RELEASE-NOTES-1.42

= MediaWiki 1.42 =

== MediaWiki 1.42.0-PRERELEASE ==

THIS IS NOT A RELEASE YET

MediaWiki 1.42 is an alpha-quality development branch, and is not recommended
for use in production.

== Upgrading notes for 1.42 ==
Don't forget to always back up your database before upgrading!

See the file UPGRADE for more detailed per-version upgrade instructions from the
oldest supported upgrading version, MediaWiki 1.35.

Some specific notes for MediaWiki 1.42 upgrades are below:
* MediaWiki now requires Composer 2.x, and any related (vendor) files generated
  by Composer must be generated by Composer 2.x. Composer 1.x is mostly end of
  life by upstream, and using it will result in slower actions when downloading
  and installing packages. See the upstream blog post at
  https://blog.packagist.com/deprecating-composer-1-support/ for further
  information.
* …

For notes on 1.41.x and older releases, see HISTORY.

=== Configuration changes for system administrators in 1.42 ===
* Composer 1.x is no longer supported, and can no longer be used with MediaWiki.
* …

==== New configuration ====
* $wgMicroStashType: The object cache backend for the MicroStash service.
* $wgEditRecoveryExpiry: Number of seconds to keep edit recovery data
  after the edit is stored.
* $wgDjvuUseBoxedCommand and $wgDjvuShell: A temporary flag to control whether
  or not to use BoxedCommand when wrapping DejaVu rendering, and the command to
  call if so.
* $wgConditionalUserOptions: Makes it possible to define user properties with
  defaults varying by user, without growing the user_properties table. Typical
  use-case is to enable a feature only for users created after a certain date.
* $wgGrantRiskGroups: Grant risk levels, used to indicate on various UIs which
  grants should be considered risky. (T290790)
* $wgTempAccountCreationThrottle: Like AccountCreationThrottle, but for managing
  temporary account creations.
* …

==== Changed configuration ====
* $wgAutoCreateTempUser: 'matchPattern' now supports multiple match patterns.
* $wgLogActionsHandlers is now ObjectFactory compatible.
* $wgBotPasswordsCluster and $wgBotPasswordsDatabase have been deprecated
  use $wgVirtualDomainsMapping['virtual-botpasswords'] instead.
* The MainPageIsDomainRoot setting is no longer considered experimental.
* $wgAutoCreateTempUser is updated to use a different format for temporary
  accounts. This configuration value is marked as unstable, so breaking
  changes were expected. If your wiki used temporary accounts before
  1.42, you will need to override the configuration value to also match
  the old format of *$1.
* …

==== Removed configuration ====
* $wgDisableCookieCheck has been removed.
* $wgStatsCacheType has been removed. Set $wgMicroStashType instead.
* $wgJobSerialCommitThreshold has been removed without deprecation,
  it wasn't used anywhere according to codesearch and any setups using this
  config will perform just fine but might be less performant.
* $wgLogoHD, deprecated since 1.35, has been removed. Use $wgLogo instead.
* $wgContentHandlerTextFallback, deprecated since 1.37, has been removed.
  No longer customizable.
* $wgSquidPurgeUseHostHeader, deprecated since 1.33, has been removed.
  No longer customizable and always true.
* $wgAllowImageTag, deprecated since 1.35, has been removed.
  Register an extension tag named <img> instead.
* $wgMinimalPasswordLength and $wgMaximalPasswordLength, deprecated since 1.26
  have been dropped. Use $wgPasswordPolicy instead.
* $wgUseMediaWikiUIEverywhere has been removed.
* $wgHTMLFormAllowTableFormat has been removed.
* $wgOpenSearchTemplate, deprecated since 1.25, has been removed
  Use $wgOpenSearchTemplates['application/x-suggestions+json'] instead.
* $wgUseSameSiteLegacyCookies has been removed.
* …

=== New user-facing features in 1.42 ===
* (T308160) filter: is now allowed in inline CSS in wikitext
* …

=== New features for sysadmins in 1.42 ===
* …

=== New developer features in 1.42 ===
* (T326466) MediaWikiIntegrationTestCase's database and set-up code now avoids
  using dynamic properties, which was causing deprecation warnings in PHP 8.2.
* (T13555) MediaWiki now includes styles that allow more accessible markup for
  section headings. MediaWiki's own HTML output will be changed in the future.
  More information: https://www.mediawiki.org/wiki/Heading_HTML_changes
* (T193472) PHP Notice and Warning errors that are silenced (e.g. by the "@"
  operator, error_reporting directive, or Wikimedia\AtEase) are now logged to
  a new "silenced-error" channel.
* (T347347) The CLI installer accepts a "--with-developmentsettings" argument
  to require the DevelopmentSettings.php file at install time.
* (T350054) MediaWiki's ResourceLoader has been updated to add basic support
  for code-splitting (aka "tree-shaking") when using the Codex component
  library. A ResourceLoader module can now specify a list of "codexComponents"
  in its module defintion and ensure that only the code for those components
  gets sent to the client. More information:
  https://www.mediawiki.org/wiki/Codex#Subset_of_components
* (T345185) The SessionProviderInterface now allows defining providers that
  are exempt from rights checks when auto creating users.
* …

