Initial pseudocode

worldedit_protection/init.lua

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+--I am assuming it's creative mode. What should I do in survival?
+
+--if there's no protection mod, no worldedit means no editing, worldedit means editing anywhere (old behaviour)
+--if there's a protection mod, no worldedit means editing only in your area, worldedit means editing in no-man's land too, areas means editing anywhere.
+
+--let the other mod load first
+minetest.after(0, function()
+	--I would use mod.soft_depend from commonlib, but there are multiple mods that could create owned land
+	PROTECTION_MOD_EXISTS = minetest.is_protected == old_is_protected
+	--else fall back to old behaviour, where
+	--worldedit privilege is permission to edit everything
+end)
+
+--this is privs= within chatcommands that actually change land
+--(should be the same functions as safe_region)
+function worldedit.get_privs()
+	if not PROTECTION_MOD_EXISTS then
+		--no protection mod, worldedit means editing anywhere
+		return {worldedit=true}
+	end
+	--protection mod, can edit inside your area without worldedit privilege
+	--(worldedit and areas let you edit in no-man's land and other-owned area)
+	return {worldedit=false} -- this array could also be empty
+end
+
+function worldedit.can_edit_volume(name)
+	--old you-can-worldedit-everything behaviour
+	if not PROTECTION_MOD_EXISTS then
+		--then if you were able to run this command, then you have the worldedit privilege.
+		return true
+	end
+	--new ownership-based behaviour
+
+	--You can set areas, so you can worldedit them too.
+	if minetest.check_player_privs(name, {areas=true}) then
+		return true
+	end
+
+	--all-or-nothing here
+	local pos1, pos2 = worldedit.pos1[name], worldedit.pos2[name]
+	--pos1, pos2 = worldedit.sort_pos(pos1, pos2) --does this matter?
+	for i in area:iterp(pos1, pos2) do
+
+		--THIS SECTION IGNORES the distinction of area that is owned by someone else, but still editable
+		--this is treated as area owned by the editor, or no-man's land depending on if it's shared with one person or everyone
+		--
+		--If it was treated differently (it's not), then single edits would not be able to cross the border between someone else's editable land, and no-man's land, to prevent accidental writes. It may cross the border between multiple people's editable land (or should it?), such as to create a bridge between two skyscrapers that were previously built separately.
+		--
+		--This needs testing for the other changes first.
+
+		--Is it owned?
+		if minetest.is_protected(i) then
+			--Is it someone else's?
+			if minetest.is_protected(i, name) then
+				--already checked the ability to make it mine (areas)
+				minetest.chat_send_player(name, "Someone else owns at least part of what you want to edit")
+				return false
+			end
+			--it's mine
+			--continue
+
+		--no-man's land
+		--can I edit that?
+		elseif not minetest.check_player_privs(name, {worldedit=true}) then --cache this check?
+			minetest.chat_send_player(name, "You can only edit area in which you own a plot (missing worldedit privilege)")
+			return false
+		end
+	end
+
+	--the whole thing is
+	--a) owned by me,
+	--b) owned by no one and I have the worldedit privilege, and/or
+	--c) owned by someone else and I have the areas privilege.
+	return true
+end