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Illegal double move spotted #5681

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ouya99 opened this issue Nov 25, 2019 · 11 comments
Open

Illegal double move spotted #5681

ouya99 opened this issue Nov 25, 2019 · 11 comments

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@ouya99
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ouya99 commented Nov 25, 2019

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.

@ouya99 ouya99 changed the title Illegal double move Illegal double move spotted Nov 25, 2019
@IsaVulpes
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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
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ouya99 commented Nov 26, 2019 via email

@ouya99
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ouya99 commented Nov 26, 2019

Bildschirmfoto 2019-11-26 um 02 30 03

@ouya99
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ouya99 commented Nov 26, 2019

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
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ornicar commented Nov 26, 2019

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

@ornicar
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ornicar commented Nov 26, 2019

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

@ouya99
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ouya99 commented Nov 26, 2019

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
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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
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ouya99 commented Nov 26, 2019

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
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@benediktwerner
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benediktwerner commented Jul 23, 2021

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