Extension for WikibaseQuality to manage constraints in Wikibase.


Build Status Coverage Status Scrutinizer Code Quality

This is a complementary extension for the Wikibase Quality base extension. It performs constraint checks in Wikibase.


If you have already installed a complementary Wikibase Quality extension you can skip the first two steps and just add the repository (second entry in "repositories" and the required version (last entry in "require") to the composer.local.json.

  • Create the file composer.local.json in the directory of your mediawiki installation.

  • Add the following lines:

    "repositories": [
            "type": "git",
            "url": ""
            "type": "git",
            "url": ""
    "require": {
        "wikibase/quality": "@dev",
        "wikibase/wikibase": "@dev",
        "wikibase/constraints": "1.x-dev"
  • Run composer install.

  • If not already done, add the following lines to your LocalSettings.php to enable Wikibase and Wikibase Quality:

$wgEnableWikibaseRepo = true;
$wgEnableWikibaseClient = false;
require_once "$IP/extensions/Wikibase/repo/Wikibase.php";
require_once "$IP/extensions/Wikibase/repo/ExampleSettings.php";
wfLoadExtension( 'WikibaseQuality' );
  • You have to add also the following line to your LocalSettings.php to enable Wikibase Quality Constraints:
wfLoadExtension( 'WikibaseQualityConstraints' );
  • Run php maintenance/update.php --quick.

  • Configure the extension. You can find the configuration settings with documentation in extension.json. (Note that the variable name for LocalSettings.php always begins with wg, e. g. $wgWBQualityConstraintsClassId for the WBQualityConstraintsClassId setting.)

    • Specify the entity IDs of entities that are used to define constraints. See the “Data import” section for an automatic way to do this.

    • If you have a SPARQL endpoint, configure it in WBQualityConstraintsSparqlEndpoint.

    • Alternatively, to check “format” constraints without running a full SPARQL server, you can use the minisparql server.

  • Run php maintenance/runScript.php extensions/WikibaseQualityConstraints/maintenance/ImportConstraintStatements.php.


The extension includes a gadget that checks constraints on entity pages and displays violations on statements. Note that you must have the Gadgets extension installed before you can use this gadget. The gadget is loaded via ResourceLoader and can be used with the following definition in MediaWiki:Gadgets-definition:

* checkConstraints[ResourceLoader|dependencies=wikibase.quality.constraints.gadget]|checkConstraints.js

checkConstraints.js (page title: MediaWiki:Gadget-checkConstraints.js) is only required because the the Gadgets extension does not support gadgets without any JS files. It can be empty (or even nonexistent), but some explanatory comment is recommended, for example:

// this gadget resides in the wikibase.quality.constraints.gadget ResourceLoader module
// its source code is available in the gadget* files at

To make the gadget display nicely in the preferences and on Special:Gadget, MediaWiki:Gadget-checkConstraints should be created, e. g. with the following content:

''checkConstraints'': Shows property constraint reports for statements on an item or property page ([[Help:Property constraints portal|help]])

The gadget can also be loaded directly as a standalone script, e. g. as a user script, by simply including modules/gadget.js in common.js and modules/gadget.css in common.css.

Data import

For local development, it’s easiest to import some data from Wikidata. You can use the WikibaseImport extension to do this; once you have installed it, you can use the following command to import the essential entities that this extension needs (stuff like the “instance of” property):

# working directory should be the MediaWiki installation folder, i.e. where LocalSettings.php is
jq -r '.config | with_entries(select(.key | endswith("Id"))) | .[] | .value' extensions/WikibaseQualityConstraints/extension.json | php extensions/WikibaseImport/maintenance/importEntities.php --stdin

Afterwards, export the resulting entity IDs to your local config (since they’ll be different than on Wikidata):

# from the MediaWiki installation folder
# or directly from the extension folder

Running the tests

There are two ways to run the tests of this extension:

  • Using the included configuration file:

    # from the MediaWiki installation folder
    php tests/phpunit/phpunit.php -c extensions/WikibaseQualityConstraints/phpunit.xml.dist

    This creates test coverage reports (in tests/coverage/ and build/logs/clover.xml) and is therefore fairly slow.

  • Without the configuration file:

    # from the MediaWiki installation folder
    php tests/phpunit/phpunit.php extensions/WikibaseQualityConstraints/tests/phpunit/

    This runs the tests without coverage report and is therefore much faster.

