SpecialWhatLinksHere.php

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<?php
namespace MediaWiki\Specials;
 
use MediaWiki\Cache\LinkBatchFactory;
use MediaWiki\Content\IContentHandlerFactory;
use MediaWiki\Deferred\LinksUpdate\ImageLinksTable;
use MediaWiki\Deferred\LinksUpdate\PageLinksTable;
use MediaWiki\Deferred\LinksUpdate\TemplateLinksTable;
use MediaWiki\Html\Html;
use MediaWiki\HTMLForm\HTMLForm;
use MediaWiki\Linker\LinksMigration;
use MediaWiki\Linker\LinkTarget;
use MediaWiki\MainConfigNames;
use MediaWiki\Message\Message;
use MediaWiki\Navigation\PagerNavigationBuilder;
use MediaWiki\Page\PageIdentity;
use MediaWiki\SpecialPage\FormSpecialPage;
use MediaWiki\Title\NamespaceInfo;
use MediaWiki\Title\Title;
use MediaWiki\Title\TitleFactory;
use SearchEngineFactory;
use stdClass;
use Wikimedia\Rdbms\IConnectionProvider;
use Wikimedia\Rdbms\IReadableDatabase;
use Wikimedia\Rdbms\SelectQueryBuilder;
 
class SpecialWhatLinksHere extends FormSpecialPage {
    protected $target;
 
    private array $formData;
    private IConnectionProvider $dbProvider;
    private LinkBatchFactory $linkBatchFactory;
    private IContentHandlerFactory $contentHandlerFactory;
    private SearchEngineFactory $searchEngineFactory;
    private NamespaceInfo $namespaceInfo;
    private TitleFactory $titleFactory;
    private LinksMigration $linksMigration;
 
    private const LIMITS = [ 20, 50, 100, 250, 500 ];
 
    public function __construct(
        IConnectionProvider $dbProvider,
        LinkBatchFactory $linkBatchFactory,
        IContentHandlerFactory $contentHandlerFactory,
        SearchEngineFactory $searchEngineFactory,
        NamespaceInfo $namespaceInfo,
        TitleFactory $titleFactory,
        LinksMigration $linksMigration
    ) {
        parent::__construct( 'Whatlinkshere' );
        $this->mIncludable = true;
        $this->dbProvider = $dbProvider;
        $this->linkBatchFactory = $linkBatchFactory;
        $this->contentHandlerFactory = $contentHandlerFactory;
        $this->searchEngineFactory = $searchEngineFactory;
        $this->namespaceInfo = $namespaceInfo;
        $this->titleFactory = $titleFactory;
        $this->linksMigration = $linksMigration;
    }
 
    protected function setParameter( $par ) {
        if ( $par ) {
            // The only difference that subpage syntax can have is the underscore.
            $par = str_replace( '_', ' ', $par );
        }
        parent::setParameter( $par );
    }
 
    public function onSuccess() {
        $this->getSkin()->setRelevantTitle( $this->target );
 
        $out = $this->getOutput();
        $out->setPageTitleMsg(
            $this->msg( 'whatlinkshere-title' )->plaintextParams( $this->target->getPrefixedText() )
        );
        $out->addBacklinkSubtitle( $this->target );
 
        [ $offsetNamespace, $offsetPageID, $dir ] = $this->parseOffsetAndDir();
 
        $this->showIndirectLinks(
            0,
            $this->target,
            $this->formData['limit'],
            $offsetNamespace,
            $offsetPageID,
            $dir
        );
    }
 
    private function parseOffsetAndDir(): array {
        $from = (int)$this->formData['from'];
 
        if ( $from ) {
            $dir = 'next';
            $offsetNamespace = null;
            $offsetPageID = $from - 1;
        } else {
            $dir = $this->formData['dir'] ?? 'next';
            [ $offsetNamespaceString, $offsetPageIDString ] = explode(
                '|',
                $this->formData['offset'] . '|'
            );
            if ( !$offsetPageIDString ) {
                $offsetPageIDString = $offsetNamespaceString;
                $offsetNamespaceString = '';
            }
            if ( is_numeric( $offsetNamespaceString ) ) {
                $offsetNamespace = (int)$offsetNamespaceString;
            } else {
                $offsetNamespace = null;
            }
            $offsetPageID = (int)$offsetPageIDString;
        }
 
