2026-04-06 09:07:40 +02:00
1 changed files with 9 additions and 1 deletions
@@ -22,7 +22,15 @@ object PgnExporter extends GameContextExport:
    var ctx = GameContext.initial
    for move <- context.moves do
      val color = ctx.turn
-      val pieceType = ctx.board.pieceAt(move.from).map(_.pieceType).getOrElse(PieceType.Pawn)
+      val pieceType = ctx.board.pieceAt(move.from)
+        .map(_.pieceType)
+        .getOrElse {
+          val fromStr = move.from.toString
+          val boardStr = ctx.board.pieces.keys.map(_.toString).mkString(",")
+          throw new IllegalStateException(
+            s"Invariant violation: no piece at $fromStr during PGN export replay. Board squares: $boardStr"
+          )
+        }
      val isCapture = ctx.board.pieceAt(move.to).isDefined || move.moveType == MoveType.EnPassant
      val castleSide = move.moveType match
        case MoveType.CastleKingside  => Some("Kingside")