This page is a guide to developing extensions for MediaWiki. Before you start, browse the complete list in: Category:Extensions by category to see if an extension already exists for your use case.
Extension development consists of these parts:
SetupTo 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.
StructureA minimal extension has the following structure:
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.)
.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.
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.
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 $wgBoilerPlateEnableFoo does not exist. If you set the variable, e.g. in LocalSettings.php then the default value given in extension.json will not be used.
For more details on how to use global variable inside custom extensions, please refer to Configuration for developers .
Preparing classes for autoloadingIf you choose to use classes to implement your extension, MediaWiki provides a simplified mechanism for helping PHP find the source file where your class is located. In most cases this should eliminate the need to write your own __autoload($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 dependenciesAssume 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 pointsMediaWiki 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 .
Generalaction 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.{{...}}) or tags (<example />). These customizations are used to generate content and to interact with MediaWiki during page rendering.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.
Warning: 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 extensionsAttributes 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 .
LocalisationWhile 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.
PublishingTo autocategorize and standardize the documentation of your existing extension, please see Template:Extension . To add your new extension to this Wiki:
A developer sharing their code in the MediaWiki code repository should expect:
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 registeringIf 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 Database field prefixes .
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 documentationYou 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.
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 and 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.There are two widespread conventions for supporting older versions of MediaWiki core:
Extension maintainers should declare with the compatibility policy parameter of the {{Extension }} template which convention they follow.
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 alsoRetroSearch is an open source project built by @garambo | Open a GitHub Issue
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