From 1315551493fca3f3fcfc137e4ee1124e16e46f47 Mon Sep 17 00:00:00 2001
From: Sebastian Lague <sebastlague@gmail.com>
Date: Tue, 1 Aug 2023 17:49:40 +0200
Subject: [PATCH] Fix stalemate detection after generating capture moves in a
 position with no captures available

#418
---
 Chess-Challenge/src/API/Board.cs                |  8 ++++++--
 .../src/Framework/Application/Helpers/Tester.cs | 17 +++++++++++++++--
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/Chess-Challenge/src/API/Board.cs b/Chess-Challenge/src/API/Board.cs
index c5418f8..aac1899 100644
--- a/Chess-Challenge/src/API/Board.cs
+++ b/Chess-Challenge/src/API/Board.cs
@@ -174,8 +174,12 @@ namespace ChessChallenge.API
 		{
 			bool includeQuietMoves = !capturesOnly;
 			moveGen.GenerateMoves(ref moveList, board, includeQuietMoves);
-            hasCachedMoveCount = true;
-            cachedMoveCount = moveList.Length;
+
+			if (!capturesOnly)
+			{
+				hasCachedMoveCount = true;
+				cachedMoveCount = moveList.Length;
+			}
         }
 
 
diff --git a/Chess-Challenge/src/Framework/Application/Helpers/Tester.cs b/Chess-Challenge/src/Framework/Application/Helpers/Tester.cs
index e732b86..fae228f 100644
--- a/Chess-Challenge/src/Framework/Application/Helpers/Tester.cs
+++ b/Chess-Challenge/src/Framework/Application/Helpers/Tester.cs
@@ -17,12 +17,12 @@ namespace ChessChallenge.Application
         public static void Run(bool runPerft)
         {
             anyFailed = false;
-            
+
             new SearchTest().Run(false);
             new SearchTest().Run(true);
             new SearchTest2().Run();
             new SearchTest3().Run();
-           
+
             RepetitionTest();
             DrawTest();
             MoveGenTest();
@@ -368,6 +368,19 @@ namespace ChessChallenge.Application
             Assert(!boardAPI.IsDraw(), "Draw wrong");
             boardAPI.MakeMove(new API.Move("f5f7", boardAPI));
             Assert(boardAPI.IsDraw(), "Draw wrong");
+            // Test stalemate bug when generating captures
+            board.LoadPosition("8/8/3k4/8/8/3K4/4Q3/8 w - - 0 1");
+            boardAPI = new API.Board(board);
+            var captures = boardAPI.GetLegalMoves(capturesOnly: true);
+            Assert(captures.Length == 0, "Wrong capture count");
+            Assert(!boardAPI.IsInStalemate(), "Stalemate wrong");
+            // Test stalemate bug when generating captures (non alloc)
+            board.LoadPosition("8/8/3k4/8/8/3K4/4Q3/8 w - - 0 1");
+            boardAPI = new API.Board(board);
+            Span<API.Move> captureSpan = stackalloc API.Move[64];
+            boardAPI.GetLegalMovesNonAlloc(ref captureSpan, capturesOnly: true);
+            Assert(captureSpan.Length == 0, "Wrong capture count");
+            Assert(!boardAPI.IsInStalemate(), "Stalemate wrong");
 
             // Insufficient material
             board = new Chess.Board();