Fix en-passant bug in Bitboard.pawn_moves_from()

niklasf · Oct 10, 2014 · 68a92e2 · 68a92e2
1 parent b5904d2
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diff --git a/CHANGELOG.rst b/CHANGELOG.rst
@@ -6,6 +6,12 @@ is more important to get things right, than to be consistent with previous
 versions. Use this changelog to see what changed in a new release, because this
 might include API breaking changes.
 
+New in v0.4.2
+-------------
+
+* Fix bug where `pawn_moves_from()` and consequently `is_legal()` weren't
+  handling en-passant correctly. Thanks to Norbert Naskov for reporting.
+
 New in v0.4.1
 -------------
 

diff --git a/chess/__init__.py b/chess/__init__.py
@@ -20,7 +20,7 @@
 
 __email__ = "niklas.fiekas@tu-clausthal.de"
 
-__version__ = "0.4.1"
+__version__ = "0.4.2"
 
 import collections
 import re
@@ -1374,7 +1374,7 @@ def pawn_moves_from(self, square):
         if not self.ep_square:
             targets |= BB_PAWN_ATTACKS[self.turn][square] & self.occupied_co[self.turn ^ 1]
         else:
-            targets |= BB_PAWN_ATTACKS[self.turn][square] & (self.occupied_co[self.turn ^ 1] | BB_SQUARES[square])
+            targets |= BB_PAWN_ATTACKS[self.turn][square] & (self.occupied_co[self.turn ^ 1] | BB_SQUARES[self.ep_square])
 
         return targets
 

diff --git a/test.py b/test.py
@@ -660,6 +660,13 @@ def test_fifty_moves(self):
         self.assertFalse(board.can_claim_fifty_moves())
         self.assertFalse(board.can_claim_draw())
 
+    def test_ep_legality(self):
+        board = chess.Bitboard("rnbqkbnr/pppppp2/7p/6pP/8/8/PPPPPPP1/RNBQKBNR w KQkq g6 0 3")
+        self.assertTrue(board.is_legal(chess.Move.from_uci("h5g6")))
+        board.push_san("Nf3")
+        board.push_san("Nf6")
+        self.assertFalse(board.is_legal(chess.Move.from_uci("h5g6")))
+
 
 class LegalMoveGeneratorTestCase(unittest.TestCase):