Infer variant (standard/chess960) from provided FEN

[kelseyde]

I added a new field to the Board, 'variant', with the enum options STANDARD and CHESS960. We need a way to set this correctly based on the FEN passed to Board.from(fen).

Currently some of the Chess960 tests are failing because of this issue.

[fathzer]

Hi,

We need a way to set this correctly based on the FEN passed to Board.from(fen)

I think it is impossible to do it only with only the FEN: A chess960 board that corresponds to the standard start position has the same FEN as the standard chess game. But, the castling moves must not be encoded the same way in chess960 and standard chess. So we can't use a standard board in chess960 context, even if the start positions are the same.

Maybe we can add an optional variant argument to Board.from?

[kelseyde]

Good point! Indeed, passing the variant to Board.from sounds like the best approach. I will have a shot doing that on a branch.