API:Extensions

From MediaWiki.org
Jump to: navigation, search

Other languages:
Deutsch • ‎English • ‎日本語
Language:Project:Language policy English  • Deutsch • 日本語
Gnome-preferences-other.svg Extensions:Manual:Extensions DevelopmentManual:Developing extensions Tag extensionsManual:Tag extensions Parser functionsManual:Parser functions HooksManual:Hooks Special pagesManual:Special pages SkinsManual:Skins Magic wordsManual:Magic words APIAPI:Extensions
Tools clipart.png This page is part of the MediaWiki action API documentation.

MediaWiki action API

v · d · e

This document covers creating an API module in an extension for use with MediaWiki 1.30 and later.

Module creation and registration[edit]

All API modules are subclasses of ApiBaseManual:ApiBase.php, but some types of modules use a derived base class. The method of registration also depends on the module type.

action modules 
Modules that provide a value for the main action parameter should subclass ApiBaseManual:ApiBase.php. They should be registered in extension.json using the APIModules key.
format modules 
Modules that provide a value for the main format parameter should subclass ApiFormatBase. They should be registered in extension.json using the APIFormatModules key. It's very uncommon for an extension to need to add a format module.
query submodules 
Modules that provide a value for the prop, list, or meta parameters to action=query should subclass ApiQueryBase (if not usable as a generator) or ApiQueryGeneratorBase (if usable as a generator). They should be registered in extension.json using the APIPropModules, APIListModules, or APIMetaModules key.

In all cases, the value for the registration key is an object with the module name (i.e. the value for the parameter) as the key and the class name as the value. Modules may also be registered conditionally using the ApiMain::moduleManager (for action and format modules) and ApiQuery::moduleManager (for query submodules) hooks.

Implementation[edit]

Prefix[edit]

In the constructor of your API module, when you call parent::__construct() you can specify an optional prefix for your module's parameters. (In the generated documentation for a module this prefix, if any, appears in parentheses in the heading for the module.) If your module is a query submodule then a prefix is required, since a client can invoke multiple submodules each with its own parameters in a single request. For action and format modules, the prefix is optional.

Parameters[edit]

Most modules require parameters. These are defined by implementing getAllowedParams(). The return value is an associative array where keys are the (unprefixed) parameter names and values are either the scalar default value for the parameter or an array defining the properties of the parameter using the PARAM_* constants defined by ApiBase.

The example illustrates the syntax and some of the more common PARAM_* constants.

    protected function getAllowedParams() {
        return [
            // An optional parameter with a default value
            'simple' => 'value',

            // A required parameter
            'required' => [
                ApiBase::PARAM_TYPE => 'string',
                ApiBase::PARAM_REQUIRED => true,
            ],

            // A parameter accepting multiple values from a list
            'variable' => [
                // The default set of values
                ApiBase::PARAM_DFLT => 'foo|bar|baz',
                // All possible values
                ApiBase::PARAM_TYPE => [ 'foo', 'bar', 'baz', 'quux', 'fred', 'blah' ],
                // Indicate that multiple values are accepted
                ApiBase::PARAM_ISMULTI => true,
                // Use standard "per value" documentation messages
                ApiBase::PARAM_HELP_MSG_PER_VALUE => [],
            ],

            // A standard "limit" parameter. It's generally best not to vary from this standard.
            'limit' => [
                ApiBase::PARAM_DFLT => 10,
                ApiBase::PARAM_TYPE => 'limit',
                ApiBase::PARAM_MIN => 1,
                ApiBase::PARAM_MAX => ApiBase::LIMIT_BIG1,
                ApiBase::PARAM_MAX2 => ApiBase::LIMIT_BIG2,
            ],
        ];
    }

Parameters are documented using MediaWiki's i18n mechanism. See #Documentation for details.

Execution and output[edit]

The code actually implementing the module goes in the execute() method. This code will generally use $this->extractRequestParameters() to get the input parameters, and will use $this->getResult() to get the ApiResult object to add any output to.

Query prop submodules should use $this->getPageSet() to access the set of pages to operate on.

Query submodules that can be used as generators will also need to implement {{{method}}} which is passed an ApiPageSet that should be filled with the generated pages. In this case, the ApiResult should generally not be used.

Caching[edit]

By default API responses are marked as not cacheable ('Cache-Control: private')! For action modules, you can allow caching by calling $this->getMain()->setCacheMode(). This still requires clients pass the maxage or smaxage parameters to actually enable caching. You can force caching by also calling $this->getMain()->setCacheMaxAge().

For query modules, do not call those methods. You can allow caching by instead implementing getCacheMode().

In either case, be sure that private data is not exposed.

Token handling[edit]

If your action module changes the wiki in any way, it should require a token of some kind. To have this handled automatically, implement the needsToken() method, returning the token that your module requires (probably the 'csrf' edit token). The API base code will then automatically validate the token that clients provide in API requests in a token parameter.

Master database access[edit]

If your module accesses the master database, it should implement the isWriteMode() method to return true.

Returning errors[edit]

ApiBase includes several methods for performing various checks, for example,

But you will often run into cases where you need to raise an error of your own. The usual way to do that is to call $this->dieWithError(), although if you have a StatusValue with the error information you could pass it to $this->dieStatus() instead.

If you need to issue a warning rather than an error, use $this->addWarning(), or $this->addDeprecation() if it's a deprecation warning.

Documentation[edit]

The API is documented using MediaWiki's i18n mechanism. Needed messages generally have default names based on the modules "path". For action and format modules, the path is the same as the module's name used during registration. For query submodules, it's the name prefixed with "query+".

Every module will need a apihelp-$path-summary message, which should be a one-line description of the module. If additional help text is needed, apihelp-$path-extended-description may be created as well. Each parameter will need a apihelp-$path-param-$name message, and parameters using PARAM_HELP_MSG_PER_VALUE will also need a apihelp-$path-paramvalue-$name-$value for each value.

More details on API documentation are available at API:LocalisationAPI:Localisation.

Extending core modules[edit]

Since MediaWiki 1.14, it's possible to extend core modules' functionality using the following hooks:

List of extensions with API functionality[edit]

See API extensions for examples of extensions that add to or extend the API.

Testing your extension[edit]

  • Visit api.php and navigate to the generated help for your module or query submodule. Your extension's help information should be correct.
    • The example URLs you provided in getExamplesMessages() should appear under "Examples", try clicking them.
    • Omit and mangle URL parameters in the query string, check your extension's response.
  • Install Extension:ApiSandboxExtension:ApiSandbox and interactively explore your API.
  • Visit to see additional information about your extension.