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MediaWikin laajennukset

This page is a guide to developing extensions for MediaWiki. Before you start, browse the list of extensions to see if an extension already exists for your use case.

Extension development consists of these parts:

  1. Setup
  2. Implementation
  3. Lokalisointi
  4. Publication

Asennus

To set up a new extension, start by setting up a local development environment for MediaWiki , and follow the instructions to install and copy the BoilerPlate extension.

While developing, you may want to disable caching by setting $wgMainCacheType = CACHE_NONE and $wgCacheDirectory = false, otherwise system messages and other changes may not show up.

Structure

A minimal extension has the following structure:

MyExtension/extension.json
Stores the setup instructions. The file name must be extension.json. (Prior to MediaWiki 1.25 the setup instructions were in a MyExtension/MyExtension.php file named after the extension. Many extensions still have backwards-compatibility shims in this PHP file.)
MyExtension/includes/ (or MyExtension/src/)
Stores the PHP execution code for the extension.
MyExtension/resources/ (or MyExtension/modules/)
Stores the client-side resources such as JavaScript, CSS and LESS for the extension.
MyExtension/i18n/*.json
Stores localisation information for the extension.
MyExtension/README.md
Good practice is to add a README file with basic info about how to install and configure the extension. Use either plain text or Markdown. For a plain text example, see the Phabricator Diffusion page for the Extension:Page Forms . If markdown is used, add the file extension .md. For example, see the README.md file for Parsoid on Phabricator Diffusion.

When you develop an extension, replace MyExtension above with the name of your extension. Use UpperCamelCase names for its directory and PHP files; this is the general file naming convention.[1]

Registration

MediaWiki version:
≥ 1.25

The extension.json file contains the configuration data for the extension. Here is an example of a minimal extension.json: 

{
	"name": "MyExtension",
	"author": "John Doe",
	"url": "https://www.mediawiki.org/wiki/Extension:MyExtension",
	"description": "This extension is an example.",
	"version": "1.5",
	"license-name": "GPL-2.0-or-later",
	"type": "validextensiontype",
	"manifest_version": 2
}

Many of the fields are optional, but it's still good practice to fill them out. For a more complete example of extension.json, see the BoilerPlate extension.

The manifest_version refers to the version of the schema the extension.json file is written against. See the documentation on this feature. Unless you need to support an older version of MediaWiki, pick the latest version.

Once you have an extension.json file set up for your extension, the extension will appear on your local Special:Version page.

License


MediaWiki is an open-source project and users are encouraged to make any MediaWiki extensions under an Open Source Initiative (OSI) approved license compatible with GPL-2.0-or-later (Wikimedia's standard software license).

We recommend adopting one of the following compatible licenses for your projects in Gerrit:

For extensions that have a compatible license, you can request developer access to the MediaWiki source repositories for extensions. To specify the licence in code and with "license-name" a key should be used to provide its short name, e.g. "GPL-2.0-or-later" or "MIT" adhering to the list of identifiers at spdx.org.

Making your extension user configurable

Ideally, users should be able to install your extension by adding only one line to LocalSettings.php: 

wfLoadExtension( 'MyExtension' );

If you want to make your extension user configurable, you need to define and document some configuration parameters and your users' setup should look something like this: 

wfLoadExtension( 'MyExtension' );
$wgMyExtensionConfigThis = 1;
$wgMyExtensionConfigThat = false;

If you want your user to be able to configure your extension, you'll need to provide one or more configuration variables. It is a good idea to give those variables a unique name. They should also follow MediaWiki naming conventions (e.g. global variables should begin with $wg).

For example, if your extension is named MyExtension, you might want to name all your configuration variables to begin with $wgMyExtension. It is important that none of the MediaWiki core begins its variables this way and you have done a reasonable job of checking to see that none of the published extensions begin their variables this way. Users won't take kindly to having to choose between your extension and some other extensions because you chose overlapping variable names.

It is also a good idea to include extensive documentation of any configuration variables in your installation notes.

Here is an example of how to set up a configuration variable in extension.json: 

{
	"config": {
		"BoilerPlateEnableFoo": {
			"value": true,
			"description": "Enables the foo functionality"
		}
	}
}

Note that after calling wfLoadExtension( 'BoilerPlate' ); the global variable $wgBoilerPlateEnableFoo does not exist. If you set the variable, e.g. in LocalSettings.php then the default value given in extension.json will not be used.

For more details on how to use global variable inside custom extensions, please refer to Configuration for developers .

Preparing classes for autoloading

If you choose to use classes to implement your extension, MediaWiki provides a simplified mechanism for helping PHP find the source file where your class is located. In most cases this should eliminate the need to write your own __autoload($classname) method.

To use MediaWiki's autoloading mechanism, you add entries to the AutoloadClasses field. The key of each entry is the class name; the value is the file that stores the definition of the class. For a simple one class extension, the class is usually given the same name as the extension, so your autoloading section might look like this (extension is named MyExtension): 

{
	"AutoloadClasses": {
		"MyExtension": "includes/MyExtension.php"
	}
}

The filename is relative to the directory the extension.json file is in.

