TYPO3.Flow

The above is the Doctrine proxy, here is the FLOW3 proxy:

    /**
     * Autogenerated Proxy Method
     */
     public function __wakeup() {
        $this->FLOW3_AOP_Proxy_buildMethodsAndAdvicesArray();

    if (property_exists($this, 'FLOW3_Persistence_RelatedEntities') && is_array($this->FLOW3_Persistence_RelatedEntities)) {
        $persistenceManager = \F3\FLOW3\Core\Bootstrap::$staticObjectManager->get('F3\FLOW3\Persistence\PersistenceManagerInterface');
        foreach ($this->FLOW3_Persistence_RelatedEntities as $entityInformation) {
            $this->$entityInformation['propertyName'] = $persistenceManager->getObjectByIdentifier($entityInformation['identifier'], $entityInformation['entityType']);
        }
        unset($this->FLOW3_Persistence_RelatedEntities);
    }
                $this->FLOW3_Proxy_injectProperties();
        $result = NULL;
        if (is_callable('parent::__wakeup')) parent::__wakeup();

        $this->initializeObject(2);
        return $result;
    }

At least one case where this happens is when reconstituting objects from db. Not with lazy loading, but completely create them at once. Doctrine creates the class by unserializing an empty object of the entity class and then fills it with the properties. But unserialize does call __wakeup() and therefore initializeObject(). I think this changed at some point in Doctrine, when Andi reported this I believe Doctrine unserialized every new instance, but in current version I find that the unserialized instance is cached in Doctrine (which might lead to even more unpredictable behavior in this context). Hope this clears it up a bit.

Currently, I work around this by defining initializeObject() as a PostLoad lifecycle callback and check that everything I need is there before doing anything.

Also stumbled upon that behavior currently.
Note #5 boils it down; in \Doctrine\ORM\Mapping\ClassMetadataInfo::newInstance you can find

 1     /**
 2      * Creates a new instance of the mapped class, without invoking the constructor.
 3      *
 4      * @return object
 5      */
 6     public function newInstance()
 7     {
 8         if ($this->_prototype === null) {
 9             $this->_prototype = unserialize(sprintf('O:%d:"%s":0:{}', strlen($this->name), $this->name));
10         }
11 
12         return clone $this->_prototype;
13     }

Line 9 in that example calls, e.g., unserialize("O:52:"Acme\Acme\Domain\Model\Foo\Bar":0:{}"), which invokes __wakeup and immediately after that, initializeObject(), but with obviously no data to work on (see what has been unserialized...)