=== External library changes in 1.42 ===

==== New external libraries ====
* Added mediawiki/json-codec at v2.2.1.
* Added mck89/peast at v1.16.2.
* …

===== New development-only external libraries =====
* …

==== Changed external libraries ====
* Updated OOUI from v0.48.1 to v0.49.1.
* Updated OOjs Router from 0.3.0 to 0.5.0.
* Updated codex, codex-design-tokens and codex-icons
  from v1.0.0 to v1.3.6.
* Updated Vue from v3.2.37-compat to v3.3.9.
* Updated composer/semver from 3.3.2 to 3.4.0.
* Updated guzzlehttp/guzzle from 7.5.3 to 7.7.1.
* Updated monolog/monolog from 2.2.0 to 2.9.2.
* Updated pear/mail from 1.5.1 to 1.6.0.
* Updated pear/mail_mime from 1.10.11 to 1.10.12.
* Updated pear/net_smtp from 1.10.1 to 1.11.1.
* Updated psr/http-message from 1.0.1 to 1.1.
* Updated symfony/polyfill-php80 from 1.28.0 to 1.29.0.
* Updated symfony/polyfill-php81 from 1.28.0 to 1.29.0.
* Updated symfony/polyfill-php82 from 1.28.0 to 1.29.0.
* Updated symfony/polyfill-php83 from 1.28.0 to 1.29.0.
* Updated symfony/yaml from 5.4.23 to 5.4.35.
* Updated wikimedia/less.php from 4.1.1 to 4.2.1.
* Updated wikimedia/remex-html from 4.0.1 to 4.1.0.
* Updated wikimedia/minify from 2.5.1 to 2.7.0.
* Updated wikimedia/relpath from 3.0.0 to 4.0.0.
* Updated wikimedia/shellbox from 4.0.0 to 4.0.1.
* …

===== Changed development-only external libraries =====
* Updated QUnit from v2.19.4 to v2.20.0.
* Updated composer/spdx-licenses from 1.5.7 to 1.5.8.
* Updated doctrine/dbal from 3.4.2 to 3.7.2.
* Updated doctrine/sql-formatter from 1.1.1 to 1.1.3.
* Updated grunt-banana-checker from 0.11.0 to 0.11.1.
* Updated mediawiki/mediawiki-codesniffer from 42.0.0 to 43.0.0.
* Updated mediawiki/mediawiki-phan-config from 0.13.0 to 0.14.0.
* Updated php-parallel-lint/php-parallel-lint from 1.3.2 to 1.4.0.
* Updated phpunit/phpunit from 9.5.28 to 9.6.16.
* Updated psy/psysh from ^0.11.1 to ^0.12.3.
* Updated seld/jsonlint from 1.8.3 to 1.10.1.
* Updated wikimedia/testing-access-wrapper from 2.0.0 to 3.0.0.
* …

==== Removed external libraries ====
* …

=== Bug fixes in 1.42 ===
* …

=== Action API changes in 1.42 ===
* APIQueryTags now includes "software" in the "source" array for software
  generated tags. Reliance on the "extension" entries in this array is now
  deprecated, but they will remain for backwards compatibility.
* …

=== Action API internal changes in 1.42 ===
* …

=== Languages updated in 1.42 ===
MediaWiki supports over 350 languages. Many localisations are updated regularly.
Below only new and removed languages are listed, as well as changes to languages
because of Phabricator reports.

* (T268143) Language variant conversion has been removed for Kazakh.
* (T352776) Updated autonym spelling for the Mon language (mnw).
* (T351874) Added language support for Komering (kge).
* (T351992) Added language support for Efik (efi).
* (T352954) Added language support for Rutul (rut).
* (T353058) Added language support for Arbëresh (aae).
* (T353307) Added language support for Guadeloupean Creole (gcf).
* (T353500) Added language support for Southeastern Kolami (nit).
* (T354519) Added language support for Tooro (ttj).
* (T354926) Added language support for Nyoro (nyo).
* (T356616) Added language support for Chinook Jargon (chn).
* (T357879) Added language support for Ibibio (ibb).
* …

