[Beta 14] No cave-in warning on third move if path is blocked by machine

[R-26 Lightspeed]

Normally, when moving into dug-out tiles, attempting a third move will warn you about cave-ins if it would make it impossible to exit the dug-out tiles on the fourth.

However, if you tunnel into the back of a Garrison Access machine¹ (or any other machine, interactive or not), and the third move would put you next to that machine, with no direct way out, the warning isn't given.
Here's a video example : https://imgur.com/a/no-cave-warning-due-to-garrison-s5Mo634

¹ I often tunnel into the back of guarded Garrison Access machines to seal them undetected, but in cases like these, i sometimes forget that "safe digs" are based on tiles travelled and not tiles dug, or forget to account for the return trip.

[Kyzrati]

I don't see the issue here. The warning does not predict the future, it's never done that, it merely tells you if your next move, when you're about to try to take it, will come with the possibility of a cave-in due to that move. In the recording here you're simply doing a wall -> earth -> wall movement, so there's no warning. Yes when you attempt to continue moving into dangerous territory it will then warn you, but that's consistent with its intended behavior.

[R-26 Lightspeed]

I don't see the issue here. The warning does not predict the future, it's never done that, it merely tells you if your next move, when you're about to try to take it, will come with the possibility of a cave-in due to that move.

It does kind of predict the future, though?
If you make a wall -> earth -> earth move, you'll get a warning when trying to make the third move.
The third move shouldn't be able to cause a cave-in, but there's still a warning for it that only occurs if you wouldn't be able to get out of the dig on the fourth move (ignoring any machines).

Here's proof :
https://imgur.com/a/left-left-up-warning-up-right-loKfOjR
First two moves are left. On the third move, i try to go upwards, but a warning appears instead.
I then let the warning fade (so that it could trigger again if i tried to move up again), then move up-right instead, which does not cause a warning.

[Kyzrati]

If you make a wall -> earth -> earth move, you'll get a warning when trying to make the third move.

That's because it can absolutely cave in, immediately! That's not a prediction, it's a wall->earth->earth move, which is not protected. The manual specifically states that only wall-earth-wall is safe, insofar as tunneling. Anything else can collapse, including if the third position is earth. (It's just quite rare to get collapsed on immediately in such a short tunnel, so you probably haven't noticed before.)

[R-26 Lightspeed]

That's because it can absolutely cave in, immediately! That's not a prediction, it's a wall->earth->earth move, which is not protected. The manual specifically states that only wall-earth-wall is safe, insofar as tunneling. Anything else can collapse, including if the third position is earth. (It's just quite rare to get collapsed on immediately in such a short tunnel, so you probably haven't noticed before.)

It does? Now that i think about it, i do remember a few occurrences explained by this behavior.
First i thought that cave-ins were based on number of tiles dug (which was my intuitive understanding of it), then i thought it was the number of tiles traveled, but apparently it's neither.

After some small testing, it seems wall-wall-wall-wall is also protected (which is very nice to know, for the few relevant situations), as is wall-wall-earth and i assume earth-wall-wall.
If i has to guess, earth-earth would also be protected.
I think it's like if moving on walls had a "cost" of 1 and moving on earth tiles had a "cost" of 2, and if a move causes you to reach of total "cost" of 5 or more, then the tile might collapse.