make sure a listed block is indeed loaded before writing to it

(in case the mapgen takes long enough on a server that players
have wandered off and the server has unloaded blocks)

for each block queued, make sure it and all 6 of its neighbors are
actually loaded before populating, else move the block to the end of the
queue.

init.lua

@@ -9,8 +9,6 @@
 biome_lib = {}
 biome_lib.air = {name = "air"}
 
-plantslib = setmetatable({}, { __index=function(t,k) print("Use of deprecated function:", k) return biome_lib[k] end })
-
 biome_lib.blocklist_aircheck = {}
 biome_lib.blocklist_no_aircheck = {}
 
@@ -36,7 +34,7 @@ local function tableize(s)
 	return string.split(string.trim(string.gsub(s, " ", "")))
 end
 
-local c1 minetest.settings:get("biome_lib_default_grow_through_nodes")
+local c1 = minetest.settings:get("biome_lib_default_grow_through_nodes")
 biome_lib.default_grow_through_nodes = {["air"] = true}
 if c1 then
 	for _, i in ipairs(tableize(c1)) do
@@ -46,7 +44,7 @@ else
 	biome_lib.default_grow_through_nodes["default:snow"] = true
 end
 
-local c2 minetest.settings:get("biome_lib_default_water_nodes")
+local c2 = minetest.settings:get("biome_lib_default_water_nodes")
 biome_lib.default_water_nodes = {}
 if c2 then
 	for _, i in ipairs(tableize(c2)) do
@@ -160,7 +158,7 @@ function biome_lib:set_defaults(biome)
 	biome.near_nodes_size = biome.near_nodes_size or 0
 	biome.near_nodes_count = biome.near_nodes_count or 1
 	biome.rarity = biome.rarity or 50
-	biome.max_count = biome.max_count or 5
+	biome.max_count = biome.max_count or 125
 	if biome.check_air ~= false then biome.check_air = true end
 
 -- specific to abm spawner
@@ -331,6 +329,7 @@ local function populate_single_surface(biome, pos, perlin_fertile_area, checkair
 end
 
 function biome_lib:populate_surfaces(biome, nodes_or_function_or_model, snodes, checkair)
+	local items_added = 0
 
 	biome_lib:set_defaults(biome)
 
@@ -351,10 +350,10 @@ function biome_lib:populate_surfaces(biome, nodes_or_function_or_model, snodes,
 	local num_in_biome_nodes = #in_biome_nodes
 
 	if num_in_biome_nodes == 0 then
-		return
+		return 0
 	end
 
-	for i = 1, math.min(biome.max_count, num_in_biome_nodes) do
+	for i = 1, math.min(math.ceil(biome.max_count/25), num_in_biome_nodes) do
 		local tries = 0
 		local spawned = false
 		while tries < 2 and not spawned do
@@ -423,13 +422,27 @@ function biome_lib:populate_surfaces(biome, nodes_or_function_or_model, snodes,
 				tries = tries + 1
 			end
 		end
+		if spawned then items_added = items_added + 1 end
 	end
+	return items_added
+end
+
+-- make sure the target block and all 6 neighbors are actually loaded.
+
+local function confirm_block_surroundings(pos)
+	return minetest.get_node_or_nil(pos)
+	  and minetest.get_node_or_nil({ x=pos.x-16, y=pos.y,   z=pos.z   })
+	  and minetest.get_node_or_nil({ x=pos.x+16, y=pos.y,   z=pos.z   })
+	  and minetest.get_node_or_nil({ x=pos.x,   y=pos.y-16, z=pos.z   })
+	  and minetest.get_node_or_nil({ x=pos.x,   y=pos.y+16, z=pos.z   })
+	  and minetest.get_node_or_nil({ x=pos.x,   y=pos.y,   z=pos.z-16 })
+	  and minetest.get_node_or_nil({ x=pos.x,   y=pos.y,   z=pos.z+16 })
 end
 
 -- Primary mapgen spawner, for mods that can work with air checking enabled on
 -- a surface during the initial map read stage.
 
