Module:No globals

Warning

This Lua module is used on approximately 17,800,000 pages, or roughly 202365% of all pages.
To avoid major disruption and server load, any changes should be tested in the module's /sandbox or /testcases subpages, or in your own module sandbox. The tested changes can be added to this page in a single edit. Consider discussing changes on the talk page before changing this template.

Ready for use

This module is rated as ready for general use. It has reached a mature form and is thought to be relatively bug-free and ready for use wherever appropriate. It is ready to mention on help pages and other Wikipedia resources as an option for new users to learn. To reduce server load and bad output, it should be improved by sandbox testing rather than repeated trial-and-error editing.

Protected

This module is subject to page protection. It is a highly visible module in use by a very large number of pages, or is substituted very frequently. Because vandalism or mistakes would affect many pages, and even trivial editing might cause substantial load on the servers, it is protected from editing.

This module causes an error if any nil global is read or if any global is written to, with the exception of arg. To use, add require('Module:No globals') to the top of the module using it. The arg variable is excluded because it is necessary for Scribunto's require function to work properly. (See the Scribunto source code here.)

local mt = getmetatable(_G) or {}
local oldIndex = mt.__index or function() return nil end
mt.__index = function(t, k)
	if k ~= 'name' and k ~= 'arg' then
		error('Tried to read nil global ' .. tostring(k), 2)
	end
	return oldIndex(t, k)
end
local oldNewindex = mt.__newindex or rawset
function mt.__newindex(t, k, v)
	if k ~= 'name' and k ~= 'arg' then
		error('Tried to write global ' .. tostring(k), 2)
	end
	oldNewindex(t, k, v)
end
setmetatable(_G, mt)

Module:No globals

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