Game logic: Illegal moves being accepted

[zzril]

So far, the game logic / rules of chess are not yet fully implemented.
I think it would help to have one place to track all rule violations that have been found so far, because not all of them are obvious and (at least for now) it can be hard to reproduce them.

All the illegal moves that I could produce so far:

1. King not moving out of check.
   1b. King moving into check.
   1c. King can be captured. (Should be solved if 1 and 1b are handled properly.)
2. Pawns not promoting. (You can input a move such as e8=Q, but the parser just ignores everything from the = on. The pawn will move to e8 and stay there as a pawn. Further moves with this piece will not be accepted.)
3. Stalemate not recognised. (If human is stalemated, the game still asks for a move; if computer is stalemated, game crashes (due to timeout?).)
4. "Ambiguous moves" not handled properly. (E. g. I had a case where 2 different knights could go to h2, yet the game accepted my move Nh2 and just chose one of them - correct behaviour would be to reject the move.)
5. Castling accepted after rook has moved. (E. g. I played Rh2, later Rh1, later 0-0.)
6. En-passant captures are not accepted. (At least not the notations hxg6 and hxg6e.p. or fxg6 e.p. - it's hard to get into situations where you have this move available :p )

@zzril Hey could you tell me what exactly has to be done? and how should I solve this issue?
I am new to open source...

I would like to contribute to this but I am not getting what should to be done...

[hrushikeshrv]

Thanks for your effort! Yes, I haven't implemented the rules you've listed yet. I'll add a note to the docs listing all of them while I work on their implementation. I'll also create new issues for all of them since they're pretty important and should be fixed before the next release. Thanks again :)

[hrushikeshrv]

Hi @Indrajeet-S, working on this issue will require knowledge of the core layer of the engine. I can point you to a few parts of the code base that we will need to modify to fix this - chessengine.bitboard.Board and chessengine.moves. I think you should look up how bitboards work and then try to understand how they're used in the chessengine.bitboard.Board class.

Once you understand how they are implemented, you can take a look at the move generating functions in chessengine.moves and you will be able to see how to modify them to follow the above rules. But implementing some of those rules will take modification of both the Board class as well as the move generating functions. Even I'm not sure exactly how I will implement this rules yet, so that is something that we will have to come up with.