TYPO3 Multitree without domain records in development

AdditionalConfiguration.php

<?php

use TYPO3\CMS\Core\Utility\GeneralUtility;

if (\TYPO3\CMS\Core\Core\Bootstrap::getInstance()->getApplicationContext()->isDevelopment()) {
	/**
	 * This override adds the possibility to use multitree subdomains without domain records (for SHARED_DB, vagrant, etc.)
	 * You can override the mappings or undo the override by creating a config file inside conf.d
	 *
	 * The override PageRepository checks for $subdomain . exec('hostname -f')
	 * e.g. in vagrant flastname.4pweb.vm.1drop.de is FQDN hostname, so you will get de.flastname.4pweb.vm.1drop.de etc.
	 */
	$GLOBALS['TYPO3_CONF_VARS']['SYS']['domainMapping'] = [
		'de' => 42,
		'us' => 1337,
		'uk' => 1010,
	];
	$GLOBALS['TYPO3_CONF_VARS']['SYS']['Objects']['TYPO3\\CMS\\Frontend\\Page\\PageRepository']['className'] = 'ODS\\Onedrop\\Overrides\\PageRepository';
}

/**
 * !!! IMPORTANT !!!
 *
 * To enable your local configuration add
 * one or more files in conf.d as they are
 * loaded automatically.
 */
$configurationFiles = GeneralUtility::getFilesInDir(GeneralUtility::getFileAbsFileName('typo3conf/conf.d/'), 'php', TRUE);
foreach ($configurationFiles as $file) {
	require_once($file);
}

PageRepository.php

<?php
namespace ODS\Onedrop\Overrides;

/**
 * Copyright notice
 *
 * (c) Onedrop Solutions GmbH & Co. KG, www.1drop.de
 *
 * @author Hans Höchtl <hhoechtl@1drop.de>
 *
 * @license http://www.gnu.org/licenses/gpl.html GNU General Public License, version 3 or later
 */

class PageRepository extends \TYPO3\CMS\Frontend\Page\PageRepository {

	/**
	 * Will find the page carrying the domain record matching the input domain.
	 * Might exit after sending a redirect-header IF a found domain record
	 * instructs to do so.
	 *
	 * @param string $domain Domain name to search for. Eg. "www.typo3.com". Typical the HTTP_HOST value.
	 * @param string $path Path for the current script in domain. Eg. "/somedir/subdir". Typ. supplied by \TYPO3\CMS\Core\Utility\GeneralUtility::getIndpEnv('SCRIPT_NAME')
	 * @param string $request_uri Request URI: Used to get parameters from if they should be appended. Typ. supplied by \TYPO3\CMS\Core\Utility\GeneralUtility::getIndpEnv('REQUEST_URI')
	 *
	 * @return mixed If found, returns integer with page UID where found. Otherwise blank. Might exit if location-header is sent, see description.
	 * @see \TYPO3\CMS\Frontend\Controller\TypoScriptFrontendController::findDomainRecord()
	 */
	public function getDomainStartPage( $domain, $path = '', $request_uri = '' ) {
		$domain = explode( ':', $domain );
		$domain = strtolower( preg_replace( '/\\.$/', '', $domain[0] ) );
		// Removing extra trailing slashes
		$path = trim( preg_replace( '/\\/[^\\/]*$/', '', $path ) );
		// Appending to domain string
		$domain .= $path;
		$domain = preg_replace( '/\\/*$/', '', $domain );
		/**
		 * This is the additional condition to have domain mapping without domain records
		 */
		if ( isset( $GLOBALS['TYPO3_CONF_VARS']['SYS']['domainMapping'] ) && $domain !== exec('hostname -f') ) {
			foreach ($GLOBALS['TYPO3_CONF_VARS']['SYS']['domainMapping'] as $subdomain => $pageUid) {
				if ($subdomain . '.' . exec('hostname -f') === $domain) {
					return $pageUid;
				}
			}
			throw new \RuntimeException('No Mapping for domain ' . $domain . ' defined');
		} else {
			$res = $GLOBALS['TYPO3_DB']->exec_SELECTquery( 'pages.uid,sys_domain.redirectTo,sys_domain.redirectHttpStatusCode,sys_domain.prepend_params', 'pages,sys_domain', 'pages.uid=sys_domain.pid
						AND sys_domain.hidden=0
						AND (sys_domain.domainName=' . $GLOBALS['TYPO3_DB']->fullQuoteStr( $domain, 'sys_domain' ) . ' OR sys_domain.domainName=' . $GLOBALS['TYPO3_DB']->fullQuoteStr( ( $domain . '/' ), 'sys_domain' ) . ') ' . $this->where_hid_del . $this->where_groupAccess, '', '', 1 );
			$row = $GLOBALS['TYPO3_DB']->sql_fetch_assoc( $res );
			$GLOBALS['TYPO3_DB']->sql_free_result( $res );
			if ( $row ) {
				if ( $row['redirectTo'] ) {
					$redirectUrl = $row['redirectTo'];
					if ( $row['prepend_params'] ) {
						$redirectUrl = rtrim( $redirectUrl, '/' );
						$prependStr  = ltrim( substr( $request_uri, strlen( $path ) ), '/' );
						$redirectUrl .= '/' . $prependStr;
					}
					$statusCode = (int) $row['redirectHttpStatusCode'];
					if ( $statusCode && defined( 'TYPO3\\CMS\\Core\\Utility\\HttpUtility::HTTP_STATUS_' . $statusCode ) ) {
						\TYPO3\CMS\Core\Utility\HttpUtility::redirect( $redirectUrl, constant( 'TYPO3\\CMS\\Core\\Utility\\HttpUtility::HTTP_STATUS_' . $statusCode ) );
					} else {
						\TYPO3\CMS\Core\Utility\HttpUtility::redirect( $redirectUrl, \TYPO3\CMS\Core\Utility\HttpUtility::HTTP_STATUS_301 );
					}
					die;
				} else {
					return $row['uid'];
				}
			}
		}
	}
}