Runtime error: attempt to perform arithmetic on field 'turn_rate' (a nil value)

[lortas]

I am running Minetest in version 5.9.0-dev

Server crashes after a while, when the draconis mod is enabled.

all installed mods are the most current version from github.

16:35:45: WARNING[Main]: Not registering alias, item with same name is already defined: draconis:dracolily_fire -> air
16:35:45: WARNING[Main]: Not registering alias, item with same name is already defined: draconis:dracolily_ice -> air
16:35:45: WARNING[Main]: Not registering alias, item with same name is already defined: draconis:blood_fire_dragon -> 
16:35:45: WARNING[Main]: Not registering alias, item with same name is already defined: draconis:blood_ice_dragon -> 
16:35:45: WARNING[Main]: Not registering alias, item with same name is already defined: draconis:manuscript -> 
16:37:51: WARNING[Server]: Reading initial object properties directly from an entity definition is deprecated, move it to the 'initial_properties' table instead. (Property 'physical' in entity 'draconis:ice_dragon')
16:38:03: WARNING[Server]: Reading initial object properties directly from an entity definition is deprecated, move it to the 'initial_properties' table instead. (Property 'physical' in entity 'draconis:jungle_wyvern')
16:38:03: WARNING[Server]: Deprecated call to get_bone_position, use get_bone_override instead (at /opt/minetest/bin/../mods/draconis/api/api.lua:1306)
16:38:03: WARNING[Server]: Deprecated call to set_bone_position, use set_bone_override instead (at /opt/minetest/bin/../mods/draconis/api/api.lua:1326)
16:38:03: WARNING[Server]: Deprecated call to get_bone_position, use get_bone_override instead (at /opt/minetest/bin/../mods/draconis/api/api.lua:1488)
16:38:03: WARNING[Server]: Deprecated call to set_bone_position, use set_bone_override instead (at /opt/minetest/bin/../mods/draconis/api/api.lua:1505)
16:38:03: WARNING[Server]: Deprecated call to get_bone_position, use get_bone_override instead (at /opt/minetest/bin/../mods/draconis/api/api.lua:1278)
16:38:03: WARNING[Server]: Deprecated call to set_bone_position, use set_bone_override instead (at /opt/minetest/bin/../mods/draconis/api/api.lua:1290)
16:38:08: ERROR[Main]: ServerError: AsyncErr: Lua: Runtime error from mod 'draconis' in callback luaentity_Step(): /opt/minetest/bin/../mods/draconis/api/behaviors.lua:199: attempt to perform arithmetic on field 'turn_rate' (a nil value) 
16:38:08: ERROR[Main]: stack traceback: 
16:38:08: ERROR[Main]:  /opt/minetest/bin/../mods/draconis/api/behaviors.lua:199: in function 'get_method'
16:38:08: ERROR[Main]:  /opt/minetest/bin/../mods/creatura/mob_meta.lua:1043: in function 'move_to'
16:38:08: ERROR[Main]:  /opt/minetest/bin/../mods/creatura/methods.lua:395: in function 'action'
16:38:08: ERROR[Main]:  /opt/minetest/bin/../mods/creatura/mob_meta.lua:1200: in function '_execute_utilities'
16:38:08: ERROR[Main]:  /opt/minetest/bin/../mods/creatura/mob_meta.lua:938: in function </opt/minetest/bin/../mods/creatura/mob_meta.lua:903>

[Skivling]

I am getting the same error with Minetest 5.8.0 :

