Upgrade from 2.x to 3.x (BC release)

TYPO3 versions support

3.x will support TYPO3 >= 11.5 only, if you are still on 10.4/9.5 please use 2.x branch instead.

FrontendBaseUrlInPagePreview flag will be removed. Please use headless.frontendUrls instead (available since 2.5 release)
headless.simplifiedLinkTarget flag will be removed. Setting will on by default

Stuff to be removed:

FriendsOfTYPO3\Headless\Utility\ContentUtility will be removed. Please use new CONTENT_JSON content object
FriendsOfTYPO3\Headless\Utility\FrontendBaseUtility will be removed. Please use FriendsOfTYPO3\Headless\Utility\UrlUtility
FriendsOfTYPO3\Headless\Service\SiteService will be removed. Please use FriendsOfTYPO3\Headless\Utility\UrlUtility
$GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['headless']['hooks']['redirectUrl'] hook will be removed. Please use FriendsOfTYPO3\Headless\Event\RedirectUrlEvent

Changed behavior:

FriendsOfTYPO3\Headless\Json\JsonEncoder have dropped array input as requirement, so you can now encode objects etc, also by default encoder do not checks for possible json to decode, you have manually use FriendsOfTYPO3\Headless\Json\JsonDecoder
FriendsOfTYPO3\Headless\Hooks\TypolinkHook. Main functionality is replaced with native TYPO3 core feature. TypolinkHook serving temporarily as fallback for 2.x page output only Typoscript --
By default, json output is streamlined & optimized. If you do not want to rewrite frontend app, please use Configuration/TypoScript/2.x/setup.typoscript instead default one.
If you would like to use version 2.x of page output and do not touch frontend app, please also enable headless.supportOldPageOutput (restores default behavior with dataprocessing & typolink) flag in LocalConfiguration.php or AdditionalConfiguration.php
domains listing for configure frontend endpoint in 3.x will be 835 by default instead of 1608564571, also default SiteProvider will check if domain is marked as headless