Help:Scribunto

Help:Scribunto

Scribunto is a powerful scripting engine for MediaWiki that allows you to extend the functionality of templates and modules using the Lua programming language. This page provides a beginner's guide to understanding and utilizing Scribunto, covering its core concepts, setting up your environment, writing basic scripts, and best practices. It is a crucial component for building complex and dynamic wiki features.

What is Scribunto & Why Use It?

Historically, templates in MediaWiki were limited to simple text substitution and conditional logic using parser functions. While useful, these functions often became cumbersome and difficult to maintain for complex tasks. Scribunto addresses these limitations by enabling the use of Lua, a lightweight, embeddable scripting language known for its speed, efficiency, and elegant syntax.

Here’s why you might want to use Scribunto:

Increased Complexity': Lua allows you to perform calculations, manipulate strings, access data structures, and implement complex algorithms within your templates and modules. This is far beyond the capabilities of standard parser functions.
Improved Performance': Lua is significantly faster than parser functions, especially for computationally intensive tasks. This translates to faster page rendering and a better user experience. Consider Help:Performance for more general optimization strategies.
Code Reusability': Scribunto allows you to create reusable modules that can be called from multiple templates, promoting code organization and reducing duplication. This is a key concept in software engineering.
Enhanced Maintainability': Lua code is generally easier to read and maintain than complex nested parser function calls.
Access to External Data': While limited, Scribunto allows interaction with certain MediaWiki APIs for retrieving data.
Support for Advanced Features': Features like string pattern matching (regular expressions), tables (arrays and dictionaries), and functions make complex operations much simpler. Think of Help:Variables to understand basic data handling.

Setting up Your Environment

To start using Scribunto, you need a wiki installation that has the Scribunto extension enabled. Most large wikis, including Wikipedia, already have it enabled. If you’re running your own wiki, you’ll need to install and configure the extension.

1. Check Extension Installation': Navigate to Special:Version. Look for "Scribunto" in the list of enabled extensions. If it's not listed, you need to install it. 2. Installation (if needed)': Download the Scribunto extension from the Scribunto page on MediaWiki.org. Follow the installation instructions provided there, which typically involve uploading the extension files to your wiki's `extensions/` directory and adding `'Scribunto'` to your `LocalSettings.php` file. 3. Lua Version': Scribunto typically uses Lua 5.2. Be aware of any limitations or differences specific to this version. 4. Sandbox': Before making changes to live templates and modules, it’s highly recommended to test your code in a sandbox environment. Use a test wiki or create dedicated test pages on your live wiki. See Help:Sandbox for more information.

Core Concepts

Modules': Scribunto code is organized into *modules*. A module is a dedicated wiki page (namespace `Module:`) that contains Lua code. Modules are the primary building blocks for Scribunto functionality. Modules are similar to Help:Templates in their function of encapsulating reusable code.
Templates': Templates can *call* modules to perform specific tasks. This allows you to separate complex logic from the template's presentation.
Functions': Within a module, you define *functions* that perform specific operations. These functions can be called from templates or other modules.
Parameters': Modules and functions can accept *parameters* (arguments) that allow you to customize their behavior.
Return Values': Functions *return* values, which can be used by the calling template or module.
Frames': Frames are a crucial concept, representing the call stack of templates and modules. They allow you to access arguments passed to templates and modules, as well as the context in which the code is being executed. Understanding frames is essential for writing robust Scribunto code.
Tables': Lua's primary data structure is the *table*. Tables can be used as arrays, dictionaries (associative arrays), or both. They are fundamental to data manipulation in Scribunto.

Writing Your First Module

Let's create a simple module that calculates the square of a number.

1. Create a Module Page': Create a new page named `Module:Square` (or any other descriptive name). 2. Add the Code': Add the following Lua code to the page:

```lua local p = {} -- Create a table to hold our functions

function p.square(x)

 return x * x

end

return p ```

3. Explanation':

   *   `local p = {}`: This creates a local table named `p`.  This table will hold our functions.  `local` limits the scope of the variable to the module.
   *   `function p.square(x)`: This defines a function named `square` within the `p` table.  It takes one argument, `x`.
   *   `return x * x`: This calculates the square of `x` and returns the result.
   *   `return p`: This returns the `p` table, which contains our functions.  This is required for Scribunto to recognize the module's functionality.

Calling the Module from a Template

Now, let's create a template that uses our `Module:Square` module.

1. Create a Template Page': Create a new page named `Template:Square` (or any other descriptive name). 2. Add the Code': Add the following wiki code to the page:

```wiki {{#invoke:Square|square|{{{1}}} }} ```

3. Explanation':

   *   `{{#invoke:Square|square|{{{1}}} }}`: This is the Scribunto invocation syntax.
       *   `#invoke`:  This is the magic word that tells MediaWiki to execute Scribunto code.
       *   `Square`: This is the name of the module we want to call.
       *   `square`: This is the name of the function within the module that we want to execute.
       *   `{{{1}}}`: This is the first parameter passed to the `square` function.  It represents the number we want to square.  This leverages Help:Parameters.

Using the Template

Now you can use the `Template:Square` template on any page by passing a number as a parameter:

```wiki Template:Square ```

This will render as:

``` 25 ```

Advanced Concepts and Techniques

Error Handling': Use `pcall()` to catch errors in your Lua code. This prevents your templates from breaking and provides a more graceful user experience. Consider techniques for Help:Debugging errors.
Data Structures': Master the use of tables for storing and manipulating data. Learn about different table operations, such as inserting, deleting, and iterating over elements.
String Manipulation': Lua provides powerful string manipulation functions. Use them to parse, format, and validate data.
Regular Expressions': Lua's pattern matching capabilities (regular expressions) allow you to perform complex string searches and replacements.
Module Interaction': Modules can call other modules, allowing you to create complex systems of interconnected functionality.
Frames and Arguments': Understand how to use frames to access arguments passed to templates and modules. Learn about the different frame levels and how to navigate them.
Utilizing Existing Modules': Before writing your own module, check if there's an existing module that already provides the functionality you need. Many useful modules are available on Wikipedia and other wikis. This promotes code reuse and consistency. Look at Module:Data as an example.

Best Practices

Code Comments': Add comments to your code to explain its purpose and functionality. This makes it easier for others (and your future self) to understand and maintain your code.
Code Formatting': Use consistent code formatting to improve readability. Lua has conventions for indentation, spacing and naming.
Error Handling': Implement robust error handling to prevent your templates from breaking.
Testing': Thoroughly test your code before deploying it to a live wiki. Use a sandbox environment for testing.
Documentation': Document your modules and functions clearly. Explain how to use them and what parameters they accept.
Performance Optimization': Write efficient code to minimize the impact on page rendering time. Avoid unnecessary calculations and data manipulations. Consider using caching mechanisms if appropriate.
Security Considerations': Be mindful of security vulnerabilities when writing Scribunto code. Avoid executing untrusted user input. Consult the Scribunto documentation for security best practices.

Resources

Scribunto Documentation': Scribunto Documentation
Lua Documentation': Lua Documentation
Wikipedia's Scribunto Modules': Browse the modules on Wikipedia for examples and inspiration: Wikipedia Modules
MediaWiki Help Pages': Refer to other relevant MediaWiki help pages, such as Help:Templates, Help:Variables, and Help:Debugging.

Strategies, Technical Analysis, Indicators and Trends (Links)

Help:Contents

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