IllegalMoveException on legal move

[joshrouwhorst]

Hi, I'm working on building my own PGN viewer and this package looks like it would be really helpful. I am getting an IllegalMoveException on what seems to be a legal move, however.

Here is the PGN:

[Event "?"]
[Site "?"]
[Date "?"]
[Round "?"]
[White "?"]
[Black "?"]
[Result "*"]
[ECO "C25"]
[Annotator "?"]
[PlyCount "25"]
[EventDate "?"]
[SourceDate "?"]

1. e4 e5 2. Nc3 Nc6 3. f4 (3.
Bc4 Nf6 (3... Bc5 4. Qg4
Qf6 (4... g6 5. Qf3 Nf6 6. Nge2 d6 7. d3 Bg4 8. Qg3 {[%cal Rc1g5]}) 5. Nd5
Qxf2+ 6. Kd1 Kf8 7. Nh3 Qd4 8. d3 d6 9. Qf3 Bxh3 10. Rf1 Be6 11. c3) 4. d3 Na5
(4... Bb4 5. Nge2 d5 (5... O-O 6. O-O d6 (6... h6 7.
a3 Be7 8. f4) 7. Bg5) 6. exd5 Nxd5 7. O-O
Be6 8. a3 Bxc3 9. bxc3 O-O 10. a4) (4... Bc5 5. f4 d6 6. Nf3 Ng4 (6... Bg4
7. Na4 O-O 8. Nxc5 dxc5 9. O-O Nd4 10. c3 Nxf3+ 11. gxf3
Bh3 12. Rf2 exf4 13. Bxf4) (6... O-O 7. Na4 Bg4 8. Nxc5 dxc5 9. O-O Qd6 10. Qd2
Bxf3 11. gxf3 Rad8 12. Kh1 Nh5 13. fxe5 Nxe5 14. Qg5 Nxc4 15. Qxh5 Ne5 16. f4)
7. Ng5 O-O 8. f5 Nf2 9.
Qh5) 5. Qf3 Nxc4 6. dxc4 Bc5 (6... d6 7. h3 Be6 8. b3 Be7 9. Nge2 O-O 10. O-O)
7. Be3 Bxe3 8. Qxe3 O-O 9. h3 d6 10. b3 Be6 11. Nge2) 3... exf4 (3... d6 4. Nf3 Bg4 5. Bb5
a6 6. Bxc6+ bxc6 7. h3 Bxf3 8. Qxf3) (3... Nf6 4. fxe5 Nxe5 5. d4) (3... Bc5 4.
Nf3 d6 5. Bb5 Nge7 6. Na4) 4. Nf3 g5 (4... d6 5.
d4 g5 6. d5 Ne5 7. Bb5+ Bd7 8. Bxd7+ Nxd7 9. h4 g4 10. Nd4 Qf6 11. Ncb5) 5. h4 
(5. d4 g4 6. Bc4 gxf3 7. O-O 
(7. Qxf3 Qh4+ 8. g3 Nxd4 9. Qf2 Qf6 10. Bxf4 Bb4 11. e5 Qc6
12. O-O-O Bxc3 13. Bxf7+ Kxf7 14. bxc3 Nf3 15. Rhf1) 7... fxg2 (7... Nxd4 8. Bxf4 Bc5 9. Kh1 d6 10. b4 Bb6
11. Nd5 fxg2+ 12. Kxg2 Ne6 13. Qf3) 8. Rxf4) (5. g3 g4 6. Nh4 f3 7. d4 d6
8. Be3 Be7 9. Qd2 Bxh4 10. gxh4 Qxh4+ 11. Bf2 Qh6 12. Qxh6 Nxh6 13. Nd5 Kd7 14. Kd2) 5... g4 6. Ng5 h6 7. Nxf7 Kxf7 8.
d4 d5 (8... f3 9. Bc4+ Kg7 10. gxf3 Be7 11. Be3) 9.
Bxf4 Nf6 10. Nxd5 (10. exd5
Nxd5 (10... Bd6 11. Bxd6 Qxd6 12. dxc6) 11. Bc4 Be6 12. O-O) 10... Nxd5 11. Bc4 Be6 12. exd5 Bxd5 13. O-O *

The error I get is this: IllegalMoveException: r1bqk2r/pppp1ppp/2n2n2/4p3/1bB1P3/2NP4/PPP2PPP/R1BQK1NR w KQkq - 1 5 => Nge2

I tried running the PGN through the Chess Tempo PGN viewer and did not have an issue. Unless there is something I'm missing I don't believe any Nge2 moves in this are illegal.

Let me know if any other info would be helpful! Thanks!

[shaack]

~~Yes, thanks for reporting. This looks like a problem of chess.js, because, when I initialize chess.js with this fen: r1bqk2r/pppp1ppp/2n2n2/4p3/1bB1P3/2NP4/PPP2PPP/R1BQK1NR w KQkq - 1 5~~

chess.js returns "null", when moving "Nge2":

<script src="https://cdnjs.cloudflare.com/ajax/libs/chess.js/0.10.3/chess.min.js"></script>
<script>
    let chess = new Chess("r1bqk2r/pppp1ppp/2n2n2/4p3/1bB1P3/2NP4/PPP2PPP/R1BQK1NR w KQkq - 1 5")
    let result = chess.move("Nge2")
    console.log(result) // is null
</script>

What do you think, did we both miss something or is it a failure in chess.js?

[shaack]

OK, I got it, it is described in the documentation of chess.js, under .move(move, [ options ]) about the sloppy flag, is written:

// correctly parses incorrectly disambiguated moves
chess = new Chess(
    'r2qkbnr/ppp2ppp/2n5/1B2pQ2/4P3/8/PPP2PPP/RNB1K2R b KQkq - 3 7'
)

chess.move('Nge7') // Ne7 is unambiguous because the knight on c6 is pinned
// -> null

chess.move('Nge7', { sloppy: true })
// -> { color: 'b', from: 'g8', to: 'e7', flags: 'n', piece: 'n', san: 'Ne7' }

So move Nge2 is wrong because it is unambiguous, correct would be "Ne2".

But I have adjusted something, I have now also included the "sloppy" flag in the constructor of Pgn, so now it works if you use new Pgn(sloppyPgn, {sloppy: true}).

[joshrouwhorst]

That worked for me! Thanks!