbt.Arg.ToolClasspath
 import scalafix.internal.sbt._
 
@@ -75,6 +75,13 @@ object ScalafixPlugin extends AutoPlugin {
         "Optional location to .scalafix.conf file to specify which scalafix rules should run. " +
           "Defaults to the build base directory if a .scalafix.conf file exists."
       )
+
+    val scalafixCallback: SettingKey[ScalafixMainCallback] =
+      settingKey[ScalafixMainCallback](
+        "The handler for the diagnostics emitted during scalafix execution. Can be set in ThisBuild or at project-level. " +
+          "Defaults to a wrapper around `sbt.Logger`."
+      )
+
     val scalafixSemanticdb: ModuleID =
       scalafixSemanticdb(BuildInfo.scalametaVersion)
     def scalafixSemanticdb(scalametaVersion: String): ModuleID =
@@ -161,7 +168,9 @@ object ScalafixPlugin extends AutoPlugin {
     scalafixInterfaceProvider := ScalafixInterface.fromToolClasspath(
       scalafixScalaBinaryVersion.value,
       scalafixDependencies = scalafixDependencies.value,
-      scalafixCustomResolvers = scalafixResolvers.value
+      scalafixCustomResolvers = scalafixResolvers.value,
+      logger = ScalafixInterface.defaultLogger,
+      callback = (ThisBuild / scalafixCallback).value
     ),
     update := {
       object SemanticdbScalac {
@@ -199,6 +208,7 @@ object ScalafixPlugin extends AutoPlugin {
   )
 
   override lazy val globalSettings: Seq[Def.Setting[_]] = Seq(
+    scalafixCallback := new ScalafixLogger(ScalafixInterface.defaultLogger),
     scalafixConfig := None, // let scalafix-cli try to infer $CWD/.scalafix.conf
     scalafixOnCompile := false,
     scalafixCaching := true,

src/test/scala/scalafix/internal/sbt/SbtCompletionsSuite.scala

@@ -37,7 +37,9 @@ class SbtCompletionsSuite extends AnyFunSuite {
           MavenRepository.of(
             "https://oss.sonatype.org/content/repositories/snapshots"
           )
-        )
+        ),
+        ScalafixInterface.defaultLogger,
+        new ScalafixLogger(ScalafixInterface.defaultLogger)
       )()
   val loadedRules = mainArgs.availableRules.toList
 

src/test/scala/scalafix/internal/sbt/ScalafixAPISuite.scala

@@ -41,7 +41,8 @@ class ScalafixAPISuite extends AnyFunSuite {
             "https://oss.sonatype.org/content/repositories/snapshots"
           )
         ),
-        logger
+        logger,
+        new ScalafixLogger(logger)
       )()
       .withArgs(Arg.PrintStream(new PrintStream(baos)))
     val tmp = Files.createTempFile("scalafix", "Tmp.scala")