Feature: #92562 - Frontend groups resolved directly after the Frontend User itself¶
For legacy purposes, the valid frontend user groups were added while resolving the root line in TypoScriptFrontendController. This is much later in the frontend request process than the preparation of the Frontend User, which is resolved by the session or form credentials.
There are several reasons for the historic behavior:
Special functionality like "pages.fe_login_mode" which can override groups based on the current root line
Previewing frontend user groups via the Admin Panel for backend users
However, this historic behavior led to inconsistencies, especially with the Context API to retrieve the correct usergroups in PSR-15 middlewares to build custom APIs.
In addition, this functionality is now extracted from TSFE and into the middleware, further decoupling the User authentication from the TSFE object.
When the PSR-15 middleware is setting up the FrontendUserAuthentication object at a very early stage of the frontend request, the groups are resolved directly afterwards, leaving the FrontendUserAuthentication object in a consistent state for further middlewares to work with the appropriate groups.
Please note that any existing custom AuthenticationService for resolving frontend user groups, which might rely on a valid TSFE object will have to be evaluated if it still works in TYPO3 v11.
Also: Further middlewares and TSFE itself can still override the assigned groups due to previewing behavior.