Add strict module

Also fix leaking globals found by it.

builtin/common/strict.lua

@@ -0,0 +1,47 @@
+
+-- Always warn when creating a global variable, even outside of a function.
+-- This ignores mod namespaces (variables with the same name as the current mod).
+local WARN_INIT = false
+
+
+local function warn(message)
+	print(os.date("%H:%M:%S: WARNING: ")..message)
+end
+
+
+local meta = {}
+local declared = {}
+
+
+function meta:__newindex(name, value)
+	local info = debug.getinfo(2, "Sl")
+	local desc = ("%s:%d"):format(info.short_src, info.currentline)
+	if not declared[name] then
+		if info.what ~= "main" and info.what ~= "C" then
+			warn(("Assignment to undeclared global %q inside"
+					.." a function at %s.")
+				:format(name, desc))
+		end
+		declared[name] = true
+	end
+	-- Ignore mod namespaces
+	if WARN_INIT and (not core.get_current_modname or
+			name ~= core.get_current_modname()) then
+		warn(("Global variable %q created at %s.")
+			:format(name, desc))
+	end
+	rawset(self, name, value)
+end
+
+
+function meta:__index(name)
+	local info = debug.getinfo(2, "Sl")
+	if not declared[name] and info.what ~= "C" then
+		warn(("Undeclared global variable %q accessed at %s:%s")
+				:format(name, info.short_src, info.currentline))
+	end
+	return rawget(self, name)
+end
+
+setmetatable(_G, meta)
+

builtin/game/auth.lua

@@ -7,7 +7,7 @@
 function core.string_to_privs(str, delim)
 	assert(type(str) == "string")
 	delim = delim or ','
-	privs = {}
+	local privs = {}
 	for _, priv in pairs(string.split(str, delim)) do
 		privs[priv:trim()] = true
 	end
@@ -17,7 +17,7 @@ end
 function core.privs_to_string(privs, delim)
 	assert(type(privs) == "table")
 	delim = delim or ','
-	list = {}
+	local list = {}
 	for priv, bool in pairs(privs) do
 		if bool then
 			table.insert(list, priv)

builtin/game/item_entity.lua

@@ -56,7 +56,7 @@ core.register_entity(":__builtin:item", {
 			item_texture = core.registered_items[itemname].inventory_image
 			item_type = core.registered_items[itemname].type
 		end
-		prop = {
+		local prop = {
 			is_visible = true,
 			visual = "wielditem",
 			textures = {itemname},

builtin/init.lua

@@ -17,6 +17,7 @@ local gamepath = scriptdir.."game"..DIR_DELIM
 local commonpath = scriptdir.."common"..DIR_DELIM
 local asyncpath = scriptdir.."async"..DIR_DELIM
 
+dofile(commonpath.."strict.lua")
 dofile(commonpath.."serialize.lua")
 dofile(commonpath.."misc_helpers.lua")