User:Gechy/lua-scripting

Overview

Lua is a programming language implemented on Wikipedia with some substantial restrictions via Scribunto. Its purpose is to allow you to process the data which is available on Wikipedia content pages to allow various sorts of customized display of information. Lua is supported as a scripting language in all Wikimedia Foundation sites (since March 2013), via the Scribunto extension. for example. See also [tutorial].

The Scribunto (Latin: "they shall write/let them write (in the future)") extension allows for embedding scripting languages in MediaWiki.

Currently the only supported scripting language is Lua.

Why Lua Scripting

Templates and ParserFunctions were introduced to allow end-users of MediaWiki to replicate content easily and build tools using basic logic, effectively turning wikitext into a limited programming language.

This project aims to make it possible for MediaWiki end-users to use a proper scripting language that will be more powerful and efficient than ad-hoc ParserFunctions-based logic.

Initially MediaWiki templates were pieces of wikitext that were substituted into pages instead of copy-pasting. By 2005, any other use was rare and, to some extent, controversial. In 2006, ParserFunctions were enabled, allowing users to use constructions such as {{#if}} and {{#switch}}, essentially turning wikitext into a purely functional programming language (i.e., a language that has no concept of state at any level and one part of the code may not affect any other part, it can only change its own output). This eventually caused several problems, including performance (some pages are overloaded with templates and require 40 seconds or more to parse/render) and readability (just take a look at this).

However, complex templates have caused performance issues and bottlenecks.

Installation and configuration

Scribunto comes bundled with Lua binary distributions for Linux (x86 and x86-64), Mac OS X Lion, and Windows (32- and 64-bit). For detailed explanation see mw:Extension:Scribunto.

Check out the Lua.org demo if you don't want to download Scribunto just yet.

Deep dive on Lua(Scribunto) Scripting

Setting up

The software used by Wikipedia, called MediaWiki, has an extension that provides a version of Lua that can be used within Wikipedia pages. The extension is called Scribunto.

On a MediaWiki wiki with Scribunto enabled, create a page with a title starting with "Module:", for example "Module:Bananas". Into this new page, copy the following text:

local p = {} -- p stands for package</translate>

function p.hello( frame )
    return "Hello, world!"
end

return p

Save that, then on another(non-module) page, type:

{{#invoke:Bananas|hello}}  -- Replace "Bananas" with the name of your module.

The "hello" function is exported from the module, and the result of the function is returned.

It's generally a good idea to invoke Lua code from the context of a template. This means that from the perspective of a calling page, the syntax is independent of whether the template logic is implemented in Lua or in wikitext.

For practical example on setting-up see Setting up really fast