a bug

[IFRFSX]

shoot mobs mod's animals, the minetest will exit directly

[IFRFSX]

2020-08-20 21:27:15: ERROR[Main]: ServerError: AsyncErr: ServerThread::run Lua: Runtime error from mod 'mobs_animal' in callback luaentity_Step(): ...gfsx/桌面/minetest/bin/../mods/bows/bows/arrow.lua:13: attempt to index local 'opos' (a nil value)
2020-08-20 21:27:15: ERROR[Main]: stack traceback:
2020-08-20 21:27:15: ERROR[Main]: ...gfsx/桌面/minetest/bin/../mods/bows/bows/arrow.lua:13: in function 'on_hit_object'
2020-08-20 21:27:15: ERROR[Main]: ...gfsx/桌面/minetest/bin/../mods/bows/bows/arrow.lua:150: in function <...gfsx/桌面/minetest/bin/../mods/bows/bows/arrow.lua:103>

[mferrari-incomm]

I had the same issue. The offending piece of code is in arrow.lua:

bows.on_hit_object=function(self,target,hp,user,lastpos)
	local hp2=target:get_hp()-hp
	target:set_hp(hp2)
	target:punch(target,1,{full_punch_interval=1,damage_groups={fleshy=4}},nil)
	if hp2>0 then
		local pos=self.object:get_pos()
		local opos=target:get_pos()
		local dir = user:get_look_dir()
		self.object:set_attach(target, "", {x=(opos.x-pos.x)*4,y=(pos.y-opos.y)*4,z=(pos.z-opos.z)*4},{x=0,y=-90,z=0})
	end
	return self
end

Even though hp2 is in fact bigger than 0, target:get_pos() is returning nil.

I haven't tested it yet, but I think we can hack it this way for now:

bows.on_hit_object=function(self,target,hp,user,lastpos)
	local hp2=target:get_hp()-hp
	target:set_hp(hp2)
	target:punch(target,1,{full_punch_interval=1,damage_groups={fleshy=4}},nil)
	if hp2>0 then
		local pos=self.object:get_pos()
		local opos=target:get_pos()
		local dir = user:get_look_dir()

		if pos ~= nil and opos ~= nil and dir ~= nil then
			self.object:set_attach(target, "", {x=(opos.x-pos.x)*4,y=(pos.y-opos.y)*4,z=(pos.z-opos.z)*4},{x=0,y=-90,z=0})
		end
	end
	return self
end

[IFRFSX]

@Morocotopo

I have tested your code, shot the sheep in mobs_animal with bows, and the error no longer appears.
If you are free, you can fork a bows code and submit a PR to the author.