=== Breaking changes in 1.42 ===
* (T340802) ResourceLoader: The targets system is no longer active; all modules
  will load on all platforms even if they are marked as desktop- or mobile-only
  in the 'targets' field, which is no longer read. As part of this, the internal
  methods RL\Module::setTarget() & ::getTargets(), and OutputPage::setTarget(),
  have been removed.
* TitleArray, deprecated since 1.41, has been removed.
* UserRightsProxy, deprecated since 1.38, has been removed.
* SiteConfiguration::getConfig(), deprecated in 1.41, has been removed.
* UserLoginCompleteHook is always called with its $direct parameter set to
  boolean true. The false case has been removed.
* MagicWord::load() has been marked @internal and may change in the future
  without further notice.
* All classes that implemented IDBAccessObject interface and all interfaces
  that extended it, no longer do that. See https://w.wiki/9DAX for more info.
* BagOStuff::setNewPreparedValues() now emits deprecation warnings.
* The type of the last parameter of BeforeInitializeHook::onBeforeInitialize
  and MediaWikiPerformActionHook::onMediaWikiPerformAction changed from
  MediaWiki to ActionEntryPoint. Relevant methods are still available on
  the object.
* Classes that override Maintenance::finalSetup() must now declare the
  $settings parameter and pass it on when calling the parent implementation.
  MaintenanceRunner will always provide this parameter when calling
  finalSetup().
* WebResponse::disableForPostSend() is no longer static.
* MediaWiki's virtualrest internal library has been removed in favor of the
  HTTP library like: Guzzle, MultiHttpClient or MwHttpRequest.
* Several deprecated methods have been removed from the Content interface,
  in favor of the respective methods in ContentHandlers. Callers should
  use a more narrow interface like ContentRenderer or ContentTransformer
  when possible. The following methods have been removed from Content:
  - getParserOutput()
  - preSaveTransform()
  - preloadTransform()
  - prepareSave()
* User::blockedFor() and AbstractBlock::getReason(), deprecated in 1.35, have
  been removed. Use AbstractBlock::getReasonComment() instead.
* SerializedValueContainer::newUnified(), deprecated in 1.41 has been removed.
* Use of ActorMigration for any of the following tables, deprecated since 1.34,
  is no longer supported:
  - archive
  - image
  - oldimage
  - filearchive
  - recentchanges
  - logging
  - ipblocks
* ParserOutput::setFlag() and ::getFlag(), deprecated in 1.38, were removed. You
  should use ::setOutputFlag() and ::getOutputFlag() instead.
* The parser does not substitute the default category sort key at
  parse time; this is substituted when the category links table is
  updated instead.  As a result {{DEFAULTSORT}} will affect all the
  contents of the page (not just categories added after the location
  of {{DEFAULTSORT}} in the article) and
  ParserOutput::getCategorySortKey() will return the empty string
  (still meaning "use the default sort key") instead of the immediate
  value of {{DEFAULTSORT}}.  ParserOutput::getCategorySortKey() will
  directly reflect the category link contents, instead of having
  postprocessing done to it (character references decoded, newlines
  replaced, language conversion).  That postprocessing is now done
  when the category links table is updated, and so it consistently
  applies even when categories are added directly via API.
* PostgresUpdater::addPgEnumValue() unused everywhere, have been removed
  without deprecation. Use of ENUM is highly discouraged.
* ILoadBalancer::getAnyOpenConnection() has been removed without deprecation,
  use ::getConnection() instead.
* The unused method CommentStore::getFields() has been removed without
  depreaction.
* LanguageConverter's internal properties, all deprecated in 1.35 or 1.36, have
  now had their deprecated property accessors dropped:
  - mConvRuleTitle
  - mUserVariant
  - mHeaderVariant
  - mMaxDepth
  - mVarSeparatorPattern
  - mLangObj
  - mTablesLoaded
  - mTables
  - mVariants
  - mMainLanguageCode
  - mVariantFallbacks
  - mFlags
  - mVariantNames
  - mDescCodeSep
  - mDescVarSep
* OutputPage::addParserOutputText has been marked @internal since there are no
  known users of it. Its old behavior has been deprecated and will change
  in the future without further notice.
* A some methods of ConnectionManager and SessionConsistentConnectionManager,
  previously deprecated, have been removed:
  - ::releaseConnection(), deprecated in 1.38; do not use
  - ::getWriteConnectionRef(), deprecated in 1.39; use getWriteConnection()
  - ::getReadConnectionRef(), deprecated in 1.38; use getReadConnection()
  - ::getLazyWriteConnectionRef(), deprecated in 1.39; use getWriteConnection()