        if ( $offsetNamespace === null ) {
            $offsetTitle = $this->titleFactory->newFromID( $offsetPageID );
            $offsetNamespace = $offsetTitle ? $offsetTitle->getNamespace() : NS_MAIN;
        }
 
        return [ $offsetNamespace, $offsetPageID, $dir ];
    }
 
    private function showIndirectLinks(
        $level, LinkTarget $target, $limit, $offsetNamespace = 0, $offsetPageID = 0, $dir = 'next'
    ) {
        $out = $this->getOutput();
        $dbr = $this->dbProvider->getReplicaDatabase();
        $hookRunner = $this->getHookRunner();
 
        $hidelinks = $this->formData['hidelinks'];
        $hideredirs = $this->formData['hideredirs'];
        $hidetrans = $this->formData['hidetrans'];
        $hideimages = $target->getNamespace() !== NS_FILE || ( $this->formData['hideimages'] ?? false );
 
        // For historical reasons `pagelinks` always contains an entry for the redirect target.
        // So we only need to query `redirect` if `pagelinks` isn't being queried.
        $fetchredirs = $hidelinks && !$hideredirs;
 
        // Build query conds in concert for all four tables...
        $conds = [];
        $conds['redirect'] = [
            'rd_namespace' => $target->getNamespace(),
            'rd_title' => $target->getDBkey(),
            'rd_interwiki' => '',
        ];
        $conds['pagelinks'] = $this->linksMigration->getLinksConditions( 'pagelinks', $target );
        $conds['templatelinks'] = $this->linksMigration->getLinksConditions( 'templatelinks', $target );
        $conds['imagelinks'] = [
            'il_to' => $target->getDBkey(),
        ];
 
        $namespace = $this->formData['namespace'];
        if ( $namespace !== '' ) {
            $invert = $this->formData['invert'];
            if ( $invert ) {
                // Select all namespaces except for the specified one.
                // This allows the database to use the *_from_namespace index. (T241837)
                $namespaces = array_diff(
                    $this->namespaceInfo->getValidNamespaces(), [ $namespace ] );
            } else {
                $namespaces = $namespace;
            }
        } else {
            // Select all namespaces.
            // This allows the database to use the *_from_namespace index. (T297754)
            $namespaces = $this->namespaceInfo->getValidNamespaces();
        }
        $conds['redirect']['page_namespace'] = $namespaces;
        $conds['pagelinks']['pl_from_namespace'] = $namespaces;
        $conds['templatelinks']['tl_from_namespace'] = $namespaces;
        $conds['imagelinks']['il_from_namespace'] = $namespaces;
 
        if ( $offsetPageID ) {
            $op = $dir === 'prev' ? '<' : '>';
            $conds['redirect'][] = $dbr->buildComparison( $op, [
                'rd_from' => $offsetPageID,
            ] );
            $conds['templatelinks'][] = $dbr->buildComparison( $op, [
                'tl_from_namespace' => $offsetNamespace,
                'tl_from' => $offsetPageID,
            ] );
            $conds['pagelinks'][] = $dbr->buildComparison( $op, [
                'pl_from_namespace' => $offsetNamespace,
                'pl_from' => $offsetPageID,
            ] );
            $conds['imagelinks'][] = $dbr->buildComparison( $op, [
                'il_from_namespace' => $offsetNamespace,
                'il_from' => $offsetPageID,
            ] );
        }
 
        if ( $hideredirs ) {
            // For historical reasons `pagelinks` always contains an entry for the redirect target.
            // So we hide that link when $hideredirs is set. There's unfortunately no way to tell when a
            // redirect's content also links to the target.
            $conds['pagelinks']['rd_from'] = null;
        }
 
