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Illegal double move spotted #5681

Open ouya99 opened 4 years ago

ouya99 commented 4 years ago

https://lichess.org/agtsxfZ33hvz

(move 23)

In this game I managed to do a double-move on my side, while my opponent only saw 1st move. So both sides did not continue same game. It did not resolve until the end of the game.

It occured with a bad internet connection . Suddenly my rook move was taken back by the UI (without any action of my side). Since I then wanted to move the pawn next, I did that and BOTH moves were executed on my side, before returning action back to opponent. So my chess board showed a different status. My opponent only seeing first rook move.

IsaVulpes commented 4 years ago

So you are White, I presume Did you confirm this with your opponent? It sounds extremely unlikely. Which Rook move did you "play" before it was "taken back"?

If your opponent only saw your first move, then they played 27..Ra3 instead of ..Rxa3 (nothing is there), and instead of "taking your pawn" via ..Rxa2 next move (he'd still think the pawn is there), they went 28..Rb3??, which you could just reply to with 29.axb3

Black's play gives absolutely 0 indication of this happening

ouya99 commented 4 years ago

it really happened.

i played Rcc2 (move 23) This move was taken back by the UI, so I did another move (a4) (to trick lichess) and in the end both moves were executed. I have a screenshot too.

yes bxa5 was played, but this was not possible on my board so the white pawn just moved DIAGONAL without taking my pawn.

I played with black to win, and surely BLACK does give indication (move 28, Rb3 was played to test lichess again).. and yes this confirmed my pawn was gone (taken by white)

On 11/26/19, IsaVulpes notifications@github.com wrote:

So you are White, I presume Did you confirm this with your opponent? It sounds extremely unlikely. Which Rook move did you "play" before it was "taken back"?

If your opponent only saw your first move, then they played 27..Ra3 instead of ..Rxa3 (nothing is there), and instead of "taking your pawn" via ..Rxa2 next move (he'd still think the pawn is there), they went 28..Rb3??, which you could just reply to with 29.axb3

Black's play gives absolutely 0 indication of this happening

-- You are receiving this because you authored the thread. Reply to this email directly or view it on GitHub: https://github.com/ornicar/lila/issues/5681#issuecomment-558414235

ouya99 commented 4 years ago

Bildschirmfoto 2019-11-26 um 02 30 03

ouya99 commented 4 years ago

see screenshot, my black pawn should not be on a4, but on a5, so I managed to not only move the rook to c2, but also advance the pawn to a4 in the same move

ornicar commented 4 years ago

OK I have an idea where that could come from. Thanks for the bug report.

ornicar commented 4 years ago

For the record, the server didn't record a double move. It was a display bug on your side only.

ouya99 commented 4 years ago

The display bug (UI taking back my moves) occured in several games (usually while trying to reconnect due to bad internet connection). So I assume you can reproduce having bad connection and trying to play 2 different moves. If I had played my rook move again, it would have continued in a normal way (I tested it in another game where the same thing happened -UI taking back moves). Surely this is client-side only.

IsaVulpes commented 4 years ago

Helps if you specify which colour you are, what the moves in question were, and give a screenshot .. at the same time as posting the issue, rather than letting people sit there confused about what's going on

I presumed you were White, and the display was wrong for your opponent (so Black saw White making a random rook move, instead of 23.a3), which would be a massive bug (rather than a simple client side display error) ..Rc1 is also not the move you played, but ..Rcc2? Ah whatever, thibault got this

ouya99 commented 4 years ago

Sorry corrected my typo. Rcc2 was in fact the initial move.

Also its actually 2 different bugs. UI taking back moves happened several times in different games. I have no proof for this, (would have to do a video capture). Maybe this is not a severe bug, since play is not disturbed once internet connection is back, but it looks weird

ddugovic commented 3 years ago

The UI glitch happened again https://lichess.org/forum/lichess-feedback/move-repeated-induces-error

benediktwerner commented 3 years ago

https://lichess.org/forum/lichess-feedback/opponent-king-was-in-check-when-my-king-was-in-check

https://lichess.org/9PoENdml/black

43YH5CI

  1. Kf8 is repeated. The actual game continues 33. Qxf5