Added effect stacking option to the potions API

Also:
* Frost and Food Poisoning potion now stack their effects
* fixed a crash related to tipped arrows

mods/HELP/mcl_tt/snippets_mcl.lua

@@ -162,6 +162,7 @@ tt.register_snippet(function(itemstring, _, itemstack)
 			if effect.uses_factor then factor = effect.level_to_factor(ef_level) end
 			if effect.get_tt then ef_tt = minetest.colorize("grey", effect.get_tt(factor)) else ef_tt = "" end
 			if ef_tt ~= "" then s = s.. ef_tt.. "\n" end
+			if details.effect_stacks then s = s.. minetest.colorize("grey", S("...stacks")).. "\n" end
 		end
 	end
 	return s:trim()

mods/ITEMS/mcl_potions/lingering.lua

@@ -90,6 +90,9 @@ minetest.register_globalstep(function(dtime)
 							else
 								dur = details.dur
 							end
+							if details.effect_stacks then
+								ef_level = ef_level + mcl_potions.get_effect_level(obj, name)
+							end
 							if mcl_potions.give_effect_by_level(name, obj, ef_level, dur) then
 								applied = true
 							end
@@ -97,7 +100,7 @@ minetest.register_globalstep(function(dtime)
 					end
 
 					if vals.def.custom_effect
-						and vals.def.custom_effect(obj, (vals.potency+1) * mcl_potions.LINGERING_FACTOR) then
+						and vals.def.custom_effect(obj, (vals.potency+1) * mcl_potions.LINGERING_FACTOR, plus) then
 							applied = true
 					end
 

mods/ITEMS/mcl_potions/potions.lua

@@ -64,7 +64,7 @@ function return_on_use(def, effect, dur)
 
 		--def.on_use(user, effect, dur) -- Will do effect immediately but not reduce item count until eating delay ends which makes it exploitable by deliberately not finishing delay
 
-		-- Wrapper for handling mcl_hunger delayed eating
+		-- Wrapper for handling mcl_hunger delayed eating TODO migrate to the new function
 		local name = user:get_player_name()
 		mcl_hunger.eat_internal[name]._custom_itemstack = itemstack -- Used as comparison to make sure the custom wrapper executes only when the same item is eaten
 		mcl_hunger.eat_internal[name]._custom_var = {
@@ -122,11 +122,14 @@ local function generate_on_use(effects, color, on_use, custom_effect)
 			else
 				dur = details.dur
 			end
+			if details.effect_stacks then
+				ef_level = ef_level + mcl_potions.get_effect_level(user, name)
+			end
 			mcl_potions.give_effect_by_level(name, user, ef_level, dur)
 		end
 
 		if on_use then on_use(user, potency+1) end
-		if custom_effect then custom_effect(user, potency+1) end
+		if custom_effect then custom_effect(user, potency+1, plus) end
 
 		itemstack = minetest.do_item_eat(0, "mcl_potions:glass_bottle", itemstack, user, pointed_thing)
 		if itemstack then mcl_potions._use_potion(user, color) end
@@ -162,6 +165,7 @@ end
 -- -- -- dur_variable - bool - whether variants of the potion should have the length of this effect changed -
 -- -- --   - defaults to true
 -- -- --   - if at least one effect has this set to true, the potion has a "plus" variant
+-- -- -- effect_stacks - bool - whether the effect stacks - defaults to false
 -- uses_level - bool - whether the potion should come at different levels -
 --   - defaults to true if uses_level is true for at least one effect, else false
 -- drinkable - bool - defaults to true
@@ -172,7 +176,7 @@ end
 -- default_potent_level - int - potion level used for the default potent variant - defaults to 2
 -- default_extend_level - int - extention level (amount of +) used for the default extended variant - defaults to 1
 -- custom_on_use - function(user, level) - called when the potion is drunk, returns true on success
--- custom_effect - function(object, level) - called when the potion effects are applied, returns true on success
+-- custom_effect - function(object, level, plus) - called when the potion effects are applied, returns true on success
 -- custom_splash_effect - function(pos, level) - called when the splash potion explodes, returns true on success
 -- custom_linger_effect - function(pos, radius, level) - called on the lingering potion step, returns true on success
 function mcl_potions.register_potion(def)
@@ -195,6 +199,9 @@ function mcl_potions.register_potion(def)
 		pdef.description = S("Strange Potion")
 	end
 	pdef._tt_help = def._tt
+	if def._tt and def.effect_stacks then
+		pdef._tt_help = pdef._tt_help .. "\n" .. S("Stacks the effect")
+	end
 	pdef._dynamic_tt = def._dynamic_tt
 	local potion_longdesc = def._longdesc
 	if def._effect_list then
@@ -230,6 +237,7 @@ function mcl_potions.register_potion(def)
 					level_scaling = details.level_scaling or 1,
 					dur = details.dur or mcl_potions.DURATION,
 					dur_variable = durvar,
+					effect_stacks = details.effect_stacks and true or false
 				}
 			else
 				error("Unable to register potion: effect not registered")
@@ -727,10 +735,12 @@ mcl_potions.register_potion({
 	_longdesc = S("Freezes..."),
 	color = "#5B7DAA",
 	_effect_list = {
-		frost = {},
+		frost = {
+			dur = mcl_potions.DURATION_POISON,
+			effect_stacks = true,
+		},
 	},
 	has_arrow = true,
-	-- TODO implement effect stacking?
 })
 
