Incorrect castling/gating check in FEN validation about fairy-stockfish

[ianfab]

Please specify more detailed steps to reproduce the issue such as variant config if any, CLI/GUI commands/input, expected vs actual output.

[gbtami]

It happened on pychess when he created a custom setup S-chess game with above FEN.
On server side I can see the error message from https://github.com/fairy-stockfish/Fairy-Stockfish/blob/master/src/apiutil.h#L743
I reproduced it in local install:

+0200 2024-04-22 01:05:14.198 [DEBUG] websocket_utils:70 Websocket (139974902806128) message: WSMessage(type=<WSMsgType.TEXT: 1>, data='{"type":"create_seek","user":"Anon–IBsimzx6","target":"","variant":"seirawan","fen":"rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/QBBNNRKR[HEhe] w BCDFGbcdfg - 0 1","minutes":90,"increment":90,"byoyomiPeriod":0,"day":0,"rated":false,"chess960":false,"color":"w"}', extra='')
+0200 2024-04-22 01:05:14.198 [DEBUG] wsl:124 create_seek {'type': 'create_seek', 'user': 'Anon–IBsimzx6', 'target': '', 'variant': 'seirawan', 'fen': 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/QBBNNRKR[HEhe] w BCDFGbcdfg - 0 1', 'minutes': 90, 'increment': 90, 'byoyomiPeriod': 0, 'day': 0, 'rated': False, 'chess960': False, 'color': 'w'}
create_seek None Anon–IBsimzx6: **seirawan** 90+90
+0200 2024-04-22 01:05:14.230 [INFO] aiohttp.access:211 127.0.0.1 [22/Apr/2024:00:05:14 +0100] "GET /static/images/board/8x8brown.svg HTTP/1.1" 200 0 "http://127.0.0.1:8080/static/board.css" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:125.0) Gecko/20100101 Firefox/125.0"
+0200 2024-04-22 01:05:14.231 [DEBUG] aiohttp.server:418 Ignored premature client disconnection 2
+0200 2024-04-22 01:05:14.231 [DEBUG] aiohttp.server:418 Ignored premature client disconnection.
+0200 2024-04-22 01:05:25.120 [INFO] index:88 +++ Existing user berado88 connected.
+0200 2024-04-22 01:05:25.154 [INFO] aiohttp.access:211 127.0.0.1 [22/Apr/2024:00:05:25 +0100] "GET / HTTP/1.1" 200 8619 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/112.0.0.0 Safari/537.36"
+0200 2024-04-22 01:05:25.270 [INFO] aiohttp.access:211 127.0.0.1 [22/Apr/2024:00:05:25 +0100] "GET /static/pychess-variants.js HTTP/1.1" 304 265 "http://127.0.0.1:8080/" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/112.0.0.0 Safari/537.36"
+0200 2024-04-22 01:05:25.693 [INFO] websocket_utils:49 --- NEW /wsl WEBSOCKET by berado88 from 127.0.0.1
+0200 2024-04-22 01:05:25.849 [INFO] aiohttp.access:211 127.0.0.1 [22/Apr/2024:00:05:25 +0100] "GET /notifications?p=0 HTTP/1.1" 200 244 "http://127.0.0.1:8080/" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/112.0.0.0 Safari/537.36"
+0200 2024-04-22 01:05:25.861 [INFO] aiohttp.access:211 127.0.0.1 [22/Apr/2024:00:05:25 +0100] "GET /static/images/pexels-renato-conti-2677849.jpg HTTP/1.1" 304 264 "http://127.0.0.1:8080/" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/112.0.0.0 Safari/537.36"
+0200 2024-04-22 01:05:27.911 [DEBUG] websocket_utils:70 Websocket (139974902962928) message: WSMessage(type=<WSMsgType.TEXT: 1>, data='{"type":"accept_seek","seekID":1,"player":"berado88"}', extra='')
+0200 2024-04-22 01:05:27.911 [INFO] utils:349 +++ Seek 1 joined by berado88 FEN:rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/QBBNNRKR[HEhe] w BCDFGbcdfg - 0 1 960:False
The WHITE KING has moved. Castling is no longer valid for WHITE.
+0200 2024-04-22 01:05:27.911 [DEBUG] utils:392 Failed to create game. Invalid FEN rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/QBBNNRKR[HEhe] w BCDFGbcdfg - 0 1
accept_seek None Anon–IBsimzx6: **seirawan** 90+90 accepted by berado88

[ianfab]

Thanks for the context. Technically looks correct to me though, since in a non-960 game there can't be an unmoved king on a different file than the e-file. If this also happens in 960, then I guess it would be a bug.

[gbtami]

I think I checked in 960 in the new game dialog. Or not.I have to double check this ....
Yes. It produces the same with 960 checked.