Installer.php

    public static function dumpVersionsClass(Event $composerEvent)
    {
        $io = $composerEvent->getIO();

        $io->write('<info>Generating version class...</info>');

        $composer = $composerEvent->getComposer();

        // Get root package
        $rootPackage = $composer->getPackage();
        while ($rootPackage instanceof AliasPackage) {
            $rootPackage = $rootPackage->getAliasOf();
        }

        if ('ocramius/package-versions' === $rootPackage->getName()) {
            $baseDir = dirname($composer->getConfig()->get('vendor-dir'));
        } else {
            $baseDir = $composer->getConfig()->get('vendor-dir') . '/ocramius/package-versions';
        }

        self::writeVersionClassToFile($baseDir, self::generateVersionsClass($composer));

        self::reDumpAutoloader($composer);

        $io->write('<info>...done generating version class</info>');
    }
    
        /**
     * @param string $versionClassSource
     */
    private static function writeVersionClassToFile(string $baseDir, string $versionClassSource)
    {
        file_put_contents($baseDir . '/src/PackageVersions/Versions.php', $versionClassSource, 0664);
    }