  - ::getLazyReadConnectionRef(), deprecated in 1.38; use getReadConnection()
* CoreParserFunctions::mwnamespace(), deprecated in 1.39, has been removed. Use
  CoreParserFunctions::namespace() instead.
* Processor:: and ExtensionProcessor::getExtraAutoloaderPaths(), deprecated in
  1.39, have been removed; use ::getExtractedAutoloadInfo() instead.
* MWExceptionHandler::rollbackMasterChangesAndLog(), deprecated in 1.37, has
  been removed. Use ::rollbackPrimaryChangesAndLog() instead.
* Passing a custom database connection to DatabaseBlockStore::insertBlock(),
  deprecated since 1.41, is no longer supported.
* LanguageConverterFactory::isTitleConversionDisabled(), deprecated in 1.36,
  has been removed. Use ::isLinkConversionDisabled() instead.
* MediaWikiIntegrationTestCase::$tablesUsed has been deprecated. The framework
  now detects these automatically.
* Passing an actor id to the constructor of UserIdentityValue, deprecated
  since 1.36, is no longer being supported.
* Support for setting dynamic property on StatusValue object has been removed.
  To pass your arbitrary data along the object, use StatusValue::statusData
  property (which is always declared).
* The global function wfReportTime(), deprecated since 1.40, has been removed.
* The skin template parameter 'reporttime', deprecated since 1.41, has been
  removed.
* WikiPage::getPageIsRedirectField(), deprecated since 1.41, has been removed.
* WikiPage::insertRedirect(), deprecated since 1.41, has been removed.
* Several methods in PageArchive, all deprecated in 1.38, have been removed:
  - ::listRevisions()
  - ::getRevisionRecordByTimestamp()
  - ::getArchivedRevisionRecord()
  - ::getPreviousRevisionRecord()
  - ::getLastRevisionId()
  - ::isDeleted()
  - ::getFileStatus()
  - ::getRevisionStatus()
* Database, DatabaseInstaller, DatabaseUpdater, DBPrimaryPos, ResultWrapper and
  SQLPlatform are no longer stable to extend. It is not possible to define
  database types in an extension.
* UserDef::PARAM_ALLOWED_USER_TYPES now differentiates between temporary account
  usernames and user accounts. Any endpoints that want temp users to be
  valid but were passing a name through will break. Temp users must now be
  explicitly allowed.
* The Hooks class, a legacy wrapper for HooksContainer, has been removed. All of
  its contents have been previously deprecated in 1.35 (or 1.41 for ::runner()):
  - ::register()
  - ::clear(),
  - ::isRegistered()
  - ::getHandlers()
  - ::run()
  - ::runWithoutAbort()
  - ::runner()
* Article::__get(), ::__set(), deprecated since 1.35, have been removed.
* Several API calls have been updated to return a 'temp' user flag:
  - ApiQueryImageInfo
  - ApiQueryLogEvents
  - ApiQueryRecentChanges
  - APIs extended from ApiQueryRevisionsBase
* Parser::getCustomDefaultSort() and ::setDefaultSort(), deprecated since 1.38,
  have been removed.
* UserOptionsLookup::getDefaultOptions() and
  UserOptionsLookup::getDefaultOption() now accept an UserIdentity, to
  take conditional defaults for user properties into account. When conditional
  defaults are used, calling those methods without the UserIdentity might
  produce unexpected results.
* Installer related classes have been namespaced without having aliases added.
  The following have been moved to MediaWiki\Installer:
  - CliInstaller
  - DatabaseInstaller
  - InstallDocFormatter
  - Installer
  - InstallerOverrides
  - InstallerSessionProvider
  - LocalSettingsGenerator
  - MysqlInstaller
  - PostgresInstaller
  - PostgresUpdater
  - SqliteInstaller
  - SqliteUpdater
  - WebInstaller
  - WebInstallerComplete
  - WebInstallerCopying
  - WebInstallerDBConnect
  - WebInstallerDBSettings
  - WebInstallerDocument
  - WebInstallerExistingWikis
  - WebInstallerInstall
  - WebInstallerLanguage
  - WebInstallerName
  - WebInstallerOptions
  - WebInstallerOutput
  - WebInstallerPage
  - WebInstallerReleaseNotes
  - WebInstallerRestart
  - WebInstallerUpgrade
  - WebInstallerUpgradeDoc
  - WebInstallerWelcome
* mediawiki.ui/variables.less, deprecated since 1.41, has been removed in
  favor of mediawiki.skin.variables.less.
* The module `jquery.cookie` (deprecated as of 1.41) has been removed.  Please
  use `mediawiki.cookie` instead
* The no-op module `es6-polyfills` (deprecated as of 1.41) has been removed.
* Log formatters (as defined in $wgLogActionsHandlers) are now created by
  ObjectFactory, which means their constructors must be public. Legacy log
  formatters using callbacks instead of class names are no longer supported.
* The old aliases for the namespaced ResourceLoader classes, deprecated since
  they were moved in MediaWiki 1.39, have now been dropped:
  - ResourceLoader – use MediaWiki\ResourceLoader\ResourceLoader
