Hello.

So far I've always used the mod "Will-o-the-wisps-updated 2" from Pi-C. Until then, everything always worked.
But I noticed two problems with your mod.
The first: There are hardly any will-o'-the-wisps. Sometimes none at all.
The second: If I shoot a will-o'-the-wisp, it doesn't fight back.
I did not set it on peaceful!
Now I've killed a red will-o'-the-wisp and got this error message ...:
https://drive.google.com/file/d/19XHE9O38jjjmjASIKIgLJZlrj7WkvoP3/view?usp=sharing

Add "local tags" between lines 104 and 105:

    local q, q_max, ts = MapStats.incidents, conf.incident_track_max, game.tick
local tags
if q[q.b] then

This should solve this issue, but there may be more than that. The new "strict code" thing is good at showing what was wrong before but has never been noticed, and it will crash the game so these bugs can be found, reported, and fixed. :-)

The first: There are hardly any will-o'-the-wisps. Sometimes none at all.

That's expected for first couple days at least, as the new mod will start scanning all chunks for forests and pollution during daytime.
You can speed it up by e.g. "/wisp zone rescan" command, which will do all that work all at once, but might take couple seconds, depending on explored map size.

The second: If I shoot a will-o'-the-wisp, it doesn't fight back.

They should not by design, they only get mad (in a surrounding area) once you kill one of them, not just shoot or damage one.
Previous mod versions had a bug where wisp faction was always set to be at war with you, so they were aggressive and fought back, this was a bug.

See also:
https://mods.factorio.com/mod/Will-o-the-Wisps_updated-2/discussion/5f3b667e256045642e1fc9bc
https://mods.factorio.com/mod/Will-o-the-Wisps_updated/discussion/5e779fd5bc4e78000ec5321c

Now I've killed a red will-o'-the-wisp and got this error message ...:

Yeah, that's definitely a bug, and like Pi-C already mentioned, it's indeed due to some recent changes here.
(technically it was an unintentional issue in the code before too, but now they just raise fatal errors instead of staying hidden)

Thanks for reporting all these.
Haven't had chance to play with the updated mod myself tbh, only did couple test-runs and probably missed this one because was killing wisps with different settings.

Same Error

Same Error

Attach the backtrace please - either via a screenshot or the log.
First line should be the same, but it's the rest of the backtrace that matters, and it's almost certainly in a different place, unless you run 0.3.2 and don't have a fix for this one.

After thinking a bit about these bugs, decided that there'll almost certainly be more of them surfacing like this, and user reports unfortunately aren't always useful in tracking these down, obviously.
So will just remove updated versions for now, until I'll have time to play with these myself properly, hopefully fix more bugs there, and then upload something much less broken.

Would stll be nice to get a backtrace for "Same Error" above, but not sure if factorio might decide to disable the mod once it's gone from here - no big deal either way, will probably trip same bug myself, given how easy they seem to be to stumble into.

Sorry for breaking your game guys, didn't think there'd be so many bugs in the existing code surfaced by that change (there's just quite a lot of code here, I guess), even though Pi-C did warn me :)

It was the old version I just got around to updating mods. The error was the same as the OP but in English. I print screened the error but somehow my computer forgot it before I could paste it. ( I think it got overwritten)

Oh well, maybe I removed these releases for no good reason then :)
Can't easily reupload atm, as PSU in my desktop decided to die today, so guess will go with "more testing" plan anyway.

Though anyone can just grab the latest version from github - just download Will-o-the-Wisps_updated dir from the repo there into "mods" dir and it should work exactly same as 0.3.3 release one did.

Thank you for your quick replies ...

I am not sure if I understood you correctly. Or whether I phrased my sentence correctly ...
Sorry, English is not my language. :/

I had killed several yellow will-o'-the-wisps. Still, they did not fight back.
Well, you know what happened when I killed the red will-o'-the-wisp. -> crash.
The Wisps are their own faction, and it was a bug that my turrets ALWAYS shot at them? Wow ... I didn't even know that! I thought it was normal ...
The yellow will-o'-the-wisps only attacked me when a meteor (Space Exploration) startled and injured them. They always flew past me peacefully. Only my turrets didn't like the will-o'-the-wisps, and killed everyone.
I have no idea what the game will be like if the will-o'-the-wisps behave completely differently in the future ...
Aggressive when accidentally injured. Peaceful if I don't harm them. That's how I knew it before.

Ah, the chunks ... have to recalculate everything. OK.
I didn't know that either.
Unfortunately, I can't enter the command, then I don't get any more achievements. I wait the nights ...

But I'll be happy when the mod works properly again! I love this mod ...

I had killed several yellow will-o'-the-wisps. Still, they did not fight back.

There's a setting "Wisps can retaliate"?

The Wisps are their own faction, and it was a bug that my turrets ALWAYS shot at them? Wow ... I didn't even know that! I thought it was normal ...

There's also a setting for turrets shooting at all wisps.

The yellow will-o'-the-wisps only attacked me when a meteor (Space Exploration) startled and injured them. They always flew past me peacefully. Only my turrets didn't like the will-o'-the-wisps, and killed everyone.

Also a setting (something like "only aggro on player").

