Module:Protect: Difference between revisions

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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

 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:

The above documentation is transcluded from Module:Protect/doc. (edit | history)
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Subpages of this module.

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)
	errFormat = errFormat or 'Error: %s'
	if not raw then
		errFormat = '<strong class="error">' .. errFormat .. '</strong>'
	end
	
	return function (...)
		return processResult(errFormat, pcall(func, ...))
	end
end

return protect