Wikipedia:Lua

WP:Lua (talk) Help To do Resources Reference manual

• Project subpages (mw:Lua – index at www.mediawiki.org)

This is an information page. It is not one of Wikipedia's policies or guidelines, but rather intends to describe some aspect(s) of Wikipedia's norms, customs, technicalities, or practices. It may reflect varying levels of consensus and vetting.

Lua is a programming language that is available via the Scribunto MediaWiki extension on the English Wikipedia. Since February 2013, Lua code can be embedded into wiki templates by employing the "{{#invoke:}}" functionality of Scribunto. This extension supports Lua 5.1 as of October 2022^[update].

The Lua source code is stored in pages called modules (e.g., Module:Example). These individual modules are then invoked (by code {{#invoke:<Module name>|<Function name>|(optional) param1 | param2...}}). Example:

Modules are run on normal wiki pages using the #invoke parser function. The syntax of #invoke is similar to template syntax, but with some differences. The most important difference is that you need to specify a function name. A function is a set of instructions that takes input values, processes them, and returns an output value.^[1] This is much like what a template does: you give it arguments, it processes them, and you get a result. However, you can define many functions in one Lua module, whereas you can only define one template on one page.

Furthermore, you can't just run a Lua module directly – you can only run one of the module's functions. The module is just a container for the functions, and doesn't do anything by itself. So there are two reasons that we need to input a function name: we can't run a module by itself, and without specifying a function name, Lua will not know which function it is we want to run.

The simplest way to run a module from a wiki page is like this:

{{#invoke:module name|function name}}

For example, we can run Module:Example in this way, which has a function named "hello".

• {{#invoke:Example|hello}} → Script error: No such module "Example".

{{#invoke:module name|function name|first positional argument|second positional argument|named argument = value}}

Visit Wikipedia talk:Lua to request help in writing a Lua script to perform a specific task on Wikipedia or another Wikimedia Foundation project.

Sordid history. {{qif}}, ParserFunctions, Lua extension, wiki scripting language debated (JavaScript v. Lua), mw:Extension:WikiScripts, Tim writes Scribunto with initial support for Lua.

Discussed for years, Lua was installed in 2012 for testing on test2.wikipedia.org, with open invitation to all editors to experiment with developing Lua modules. Lua was installed on the English Wikipedia in February 2013, after testing on mediawiki.org and Wikimedia test wikis.

See also Brad Jorsch's short presentation for a basic example of how to convert a wikitext template into a Lua module.

Lua is a scripting language which can be used to analyze data, calculate expressions, and format results using functions or object-oriented programming. Although some Lua scripts can be kept simple, for easy understanding, Lua allows complex structures including tables, dynamic functions, and associative arrays where index subscripts can be words as well as index numbers. Lua also supports recursion of re-nested functions, so care should be taken to avoid excessive complexity where other users would not understand how to maintain a Lua module. The following is the source code of the module used for the examples above.

A sample of Lua is highlighted by tag "<syntaxhighlight lang="lua">...</syntaxhighlight>" placed around the Lua source code. To view some more complex examples of Lua, see article: "Lua (programming language)".

For instructions on how to use Lua within MediaWiki (and hence Wikipedia), see mw:Extension:Scribunto/Lua reference manual.

A few unit testing frameworks are available for Lua scripts on Wikipedia. These allow an editor to execute the module with a given set of inputs and verify that the expected outputs are produced. They are useful for rapidly detecting software regressions, where modifications to a script introduce new (or identify old) problems.

By convention, unit tests for a module like Module:Example are placed in Module:Example/testcases, and are executed on Module talk:Example/testcases.

Module:ScribuntoUnit and Module:UnitTests are widely used test frameworks. Category:Modules for test tools has a few other to review which may be interesting.

Overall: Lua can only get input as text strings passed to the {{#invoke:}} and what can be fetched via mw.title.new(...):getContent() and frame:expandTemplate(). Lua output will not be preprocessed unless frame:preprocess() is explicitly called, meaning that template calls, parser functions, etc. in the output will not work correctly. Also, all Lua in the page is limited to 10 seconds CPU time (you can look in the source code of a rendered page to see how long a template or module took to parse). And relative to standard Lua, Scribunto's Lua lacks all sorts of functions (see mw:Extension:Scribunto/Lua reference manual § Differences from standard Lua).

This template uses Lua: Module:Example

Please place the {{lua}} template on the documentation subpage of all templates that use Lua. It will help to better communicate Lua usage and template conversions.

• Special:PrefixIndex/Module: – tracking of Lua modules can be done by using Special:PrefixIndex
• Help:Lua debugging – a how-to guide about debugging Lua modules
• Module:Sandbox provides a pseudo-namespace for experimenting with Lua modules
• WP:Lua requests – requests for Lua-based templates or tasks
• Category:Lua-based templates – groups of Lua-based templates
• Category:Lua metamodules
• Manual:Coding conventions/Lua – standards to improve the readability of code through consistency
• mw:Extension:Scribunto/Lua reference manual and all Modules.
• Wikipedia:Advanced template coding