title: Symfony2/3 Children Entity Constraint Assert ignored
body: <p>I have a situation where the validation constraints inside the entity classes are ignored...</p>
  
  <p>This one does not work (which is a children of ActivityField Entity):</p>
  
  <pre><code>&lt;?php
  namespace XXX\ActivityFieldsBundle\Entity;
  
  use Doctrine\ORM\Mapping as ORM;
  use XXX\DatabaseBundle\Entity\AbstractEntity;
  use Symfony\Component\Validator\Constraints as Assert;
  
  /**
   * @ORM\Entity(repositoryClass="XXX\ActivityFieldsBundle\Repository\ActivityFieldLanguagesRepository")
   * @ORM\HasLifecycleCallbacks
   * @ORM\Table(name="activity_field_languages")
   */
  class ActivityFieldLanguages extends AbstractEntity
  {
      /**
       * @ORM\Id
       * @ORM\Column(type="integer")
       * @ORM\GeneratedValue(strategy="AUTO")
       */
      protected $id;
  
      /**
       * @ORM\Column(name="name", type="text")
       * @Assert\NotBlank()    ----&gt; !!! this one here !!!
       */
      protected $name;
  </code></pre>
  
  <p>while this one (which is standalone does not have any connection to other entities) works:</p>
  
  <pre><code>&lt;?php
  
  namespace XXX\LanguagesBundle\Entity;
  
  use Doctrine\ORM\Mapping as ORM;
  use XXX\DatabaseBundle\Entity\AbstractEntity;
  use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;
  use XXX\CommonBundle\Validator\Constraints as SiteAssert;
  use Symfony\Component\Validator\Constraints as Assert;
  
  /**
   * @ORM\Entity(repositoryClass="XXX\LanguagesBundle\Repository\LanguagesRepository")
   * @ORM\HasLifecycleCallbacks
   * @ORM\Table(name="languages")
   *
   * @UniqueEntity(fields="name")
   * @UniqueEntity(fields="iso")
   */
  class Languages extends AbstractEntity
  {
      /**
       * @ORM\Id
       * @ORM\Column(type="integer")
       * @ORM\GeneratedValue(strategy="AUTO")
       */
      protected $id;
  
      /**
       * @ORM\Column(name="name", type="string", unique=true)
       * @Assert\NotBlank() -----&gt; this one here !!!
       * @Assert\Length(
       *     min=2,
       *     minMessage="validator.minimum.2.characters"
       * )
       */
      protected $name;
  </code></pre>
  
  <p>If i add the constraint in FormType then all is ok and working but I don't want to have that and keep everything in the Entity file as annotation.
  In my config file i have </p>
  
  <pre><code>framework:
      validation:      { enable_annotations: true }
  </code></pre>