For more complex extensions, namespaces should be considered. See Manual:Extension.json/Schema#AutoloadNamespaces for details.

Handling dependencies

Assume that an extension requires the presence of another extension, for example because functionalities or database tables are to be used and error messages are to be avoided in case of non-existence.

For example the extension CountingMarker requires the presence of the extension HitCounters for certain functions.

One way to specify this would be by using the requires key in extension.json .

Another option is using ExtensionRegistry (available since MW 1.25): 

	if ( ExtensionRegistry::getInstance()->isLoaded( 'HitCounters', '>=1.1' ) {
		/* do some extra stuff, if extension HitCounters is present in version 1.1 and above */
	}

Currently (as of February 2024, MediaWiki 1.41.0) the name of the extension-to-be-checked needs to exactly match the name in their extension.json.[2][3]

Example: if you want to check the load status of extension OpenIDConnect, you have to use it with a space 

	if ( ExtensionRegistry::getInstance()->isLoaded( 'OpenID Connect' ) {
    ...
	}

Implementation

For an overview of code architecture, structure, and conventions for extensions, see Best practices for extensions .

Extension points

MediaWiki core provides several ways for extensions to change the behavior, functionality, and appearance of a wiki. Most extensions use more than one of these extension points. For a complete list of extension points supported in extension.json, see the schema reference .

General

  • Hooks : Inject custom code at key points in MediaWiki core code, such as when a user logs in or saves a page. Extensions can also define new hooks.
  • API modules : Define API modules based on the Action API or REST API . These modules can be called by bots or clients.
  • Jobs : Add jobs to MediaWiki's JobQueue to perform process-intensive tasks asynchronously, such as sending notification emails.

Pages

  • Display a special page : Special pages provide dynamically generated content, often based on system state, database queries, and user inputs.
  • Perform a page action : The action URL parameter generates a custom page based on the current page, usually to provide information (such as page history) or to perform an action (such as edit the page). In addition to the default actions provided by MediaWiki core, extensions can define a new page action.
  • Add a tracking category : Help users find pages with similar characteristics by automatically adding pages to custom categories.

Content

  • Extend wiki markup : Extensions can add custom functionality to MediaWiki's wikitext markup using template syntax ({{...}}) or tags (‎<example />). These customizations are used to generate content and to interact with MediaWiki during page rendering.
  • Support a content model : By default, wiki pages can be stored using a few standard content models, such as wikitext and JSON. Extensions can provide support for new content models by adding a content handler.
  • Support a media type : Extensions can add to the default set of supported media file types by adding a media handler.

Moderation tools

  • Log a user or system action : On wiki, actions are tracked for transparency and collaboration. To support this feature, extensions can add custom entries and functionality to Special:Log.
  • Add a recent-changes flag : Extensions can add custom flags to the following special pages to help moderators track page changes: Special:RecentChanges, Special:Watchlist, Special:RecentChangesLinked
  • Add a revision tag : Extensions can add annotations associated with a revision or log entry, such as for edits made using the VisualEditor extension.

Authentication

  • Add a provider : Extensions can add support for new login mechanisms and session management methods.

Adding database tables

Make sure the extension doesn't modify the core database tables. Instead, extension should create new tables with foreign keys to the relevant MW tables.

  Varoitus: If your extension is used on any production WMF-hosted wiki please follow the Schema change guide.

If your extension needs to add its own database tables, use the LoadExtensionSchemaUpdates hook. See the manual page for more information on usage.

Registering attributes for other extensions

Attributes allow extensions to register something, such as a module, with another extension. For example, extensions can use attributes to register a plugin module with the VisualEditor extension. For more information, see Extension registration .

Lokalisointi

While developing, you may want to disable both cache by setting $wgMainCacheType = CACHE_NONE and $wgCacheDirectory = false, otherwise your system message changes may not show up.

If you want your extension to be used on wikis that have a multi-lingual readership, you will need to add localisation support to your extension.

Store messages in <language-key>.json

Store message definitions in a localisation JSON file, one for each language key your extension is translated in. The messages are saved with a message key and the message itself using standard JSON format. Each message id should be lowercase and may not contain spaces. Each key should begin with the lowercased extension name. An example you can find in the MobileFrontend extension. Here is an example of a minimal JSON file (in this case en.json):

en.json 

{
	"myextension-desc": "Adds the MyExtension great functionality.",
	"myextension-action-message": "This is a test message"
}

Store message documentation in qqq.json

The documentation for message keys can be stored in the JSON file for the pseudo language with code qqq. A documentation of the example above can be:

qqq.json: 

{
	"myextension-desc": "The description of MyExtension used in Extension credits.",
	"myextension-action-message": "Adds 'message' after 'action' triggered by user."
}

Load the localisation file

In your extension.json, define the location of your messages files (e.g. in directory i18n/): 

{
	"MessagesDirs": {
		"MyExtension": [
			"i18n"
		]
	}
}

Use wfMessage in PHP

In your setup and implementation code, replace each literal use of the message with a call to wfMessage( $msgID, $param1, $param2, ... ). In classes that implement IContextSource (as well as some others such as subclasses of SpecialPage), you can use $this->msg( $msgID, $param1, $param2, ... ) instead. Example: 

wfMessage( 'myextension-addition', '1', '2', '3' )->parse()

Use mw.message in JavaScript

It's possible to use i18n functions in JavaScript too. Look at Manual:Messages API for details.