        $sortDirection = $dir === 'prev' ? SelectQueryBuilder::SORT_DESC : SelectQueryBuilder::SORT_ASC;
 
        $fname = __METHOD__;
        $queryFunc = function ( IReadableDatabase $dbr, $table, $fromCol ) use (
            $conds, $target, $limit, $sortDirection, $fname, $hookRunner
        ) {
            // Read an extra row as an at-end check
            $queryLimit = $limit + 1;
            $on = [
                "rd_from = $fromCol",
                'rd_title' => $target->getDBkey(),
                'rd_namespace' => $target->getNamespace(),
                'rd_interwiki' => '',
            ];
            // Inner LIMIT is 2X in case of stale backlinks with wrong namespaces
            $subQuery = $dbr->newSelectQueryBuilder()
                ->table( $table )
                ->fields( [ $fromCol, 'rd_from', 'rd_fragment' ] )
                ->conds( $conds[$table] )
                ->orderBy( [ $fromCol . '_namespace', $fromCol ], $sortDirection )
                ->limit( 2 * $queryLimit )
                ->leftJoin( 'redirect', 'redirect', $on );
 
            $queryBuilder = $dbr->newSelectQueryBuilder()
                ->table( $subQuery, 'temp_backlink_range' )
                ->join( 'page', 'page', "$fromCol = page_id" )
                ->fields( [ 'page_id', 'page_namespace', 'page_title',
                    'rd_from', 'rd_fragment', 'page_is_redirect' ] )
                ->orderBy( [ 'page_namespace', 'page_id' ], $sortDirection )
                ->limit( $queryLimit );
 
            $hookRunner->onSpecialWhatLinksHereQuery( $table, $this->formData, $queryBuilder );
 
            return $queryBuilder->caller( $fname )->fetchResultSet();
        };
 
        if ( $fetchredirs ) {
            $queryBuilder = $dbr->newSelectQueryBuilder()
                ->table( 'redirect' )
                ->fields( [ 'page_id', 'page_namespace', 'page_title', 'rd_from', 'rd_fragment', 'page_is_redirect' ] )
                ->conds( $conds['redirect'] )
                ->orderBy( 'rd_from', $sortDirection )
                ->limit( $limit + 1 )
                ->join( 'page', 'page', 'rd_from = page_id' );
 
            $hookRunner->onSpecialWhatLinksHereQuery( 'redirect', $this->formData, $queryBuilder );
 
            $rdRes = $queryBuilder->caller( __METHOD__ )->fetchResultSet();
        }
 
        if ( !$hidelinks ) {
            $plRes = $queryFunc(
                $this->dbProvider->getReplicaDatabase( PageLinksTable::VIRTUAL_DOMAIN ),
                'pagelinks',
                'pl_from'
            );
        }
 
        if ( !$hidetrans ) {
            $tlRes = $queryFunc(
                $this->dbProvider->getReplicaDatabase( TemplateLinksTable::VIRTUAL_DOMAIN ),
                'templatelinks',
                'tl_from'
            );
        }
 
        if ( !$hideimages ) {
            $ilRes = $queryFunc(
                $this->dbProvider->getReplicaDatabase( ImageLinksTable::VIRTUAL_DOMAIN ),
                'imagelinks',
                'il_from'
            );
        }
 