-function biome_lib:generate_block_with_air_checking()
+function biome_lib:generate_block_with_air_checking(shutdown)
 	if not biome_lib.blocklist_aircheck[1] then
 		return
 	end
@@ -446,14 +459,24 @@ function biome_lib:generate_block_with_air_checking()
 		biome_lib.surface_nodes_aircheck.blockhash =
 			minetest.find_nodes_in_area_under_air(minp, maxp, biome_lib.surfaceslist_aircheck)
 		biome_lib.actioncount_aircheck.blockhash = 1
-
+		if #biome_lib.surface_nodes_aircheck.blockhash > 0 then
+			biome_lib:dbg("Mapblock at "..minetest.pos_to_string(minp).." added, with "..#biome_lib.surface_nodes_aircheck.blockhash.." surface nodes detected.")
+		end
+	elseif not shutdown and not confirm_block_surroundings(minp) and #biome_lib.blocklist_aircheck > 1 then
+		biome_lib.blocklist_aircheck[#biome_lib.blocklist_aircheck+1] = biome_lib.blocklist_aircheck[1]
+		table.remove(biome_lib.blocklist_aircheck, 1)
+		biome_lib:dbg("Mapblock at "..minetest.pos_to_string(minp).." had an unloaded neighbor, moved it to the end of the queue.")
 	else
 		if biome_lib.actionslist_aircheck[biome_lib.actioncount_aircheck.blockhash] then
 			-- [1] is biome, [2] is node/function/model
-			biome_lib:populate_surfaces(
+			local added = biome_lib:populate_surfaces(
 				biome_lib.actionslist_aircheck[biome_lib.actioncount_aircheck.blockhash][1],
 				biome_lib.actionslist_aircheck[biome_lib.actioncount_aircheck.blockhash][2],
 				biome_lib.surface_nodes_aircheck.blockhash, true)
+			if added > 0 then
+				biome_lib:dbg("Ran biome_lib:populate_surfaces for block at "..minetest.pos_to_string(minp)..
+					".  Entry #"..biome_lib.actioncount_aircheck.blockhash.." added "..added.." items.")
+			end
 			biome_lib.actioncount_aircheck.blockhash = biome_lib.actioncount_aircheck.blockhash + 1
 		else
 			table.remove(biome_lib.blocklist_aircheck, 1)
@@ -466,7 +489,7 @@ end
 -- Secondary mapgen spawner, for mods that require disabling of
 -- checking for air during the initial map read stage.
 
-function biome_lib:generate_block_no_aircheck()
+function biome_lib:generate_block_no_aircheck(shutdown)
 	if not biome_lib.blocklist_no_aircheck[1] then
 		return
 	end
@@ -480,7 +503,9 @@ function biome_lib:generate_block_no_aircheck()
 		biome_lib.surface_nodes_no_aircheck.blockhash =
 			minetest.find_nodes_in_area(minp, maxp, biome_lib.surfaceslist_no_aircheck)
 		biome_lib.actioncount_no_aircheck.blockhash = 1
-
+	elseif not shutdown and not confirm_block_surroundings(minp) and #biome_lib.blocklist_no_aircheck > 1 then
+		biome_lib.blocklist_no_aircheck[#biome_lib.blocklist_no_aircheck+1] = biome_lib.blocklist_no_aircheck[1]
+		table.remove(biome_lib.blocklist_no_aircheck, 1)
 	else
 		if biome_lib.actionslist_no_aircheck[biome_lib.actioncount_no_aircheck.blockhash] then
 			biome_lib:populate_surfaces(
@@ -511,10 +536,10 @@ minetest.register_globalstep(function(dtime)
 	while (#biome_lib.blocklist_aircheck > 0 or #biome_lib.blocklist_no_aircheck > 0)
 	  and biome_lib.globalstep_runtime < 200000 do  -- 0.2 seconds, in uS.
 		if #biome_lib.blocklist_aircheck > 0 then
-			biome_lib:generate_block_with_air_checking()
+			biome_lib:generate_block_with_air_checking(false)
 		end
 		if #biome_lib.blocklist_no_aircheck > 0 then
-			biome_lib:generate_block_no_aircheck()
+			biome_lib:generate_block_no_aircheck(false)
 		end
 		biome_lib.globalstep_runtime = minetest.get_us_time() - biome_lib.globalstep_start_time
 	end
@@ -531,7 +556,7 @@ minetest.register_on_shutdown(function()
 	print("[biome_lib] Stand by, playing out the rest of the aircheck mapblock log")
 	print("(there are "..#biome_lib.blocklist_aircheck.." entries)...")
 	while #biome_lib.blocklist_aircheck > 0 do
-		biome_lib:generate_block_with_air_checking(0.1)
+		biome_lib:generate_block_with_air_checking(true)
 	end
 end)
 
@@ -543,7 +568,7 @@ minetest.register_on_shutdown(function()
 	print("[biome_lib] Stand by, playing out the rest of the no-aircheck mapblock log")
 	print("(there are "..#biome_lib.blocklist_no_aircheck.." entries)...")
 	while #biome_lib.blocklist_no_aircheck > 0 do
-		biome_lib:generate_block_no_aircheck(0.1)
+		biome_lib:generate_block_no_aircheck(true)
 	end
 end)