Deprecation: #101559 - Extbase uses ext:core ViewInterface
See forge#101559
Description
The default view of ext:extbase now returns a view that implements
        \TYPO3\ and not only
        \TYPO3Fluid\ anymore. This allows
implementing any view that implements 
        View,
and frees the direct dependency to Fluid.
The default return object is an instance of
        \TYPO3\ which implements all
special methods tailored for Fluid. Extbase controllers should
check for instance of this object before calling these methods,
especially:
- get- Rendering - Context - () 
- set- Rendering - Context - () 
- render- Section - () 
- render- Partial - () 
Method calls not being part of 
        View or the above
listed method names have been marked as deprecated and will be removed in TYPO3 v14.
Impact
Extbase controllers that extend 
        Action
and call methods not part of 
        View, should
test for 
        $view instanceof Fluid before calling
        get, 
        set, php:render
and 
        render.
All other Fluid related methods called on 
        $view have been marked as
deprecated and will log a deprecation level error message.
Affected installations
Instances with Extbase based extensions that call 
        $view methods without
testing for 
        Fluid.
Migration
Methods on "old" Fluid instances were wrapper methods for
        Rendering. Controllers
should call 
        $view->get
to perform operations instead.