        // @phan-suppress-next-line PhanPossiblyUndeclaredVariable $rdRes is declared when fetching redirs
        if ( ( !$fetchredirs || !$rdRes->numRows() )
            // @phan-suppress-next-line PhanPossiblyUndeclaredVariable $plRes is declared when fetching links
            && ( $hidelinks || !$plRes->numRows() )
            // @phan-suppress-next-line PhanPossiblyUndeclaredVariable $tlRes is declared when fetching trans
            && ( $hidetrans || !$tlRes->numRows() )
            // @phan-suppress-next-line PhanPossiblyUndeclaredVariable $ilRes is declared when fetching images
            && ( $hideimages || !$ilRes->numRows() )
        ) {
            if ( $level == 0 && !$this->including() ) {
                if ( $hidelinks || $hidetrans || $hideredirs ) {
                    $msgKey = 'nolinkshere-filter';
                } elseif ( $namespace !== '' ) {
                    $msgKey = 'nolinkshere-ns';
                } else {
                    $msgKey = 'nolinkshere';
                }
                $link = $this->getLinkRenderer()->makeLink(
                    $this->target,
                    null,
                    [],
                    $this->target->isRedirect() ? [ 'redirect' => 'no' ] : []
                );
 
                $errMsg = $this->msg( $msgKey )
                    ->params( $this->target->getPrefixedText() )
                    ->rawParams( $link )
                    ->parseAsBlock();
                $out->addHTML( $errMsg );
                $out->setStatusCode( 404 );
            }
 
            return;
        }
 
        // Read the rows into an array and remove duplicates
        // templatelinks comes third so that the templatelinks row overwrites the
        // pagelinks/redirect row, so we get (inclusion) rather than nothing
        $rows = [];
        if ( $fetchredirs ) {
            // @phan-suppress-next-line PhanPossiblyUndeclaredVariable $rdRes is declared when fetching redirs
            foreach ( $rdRes as $row ) {
                $row->is_template = 0;
                $row->is_image = 0;
                $rows[$row->page_id] = $row;
            }
        }
        if ( !$hidelinks ) {
            // @phan-suppress-next-line PhanPossiblyUndeclaredVariable $plRes is declared when fetching links
            foreach ( $plRes as $row ) {
                $row->is_template = 0;
                $row->is_image = 0;
                $rows[$row->page_id] = $row;
            }
        }
        if ( !$hidetrans ) {
            // @phan-suppress-next-line PhanPossiblyUndeclaredVariable $tlRes is declared when fetching trans
            foreach ( $tlRes as $row ) {
                $row->is_template = 1;
                $row->is_image = 0;
                $rows[$row->page_id] = $row;
            }
        }
        if ( !$hideimages ) {
            // @phan-suppress-next-line PhanPossiblyUndeclaredVariable $ilRes is declared when fetching images
            foreach ( $ilRes as $row ) {
                $row->is_template = 0;
                $row->is_image = 1;
                $rows[$row->page_id] = $row;
            }
        }
 
        // Sort by namespace + page ID, changing the keys to 0-based indices
        usort( $rows, static function ( $rowA, $rowB ) {
            if ( $rowA->page_namespace !== $rowB->page_namespace ) {
                return $rowA->page_namespace < $rowB->page_namespace ? -1 : 1;
            }
            if ( $rowA->page_id !== $rowB->page_id ) {
                return $rowA->page_id < $rowB->page_id ? -1 : 1;
            }
            return 0;
        } );
 
        $numRows = count( $rows );
 
        // Work out the start and end IDs, for prev/next links
        if ( !$limit ) { // T289351
            $nextNamespace = $nextPageId = $prevNamespace = $prevPageId = false;
            $rows = [];
        } elseif ( $dir === 'prev' ) {
            if ( $numRows > $limit ) {
                // More rows available after these ones
                // Get the next row from the last row in the result set
                $nextNamespace = $rows[$limit]->page_namespace;
                $nextPageId = $rows[$limit]->page_id;
                // Remove undisplayed rows, for dir='prev' we need to discard first record after sorting
                $rows = array_slice( $rows, 1, $limit );
                // Get the prev row from the first displayed row
                $prevNamespace = $rows[0]->page_namespace;
                $prevPageId = $rows[0]->page_id;
            } else {
                // Get the next row from the last displayed row
                $nextNamespace = $rows[$numRows - 1]->page_namespace;
                $nextPageId = $rows[$numRows - 1]->page_id;
                $prevNamespace = false;
                $prevPageId = false;
            }
        } else {
            // If offset is not set disable prev link
            $prevNamespace = $offsetPageID ? $rows[0]->page_namespace : false;
            $prevPageId = $offsetPageID ? $rows[0]->page_id : false;
            if ( $numRows > $limit ) {
                // Get the next row from the last displayed row
                $nextNamespace = $rows[$limit - 1]->page_namespace ?? false;
                $nextPageId = $rows[$limit - 1]->page_id ?? false;
                // Remove undisplayed rows
                $rows = array_slice( $rows, 0, $limit );
            } else {
                $nextNamespace = false;
                $nextPageId = false;
            }
        }
 
