better FEN setup checks

app/controllers/Setup.scala

@@ -144,7 +144,7 @@ object Setup extends LilaController with TheftPrevention {
     OpenBody { ctx ⇒
       implicit val req = ctx.body
       FuRedirect(form(ctx).bindFromRequest.fold(
-        f ⇒ fulogwarn(f.errors.toString) inject routes.Lobby.home,
+        f ⇒ fuloginfo(f.errors.toString) inject routes.Lobby.home,
         config ⇒ op(config)(ctx)
       ))
     }

modules/setup/src/main/AiConfig.scala

@@ -13,6 +13,8 @@ case class AiConfig(
     color: Color,
     fen: Option[String] = None) extends Config with GameGenerator with Positional {
 
+  val strictFen = true
+
   def >> = (variant.id, clock, time, increment, level, color.name, fen).some
 
   def game = fenGame { chessGame ⇒

modules/setup/src/main/Config.scala

@@ -1,7 +1,8 @@
 package lila.setup
 
 import chess.format.Forsyth
-import chess.{ Game => ChessGame, Board, Situation, Variant, Clock, Speed }
+import chess.{ Game ⇒ ChessGame, Board, Situation, Variant, Clock, Speed }
+
 import lila.game.{ GameRepo, Game, Pov }
 import lila.lobby.Color
 
@@ -44,6 +45,12 @@ trait Positional { self: Config ⇒
 
   def fen: Option[String]
 
+  def strictFen: Boolean
+
+  lazy val validFen = variant != Variant.FromPosition || {
+    fen ?? { f ⇒ ~(Forsyth <<< f).map(_.situation playable strictFen) }
+  }
+
   def fenGame(builder: ChessGame ⇒ Game): Game = {
     val state = fen filter (_ ⇒ variant == Variant.FromPosition) flatMap Forsyth.<<<
     val chessGame = state.fold(makeGame) {

modules/setup/src/main/FormFactory.scala

@@ -42,8 +42,9 @@ private[setup] final class FormFactory {
       "increment" -> increment,
       "level" -> level,
       "color" -> color,
-      "fen" -> fen(true)
+      "fen" -> fen
     )(AiConfig.<<)(_.>>)
+      .verifying("Invalid FEN", _.validFen)
   )
 
   def aiConfig(implicit ctx: Context): Fu[AiConfig] = savedConfig map (_.ai)
@@ -63,8 +64,10 @@ private[setup] final class FormFactory {
       "increment" -> increment,
       "mode" -> mode(ctx.isAuth),
       "color" -> color,
-      "fen" -> fen(false)
-    )(FriendConfig.<<)(_.>>) verifying ("Invalid clock", _.validClock)
+      "fen" -> fen
+    )(FriendConfig.<<)(_.>>)
+      .verifying("Invalid clock", _.validClock)
+      .verifying("Invalid FEN", _.validFen)
   )
 
   def friendConfig(implicit ctx: Context): Fu[FriendConfig] = savedConfig map (_.friend)

modules/setup/src/main/FriendConfig.scala

@@ -14,6 +14,8 @@ case class FriendConfig(
     color: Color,
     fen: Option[String] = None) extends HumanConfig with GameGenerator with Positional {
 
+  val strictFen = false
+
   def >> = (variant.id, clock, time, increment, mode.id.some, color.name, fen).some
 
   def game = fenGame { chessGame ⇒

modules/setup/src/main/Mappings.scala

@@ -21,8 +21,5 @@ object Mappings {
   val color = nonEmptyText.verifying(Color.names contains _)
   val level = number.verifying(AiConfig.levels contains _)
   val speed = number.verifying(Config.speeds contains _)
-
-  def fen(strict: Boolean) = optional {
-    nonEmptyText verifying { source ⇒ ~(Forsyth <<< source).map(_.situation playable strict) }
-  }
+  val fen = optional(nonEmptyText)
 }