  - ResourceLoaderCircularDependencyError
    – use MediaWiki\ResourceLoader\CircularDependencyError
  - ResourceLoaderClientHtml – use MediaWiki\ResourceLoader\ClientHtml
  - ResourceLoaderCodexModule – use MediaWiki\ResourceLoader\CodexModule
  - ResourceLoaderContext – use MediaWiki\ResourceLoader\Context
  - ResourceLoaderFileModule – use MediaWiki\ResourceLoader\FileModule
  - ResourceLoaderFilePath – use MediaWiki\ResourceLoader\FilePath
  - ResourceLoaderForeignApiModule
    – use MediaWiki\ResourceLoader\ForeignApiModule
  - ResourceLoaderImage – use MediaWiki\ResourceLoader\Image
  - ResourceLoaderImageModule – use MediaWiki\ResourceLoader\ImageModule
  - ResourceLoaderLessVarFileModule
    – use MediaWiki\ResourceLoader\LessVarFileModule
  - ResourceLoaderModule – use MediaWiki\ResourceLoader\Module
  - ResourceLoaderMwUrlModule – use MediaWiki\ResourceLoader\MwUrlModule
  - ResourceLoaderOOUIFileModule – use MediaWiki\ResourceLoader\OOUIFileModule
  - ResourceLoaderOOUIIconPackModule
    – use MediaWiki\ResourceLoader\OOUIIconPackModule
  - ResourceLoaderOOUIImageModule
    – use MediaWiki\ResourceLoader\OOUIImageModule
  - ResourceLoaderOOUIModule – use MediaWiki\ResourceLoader\OOUIModule
  - ResourceLoaderSiteModule – use MediaWiki\ResourceLoader\SiteModule
  - ResourceLoaderSiteStylesModule
    – use MediaWiki\ResourceLoader\SiteStylesModule
  - ResourceLoaderSkinModule – use MediaWiki\ResourceLoader\SkinModule
  - ResourceLoaderStartUpModule – use MediaWiki\ResourceLoader\StartUpModule
  - ResourceLoaderUserModule – use MediaWiki\ResourceLoader\UserModule
  - ResourceLoaderUserOptionsModule
    – use MediaWiki\ResourceLoader\UserOptionsModule
  - ResourceLoaderUserStylesModule
    – use MediaWiki\ResourceLoader\UserStylesModule
  - ResourceLoaderWikiModule – use MediaWiki\ResourceLoader\WikiModule
  - DerivativeResourceLoaderContext
    – use MediaWiki\ResourceLoader\DerivativeContext
  - MessageBlobStore – use MediaWiki\ResourceLoader\MessageBlobStore
  - VueComponentParser – use MediaWiki\ResourceLoader\VueComponentParser
* (T318989) Skin::lastModified, deprecated since 1.40, has been removed.
* Composer 1.x is no longer supported, and can no longer be used with MediaWiki.
* Title::GAID_FOR_UPDATE, deprecated in 1.34, has been removed. Instead, your
  code should use IDBAccessObject::READ_LATEST.
* Six private Title class members, deprecated in 1.37, are now fully private;
  use their corresponding accessor methods:
   - $mTextform   -> getText()
   - $mUrlform    -> getPartialURL()
   - $mDbkeyform  -> getDBkey()
   - $mNamespace  -> getNamespace()
   - $mInterwiki  -> getInterwiki()
   - $mFragment   -> getFragment()
* Skin::bottomScripts, deprecated since 1.37, has been removed.
* Fallback index and options have been removed from
  DBAccessObjectUtils::getDBOptions() without deprecation.
* The deprecated class aliases for now-namespaced or renamed PHP classes that
  were added in or before 1.39 LTS have now been removed:
   - Blob -> Wikimedia\Rdbms\Blob
   - Block -> MediaWiki\Block\DatabaseBlock
   - DBAccessError -> Wikimedia\Rdbms\DBAccessError
   - DBConnectionError -> Wikimedia\Rdbms\DBConnectionError
   - DBError -> Wikimedia\Rdbms\DBError
   - DBExpectedError -> Wikimedia\Rdbms\DBExpectedError
   - DBQueryError -> Wikimedia\Rdbms\DBQueryError
   - DBReadOnlyError -> Wikimedia\Rdbms\DBReadOnlyError
   - DBReplicationWaitError -> Wikimedia\Rdbms\DBReplicationWaitError
   - DBTransactionError -> Wikimedia\Rdbms\DBTransactionError
   - DBTransactionSizeError -> Wikimedia\Rdbms\DBTransactionSizeError
   - DBUnexpectedError -> Wikimedia\Rdbms\DBUnexpectedError
   - DatabaseMysqlBase -> Wikimedia\Rdbms\DatabaseMySQL
   - DatabaseMysqli -> Wikimedia\Rdbms\DatabaseMySQL
   - EasyDeflate -> Deflate
   - Field -> Wikimedia\Rdbms\Field
   - IMaintainableDatabase -> Wikimedia\Rdbms\IMaintainableDatabase
   - LinksDeletionUpdate -> MediaWiki\Deferred\LinksUpdate\LinksDeletionUpdate
   - LinksUpdate -> MediaWiki\Deferred\LinksUpdate\LinksUpdate
   - LoadBalancer -> Wikimedia\Rdbms\LoadBalancer
   - LoadBalancerSingle -> Wikimedia\Rdbms\LoadBalancerSingle
   - RCFeedEngine -> FormattedRCFeed
   - RandomPage -> MediaWiki\Specials\SpecialRandomPage
* The return value of IDatabase::upsert(), deprecated since 1.33, has been
  removed.
* Instancing MediaWiki\Specials\SpecialRandomPage without injected services has
  been removed.
* mediawiki.ui/utilities.less with its three layout CSS classes has been removed
* SpecialPage::listed() and ::setListed(), deprecated since 1.35, have both been
  removed. Use ::isListed() to read, and over-ride by implementing isListed() or
  by sub-classing UnlistedSpecialPage.
* BlockListPager::getTotalAutoblocks() was removed.
* …

