Module:Protect

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

<syntaxhighlight lang="lua">

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

</syntaxhighlight>

Arguments

• <syntaxhighlight lang="text" class="" style="" inline="1">func</syntaxhighlight>

  Function to be transformed.

• <syntaxhighlight lang="text" class="" style="" inline="1">errFormat</syntaxhighlight> (default: <syntaxhighlight lang="text" class="" style="" inline="1">'Error: %s'</syntaxhighlight>)

  Custom error message.

  Use <syntaxhighlight lang="text" class="" style="" inline="1">'%s'</syntaxhighlight> to include the message from a caught error.

• <syntaxhighlight lang="text" class="" style="" inline="1">options</syntaxhighlight> – optional table with the following fields:
  • <syntaxhighlight lang="text" class="" style="" inline="1">raw</syntaxhighlight> (default: false)

    If true, then <syntaxhighlight lang="text" class="" style="" inline="1">errFormat</syntaxhighlight> will be used as is, otherwise it will be wrapped inside a tag <strong class="error">.

  • <syntaxhighlight lang="text" class="" style="" inline="1">removeLocation</syntaxhighlight> (default: true)

    If true, removes location information from caught error messages.

Return value

The resulting <syntaxhighlight lang="text" class="" style="" inline="1">protectedFunc</syntaxhighlight> is a function, which calls the original function <syntaxhighlight lang="text" class="" style="" inline="1">func</syntaxhighlight>, passing all arguments to it, and returns all its return values. If <syntaxhighlight lang="text" class="" style="" inline="1">func</syntaxhighlight> throws an error, the specified error message is returned instead.

Example

<syntaxhighlight lang="lua"> 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 </syntaxhighlight> Invoking the main function without arguments will output:

---

Script error: Lua error: Internal error: The interpreter exited with status 127.

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