Publishing

To autocategorize and standardize the documentation of your existing extension, please see Malline:Laajennus . To add your new extension to this Wiki:


A developer sharing their code in the MediaWiki code repository should expect:

Feedback / Criticism / Code reviews
Review and comments by other developers on things like framework use, security, efficiency and usability.
Developer tweaking
Other developers modifying your submission to improve or clean-up your code to meet new framework classes and methods, coding conventions and translations.
Improved access for wiki sysadmins
If you do decide to put your code on the wiki, another developer may decide to move it to the MediaWiki code repository for easier maintenance. You may then create a developer account to continue maintaining it.
Future versions by other developers
New branches of your code being created automatically as new versions of MediaWiki are released. You should backport to these branches if you want to support older versions.
Incorporation of your code into other extensions with duplicate or similar purposes — incorporating the best features from each extension.
Credit
Credit for your work being preserved in future versions — including any merged extensions.
Similarly, you should credit the developers of any extensions whose code you borrow from — especially when performing a merger.

Any developer who is uncomfortable with any of these actions occurring should not host in the code repository. You are still encouraged to create a summary page for your extension on the wiki to let people know about the extension, and where to download it.

Deploying and registering

If you intend to have your extension deployed on Wikimedia sites (including possibly Wikipedia), additional scrutiny is warranted in terms of performance and security. Consult Writing an extension for deployment .

If your extension adds namespaces, you may wish to register its default namespaces; likewise, if it adds database tables or fields, you may want to register those at Tietokantataulujen etuliitteet .

Please be aware that review and deployment of new extensions on Wikimedia sites can be extremely slow, and in some cases has taken more than two years.[4]

Help documentation

You should provide public domain help documentation for features provided by your extension. The convention is for extensions to have their user-focused help pages under a pseudo-namespace of Help:Extension:<ExtensionName>, with whatever subpages are required (the top level page will be automatically linked from the extension infobox if it exists). Help:CirrusSearch is a example of good documentation. You should give users a link to the documentation via the addHelpLink() function.

Releasing updates

There are a number of common approaches to releasing updates to extensions. These are generally defined according to the compatibility policy of the extension (master, rel, or ltsrel):

  • master – Releases may be tagged with version numbers on the master branch, and documentation provided on the extension's homepage describing which extension versions are compatible with which core versions. Release branches will still be created automatically, and you may wish to delete these if they are not intended to be used.
  • rel ja ltsrel – Release by backporting changes to the REL1_* branches (either all changes, or only critical ones). Version numbers are generally not needed unless the extension is a dependency of another (the version number can then be provided in the other extension's configuration to ensure that incompatible combinations aren't installed). Many extensions will stay at the same version number for years.

Support other core versions

There are two widespread conventions for supporting older versions of MediaWiki core:

  • Master: the master branch of the extension is compatible with as many old versions of core as possible. This results in a maintenance burden (backwards-compatibility hacks need to be kept around for a long time, and changes to the extension need to be tested with several versions of MediaWiki), but sites running old MediaWiki versions benefit from functionality recently added to the extension.
  • Release branches: release branches of the extension are compatible with matching branches of core, e.g. sites using MediaWiki 1.43 need to use the REL1_43 branch of the extension. (For extensions hosted on Gerrit, these branches are automatically created when new versions of MediaWiki are released.) This results in cleaner code and faster development but users on old core versions do not benefit from bugfixes and new features unless they are backported manually.

Extension maintainers should declare with the compatibility policy parameter of the {{Laajennus }} template which convention they follow.

Providing support / collaboration

Extension developers should open an account on Wikimedia's Phabricator , and request a new project for the extension. This provides a public venue where users can submit issues and suggestions, and you can collaborate with users and other developers to triage bugs and plan features of your extension.

See also

Learn by example

    • Allows you to get going quickly with your own extension.


References

  1. ↑ mailarchive:wikitech-l/2011-August/054839.html
  2. ↑ https://www.mediawiki.org/wiki/Project%3ASupport%20desk/Flow/2024/02#h-%5BDeveloper_question%5D_ExtensionRegistry%3A%3AgetInstance%28%29-%3EisLoaded%28_%27OpenIDConnect%27-20240204084500
  3. ↑ https://phabricator.wikimedia.org/T356596
  4. ↑ phabricator:T148848
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