=== Deprecations in 1.42 ===
* (T273239) wfGetDB(), deprecated in 1.39, now emits deprecation warnings. Most
  code can migrate to MediaWikiServices::getInstance()->getConnectionProvider()
  ->getReplicaDatabase() or …->getPrimaryDatabase() as appropriate.
* (T166010) All PHP code in MediaWiki is slowly being moved to be in a class
  namespace as appropriate, so that we can use PSR-4 auto-loading, which will
  speed up general code loading of MediaWiki. The old global namespace class
  names are being left behind as deprecated aliases.

  In this release of MediaWiki, XYZ classes now have a namespace and XYZ do
  not yet (XYZ% done, up from 63% in MediaWiki 1.41.0). The following have newly
  been moved:
  - MediaWiki\Cache:
    - BacklinkCache
    - FileCacheBase
    - GenderCache
    - HTMLCacheUpdater (and fix case for consistency with HTMLFileCache)
    - LinkBatch
    - LinkCache
    - UserCache
  - MediaWiki\Context:
    - ContextSource
    - DerivativeContextSource
    - IContextSource
    - MutableContext
    - RequestContext
  - MediaWiki\Deferred:
    - AtomicSectionUpdate
    - AutoCommitUpdate
    - CdnCacheUpdate
    - DataUpdate
    - DeferrableCallback
    - DeferrableUpdate
    - DeferredUpdates
    - DeferredUpdatesScope
    - DeferredUpdatesScopeMediaWikiStack
    - DeferredUpdatesScopeStack
    - EnqueueableDataUpdate
    - HtmlFileCacheUpdate
    - JobQueueEnqueueUpdate
    - MWCallableUpdate
    - MergeableUpdate
    - MessageCacheUpdate
    - SearchUpdate
    - SendPasswordResetEmailUpdate
    - SiteStatsUpdate
    - TransactionRoundAwareUpdate
    - TransactionRoundDefiningUpdate
    - UserEditCountInfo
    - UserEditCountUpdate
  - MediaWiki\HTMLForm:
    - CodexHTMLForm
    - CollapsibleFieldsetLayout
    - HTMLForm
    - HTMLFormActionFieldLayout
    - HTMLFormElement
    - HTMLFormField
    - HTMLFormFieldLayout
    - HTMLFormFieldRequiredOptionsException
    - HTMLNestedFilterable
    - OOUIHTMLForm
    - VFormHTMLForm
    - MediaWiki\HTMLForm\Field:
      - HTMLApiField
      - HTMLAutoCompleteSelectField
      - HTMLButtonField
      - HTMLCheckField
      - HTMLCheckMatrix
      - HTMLComboboxField
      - HTMLDateTimeField
      - HTMLEditTools
      - HTMLExpiryField
      - HTMLFileField
      - HTMLFloatField
      - HTMLFormFieldCloner
      - HTMLFormFieldWithButton
      - HTMLHiddenField
      - HTMLInfoField
      - HTMLIntField
      - HTMLMultiSelectField
      - HTMLNamespacesMultiselectField
      - HTMLRadioField
      - HTMLRestrictionsField
      - HTMLSelectAndOtherField
      - HTMLSelectField
      - HTMLSelectLanguageField
      - HTMLSelectLimitField
      - HTMLSelectNamespace
      - HTMLSelectNamespaceWithButton
      - HTMLSelectOrOtherField
      - HTMLSizeFilterField
      - HTMLSubmitField
      - HTMLTagFilter
      - HTMLTagMultiselectField
      - HTMLTextAreaField
      - HTMLTextField
      - HTMLTextFieldWithButton
      - HTMLTimezoneField
      - HTMLTitleTextField
      - HTMLTitlesMultiselectField
      - HTMLToggleSwitchField
      - HTMLUserTextField
      - HTMLUsersMultiselectField
  - MediaWiki\Installer:
    - DatabaseUpdater
    - MysqlUpdater
  - MediaWiki\LinkedData:
    - PageDataRequestHandler
  - MediaWiki\Maintenance:
    - Version
  - MediaWiki\Message:
    - Message
  - MediaWiki\Parser:
    - Parser
    - ParserOutput
  - MediaWiki\PoolCounter:
    - PoolCounter
    - PoolCounterNull
    - PoolCounterRedis
    - PoolCounterWork
    - PoolCounterWorkViaCallback
    - PoolWorkArticleView
    - PoolWorkArticleViewCurrent
    - PoolWorkArticleViewOld
  - MediaWiki\Site:
    - CachingSiteStore
    - DBSiteStore
    - HashSiteStore
    - MediaWikiSite
    - Site
    - SiteExporter
    - SiteImporter
    - SiteList
    - SiteLookup
    - SiteStore
  - (T352284) MediaWiki\User\Options:
    - DefaultOptionsLookup
    - UserOptionsLookup
    - UserOptionsManager
    - StaticUserOptionsLookup
* Some hook classes have been moved from the generic MediaWiki\Hooks namespace
  to live closer to the code which uses them:
  - MediaWiki\Output\Hook:
    - AfterBuildFeedLinksHook
    - AfterFinalPageOutputHook
    - BeforePageDisplayHook
    - BeforePageRedirectHook
    - GetCacheVaryCookiesHook
    - LanguageLinksHook
    - MakeGlobalVariablesScriptHook
    - OutputPageAfterGetHeadLinksArrayHook
    - OutputPageBeforeHTMLHook
    - OutputPageBodyAttributesHook
    - OutputPageCheckLastModifiedHook
    - OutputPageMakeCategoryLinksHook
    - OutputPageParserOutputHook
* API modules using ApiBase::requirePostedParameters() must also override
  mustBePosted() to return true.
* Overriding MWException::getHTML(), ::getText(), ::getPageTitle(), and
  ::reportHTML() in order to display custom exception messages is now
  deprecated. Provide the error message when constructing the Exception,
  or if you need a whole custom error page, use ErrorPageError instead.
* Using `new ImportReporter( … )` or `new ApiImportReporter( … )` without
  the $context parameter is now deprecated.
* Using `WikiImporterFactory::getWikiImporter()` without the $performer
  parameter is now deprecated.
* BlockManager::getUserBlock() was deprecated. Instead use
  BlockManager::getBlock(), which expects the caller to do ipblock-exempt
  checking.
* The `composer phpunit:entrypoint` entrypoint has been deprecated, along with
  bootstrap.integration.php and suite.xml. Run tests with `composer phpunit`
  instead, or simply `vendor/bin/phpunit`, which use bootstrap.php and
  phpunit.xml.dist.
* The global variable $wgCommandLineMode is deprecated. In most cases checks
  for `$wgCommandLineMode` can be replaced with `MW_ENTRY_POINT === 'cli'`.
* The global function wfUnpack is deprecated and emits deprecation
  warnings. Use StringUtils::unpack instead.
* SpecialEmailUser::getTarget() has been deprecated.
* User::isBlocked(), ::isBlockedFromCreateAccount() and ::isBlockedFrom() now
  emit deprecation warnings. They were deprecated since 1.34, 1.37 and 1.33
  respectively.
* DatabaseBlock::newFromID() was deprecated and will emit deprecation warnings.
  Instead use DatabaseBlockStore::newFromID().
* DatabaseBlock::getAutoblockExpiry() was deprecated without replacement.
* MagicWord::getId() has been deprecated.
