Crazyhouse en passant bug with DropMove

lib/src/debug.dart

@@ -3,6 +3,7 @@ import './models.dart';
 import './position.dart';
 import './square_set.dart';
 import './utils.dart';
+import './setup.dart';
 
 /// Takes a string and returns a SquareSet. Useful for debugging/testing purposes.
 ///
@@ -55,8 +56,11 @@ String humanReadableSquareSet(SquareSet sq) {
 }
 
 /// Prints the board as a human readable string format
-String humanReadableBoard(Board board) {
+String humanReadableBoard(Board board, [Pockets? pockets]) {
   final buffer = StringBuffer();
+  if (pockets != null) {
+    buffer.write('Pockets: $pockets\n');
+  }
   for (int y = 7; y >= 0; y--) {
     for (int x = 0; x < 8; x++) {
       final square = x + y * 8;

lib/src/position.dart

@@ -557,6 +557,17 @@ abstract class Position<T extends Position<T>> {
     }
   }
 
+  /// Plays a move from a Standard Algebraic Notation string.
+  ///
+  /// Throws a [PlayError] if the move is not legal.
+  Position<T> playSan(String san) {
+    final move = parseSan(san);
+    if (move == null) {
+      throw PlayError('Invalid SAN $san');
+    }
+    return play(move);
+  }
+
   /// Plays a move without checking if the move is legal.
   Position<T> playUnchecked(Move move) {
     assert(move is NormalMove || move is DropMove);
@@ -1526,7 +1537,7 @@ class Crazyhouse extends Position<Crazyhouse> {
       pockets: pockets != null ? pockets.value : this.pockets,
       turn: turn ?? this.turn,
       castles: castles ?? this.castles,
-      epSquare: epSquare != null ? epSquare.value : this.epSquare,
+      epSquare: epSquare?.value,
       halfmoves: halfmoves ?? this.halfmoves,
       fullmoves: fullmoves ?? this.fullmoves,
     );

lib/src/setup.dart

@@ -268,6 +268,11 @@ class Pockets {
 
   @override
   int get hashCode => value.hashCode;
+
+  @override
+  String toString() {
+    return _makePockets(this);
+  }
 }
 
 Pockets _parsePockets(String pocketPart) {

test/crazyhouse_test.dart

@@ -0,0 +1,48 @@
+import 'package:dartchess/dartchess.dart';
+import 'package:test/test.dart';
+import 'db_testing_lib.dart';
+
+void main() {
+  test('Crazyhouse - issue #23: Crazyhouse en passant bug with DropMove', () {
+    Position a = Crazyhouse.initial;
+    a = a.playSan('d4');
+    a = a.playSan('e5');
+    a = a.playSan('Nf3');
+    a = a.playSan('Qg5');
+    a = a.playSan('Nxg5');
+    a = a.playSan('Be7');
+    a = a.playSan('dxe5');
+    a = a.playSan('Bd8');
+
+    a = a.playSan('Nc3');
+    printBoard(a, printLegalMoves: true);
+
+    a = a.playSan('f5'); // creates epSquare at f6 for White
+    printBoard(a, printLegalMoves: true);
+
+    a = a.playSan(
+        'Q@f7'); // Bug: copyWith() is given null for epSquare, which then copies White's epSquare of f6 forward to Black
+    final List<Move> legalMoves = printBoard(a, printLegalMoves: true);
+    const MyExpectations myExpectations = MyExpectations(
+      legalMoves: 0,
+      legalDrops: 0,
+      legalDropZone: DropZone.anywhere,
+      rolesThatCanDrop: [],
+      rolesThatCantDrop: [
+        Role.king,
+        Role.queen,
+        Role.rook,
+        Role.bishop,
+        Role.knight,
+        Role.pawn,
+      ],
+    );
+
+    expect(myExpectations.testLegalMoves(legalMoves), '');
+
+    expect(a.outcome, Outcome.whiteWins);
+
+    // a = a.playSan('gxf6'); // captures the Queen at f7!
+    // printBoard(a, printLegalMoves: true);
+  });
+}