2024-03-06 21:09:55: ERROR[Main]: ServerError: AsyncErr: Lua: Runtime error from mod 'draconis' in callback luaentity_Step(): /home/user/.minetest/mods/draconis/api/behaviors.lua:199: attempt to perform arithmetic on field 'turn_rate' (a nil value)
2024-03-06 21:09:55: ERROR[Main]: stack traceback:
2024-03-06 21:09:55: ERROR[Main]: 	/home/user/.minetest/mods/draconis/api/behaviors.lua:199: in function 'get_method'
2024-03-06 21:09:55: ERROR[Main]: 	/home/user/.minetest/mods/creatura/mob_meta.lua:1043: in function 'move_to'
2024-03-06 21:09:55: ERROR[Main]: 	/home/user/.minetest/mods/creatura/methods.lua:395: in function 'action'
2024-03-06 21:09:55: ERROR[Main]: 	/home/user/.minetest/mods/creatura/mob_meta.lua:1200: in function '_execute_utilities'
2024-03-06 21:09:55: ERROR[Main]: 	/home/user/.minetest/mods/creatura/mob_meta.lua:938: in function </home/user/.minetest/mods/creatura/mob_meta.lua:903>
2024-03-06 21:09:55: ACTION[Main]: Server: Shutting down

[BobOmbuzal]

Same as #33
Fixed by #37
Just replace all "self.turn_rate" with "self.turn_rate or 6"

[fitfot]

I'm getting this error on Luanti server 5.11.0 (installed via flatpak on Debian 12) with Draconis release 23494:

2025-03-09 15:46:25: ACTION[Main]: Server: Shutting down
2025-03-09 15:46:25: ERROR[Main]: ServerError: AsyncErr: Lua: Runtime error from mod 'draconis' in callback luaentity_Step(): ...etest.Minetest/.minetest/mods/draconis/api/behaviors.lua:199: attempt to perform arithmetic on field 'turn_rate' (a nil value)
2025-03-09 15:46:25: ERROR[Main]: stack traceback:
2025-03-09 15:46:25: ERROR[Main]: 	...etest.Minetest/.minetest/mods/draconis/api/behaviors.lua:199: in function 'get_method'
2025-03-09 15:46:25: ERROR[Main]: 	...t.minetest.Minetest/.minetest/mods/creatura/mob_meta.lua:1043: in function 'move_to'
2025-03-09 15:46:25: ERROR[Main]: 	...et.minetest.Minetest/.minetest/mods/creatura/methods.lua:395: in function 'action'
2025-03-09 15:46:25: ERROR[Main]: 	...t.minetest.Minetest/.minetest/mods/creatura/mob_meta.lua:1200: in function '_execute_utilities'
2025-03-09 15:46:25: ERROR[Main]: 	...t.minetest.Minetest/.minetest/mods/creatura/mob_meta.lua:938: in function <...t.minetest.Minetest/.minetest/mods/creatura/mob_meta.lua:903>

I asked Copilot for some help on this, and it replied, "It looks like the crash is happening due to a nil value in the turn_rate field"

A grep search within the draconis mod directory for the string self.turn_rate gives:

api/behaviors.lua:	local wayp_threshold = width + (width / self.turn_rate)
api/behaviors.lua:		_self:tilt_to(goal_yaw, _self.turn_rate or 6)
api/behaviors.lua:	local wayp_threshold = width + (width / self.turn_rate)
api/behaviors.lua:		local turn_rate = abs(_self.turn_rate or 5)
api/api.lua:	self.turn_rate = 6 - 3 * clamp((self.growth_scale), 0.1, 1) -- Turning radius widens with size
api/api.lua:		self.turn_rate = self.turn_rate * 1.5 -- Turning radius reduced when landed
api/api.lua:		self.turn_rate = 5
api/api.lua:			self.turn_rate = self.turn_rate * 0.75 -- Turning radius incrased when flying

I asked Copilot about this, and it says "it seems like self.turn_rate should always have a value. However, there might be a case where self.growth_scale is causing self.turn_rate to be nil. To prevent this, you can add a check to ensure self.turn_rate always has a valid value." Then gives this example of how to do this. I'd like to know if someone can assess this, if it's even a good idea or not:

self.turn_rate = self.turn_rate * 1.5 or self.turn_rate
self.turn_rate = 5 or self.turn_rate
self.turn_rate = self.turn_rate * 0.75 or self.turn_rate

It explains: "Adding or self.turn_rate ensures that if any calculation results in nil, the previous value of self.turn_rate will be used instead. "