Module:No globals

Lua

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Module:No globals is deprecated. Please see mw:Extension:Scribunto/Lua reference manual#strict instead.

Note: This module is used on a lot of pages. In order not to put too much load on the servers, edits should be kept to a bare minimum. Please discuss proposed changes on the talk page first. Editing a module causes all pages that use the module to be re-rendered. If the module is used often, this can put a lot of load on the servers since it fills up the job queue. Keep in mind that displays produced by modules used on file description pages also show up on other wikis. This module has been protected from editing to prevent vandalism. Only administrators can edit it. Get their attention by placing {{Edit protected}} at the talk page.

This module is rated as ready for general use. It has reached a mature form and is thought to be bug-free and ready for use wherever appropriate. To reduce server load and bad output, it should be improved by sandbox testing rather than repeated trial-and-error editing.

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.)

Code

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