* MagicWordFactory::getSubstIDs() has been deprecated.
* Status::setMessageLocalizer is deprecated. Callers that want to control the
  localization of the Status object should obtain a StatusFormatter from
  the StatusFormatterFactory.
* Html::buttonAttributes() and Html::getTextInputAttributes() methods
  no longer do anything and have been deprecated.
* DatabaseBlock::doAutoblock and ::updateTimestamp are now deprecated, use
  DatabaseBlockStore::doAutoblock and ::updateTimestamp instead.
* The MediaWiki class has been deprecated. Type hints in hooks should be
  changed to refer to MediaWikiEntryPoint instead. Note that extensions should
  not define their own entry points and should not interfere with the state of
  MediaWikiEntryPoint instances.
* Various methods in ObjectCache have been deprecated and their equivalent made
  available in ObjectCacheFactory, use them instead:
  - ::getInstance() -> ObjectCacheFactory::getInstance()
  - ::newFromParams() -> ObjectCacheFactory::newFromParams()
  - ::newAnything() -> ObjectCacheFactory::newInstance(
         ObjectCache::getAnythingId() )
  - ::getLocalServerInstance() -> ObjectCacheFactory::getLocalServerInstance()
  - ::clear() -> ObjectCacheFactory::clear()
  - In addition, the ObjectCache::$instances member has been deprecated as well.
* Vuex has been deprecated in favor of its successor, Pinia. Though deprecated,
  Vuex 4 will remain accessible for the foreseeable future. Pinia should be used
  for new projects.
* Linker::makeHeadline() has been deprecated.
* SerializedValueContainer::isUnified() has been deprecated and now emits
  deprecation warnings since 1.42.
* Linker::generateTOC(), Linker::tocIndent(), Linker::tocUnindent(),
  Linker::tocLine(), Linker::tocLineEnd(), Linker::tocList() are deprecated.
* Title::getBrokenLinksFrom() has been deprecated.
* LogFormatter subclasses now emit deprecation warnings unless they are
  constructed using LogFormatterFactory.
* ReplicatedBagOStuff has been deprecated since 1.42.
* The third argument to ContentRenderer::getParserOutput() now accepts a
  RevisionRecord or WikiRevision; passing an integer revision id has been
  deprecated and emits a warning.
* Passing a null value to ParserOutput::setPageProperty() has been deprecated
  and emits a warning; pass an empty string or use `::unsetPageProperty()`
  instead.
* Passing a non-string value to ParserOutput::setPageProperty() has been
  deprecated; use ::setIndexedPageProperty() instead.
* Passing a non-scalar value to ParserOutput::setPageProperty() will emit
  a warning (it has never worked).
* ParserOutput::setLanguageLinks() has been deprecated.
* ParserOutput::getTimestamp() and ::setTimestamp() have been deprecated; use
  ::getRevisionTimestamp() and ::setRevisionTimestamp() instead.
* ParserOutput::setText() has been deprecated; use ::setRawText() instead which
  matches the name of the corresponding getter, ParserOutput::getRawText().
* ParserOutput::addTemplate() will emit a deprecation warning if it is called
  with a non-local title, such as an interwiki link.  In a future release
  it will throw InvalidArgumentException.
* ApiQueryBlockInfoTrait::addBlockInfoToQuery() will emit deprecation warnings
  and will soon stop working due to schema changes. Instead use
  addDeletedUserFilter() or getBlockDetailsForRows().
* UploadBase::getImageInfo was deprecated, subclasses of ApiUpload can use
  ApiUpload::getUploadImageInfo() instead.
* DatabaseBlockStore::updateTimestamp() is now internal and should not be
  called.
* The LocalisationCache helper class GlobalDependency has been deprecated,
  use MainConfigDependency instead.
* The module `mediawiki.icon` has been deprecated. Use the Codex mixin instead
  (T351681).
* ConfigRepository::class and MediaWikiServices::getConfigRepository() have been
  deprecated, they are unused.
* Passing a WikiPage to PageEditStash::parseAndCache() has been deprecated.
  Use PageUpdater instance.
* SpecialBlock::getSuggestedDurations() has been deprecated, use
  Language::getBlockDurations() instead.
* MediaWikiServices::getBlockErrorFormatter() has been deprecated, use
  MediaWikiServices::getFormatterFactory()->getBlockErrorFormatter() instead.
* DummyLinker has been deprecated. The DummyLinker parameter to the
  'ImageBeforeProduceHTML' hook will become null in the future.
* Database::listViews() has been deprecated. This was previously used to filter
  views out of the return value of Database::listTables(). Now listTables()
  will not include views. MediaWiki does not use views.
* (T207621) UserMailer::rfc822Phrase() has been hard deprecated.
* TempUserConfig::getMatchPattern has been deprecated, use
  TempUserConfig::getMatchPatterns instead.
* (T230025) Title::purgeSquid(), deprecated in 1.35, now emits warnings.
* Title::getCdnUrls(), deprecated in 1.35, now emits warnings.
* The rarely-used convenience method Xml::wrapClass() is now deprecated. Instead
  you can use Xml::tags('span', ['class'=>'foo'], 'bar').
* WebRequest::getCrossSiteCookie() has been deprecated due to the removal of
  $wgUseSameSiteLegacyCookies. It will emit deprecation warnings. Use
  WebRequest::getCookie().
* Using the array_merge_recursive merge strategy in extension.json and skin.json
  has been hard deprecated.
* DBAccessObjectUtils::getDBFromIndex() is now deprecated, use
  ::getDBFromRecency() instead.
* Many Xml methods that are specific to HTML but not XML are deprecated:
  - Xml::buildForm
  - Xml::buildTable
  - Xml::buildTableRow
  - Xml::check
  - Xml::checkLabel
  - Xml::dateMenu
  - Xml::fieldset
  - Xml::input
  - Xml::inputLabel
  - Xml::inputLabelSep
  - Xml::label
  - Xml::languageSelector
  - Xml::listDropdown
  - Xml::listDropdownOptions
  - Xml::listDropdownOptionsOoui
  - Xml::monthSelector
  - Xml::option
  - Xml::password
  - Xml::radio
  - Xml::radioLabel
  - Xml::span
  - Xml::submitButton
  - Xml::textarea
  - Xml::attrib (only for use in HTML, not XML contexts)
* IMaintainableDatabase::truncate() has been deprecated. Use truncateTable()
  instead.
* TextConflictHelper->incrementStatsByUserEdits() is now deprecated.  The
  action this function previously handled should be moved into
  incrementConflictStats() and incrementResolvedStats().
* SQLPlatform::getQueryVerb() is now deprecated.
* …

