ParserObserver.php

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<?php
 
namespace MediaWiki\Parser;
 
use MediaWiki\Content\Content;
use MediaWiki\Page\CacheKeyHelper;
use MediaWiki\Page\PageReference;
use MediaWiki\Title\Title;
use Psr\Log\LoggerInterface;
use RuntimeException;
use Wikimedia\MapCacheLRU\MapCacheLRU;
 
class ParserObserver {
    private readonly MapCacheLRU $previousParseStackTraces;
 
    public function __construct( private readonly LoggerInterface $logger ) {
        $this->previousParseStackTraces = new MapCacheLRU( 10 );
    }
 
    public function notifyParse(
        PageReference $page, ?int $revId, ParserOptions $options, Content $content, ParserOutput $output
    ) {
        $pageKey = CacheKeyHelper::getKeyForPage( $page );
 
        $optionsHash = $options->optionsHash(
            $output->getUsedOptions(),
            Title::newFromPageReference( $page )
        );
 
        $contentStr = $content->isValid() ? $content->serialize() : null;
        // $contentStr may be null if the content could not be serialized
        $contentSha1 = $contentStr ? sha1( $contentStr ) : 'INVALID';
 
        $index = $this->getParseId( $pageKey, $revId, $optionsHash, $contentSha1 );
 
        $stackTrace = ( new RuntimeException() )->getTraceAsString();
        if ( $this->previousParseStackTraces->has( $index ) ) {
 
            // NOTE: there may be legitimate changes to re-parse the same WikiText content,
            // e.g. if predicted revision ID for the REVISIONID magic word mismatched.
            // But that should be rare.
            $this->logger->debug(
                __METHOD__ . ': Possibly redundant parse!',
                [
                    'page' => $pageKey,
                    'rev' => $revId,
                    'options-hash' => $optionsHash,
                    'contentSha1' => $contentSha1,
                    'trace' => $stackTrace,
                    'previous-trace' => $this->previousParseStackTraces->get( $index ),
                ]
            );
        }
        $this->previousParseStackTraces->set( $index, $stackTrace );
    }
 
    private function getParseId( string $titleStr, ?int $revId, string $optionsHash, string $contentSha1 ): string {
        // $revId may be null when previewing a new page
        $revIdStr = $revId ?? "";
 
        return "$titleStr.$revIdStr.$optionsHash.$contentSha1";
    }
 
}