        // Optimization: Batch preload all Title data in one query
        $lb = $this->linkBatchFactory->newLinkBatch()->setCaller( __METHOD__ );
        foreach ( $rows as $row ) {
            $lb->add( $row->page_namespace, $row->page_title );
        }
        $lb->execute();
 
        if ( $level == 0 && !$this->including() ) {
            $link = $this->getLinkRenderer()->makeLink(
                $this->target,
                null,
                [],
                $this->target->isRedirect() ? [ 'redirect' => 'no' ] : []
            );
 
            $msg = $this->msg( 'linkshere' )
                ->params( $this->target->getPrefixedText() )
                ->rawParams( $link )
                ->parseAsBlock();
            $out->addHTML( $msg );
 
            $out->addWikiMsg( 'whatlinkshere-count', Message::numParam( count( $rows ) ) );
 
            $prevnext = $this->getPrevNext( $prevNamespace, $prevPageId, $nextNamespace, $nextPageId );
            $out->addHTML( $prevnext );
        }
        $out->addHTML( $this->listStart( $level ) );
        foreach ( $rows as $row ) {
            $nt = Title::makeTitle( $row->page_namespace, $row->page_title );
 
            if ( $row->rd_from && $level < 2 ) {
                $out->addHTML( $this->listItem( $row, $nt, $target, true ) );
                $this->showIndirectLinks(
                    $level + 1,
                    $nt,
                    $this->getConfig()->get( MainConfigNames::MaxRedirectLinksRetrieved )
                );
                $out->addHTML( Html::closeElement( 'li' ) );
            } else {
                $out->addHTML( $this->listItem( $row, $nt, $target ) );
            }
        }
 
        $out->addHTML( $this->listEnd() );
 
        if ( $level == 0 && !$this->including() ) {
            // @phan-suppress-next-next-line PhanPossiblyUndeclaredVariable $prevnext is defined with $level is 0
            // @phan-suppress-next-line PhanTypeMismatchArgumentNullable prevnext is set when used
            $out->addHTML( $prevnext );
        }
    }
 
    protected function listStart( int $level ): string {
        return Html::openElement( 'ul', ( $level ? [] : [ 'id' => 'mw-whatlinkshere-list' ] ) );
    }
 
    private function listItem( stdClass $row, PageIdentity $nt, LinkTarget $target, bool $notClose = false ): string {
        $legacyTitle = $this->titleFactory->newFromPageIdentity( $nt );
 
        if ( $row->rd_from || $row->page_is_redirect ) {
            $query = [ 'redirect' => 'no' ];
        } else {
            $query = [];
        }
 
        $dir = $this->getLanguage()->getDir();
        $link = Html::rawElement( 'bdi', [ 'dir' => $dir ], $this->getLinkRenderer()->makeKnownLink(
            $nt,
            null,
            $row->page_is_redirect ? [ 'class' => 'mw-redirect' ] : [],
            $query
        ) );
 
        // Display properties (redirect or template)
        $propsText = '';
        $props = [];
        if ( (string)$row->rd_fragment !== '' ) {
            $props[] = $this->msg( 'whatlinkshere-sectionredir' )
                ->rawParams( $this->getLinkRenderer()->makeLink(
                    $target->createFragmentTarget( $row->rd_fragment ),
                    $row->rd_fragment
                ) )->escaped();
        } elseif ( $row->rd_from ) {
            $props[] = $this->msg( 'isredirect' )->escaped();
        }
        if ( $row->is_template ) {
            $props[] = $this->msg( 'istemplate' )->escaped();
        }
        if ( $row->is_image ) {
            $props[] = $this->msg( 'isimage' )->escaped();
        }
 