test/db_testing_lib.dart

@@ -0,0 +1,164 @@
+import 'package:dartchess/dartchess.dart';
+
+const verbosePrinting = false;
+bool printedNotice = false;
+
+void conditionalPrint(Object? a) {
+  if (!printedNotice) {
+    printedNotice = true;
+    print('=' * 60);
+    print('${'=\tVERBOSE PRINTING'.padRight(53)}=');
+    if (verbosePrinting) {
+      print('${'=\tverbosePrinting is ON'.padRight(53)}=');
+      print('${'=\t'.padRight(53)}=');
+      print('${'=\tTo disable, set the "verbosePrinting"'.padRight(53)}=');
+      print('${'=\tconstant to false'.padRight(53)}=');
+    } else {
+      print('${'=\tverbosePrinting is OFF'.padRight(53)}=');
+      print('${'=\t'.padRight(53)}=');
+      print(
+          '${'=\tSet the "verbosePrinting" constant to true to help'.padRight(53)}=');
+      print('${'=\twith debugging these tests'.padRight(53)}=');
+    }
+    print('${'=\t(line 3 of \\test\\db_testing_lib.dart)'.padRight(53)}=');
+    print('=' * 60);
+  }
+  if (verbosePrinting) {
+    print(a);
+  }
+}
+
+enum DropZone { none, whiteHomeRow, blackHomeRow, anywhere }
+
+const noDrops = <int>[];
+const whiteHomeRow = <int>[
+  0,
+  1,
+  2,
+  3,
+  4,
+  5,
+  6,
+  7,
+];
+const blackHomeRow = <int>[
+  56,
+  57,
+  58,
+  59,
+  60,
+  61,
+  62,
+  63,
+];
+
+class MyExpectations {
+  final int legalDrops;
+  final int legalMoves;
+  final DropZone legalDropZone;
+  final List<Role> rolesThatCanDrop;
+  final List<Role> rolesThatCantDrop;
+
+  const MyExpectations(
+      {required this.legalMoves,
+      required this.legalDrops,
+      required this.legalDropZone,
+      required this.rolesThatCanDrop,
+      required this.rolesThatCantDrop});
+
+  String testLegalMoves(List<Move> a) {
+    if (a.whereType<NormalMove>().length != legalMoves) {
+      return 'Expected $legalMoves legal moves, got ${a.whereType<NormalMove>().length}';
+    }
+    if (a.whereType<DropMove>().length != legalDrops) {
+      return 'Expected $legalDrops legal drops, got ${a.whereType<DropMove>().length}';
+    }
+    for (final move in a) {
+      if (move is DropMove) {
+        if (rolesThatCantDrop.contains(move.role)) {
+          return '${move.role} is listed in rolesThatCantDrop';
+        }
+        if (!rolesThatCanDrop.contains(move.role)) {
+          return '${move.role} is not listed in rolesThatCanDrop';
+        }
+        if (legalDropZone == DropZone.anywhere &&
+            move.role == Role.pawn &&
+            (whiteHomeRow.contains(move.to) ||
+                blackHomeRow.contains(move.to))) {
+          return 'Drop zone is anywhere, but a pawn cannot be dropped in rows 1 or 8';
+        } else if (legalDropZone == DropZone.whiteHomeRow &&
+            !whiteHomeRow.contains(move.to)) {
+          return 'Drop zone is whiteHomeRow, but ${move.to} is not in whiteHomeRow';
+        } else if (legalDropZone == DropZone.blackHomeRow &&
+            !blackHomeRow.contains(move.to)) {
+          return 'Drop zone is blackHomeRow, but ${move.to} is not in whiteHomeRow';
+        } else if (legalDropZone == DropZone.none &&
+            !noDrops.contains(move.to)) {
+          return 'Drop zone is none, but ${move.to} is not in noDrops';
+        }
+      }
+    }
+    return '';
+  }
+}
+
+List<DropMove> dropTestEachSquare(Position position) {
+  final legalDrops = <DropMove>[];
+  final allRoles = <Role>[
+    Role.pawn,
+    Role.knight,
+    Role.bishop,
+    Role.rook,
+    Role.queen,
+    Role.king
+  ];
+  for (final pieceRole in allRoles) {
+    for (int a = 0; a < 64; a++) {
+      if (position.isLegal(DropMove(role: pieceRole, to: a))) {
+        legalDrops.add(DropMove(role: pieceRole, to: a));
+      }
+    }
+  }
+  return legalDrops;
+}
+
+List<NormalMove> moveTestEachSquare(Position position) {
+  final legalMoves = <NormalMove>[];
+  for (int a = 0; a < 64; a++) {
+    for (int b = 0; b < 64; b++) {
+      if (position.isLegal(NormalMove(from: a, to: b))) {
+        legalMoves.add(NormalMove(from: a, to: b));
+      }
+    }
+  }
+  return legalMoves;
+}
+
+List<Move> printBoard(Position a, {bool printLegalMoves = false}) {
+  final z = StringBuffer();
+  final y = StringBuffer();
+  String x = '';
+  int moves = 0;
+  int drops = 0;
+
+  final legalMoves = <Move>[];
+  if (printLegalMoves) {
+    for (final move in moveTestEachSquare(a)) {
+      z.write('${move.uci}, ');
+      legalMoves.add(move);
+      moves++;
+    }
+    x = 'Legal Moves ($moves):\n$z\n';
+    for (final drop in dropTestEachSquare(a)) {
+      y.write('${drop.uci}, ');
+      legalMoves.add(drop);
+      drops++;
+    }
+    x += 'Legal Drops ($drops):\n$y';
+  }
+
+  conditionalPrint('${humanReadableBoard(a.board, a.pockets)}$x');
+  conditionalPrint(
+      '------------------------------------------------------------');
+  return legalMoves;
+}