Module:Protect - Wikipedia

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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.

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 Lua module is used in system messages, and on approximately 118,000 pages.
Changes to it can cause immediate changes to the Wikipedia user interface.
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. Please discuss changes on the talk page before implementing them.

This metamodule simplifies error handling in other modules. It transforms a function, which may throw an error, into a function, which returns a specified error message in that case.

Usage

 local protect = require('Module:Protect')
 local protectedFunc = protect(func, errFormat, options)

Arguments

func
Function to be transformed.
errFormat (default: 'Error: %s')
Custom error message.

Use '%s' to include the message from a caught error.
options – optional table with the following fields:
- raw (default: false)
  If true, then errFormat will be used as is, otherwise it will be wrapped inside a tag <strong class="error">.
- removeLocation (default: true)
  If true, removes location information from caught error messages.

Return value

The resulting protectedFunc is a function, which calls the original function func, passing all arguments to it, and returns all its return values. If func throws an error, the specified error message is returned instead.

Example

local protect = require('Module:Protect')

local p = {}

function p.main(frame)
    if not frame.args[1] then
        error('missing argument')
    end
    return frame.args[1]
end

p.main = protect(p.main)

return p

Invoking the main function without arguments will output: Error: missing argument

The above documentation is transcluded from Module:Protect/doc. (edit | history)
Editors can experiment in this module's sandbox (create | mirror) and testcases (edit | run) pages.
Subpages of this module.

local function wrapMessage(errMessage)
	return '<span class="error">' .. errMessage .. '</span>'
end

local defaultFormat = wrapMessage('Error: %s')

local function processResult(errFormat, success, ...)
	if not success then
		return string.format(errFormat, tostring(... or '(no message)'))
	end
	return ...
end

local function protect(func, errFormat, raw)
	if not errFormat then
		errFormat = defaultFormat
	elseif not raw then
		errFormat = wrapMessage(errFormat)
	end
	
	return function (...)
		return processResult(errFormat, pcall(func, ...))
	end
end

return protect