        $legacyTarget = $this->titleFactory->newFromLinkTarget( $target );
        $this->getHookRunner()->onWhatLinksHereProps( $row, $legacyTitle, $legacyTarget, $props );
 
        if ( count( $props ) ) {
            $propsText = $this->msg( 'parentheses' )
                ->rawParams( $this->getLanguage()->semicolonList( $props ) )->escaped();
        }
 
        # Space for utilities links, with a what-links-here link provided
        $wlhLink = $this->wlhLink(
            $legacyTitle,
            $this->msg( 'whatlinkshere-links' )->text(),
            $this->msg( 'editlink' )->text()
        );
        $wlh = Html::rawElement(
            'span',
            [ 'class' => 'mw-whatlinkshere-tools' ],
            $this->msg( 'parentheses' )->rawParams( $wlhLink )->escaped()
        );
 
        return $notClose ?
            Html::openElement( 'li' ) . "$link $propsText $wlh\n" :
            Html::rawElement( 'li', [], "$link $propsText $wlh" ) . "\n";
    }
 
    protected function listEnd(): string {
        return Html::closeElement( 'ul' );
    }
 
    protected function wlhLink( Title $target, string $text, string $editText ): string {
        static $title = null;
        $title ??= $this->getPageTitle();
 
        $linkRenderer = $this->getLinkRenderer();
 
        // always show a "<- Links" link
        $links = [
            'links' => $linkRenderer->makeKnownLink(
                $title,
                $text,
                [],
                [ 'target' => $target->getPrefixedText() ]
            ),
        ];
 
        // if the page is editable, add an edit link
        if (
            // check user permissions
            $this->getAuthority()->isAllowed( 'edit' ) &&
            // check, if the content model is editable through action=edit
            $this->contentHandlerFactory->getContentHandler( $target->getContentModel() )
                ->supportsDirectEditing()
        ) {
            $links['edit'] = $linkRenderer->makeKnownLink(
                $target,
                $editText,
                [],
                [ 'action' => 'edit' ]
            );
        }
 
        // build the links html
        return $this->getLanguage()->pipeList( $links );
    }
 
    private function getPrevNext( $prevNamespace, $prevPageId, $nextNamespace, $nextPageId ): string {
        $navBuilder = new PagerNavigationBuilder( $this->getContext() );
 
        $navBuilder
            ->setPage( $this->getPageTitle( $this->target->getPrefixedDBkey() ) )
            // Remove 'target', already included in the request title
            ->setLinkQuery(
                array_diff_key(
                    array_filter(
                        $this->formData,
                        static fn ( $value ) => $value !== null && $value !== '' && $value !== false
                    ),
                    [ 'target' => null, 'from' => null ]
                )
            )
            ->setLimits( self::LIMITS )
            ->setLimitLinkQueryParam( 'limit' )
            ->setCurrentLimit( $this->formData['limit'] )
            ->setPrevMsg( 'whatlinkshere-prev' )
            ->setNextMsg( 'whatlinkshere-next' );
 
        if ( $prevPageId != 0 ) {
            $navBuilder->setPrevLinkQuery( [ 'dir' => 'prev', 'offset' => "$prevNamespace|$prevPageId" ] );
        }
        if ( $nextPageId != 0 ) {
            $navBuilder->setNextLinkQuery( [ 'dir' => 'next', 'offset' => "$nextNamespace|$nextPageId" ] );
        }
 
        return $navBuilder->getHtml();
    }
 
    protected function getFormFields() {
        $this->addHelpLink( 'Help:What links here' );
        $this->getOutput()->addModuleStyles( 'mediawiki.special' );
 
