[TYPO3-mvc] [TYPO3 mvc] Fluid: SelectViewHelper and LazyLoading

[Daan Wissing]

Hi all,

I might have stumbled across an issue introduced in TYPO3 6.1, considering the SelectViewHelper and the rewritten PersistenceManager. 

Situation: I have a model (generated with the Extension Manager) as follows: a Driver drives for one Transporter, while a Transporter can have many Drivers (a 1:n relation). Meanwhile, the Transporter can transport for one or more Customers, while a Customer can have multiple Transporters (a m:n relation). Both relations are defined as @lazy.

Now, I want to edit a Driver and use a Fluid SelectViewHelper to choose from any Transporter. Fluid code:
<f:form.select options="{transporters}" property="transporter" optionLabelField="name" />
{transporters} is a QueryResult containing all transporters.

In 6.0, this worked like a charm. But when upgrading to 6.1, I got an Exception:  Object of class TYPO3\CMS\Extbase\Persistence\Generic\LazyObjectStorage could not be converted to string.

After a lot of investigating, I came upon the following:
1. In 6.0, the function PersistenceManager::getIdentifierByObject() would load a lazy object if it was not loaded yet. In 6.1 this is not the case, the object is merely checked to be loaded in the persistenceSession.
2. Because of this, the function SelectViewHelper::getSelectedValue() will get a LazyLoadedProxy object (a Transporter) as current Value. 
3. Because LazyLoadedProxy implements \Iterator, getSelectedValue() will iterate over all properties of the Transporter, including the connected Customers. 
4. Customers is lazily loaded, so in this stage it is still a LazyObjectStorage. But the function SelectViewHelper::getOptionValueScalar() tries to call the __toString() method on this storage, which is not implemented, thus throwing the Exception.

I suspect that iterating over all the properties of a Transporter in point 3 is not intended behaviour, as this chunck of code is (I think) intended for dealing with multi selects. I have found a work-around for this (defining optionValueField="uid" in the f:form.select), but I am not sure if this is the intended method and I have been using an undocumented feature(tm), or if this is truly a bug.