 mcl_potions.register_potion({
@@ -764,10 +774,12 @@ mcl_potions.register_potion({
 	_longdesc = S("Moves bowels too fast."),
 	color = "#83A061",
 	_effect_list = {
-		food_poisoning = {dur=mcl_potions.DURATION_POISON},
+		food_poisoning = {
+			dur = mcl_potions.DURATION_POISON,
+			effect_stacks = true,
+		},
 	},
 	has_arrow = true,
-	-- TODO implement effect stacking?
 })
 
 mcl_potions.register_potion({

mods/ITEMS/mcl_potions/splash.lua

@@ -151,6 +151,9 @@ function mcl_potions.register_splash(name, descr, color, def)
 								else
 									dur = details.dur
 								end
+								if details.effect_stacks then
+									ef_level = ef_level + mcl_potions.get_effect_level(obj, name)
+								end
 								if rad > 0 then
 									mcl_potions.give_effect_by_level(name, obj, ef_level, redux_map[rad]*dur)
 								else
@@ -162,9 +165,9 @@ function mcl_potions.register_splash(name, descr, color, def)
 						if def.custom_effect then
 							local power = (potency+1) * mcl_potions.SPLASH_FACTOR
 							if rad > 0 then
-								def.custom_effect(obj, redux_map[rad] * power)
+								def.custom_effect(obj, redux_map[rad] * power, plus)
 							else
-								def.custom_effect(obj, power)
+								def.custom_effect(obj, power, plus)
 							end
 						end
 					end

mods/ITEMS/mcl_potions/tipped_arrow.lua

@@ -301,10 +301,14 @@ function mcl_potions.register_arrow(name, desc, color, def)
 										else
 											dur = details.dur
 										end
+										dur = dur * mcl_potions.SPLASH_FACTOR
+										if details.effect_stacks then
+											ef_level = ef_level + mcl_potions.get_effect_level(obj, name)
+										end
 										mcl_potions.give_effect_by_level(name, obj, ef_level, dur)
 									end
 								end
-								if def.custom_effect then def.custom_effect(obj, potency+1) end
+								if def.custom_effect then def.custom_effect(obj, potency+1, plus) end
 							end
 						else
 							obj:punch(self.object, 1.0, {
@@ -329,14 +333,13 @@ function mcl_potions.register_arrow(name, desc, color, def)
 										dur = details.dur
 									end
 									dur = dur * mcl_potions.SPLASH_FACTOR
-									if rad > 0 then
+									if details.effect_stacks then
-										mcl_potions.give_effect_by_level(name, obj, ef_level, redux_map[rad]*dur)
+										ef_level = ef_level + mcl_potions.get_effect_level(obj, name)
-									else
+									end
 									mcl_potions.give_effect_by_level(name, obj, ef_level, dur)
 								end
 							end
-							end
+							if def.custom_effect then def.custom_effect(obj, potency+1, plus) end
-							if def.custom_effect then def.custom_effect(obj, potency+1) end
 						end
 
 						if is_player then