Adding a new constraint type

To add a new constraint type, the following steps are necessary:

  • Define the constraint checker class.
    • It should be defined in a new file in src/ConstraintCheck/Checker/, named after the class name. It should be in the WikibaseQuality\ConstraintReport\ConstraintCheck\Checker namespace.
    • The class name should follow the constraint type name (in English), ending in “Checker”.
    • The class must implement the ConstraintChecker interface.
    • It should have at least the following class-level documentation comment:
       * @author YOUR NAME HERE
       * @license GPL-2.0-or-later
    • Any services you need (Config, EntityLookup, …) should be injected as constructor parameters.
    • If the constraint has parameters, add support for parsing them to ConstraintParameterParser (add a config setting for the associated property in extension.json and a method to parse the parameter in ConstraintParameterParser), and then add tests for them in ConstraintParameterParserTest. This should be done in a separate commit.
  • Define new messages (at least a violation message for the constraint type).
    • Define the message in i18n/en.json. A violation message should have a key like wbqc-violation-message-constraintType.
    • Document the message in i18n/qqq.json. Use the same message key, and insert the documentation in the same location where you also added the message in en.json (that is, en.json and qqq.json should contain message keys in the same order).
  • Add a configuration setting for the constraint type item ID.
    • Configuration settings are defined in extension.json, as members of the config object.
    • It should be added right after the current last …ConstraintId entry.
    • It should be named after the constraint type item’s English label, following the pattern WBQualityConstraints…ConstraintId.
    • The default value should be the item ID on Wikidata, so that no extra configuration is required for Wikidata and importing the constraint type item (see “Data import” section) works.
    • The first part of the description can be copied from similar settings, the rest should contain a short description of the constraint type.
    • The ID can always be public ("public": true).
  • Configure the constraint type checker in ConstraintReportFactory.
    • Add an array entry like
      $this->config->get( 'WBQualityConstraints…ConstraintId' )
      	=> new …Checker(
      		// injected services
      at the end of the getConstraintCheckerMap() function.
  • Add tests for the new constraint checker.
    • The test class name should be the same as the checker class name, with an additional suffix Test (i. e., …CheckerTest).
    • The test class should be placed somewhere in tests/phpunit/Checker/, either in the most suitable subdirectory or directly in that directory if none of the subdirectories are suitable. (The division into subdirectories there is dubious anyways, and we may get rid of it in the future.)
    • It should have at least the following class-level documentation comment:
       * @covers WikibaseQuality\ConstraintReport\ConstraintCheck\Checker\…Checker
       * @group WikibaseQualityConstraints
       * @author YOUR NAME HERE
       * @license GPL-2.0-or-later
    • It should have at least one test for compliance with a constraint, one test for a constraint violation, one test for behavior on a deprecated statement, and one test for the checkConstraintParameters method.
    • Use the ResultAssertions trait’s methods to check constraint check results.
    • Use the NewItem and NewStatement builders to construct test data. (You might see JsonFileEntityLookup and separate JSON files used in some existing tests, but that’s a lot less readable.)
    • If the checker uses a Config, use the DefaultConfig trait.
    • If the constraint has parameters, add methods for them to the ConstraintParameters trait and use it in the tests.
    • You can copy+paste a getConstraintMock function from one of the existing tests, adjusting the getConstraintTypeItemId mocked return value. (Hopefully we’ll improve this in the future.)
  • Update the tests for DelegatingConstraintChecker.
    • In DelegatingConstraintCheckerTest, add an entry for your constraint type to the $constraints array in addDBData().
    • The constraint_guid should be P1$, followed by a new UUID (e. g. cat /proc/sys/kernel/random/uuid or journalctl --new-id128).
    • The pid should be 1. (Not '1'!)
    • The constraint_type_qid should be $this->getConstraintTypeItemId( '…' ), where is just the part of the WBQualityConstraints…ConstraintId extension.json config key.
    • The constraint_parameters should be a valid JSON serialization of constraint parameters. If the constraint type doesn’t have any parameters, you can pass {}, otherwise there should ideally be methods to create the parameters in the ConstraintParameters trait so that you can use json_encode( $this->…Parameter( … ) ) (perhaps with array_merge if there are multiple parameters).
  • Ask someone with grafana-admin access to update the “constraint types” panel in the wikidata-quality board to add the new constraint type.

An example commit that performs almost all of these steps is Change Ica05406e14.