Attempt to index nil value caused by nodes with invalid param2

[debagos]

I use the latest master on Minetest 5.5.0

ERROR[Main]: ServerError: AsyncErr: Lua: Runtime error from mod 'wielded_light' in callback environment_Step(): ...minetest-5.5.0/bin/../mods/mesecons/mesecons/presets.lua:67: attempt to index local 'dir' (a nil value)
ERROR[Main]: stack traceback:
ERROR[Main]: 	...minetest-5.5.0/bin/../mods/mesecons/mesecons/presets.lua:67: in function 'get_any_inputrules'
ERROR[Main]: 	...inetest-5.5.0/bin/../mods/mesecons/mesecons/internal.lua:97: in function 'get_any_rules'
ERROR[Main]: 	...etest-5.5.0/bin/../mods/mesecons/mesecons_wires/init.lua:81: in function <...etest-5.5.0/bin/../mods/mesecons/mesecons_wires/init.lua:67>
ERROR[Main]: 	...test-5.5.0/bin/../mods/mesecons/mesecons/actionqueue.lua:137: in function 'execute'
ERROR[Main]: 	...test-5.5.0/bin/../mods/mesecons/mesecons/actionqueue.lua:111: in function <...test-5.5.0/bin/../mods/mesecons/mesecons/actionqueue.lua:73>
ERROR[Main]: 	...i/github/minetest-5.5.0/bin/../builtin/game/register.lua:425: in function <...i/github/minetest-5.5.0/bin/../builtin/game/register.lua:409>

I have no clue what went wrong or how to reproduce it...
And keep in mind that 'wielded_light' is blamed wrongfully here: #609
The 'wielded_light' mod has no variable called "dir", but https://github.com/minetest-mods/mesecons/blob/master/mesecons/presets.lua#L66 does.

[TurkeyMcMac]

This is probably due to an invalid param2 value on a node whose paramtype2 is facedir or wallmounted. If paramtype2 is facedir, then it must hold that param2 % 32 < 24. If paramtype2 is wallmounted, then it must hold that param2 % 8 < 6.

Possible culprits are buttons, levers, solar panels, and wall-mounted lamps. There may be others depending on what other mods you have that use Mesecons.

[debagos]

Server crashed again, just a few moments ago.

ERROR[Main]: ServerError: AsyncErr: Lua: Runtime error from mod 'wielded_light' in callback environment_Step(): ...minetest-5.5.0/bin/../mods/mesecons/mesecons/presets.lua:67: attempt to index local 'dir' (a nil value)
ERROR[Main]: stack traceback:
ERROR[Main]: 	...minetest-5.5.0/bin/../mods/mesecons/mesecons/presets.lua:67: in function 'get_any_inputrules'
ERROR[Main]: 	...inetest-5.5.0/bin/../mods/mesecons/mesecons/internal.lua:97: in function 'get_any_rules'
ERROR[Main]: 	...etest-5.5.0/bin/../mods/mesecons/mesecons_wires/init.lua:81: in function <...etest-5.5.0/bin/../mods/mesecons/mesecons_wires/init.lua:67>
ERROR[Main]: 	...test-5.5.0/bin/../mods/mesecons/mesecons/actionqueue.lua:137: in function 'execute'
ERROR[Main]: 	...test-5.5.0/bin/../mods/mesecons/mesecons/actionqueue.lua:111: in function <...test-5.5.0/bin/../mods/mesecons/mesecons/actionqueue.lua:73>
ERROR[Main]: 	...i/github/minetest-5.5.0/bin/../builtin/game/register.lua:425: in function <...i/github/minetest-5.5.0/bin/../builtin/game/register.lua:409>

I discovered something interesting, everytime this crash happens, a player digs this node: homedecor:glowlight_small_cube_14 and there are two mentions in the homedecor_lighting init.lua of the mesecon.rules.wallmounted_get function, which internally calls the rules_from_dir, which then attempts to index hte parameter 2 (dir) with no data/nil.
So I guess this issued should be closed an reopened in the homedecor repository.
If you have some idea how I could (hot)fix this, I would appreciate it a lot!

[TurkeyMcMac]

Can you see what the param2 value is before the node is dug? (Using the F5 debug info.)

[debagos]

paramtype2 = "colorwallmounted"
param2 = 30
and the nodebox is wrong:

Please not that this node got colored with white dye.

[TurkeyMcMac]

I can reproduce the crash. It makes sense, since 30 % 8 = 6. But I don't know how the node got that way.

To prevent the crash, this patch to Mesecons should work:

diff --git a/mesecons/presets.lua b/mesecons/presets.lua
index e10dd36..64f2bff 100644
--- a/mesecons/presets.lua
+++ b/mesecons/presets.lua
@@ -74,6 +74,7 @@ end
 
 mesecon.rules.wallmounted_get = function(node)
 	local dir = minetest.wallmounted_to_dir(node.param2)
+	if not dir then return {} end
 	return rules_from_dir(rules_wallmounted, dir)
 end

[debagos]

Thank you very much for your help @TurkeyMcMac, your information about the param2 stuff and the little hotfix! ❤️

[Niklp09]

@TurkeyMcMac can you make a PR with your patch?

[TurkeyMcMac]

Will do.