Ah, the chunks ... have to recalculate everything. OK.
I didn't know that either.
Unfortunately, I can't enter the command, then I don't get any more achievements. I wait the nights ...

If you mean the code I've posted above: You were not supposed to enter in in the game, but edit a file from the mod (control.lua). That shouldn't break any achievements.

But I'll be happy when the mod works properly again! I love this mod ...

This issue was fixed in 0.3.3. But mk-fg has some technical problems and thought it would be better to remove the new versions for now, as there are likely to be more crashes because of internal code changes. I'd suggest you use my fork for a while. We use basically the same code, so new errors should pop up there as well -- but I can fix those sooner, and the fixes will be included here once mk-fg can work on this mod again.

I had killed several yellow will-o'-the-wisps. Still, they did not fight back.

There's a setting "Wisps can retaliate"?
I have the default setting. Activated.

The Wisps are their own faction, and it was a bug that my turrets ALWAYS shot at them? Wow ... I didn't even know that! I thought it was normal ...

There's also a setting for turrets shooting at all wisps.
I have the default setting. Disabled.

The yellow will-o'-the-wisps only attacked me when a meteor (Space Exploration) startled and injured them. They always flew past me peacefully. Only my turrets didn't like the will-o'-the-wisps, and killed everyone.

Also a setting (something like "only aggro on player").
Aggression factor of the will-o'-the-wisps? Default. -> 0
Or do you mean:
Wisps will only react aggressively to player actions? Default ->Disabled

Ah, the chunks ... have to recalculate everything. OK.
I didn't know that either.
Unfortunately, I can't enter the command, then I don't get any more achievements. I wait the nights ...

If you mean the code I've posted above: You were not supposed to enter in in the game, but edit a file from the mod (control.lua). That shouldn't break any achievements.
What exactly does the code do?
Higher Wisp Spawn?
In the settings, "Maximum number of will-o'-the-wisps on the map" is Default -> 1250

But I'll be happy when the mod works properly again! I love this mod ...

This issue was fixed in 0.3.3. But mk-fg has some technical problems and thought it would be better to remove the new versions for now, as there are likely to be more crashes because of internal code changes. I'd suggest you use my fork for a while. We use basically the same code, so new errors should pop up there as well -- but I can fix those sooner, and the fixes will be included here once mk-fg can work on this mod again.

I am already using your mod. Is the only one that currently works. Even if the Wisp spawn seems a bit reduced here after the last update. (I could be wrong. A couple of nights have passed.)
It's good if you and mk-fg take care of the mod.

If you mean the code I've posted above: You were not supposed to enter in in the game, but edit a file from the mod (control.lua). That shouldn't break any achievements.

I think it was about "/wisp zone rescan" command that I've suggested, and yeah, it'd indeed be bad for 'chivos.

Scanning is very spread-out over time like that (and only during days when there's no other wisp-related stuff too) to have minimal UPS load, as that rarely needs to be updated - forests in normal factorio don't just appear/disappear all the time, and pollution is pretty slow to spread too, but yeah, might be relevant for when loading the mod first in an established game.

Even if the Wisp spawn seems a bit reduced here after the last update.

Don't think there are any differences in that regard since old 0.17.x versions, so gotta be just the artifact of scanning (them not appearing in same places) or something like that.
There are options for types of wisps to spawn too btw, though don't remember off-hand if they can be used to spawn more of them, I think there's one for non-relative spawn chance. You can always tweak way more in config.lua btw, and control.lua has some of the more complicated mechanics formulas at the top.

But mk-fg has some technical problems and thought it would be better to remove the new versions for now, as there are likely to be more crashes because of internal code changes.

Gist here is that I've updated the mod, planned to catch-up on work a bit and then play factorio and test it properly.

But after I did an update my computer broke, and as bug reports started piling-on here, and I know that even after replacing hardware I'll need to work for a couple days before having time to play, decided that it'd be a bad idea to have mod griefing people by crashing their games and loosing progress like that, while I can't really update and test it properly.
So just removed the releases for now, as mentioned, will upload 0.3.4 once I get time to merge some more changes from forks and test it myself a bit more.

It was the old version I just got around to updating mods. The error was the same as the OP but in English.

Yeah, looks like it was same exact issue from 0.3.2, and the last one of its kind (so far, at least).
Haven't bumped into more of these today, so uploaded 0.3.4, should probably work (tm), has couple more mostly-cosmetic changes.

I don't need to change anything in the code! The problem solved itself. The mod works wonderfully!
After a few days, the will-o'-the-wisp spawn normalized.
I find it very pleasant that my turrets only shoot aggressive will-o'-the-wisps. I also find the improvement of the UV lamps better. The will-o'-the-wisps fearfully disappear when they are damaged by a UV lamp. That wasn't before. She cared little. The corrosive will-o'-the-wisps also stayed a long time, or flew over my UV lights. Before that, the UV lamps were pretty much useless.

It is really annoying when the computer breaks down due to hardware failure. I know that ...
My last computer could not be updated. It froze or gave a blue screen. And even the blue screen froze.
Later I had picture noise when displaying the bios.
But strange. The system worked as long as I didn't install an update!

Last but not least: Thank you and Pi-C for the updates of the mod.
Will-o'-the-wisps! is one of the best mods I know for Factorio.