Add game-over detection and PGN save support - #4
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Engine additions on game/game.py: - is_in_check / has_legal_moves / is_checkmate / is_stalemate / is_game_over / result. Detection walks every legal move for the player to move via game.move(.., can_commit=False). has_legal_moves tries the king's own moves first as a fast path so the common "check, but the king has an escape" case exits after a handful of probes instead of probing all 16 pieces. - After move() commits, if the position is checkmate, the trailing '+' in the just-logged elog token is swapped for '#'. Removes the long-standing `# TODO: Append annotation for Checkmate` marker. - parse_pgn_move now also strips '#' and accepts '*' as a result token so a save_pgn output can be re-read by PGNFile. PGN serialization: - Game.save_pgn(filename, headers=None) writes the Seven Tag Roster (Event, Site, Date, Round, White, Black, Result) plus PlyCount, with sensible defaults (Casual Game / Chess.py vX.Y.Z / today / '?' / '?' / '?' / derived / counted). Result is derived from self.result(); '*' for games in progress, '0-1' / '1-0' / '1/2-1/2' for terminal positions. Movetext is wrapped at <= 80 chars. - Headers can be overridden by caller. UI wiring on chess.py: - save_pgn entry de-dimmed in the save menu and wired to a Chess._save_pgn handler that mirrors _save_json (no game / generic exception / FileNotFoundError branches each draw an error message, successful save returns True so _fileprompt closes and the enclosing save_pgn raises KeyboardInterrupt to exit). - A_DIM import removed (no remaining use site). Tests (~10 new): - engine: Fool's mate detected as checkmate (with '#' annotation), Sam Loyd 1899 stalemate detected as draw, starting position and in-progress check positions return '*', save_pgn writes the STR and PlyCount, Result reflects engine state, headers override, movetext contains the log and wraps at <=80, save_pgn -> PGNFile roundtrip preserves move sequence both for a regular opening and a mate-ending game. - UI: _save_pgn handler matrix (no game, success, FileNotFound, generic exception), save_pgn UI no-op + success flows.
Recorded PGN games vary on whether checkmate moves are written 'Qh4+' or 'Qh4#' — Carlsen.pgn never uses '#' even on positions that are actual mates. With the engine's new mate detection emitting '#', the sequence-equality assertion in test_load_pgn_file now sees 'Rd1+' on the PGN side vs 'Rd1#' on the log side at game 9 / ply 75 (and several others). Normalize both sides by stripping trailing '+' / '#' before comparing. The test is about whether the replay reaches the same move sequence, not about annotation style.
The annotate() helper inside promote() handled the case where the pre-promotion move() had left a '+' on the elog token, but didn't account for the '#' marker mate detection now produces. Six Carlsen games (with promotion-while-in-check or promote-into-check patterns) were emitting malformed tokens like 'exd8#=R' / 'c8#=Q' — the marker landed before '=PIECE' instead of after it. Strip any pre-existing '+' / '#' first, append '=PIECE', then re-derive the marker by checking opponent.king.is_safe and (if in check) calling has_legal_moves() to distinguish mate from check. Self.turn correctly points at the opponent at this point in the flow (move() set _last_turn; promote() doesn't touch it), so the mate probe runs on the right team. Verified against all six failing Carlsen positions.
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Summary
Two-part change:
is_in_check,has_legal_moves,is_checkmate,is_stalemate,is_game_over, andresult()onGame. The TODO atgame/game.py:458(# TODO: Append annotation for Checkmate) is now implemented: after a check move commits, if the position is mate, the trailing+on the just-logged algebraic token is swapped for#.Game.save_pgn(filename, headers=None)writes the Seven Tag Roster plusPlyCount, with sensible defaults. The save_pgn menu entry (previously a dimmed stub) is now wired to a real handler.Resultis derived fromGame.result().Commits
07a376d— Add game-over detection and PGN save support.Game.is_in_check / has_legal_moves / is_checkmate / is_stalemate / is_game_over / result.has_legal_movestries the king's escape squares first as a fast path so non-mate check positions exit after a handful of probes instead of scanning every piece.#swap insideGame.moveafter a check move commits. Removes the# TODO: Append annotation for Checkmatemarker.Game.parse_pgn_movenow also strips#and accepts*as a result token, so anythingsave_pgnwrites round-trips throughPGNFile.Game.save_pgn— STR +PlyCount, defaults for unset tags (Casual Game/Chess.py vX.Y.Z/ today /?/?/?/ derived / counted). Movetext wrapped at ≤ 80 chars. Headers overridable.save_pgnentry de-dimmed in the save menu;Chess._save_pgnmirrors_save_json(no game / FileNotFound / generic exception branches)._save_pgnUI test matrix mirroring_save_json.1f06861— Strip+/#intest_load_pgn_fileequality assertion. Recorded PGN games vary on whether mates are writtenQh4+orQh4#— Carlsen never uses#even on actual mates. With the engine's new mate detection emitting#, the assertion now strips both annotations before comparing. The test is about move sequence equivalence, not annotation style.0f42b90— Re-derive promotion's check/mate annotation from post-promote state. Six Carlsen games (promotion while in check, or promote-into-check) emitted malformed tokens likeexd8#=Rbecause theannotate()helper inpromote()only knew how to relocate+, not#. Now strips any pre-existing+/#first, appends=PIECE, then re-derives the marker from the post-promotion state (runninghas_legal_moves()against the opponent to distinguish mate from check).Why the existing engine tests didn't surface this
The
test_load_pgn_fileparametrize on Carlsen/Nakamura was the safety net, but it was annotation-strict. Before this PR the engine never emitted#, so the assertion only ever compared engine+against PGN+and the gap was invisible. Once mate detection switched things on, the slow test caught 6 promotion-related mismatches in Carlsen which led to theannotate()fix. The new fast-suite tests (Fool's mate, Sam Loyd stalemate, save→reload roundtrip on a mate game) keep this regression net in place going forward.Performance impact
has_legal_movesruns once per+-annotated move (~5% of moves typically) plus once per promotion. The king-first fast path makes the common "check, king has an escape" case exit fast. Empirically:Daily
pytest(skipsslow) unchanged: ~1.2 s.Test plan
make test— fast suite passes (207 passed, 2 deselected).make test-all— full sweep including Carlsen/Nakamura passes in ~8.3 min.coverage reportaftermake testshows TOTAL 100%.1.f3 e5 2.g4 Qh4#), open the save menu, select PGN, type a path, hit Enter — file written with[Result "0-1"]and movetext endingQh4#.[Result "*"].https://claude.ai/code/session_01RnQvxtXfn9JFTN8jpNyriL
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