Assertion failures when units and cities have 0 vision radius in the ruleset

[XHawk87]

Describe the bug
The server console gets spammed with assertions when units and cities have 0 vision radius in the ruleset.

To Reproduce
Steps to reproduce the behaviour:

1. Checkout this branch: https://github.com/XHawk87/LTT-LTX/tree/zero_vision_bug
2. Start up the server
3. Play the first turn and see console for errors

Expected behaviour
I wouldn't expect to see any assertion errors. Subsurface and Stealth vision radius should be automatically capped at the Main vision radius. Units with 0 vision radius should only be able to see their own tile, and that's it.

Logs

[critical] freeciv21-server (/home/xhawk87/sources/freeciv21/server/maphand.cpp:1004) - T001: Assertion plrtile->seen_count[V_INVIS] + !game.info.fogofwar <= plrtile->seen_count[V_MAIN] failed

[critical] freeciv21-server (/home/xhawk87/sources/freeciv21/server/maphand.cpp:1006) - T001: Assertion plrtile->seen_count[V_SUBSURFACE] + !game.info.fogofwar <= plrtile->seen_count[V_MAIN] failed

[critical] freeciv21-server (/home/xhawk87/sources/freeciv21/server/citytools.cpp:3270) - T001: Assertion (pcity->server.vision)->radius_sq[V_MAIN] >= (pcity->server.vision)->radius_sq[V_INVIS] failed

[critical] freeciv21-server (/home/xhawk87/sources/freeciv21/server/citytools.cpp:3270) - T001: Assertion (pcity->server.vision)->radius_sq[V_MAIN] >= (pcity->server.vision)->radius_sq[V_SUBSURFACE] failed

[critical] freeciv21-server (/home/xhawk87/sources/freeciv21/server/sanitycheck.cpp:136) - T001: Assertion plr_tile->seen_count[V_INVIS] <= plr_tile->seen_count[V_MAIN] failed
[critical] freeciv21-server (/home/xhawk87/sources/freeciv21/server/sanitycheck.cpp:136) - T001: (  82,   19) at "Lake"

Platform and version (please complete the following information):

• OS: Linux
• Freeciv21 version: 3.1-rc.1
• Ruleset/Longturn game (if applicable): Chaos

Additional context
Discord

[XHawk87]

Blocks longturn/rules-of-chaos#16

[lmoureaux]

Why should Subsurface and Stealth be capped to Main?

[XHawk87]

If they were higher, it would mean being able to detect spies or submarines in tiles you can't see.

[lmoureaux]

Airport radars can see 100km away, I guess that's about a modern city's working area... capping might make sense but I'm still not fully convinced.

The assertion is caused by an effect that's implicitly added to the ruleset for backward compatibility because +Vision_Layer is not part of the effects.ruleset capabilities (this is documented here). Adding the capability solves the issue in your case.

[XHawk87]

Is the client capable of showing units in tiles that are in fog? I don't have a problem with it, per se. One unit could give vision of the tile, and you could know about hidden units there due to another, I guess.

The assertion is caused by an effect that's implicitly added to the ruleset for backward compatibility because +Vision_Layer is not part of the effects.ruleset capabilities (this is documented here). Adding the capability solves the issue in your case.

I used the VisionLayer option in effects.ruleset in my Chaos test (after being told that +VisionLayer isn't a thing, despite what the docs claim). Is it really +Vision_Layer?

[lmoureaux]

Is the client capable of showing units in tiles that are in fog?

I don't know, most likely not...

Is it really +Vision_Layer?

Nice finding, the capability is called Vision_Layer and the docs are wrong (the + means the ruleset needs the server to support it). The requirement type is called VisionLayer without underscore.

[XHawk87]

Well, if it doesn't cause problems, I would suggest removing the assertions that Stealth vision and Subsurface vision can't exceed Main vision, since in that case they're not valid assertions.

If it does cause problems that can't easily be addressed, it might be better to cap them to Main vision.

[lmoureaux]

I don't see anything in the server code that would require this limitation, but I also can't make it work, so I assume the assertions make sense.

I believe this should "just work" without clipping or anything like that, so my current plan is to document the limitation and open an issue for it.