move tree outside of the socket module

modules/round/src/main/TreeBuilder.scala

@@ -7,8 +7,6 @@ import chess.variant.Variant
 import lila.analyse.{ Analysis, Info, Advice }
 import lila.socket.tree._
 
-import play.api.libs.json._
-
 object TreeBuilder {
 
   private type Ply = Int

modules/tree/src/main/tree.scala

@@ -37,7 +37,7 @@ sealed trait Node {
   def color = chess.Color(ply % 2 == 0)
 
   def mainlineNodeList: List[Node] =
-    dropFirstChild :: children.headOption.??(_.mainlineNodeList)
+    dropFirstChild :: children.headOption.fold(List.empty[Node])(_.mainlineNodeList)
 }
 
 case class Root(
@@ -120,7 +120,7 @@ object Node {
     case class Text(value: String) extends AnyVal {
       def removeMeta: Option[Text] = {
         val v = metaReg.replaceAllIn(value, "").trim
-        v.nonEmpty option Text(v)
+        if (v.nonEmpty) Some(Text(v)) else None
       }
     }
     sealed trait Author

project/Build.scala

@@ -327,7 +327,11 @@ object ApplicationBuild extends Build {
     libraryDependencies ++= provided(play.api)
   )
 
-  lazy val socket = project("socket", Seq(common, hub, memo)).settings(
+  lazy val tree = project("tree", Seq(chess)).settings(
+    libraryDependencies ++= provided(play.api)
+  )
+
+  lazy val socket = project("socket", Seq(common, hub, memo, tree)).settings(
     libraryDependencies ++= provided(play.api)
   )