Module:Protect

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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[change source]

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

Arguments[change source]

  • 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[change source]

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[change source]

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


local function processResult(options, success, ...)
	if not success then
		local message = tostring(... or '(no message)')
		if options.removeLocation then
			message = string.gsub(message, '^Module:[^:]+:%d+: ', '', 1)
		end
		return string.format(options.errFormat, message)
	end
	return ...
end

local function protect(func, errFormat, options)
	if type(errFormat) == 'table' then
		options = options or errFormat
		errFormat = nil
	end
	options = mw.clone(options) or {}
	options.errFormat = errFormat or options.errFormat or 'Error: %s'
	if not options.raw then
		options.errFormat = '<strong class="error">' .. options.errFormat .. '</strong>'
	end
	options.removeLocation = options.removeLocation == nil or options.removeLocation
	
	return function (...)
		return processResult(options, pcall(func, ...))
	end
end

return protect