        $fields = [
            'target' => [
                'type' => 'title',
                'name' => 'target',
                'id' => 'mw-whatlinkshere-target',
                'label-message' => 'whatlinkshere-page',
                'section' => 'whatlinkshere-target',
                'creatable' => true,
            ],
            'namespace' => [
                'type' => 'namespaceselect',
                'name' => 'namespace',
                'id' => 'namespace',
                'label-message' => 'namespace',
                'all' => '',
                'default' => '',
                'filter-callback' => static function ( $value ) {
                    return $value !== '' ? intval( $value ) : '';
                },
                'in-user-lang' => true,
                'section' => 'whatlinkshere-ns',
            ],
            'invert' => [
                'type' => 'check',
                'name' => 'invert',
                'id' => 'nsinvert',
                'hide-if' => [ '===', 'namespace', '' ],
                'label-message' => 'invert',
                'help-message' => 'tooltip-whatlinkshere-invert',
                'help-inline' => false,
                'section' => 'whatlinkshere-ns'
            ],
            'limit' => [
                'type' => 'hidden',
                'name' => 'limit',
                'default' => $this->getConfig()->get( MainConfigNames::QueryPageDefaultLimit ),
                'filter-callback' => static fn ( $value ) => max( 0, min( intval( $value ), 5000 ) ),
            ],
            'offset' => [
                'type' => 'api',
                'name' => 'offset',
                'default' => '',
            ],
            'dir' => [
                'type' => 'api',
                'name' => 'dir',
            ],
            'from' => [
                'type' => 'api',
                'name' => 'from',
                'default' => 0,
            ]
        ];
 
        $filters = [ 'hidetrans', 'hidelinks', 'hideredirs' ];
 
        // Combined message keys: 'whatlinkshere-hideredirs', 'whatlinkshere-hidetrans',
        // 'whatlinkshere-hidelinks'
        // To be sure they will be found by grep
        foreach ( $filters as $filter ) {
            // Parameter only provided for backwards-compatibility with old translations
            $hide = $this->msg( 'hide' )->text();
            $msg = $this->msg( "whatlinkshere-{$filter}", $hide )->text();
            $fields[$filter] = [
                'type' => 'check',
                'name' => $filter,
                'label' => $msg,
                'section' => 'whatlinkshere-filter',
            ];
        }
 
        return $fields;
    }
 
    protected function alterForm( HTMLForm $form ) {
        // This parameter from the subpage syntax is only added after constructing the form,
        // so we should add the dynamic field that depends on the user input here.
 
        // TODO: This looks not good. Ideally we can initialize it in onSubmit().
        // Maybe extend the hide-if feature to match prefixes on the client side.
        $this->target = Title::newFromText( $this->getRequest()->getText( 'target' ) );
        if ( $this->target && $this->target->getNamespace() == NS_FILE ) {
            $hide = $this->msg( 'hide' )->text();
            $msg = $this->msg( 'whatlinkshere-hideimages', $hide )->text();
            $form->addFields( [
                'hideimages' => [
                    'type' => 'check',
                    'name' => 'hideimages',
                    'label' => $msg,
                    'section' => 'whatlinkshere-filter',
                ]
            ] );
        }
 
        $form->setWrapperLegendMsg( 'whatlinkshere' )
            ->setSubmitTextMsg( 'whatlinkshere-submit' );
    }
 
    protected function getShowAlways() {
        return true;
    }
 
    protected function getSubpageField() {
        return 'target';
    }
 
    public function onSubmit( array $data ) {
        $this->formData = $data;
        return true;
    }
 
    public function requiresPost() {
        return false;
    }
 
    protected function getDisplayFormat() {
        return 'ooui';
    }
 
    public function prefixSearchSubpages( $search, $limit, $offset ) {
        return $this->prefixSearchString( $search, $limit, $offset, $this->searchEngineFactory );
    }
 
    protected function getGroupName() {
        return 'pagetools';
    }
}
 
class_alias( SpecialWhatLinksHere::class, 'SpecialWhatLinksHere' );