=== Other changes in 1.42 ===
* Gallery: Image captions are no longer wrapped in <p> tags. Skins that
  customize rendering for galleries may need to tweak their CSS.
* Scripts under maintenance/dev/, for quickly setup a local MediaWiki for
  development purposes, have been removed, see DEVELOPERS.md for alternatives.
* …

== Compatibility ==

MediaWiki 1.42 requires PHP 7.4.3 or later and the following PHP extensions:

* ctype
* dom
* fileinfo
* iconv
* intl
* json
* mbstring
* xml

MariaDB is the recommended database software. MySQL, PostgreSQL, or SQLite can
be used instead, but support for them is somewhat less mature.

The supported versions are:

* MariaDB 10.3 or higher
* MySQL 5.7.0 or higher
* PostgreSQL 10 or later
* SQLite 3.8.0 or later

== Online documentation ==
Documentation for both end-users and site administrators is available on
MediaWiki.org, and is covered under the GNU Free Documentation License (except
for pages that explicitly state that their contents are in the public domain):

  https://www.mediawiki.org/wiki/Special:MyLanguage/Documentation

== Mailing list ==
A mailing list is available for MediaWiki user support and discussion:

  https://lists.wikimedia.org/postorius/lists/mediawiki-l.lists.wikimedia.org/

A low-traffic announcements-only list is also available:

  https://lists.wikimedia.org/postorius/lists/mediawiki-announce.lists.wikimedia.org/

It's highly recommended that you sign up for one of these lists if you're
going to run a public MediaWiki, so you can be notified of security fixes.

== IRC help ==
There's usually someone online in #mediawiki on irc.libera.chat.