Core

Lazy loaded objects cannot be edited through Fluid forms.

Given the following form:

<f:form name="bar" object="{foo.bar}">
  <f:form.textfield property="propertyOfBar"/>
  <f:form.submit value="Update"/>
</f:form>

If "bar" of "foo" is an instance of TYPO3\CMS\Extbase\Persistence\Generic\LazyLoadingProxy the initial check in TYPO3\CMS\Fluid\ViewHelpers\Form\AbstractFormViewHelper::renderHiddenIdentityField fails because the LazyLoadingProxy instance cannot be an instance of TYPO3\CMS\Extbase\DomainObject\AbstractDomainObject. This prevents the hidden identity field from being rendered which makes editing impossible.