Default to different scalafmt versions depending on Java version

build.sc

@@ -188,8 +188,9 @@ trait ScalaKernelApi extends Cross.Module[String] with AlmondModule with Depende
   def propertyFilePath = "almond/almond.properties"
   def propertyExtra = T {
     Seq(
-      "default-scalafmt-version" -> Deps.scalafmtDynamic.dep.version,
-      "scala-version"            -> crossScalaVersion
+      "default-scalafmt-version"        -> Deps.scalafmtDynamic.dep.version,
+      "default-scalafmt-version-java-8" -> Versions.scalafmtJava8,
+      "scala-version"                   -> crossScalaVersion
     )
   }
 }

modules/scala/scala-kernel-api/src/main/scala/almond/api/Properties.scala

@@ -27,6 +27,14 @@ object Properties {
   lazy val ammoniteSparkVersion =
     Option(props.getProperty("ammonite-spark-version")).getOrElse("[unknown]")
   lazy val defaultScalafmtVersionOpt = Option(props.getProperty("default-scalafmt-version"))
+  lazy val defaultScalafmtVersionJava8Opt =
+    Option(props.getProperty("default-scalafmt-version-java-8"))
+
+  def defaultScalafmtVersion(javaVersion: String): Option[String] =
+    if (javaVersion.startsWith("1.")) defaultScalafmtVersionJava8Opt
+    else defaultScalafmtVersionOpt
+  def defaultScalafmtVersion(): Option[String] =
+    defaultScalafmtVersion(sys.props("java.version"))
 
   lazy val actualScalaVersion = Option(props.getProperty("scala-version")).getOrElse("[unknown]")
 

modules/scala/scala-kernel/src/main/scala/almond/Scalafmt.scala

@@ -20,7 +20,7 @@ final class Scalafmt(
   queueEc: ExecutionContext,
   logCtx: LoggerContext,
   defaultDialect: String,
-  defaultVersion: String = almond.api.Properties.defaultScalafmtVersionOpt.getOrElse("2.7.5")
+  defaultVersion: String = almond.api.Properties.defaultScalafmtVersion().getOrElse("3.7.15")
 ) {
 
   private val log = logCtx(getClass)

project/deps.sc

@@ -7,6 +7,7 @@ object Versions {
   def coursier      = "2.1.10"
   def jsoniterScala = "2.13.5"
   def scalafmt      = "3.7.15"
+  def scalafmtJava8 = "3.7.15"
 }
 
 implicit class DepOps(private val dep: Dep) {