Manual:Coding conventions/Lua

This is an essay. It expresses the opinions and ideas of some mediawiki.org users, but may not have wide support. Feel free to update this page as needed, or use the discussion page to propose major changes.

1. Use tabs for indentation. Previously we used 4 spaces, but we have now switched to tabs after the default behaviour of Wikipedia's code editor changed.
2. Try to limit the length of a single line, so people with smaller monitors can read the code easily.
3. Avoid extraneous whitespace when calling a function or subscripting an array or dictionary. No spaces should be used immediately before or inside a bracketing character ([, (, { and their matches).

-- Yes:
hi = {1, 2, 3}
foo(hi[1], blah['a'])

-- No:
hi = { 1, 2, 3 }
foo( hi[ 1 ], blah[ 'a' ] )
blah ['b'] = hi [3]
foo (0, '')

Putting multiple statements on one line is discouraged, unless the expression is very short. Try to avoid this with multi-clause statements, too.

-- Yes:
if 1 then
	foo()
	bar()
else
	baz()
end

if 1 then foo() end

foo(); bar(); baz();

-- No:
if 1 then foo(); bar(); else baz(); end

if 1 then foo(); bar(); baz();
else lorem(); ipsum(); end

foo(); bar(); baz(); spam(); eggs(); lorem(); ipsum(); dolor(); sit(); amet();

If a single line would be too long, you can split a large statement over multiple lines with a hanging indent that aligns with the opening delimiter. For if statements, the conditions should be placed on the next line.

-- Example:

hello = long_function_name(var_one, var_two,
                           var_three, var_four)

if ((condition1
	or condition2)
	and condition3
	and condition4) then
	foo()
	bar()
	baz()
end

Define the entry method as simply unpacking the parameters from the frame, and then passing those through a function with the same name prefixed with a single underscore. This can be disregarded if the function is only useful from wikitext, or if it needs a frame for something other than its arguments.

In the standard library, function names consisting of multiple words are simply put together (e.g. setmetatable). Note that camelCase is the preferred way to name functions, in order to avoid potential garden-path function names.

-- See https://en.wikipedia.org/w/index.php?oldid=540791109 for code

local p = {}

function p._url(url, text)
	-- Code goes here
end

function p.url(frame)
	-- Take parameters out of the frame and pass them to p._url(). Return the result.
	-- Adapt the below code to your specific template arguments
	local templateArgs = frame.args
	local url = templateArgs[1] or ''
	local text = templateArgs[2] or ''
	return p._url(url, text)
end

return p

Outside of a module (like on talkpages), code highlighting can be added using the <syntaxhighlight> tag with the attribute lang="lua":

--code snippet
	function p.main()
		return "Hello world"
	end

Produces:

--code snippet
	function p.main()
		return "Hello world"
	end

• Manual:Coding conventions